2005 ANNUAL REPORT OF THE ASSOCIATE LABORATORY ON PLASMA PHYSICS AND ENGINEERING Centro de Fusão Nuclear e Centro de Física dos Plasmas

1 1. INTRODUCTION 1.1. FOREWORD This document presents the main activities carried out in 2005 in the frame of the Contract of Association (CoA) signed in 1990 by the European Atomic Energy Community (EURATOM) and “Instituto Superior Técnico” (IST), hereinafter referred to as Association EURATOM/IST, and of the Contract of Associated Laboratory on Plasma Physics and Engineering signed in 2001 by “Fundação para a Ciência e a Tecnologia” (FCT) and IST, hereinafter referred to as Associated Laboratory (AL). The CoA activities are described in chapters 2 to 12, while the AL activities are presented in chapters 2 to 9, 12 and 13 to 18. Chapter 19 contains the list of publications, laboratorial prototypes, prizes and awards. The activities described in this document were mainly performed by “Centro de Fusão Nuclear” (CFN) and “Centro de Física de Plasmas” (CFP), two Research Units of IST (Figure 1.1). The other collaborating Institutions are presented in Figure 1.1 and Table 1.1. 1.2. ASSOCIATION EURATOM/IST The Contract of Association EURATOM/IST frames the Portuguese participation in the EURATOM Specific Research and Training Programme in the Field of Nuclear Fusion Energy, hereinafter referred as Community Fusion Programme. This Programme has as its long-term objective the development of a prototype commercial fusion power plant. It is presently implemented through several Agreements, in particular: (i) Contracts of Association signed between EURATOM and Institutions of the Member States of the European Union and Switzerland (Associates); (ii) the European Fusion Development Agreement (EFDA); and (iii) the Mobility Agreement, both signed by EURATOM and its Associates. The work programme of the Association EURATOM/IST includes activities carried out in Portugal (mainly related with the tokamak ISTTOK) and abroad related with the operation and scientific exploitation of large and medium-sized tokamaks and stellarator (JET, (Figure 1.2) ASDEX-Upgrade, TCV, and TJ-II) as well as with the design of the next generation fusion devices (ITER (Figure 1.3) and W7-X). 1.3. MAIN PROJECTS IN 2005 The Association EURATOM/IST had in 2005 the following main Projects:  Tokamak ISTTOK;  Participation in the collective use of the JET facilities by the EFDA Associates;  Participation in the ASDEX-UPGRADE Programme;  Participation in the TCV Programme; Figure 1.1 – Organization of the Associated Laboratory and Association EURATOM/IST 2  Participation in the ITER Project;  Other activities on theory and modelling;  Participation in the TJ-II Programme;  Other activities on control, data acquisition and signal processing;  Keep-in-touch activities on inertial fusion energy;  Participation in the Fusion Technology Programme;  Other fusion-related activities. Table 1.1 presents information about the responsible person(s) and the Institutions involved in each project. Project Responsible Person(s) Collaborating Institutions Portuguese Other Tokamak ISTTOK Carlos Varandas CFN1 UBI2 CEI3, CFA4 CIEMAT5, IPP-Kharkov6, UI7, IFUR8, IFUSP9 Participation in the collective use of the JET Facilities by the EFDA Associates Fernando Serra CFN, CEI, UBI EFDA10 CSU11 Culham UKAEA12 Participation in the ASDEX Upgrade programme Maria Emília Manso Fernando Serra CFN IPP-Garching13 Participation in the ITER Project Carlos Varandas Maria Emília Manso CFN EFDA CSU Garching Participation in the TJ-II programme Carlos Varandas CFN, CEI CIEMAT Maria Emília Manso Participation in the TCV programme Carlos Varandas CFN CRPP14 Other studies on theory and modelling Fernando Serra CFN IFP15, PT16, DFRC17 J. Pedro Bizarro Other activities on control and data acquisition Carlos Varandas CFN, CEI IFUSP Keep-in-touch activities on inertial fusion energy J.T. Mendonça CFP18 Participation in the Fusion Technology Programme E. Alves ITN19 Table 1.1 – Responsible person(s) and collaborating Institutions in the 2005 projects of the Association EURATOM/IST 1 CFN means “Centro de Fusão Nuclear” 2 UBI means “Universidade da Beira Interior” 3 CEI means “Centro de Electrónica e Instrumentação da Faculdade de Ciências e Tecnologia da Universidade de Coimbra” 4 CFA means “Centro de Física Atómica da Universidade de Lisboa” 5 CIEMAT means “Centro de Investigaciones Energeticas Medioambientales y Tecnologicas” 6 IPP- Kharkov means “Institute of Plasma Physics of the National Science Center” “Kharkov Institute of Physics & Technology”. 7 UI means “University of Innsbruck”. 8 IFUR means “Institute of Physics of the University of Riga” 9 IFUSP means “Instituto de Física da Universidade de São Paulo” 10 EFDA means “European Fusion Development Agreement” 11 CSU means “Close Support Unit” 12 UKAEA means “United Kingdon Atomic Energy Authority” 13 IPP-Garching means “Max-Planck-Institut für PlasmaPhysik” 14 CRPP means “entre de Recherches en Physique des Plasmas de École Polytechnique Fédérale de Lausanne” 15 IFP means “Istituto di Física del Plasma” 16 PT means “Politécnico di Turino” 17 DFRC means “Department de Recherches sur la Fusion Controlée”. 18 CFP means “Centro de Física dos Plasmas” 19 ITN means “Instituto Tecnológico e Nuclear” 3 Figure 1.2 – Tokamak JET Figure 1.3 – Tokamak ITER 1.4. ASSOCIATED LABORATORY The Associated Laboratory on Plasma Physics and Engineering has two thematic areas: o Controlled Nuclear Fusion; o Technologies of Plasmas and High-Power Lasers where the following main Projects were carried out in 2005: • Tokamak ISTTOK; • Participation in the collective use of the JET facilities by the EFDA Associates; • Participation in the ASDEX-UPGRADE Programme; • Participation in the ITER Project; • Participation in the TJ-II Programme; • Participation in the TCV Programme; • Other activities on theory and modelling; • Other activities on control, data acquisition and signal processing; • Keep-in-touch activities on inertial fusion energy; • Other fusion-related activities; • Theory and simulations on high energy density science and astrophysical and space plasma physics; • Experimental physics and technological developments on ultra intense lasers, radiation sources, plasma based accelerators and biomedical optics (Figure 1.4); Figure 1.4 - Detail of the compressor stage at the Laboratory for Intense Lasers. • Space plasma physics; • Environmental engineering plasma laboratory; • Modelling of plasma reactors (Figure 1.5); • Non-equilibrium kinetics and simulation of discharges, afterglow plasmas and high-speed planetary entries. Figure 1.5 - Plasma torch, developed at the University of Cordoba (Spain), and modeled at CFP. 5 2. TOKAMAK ISTTOK C.A.F. Varandas (Head), H. Fernandes and C. Silva (Deputy Heads), A. Soares, A. Vannucci, B.B. Carvalho, D. Valcárcel, I. Carvalho, I. Nedzelskij, M.P. Alonso, P. Carvalho, R. Coelho, H. Figueiredo, J. Figueiredo, J. Fortunato, R. Gomes, A. Neto, T. Pereira, V. Plyusnin, Y. Tashchev 2.1. INTRODUCTION ISTTOK is a small-size (R=46 cm, a=8.5 cm), large aspectratio, low magnetic field (0.46 T) limiter tokamak with an iron core transformer (flux swing of 0.22 Vs), equipped with a distributed VME control and data acquisition system. Its low temperature (150 eV), low density (8x1018 m-3) plasmas are diagnosed by electric and magnetic probes, a microwave interferometer, a heavy ion beam diagnostic and spectroscopic diagnostics. The main objectives of this project are: (i) development of new diagnostic and control and data acquisition systems; (ii) testing of new operation scenarios (liquid metal limiter and alternating plasma current); (iii) study of the influence of external applied signals on the plasma confinement and stability; and (iv) education and training on tokamak physics and engineering. This project included in 2005 work in the following main research areas: • Testing of the liquid metal limiter concept; • Optimization of the ISTTOK operation; • Diagnostics; • Control and data acquisition; • Plasma physics studies. 2.2. TESTING OF THE LIQUID METAL LIMITER CONCEPT1 IST/CFN has proceeded with the testing of the liquid metal limiter concept. The liquid metal loop experimental facility has been successful filled with oxide-free Gallium. The overall setup has been tested showing satisfactory operation of the device. The jet stability and reproducibility has been studied for the 2.30 mm diameter nozzle, which is planned to be used in the tokamak, since it produces a close to 13 cm continuous jet length. The time evolution for a 6 s main valve opening is shown in Figure 2.1. Gallium jet flow velocities and jet Break-Up Length parameter (BUL) have been measured for 1.45, 1.80, 2.09, 2.30 and 2.40 mm nozzle diameters. The results are presented in Figures 2.2 and 2.3. 1 Work carried out in collaboration with the Association EURATOM/University of Latvia. Contact Person: O. Lielausis Figure 2.1 - The gallium jet time evolution for a 6 s valve opening using a 2.30 mm nozzle. Each frame was obtained using a 700 µ s exposition. The influence of a pulsed magnetic field (0.25 T, 60 ms) on the jet characteristics has been analysed for both spatially uniform line distribution and with a high gradient perturbation. Transients in the magnetic field were found not to perturb significantly the jet behaviour; Finally, careful studies have been carried out on the observed scattering of Gallium droplets from the lower collector to the main chamber. A damping device has already been tested. Although it has shown a clear reduction on the number of large size (~ 0.5 to 0.2 mm) droplets, until now, it has been unsuccessful to fully eliminate the appearance of small (~10 to 200 µm size) ones. A more technically advanced damping device is under development in order to achieve a full elimination of the droplets that could reach the tokamak vessel. 024681012 0 2 4 6 8 10 12 v = 2.5 m/s v = 2.9 m/s v = 3.1 m/s v = 3.3 m/s flow-rate (cm3/s) valve time opening (s) Nozzle 1.45 mm Nozzle 1.80 mm Nozzle 2.09 mm Nozzle 2.30 mm Figure 2.2 - Flow rate and flow velocity for several nozzle sizes. 6 Figure 2.3 - Break-up length (L) for several nozzle sizes and as a function of Weber number. 2.3 OPTIMIZATION OF THE ISTTOK OPERATION Aiming at optimizing the ISTTOK operation, the gas injection system has been upgrade by using a fast valve to allow a better control of the plasma density. The RF generator used for the discharge pre-ionization has been replaced by a biased tungsten filament. The new set of external coils has been simultaneously used as the transformer primary and as a partial vertical field generator. This approach allows a smaller current on the vertical field quadrupole, with a much higher response time for feedback proposes. 2.4. DIAGNOSTICS 2.4.1. Main activities This research line included activities on spectroscopy for the analysis of Gallium impurities2, X-ray tomography, retarding field energy analyzer and emissive probes. The spectroscopy diagnostic, designed to measure neutral Ga density on ISTTOK, has been improved by introducing a multi-channel (x8) fiber in order to acquire Ga spatial density profiles at the plasma edge. The required software has been modified and the diagnostic tested using tokamak cleaning discharges as a plasma source. A commercial, low cost, CCD video camera has been tested. The test proved that these types of cameras are not adequate to be used as detectors in a soft X-ray tomography diagnostic due to the high noise level and the slow acquisition rate. A new diagnostic based on three linear 10- pixel detectors to perform real-time tomography from three different views has been designed. The design, installation and testing of a retarding field energy analyzer for the measurement of the edge ion temperature has been performed. An improved version of the multi-pin array of emissive probes has been installed on ISTTOK (Figure 2.4), which allows the simultaneous measurement of the density, 2 Work carried out in collaboration with the Association EURATOM/University of Látvia. Contact Person: Ivars Tale. poloidal and radial electric field, and their fluctuations in a spatial scale smaller than the turbulence correlation length. 2.4.2. Retarding Field Energy Analyzer The retarding field energy analyzer (Figure 2.5) is rather compact (D14×L23 mm2) and consits of an input 0.6 mm stainless steel pinhole (S), three Ni grids (G1, G2, G3) and a Cu collector plate (C) separated by MICA insulators. The grid stack is assembled in a boron nitride cup with a 14 mm of external diameter and with 2 mm diameter opening on the pinhole side. Figure 2.4 - The ISTTOK probe system, consisting of three emissive probes and one cold probe. Figure 2.5 - Photograph and schematically illustration of the retarding field energy analyser 5pin Cbl P Shaf Suppo C Pin Wa Colle MI G Shaft Plu Cu Support Cables Collector Pinhol MICA G Washe 5 pin 1,4 1,6 1,8 2,0 2,2 2,4 2,6 0 20 40 60 80 100 120 140 160 BUL (mm) Nozzle diameter (mm) 0 10 20 30 40 50 60 70 80 0 50 100 150 200 We L/d ISTTOK data 5.9*We^0.48 7 A +100 V sawtooth voltage is applied to the second grid G2 to obtain the ions characteristic, while grids G1 and G3 are kept at –50 V to suppress the respective electron flux from plasma and secondary electrons from collector. Figure 2.6 shows a typical characteristic obtained in the ISTTOK scrape-off layer (1.3 cm outside the limiter) as well as an exponential fit to the experimental data. The derived ion temperature (Ti = 14 eV) is typically a factor of two larger than that of the electrons at the same location, which is in agreement with the results of the scrape-off layer models. 0 102030405060708090100 -0.1 0.0 0.1 0.2 0.3 0.4 Ti = 14 eV Ushift = 18 V shot #12137 0.3*exp(-(x/0.002-18)/14)-0.08 irfea, a. u. Us, V Figure 2.6 - Typical characteristic obtained in the ISTTOK scrape-off layer 2.5. CONTROL AND DATA ACQUISITION 2.5.1. Main activities In 2005, a real-time controller for the horizontal plasma position, a PCI timing board, a new version of software for shared remote data consulting and analysis and remote data analysis tools have been developed. New power supplies have been designed and commissioned with optically isolated communication circuits and with local processing capabilities for self-implementation of control algorithms. 2.5.2. Real-time controller for the horizontal plasma position The real-time controller for the horizontal plasma position allows controlling the vertical magnetic equilibrium field using a novel power supply. This controller is based on an existing PCI module (PCI-TR-256), developed at CFN. The main technical characteristics of this module are:  8 galvanic isolated channels, with 14-bit ADC @ 2 MHz;  a Texas Instruments Fixed-Point DSP @ 500 MHz (TMS320C6415);  a Xillinx FPGA (Spartan-IIE XC2S400E);  512 MB SDRAM memory module; The module software acquires data from 8 poloidal magnetic probes, removes the offset present in the signals, numerically integrates them, calculates the plasma position using the current filaments method and generates a power supply control signal with a PI controller. Off-line tests show that this system is capable of performing the plasma position calculation in 74 µs and that its time evolution is similar to the plasma position calculated offline with floating-point numerical codes running in MatLab. 2.5.3. Timing board A new PCI-EPN board is intended to improve the trigger and the synchronism between the various ISTTOK diagnostics and allowing the migration of the ISTTOK CODAS to an event based system. The boards are on prototype stage and are planned to be operational earlier 2006. 2.5.4 New power supplies A new concept of switched power supplies (57 kHz) were designed and completed with an embedded microcontroller, for the necessary current drive of the vertical and horizontal magnetic fields. This option allows a direct implementation of PID algorithms with a faster response time. Each power supply will allow a maximum current of 100A, with a very compact design and bipolar capabilities. 2.5.5. Cooperative software for shared tokamak operation A new version of a multi-user platform, based on standards like CORBA, XML and JAVA, has been developed for remote control and data acquisition experiments. The main objective of this tool is to detach the machine operation from a single computer, allowing hardware configuration, experiment follow and data share by all the connected users. Among the main features it has a built-in chat, profile saving and sharing and remote calculation invocation. Since it was developed in JAVA and deployed with JAVA Web-Start technology, it can run in all the most common operating systems and computer platforms like PCs, Solaris and Mac in a very intuitive way. The software is plugin based, providing an easy way of adding new hardware, data viewers and data calculation algorithms. Since every hardware is described in a XML file, the program automatically creates configurators to the hardware. Every time a configuration is changed, the information is sent to hardware controller so that in the next discharge the hardware is programmed accordingly. 2.5.6. Remote data analysis tools Based on the Extensible Markup Language (XML) and the Remote Method Invocation (RMI) standards, a client/server remote data analysis application has been developed for intensive data processing. This GRID oriented philosophy presents a powerful tool to maintain centralized computational resources (Figure 2.7). Another major feature is the ability to share proprietary algorithms in remote computers without the need of local code and 8 libraries installation and maintenance. The 16 CPU Orionte cluster in operation at CFN is currently used to provide remote data analysis. The codes running in languages such as Octave, C, Fortran or IDL are called through a script remote invocation and data is released to the client as soon as available. The remote calculations parameters are described in a XML file containing the configuration for the server runtime environment. Since the execution is made by calling a script any program can be launched to perform the analysis. Some properties of the ISTTOK plasma that require heavy computational resources are already obtained using this approach, allowing ready intershot analysis and parameterization decisions. Figure 2.7 - The remote data analysis protocol scheme 2.6. PLASMA PHYSICS STUDIES 2.6.1. Introduction The ISTTOK plasma physics studies were related in 2005 with: o Control of edge transport by emissive electrode biasing; o Plasma SOL flow measurements; o Emissive probe measurements. 2.6.2. Control of edge turbulent transport by emissive electrode biasing Emissive electrode biasing experiments have been previously investigated on ISTTOK. Experiments revealed that although a large radial electric field is induced by emissive electrode bias for both polarities (up to ±15 kV/m), a significant improvement in particle confinement is only observed for negative bias. The main motivation for this work is therefore to contribute to the better understanding of the distinct plasma behaviour with positive and negative bias. The boundary plasma was further characterized with focus on the relation between ExB sheared flows and particle transport. The use of emissive electrodes allowed, for the first time, the extension of this investigation to negative bias. The ExB flow shear has been independently estimated from a radial array of Langmuir probes and a Gundestrup probe, which measures the parallel and perpendicular plasma flows. A good agreement has been found both in the profile and the absolute magnitude. We have observed that the magnitude of the ExB flow shear, in the region just inside the limiter position, is larger for negative bias. The ExB sheared flows induced by negative bias exceeds significantly the turbulence de-correlation time across most of the boundary plasma, while for positive bias this is only valid near the LCFS (r-a>-4 mm). The importance of the ExB flow shear on the global particle confinement has been demonstrated by the good correlation observed between these two quantities for both polarities in a wide range of bias conditions (Figure 2.8). We have found that above a certain threshold value of the ExB shearing rate (~1x106 kV/m2) an improvement in particle confinement is observed for both polarities, being that value a factor of three larger than the turbulence de-correlation time. Results support therefore that the distinct particle confinement behaviour observed for positive and negative bias is related with the different ExB flow profile induced by edge biasing. 0 5 10 15 20 25 30 ExB flow shear (10 5 V/m 2 ) 0.5 1.0 1.5 2.0 2.5 (n/Hα) Bias /(n/Hα) No Bias Negative bias Positive bias Figure 2.8 - Dependence of the modification in particle confinement induced by electrode biasing ([n/Hα]Bias/[n/Hα]No Bias) with the ExB shearing rate in the region just inside the LCFS. The effect of electrode bias on the edge turbulent transport has also been investigated identifying the changes induced on the fluctuations frequency spectrum and probability distribution function, PDF. We have observed that negative electrode bias reduces the large amplitude, low frequency events, resulting in low amplitude fluctuations with a near Gaussian distribution across most of the scanned region. For positive bias, a substantial reduction of the fluctuations is also observed in the SOL. However, large amplitude, broad spectrum fluctuations appear in the core periphery, which increase the cross-field transport and contribute to the observed asymmetry in particle confinement with the bias polarity. 2.6.3. Plasma SOL flow measurements Plasma SOL flow measurements were made using a Gundestrup Probe. A 1D fluid probe model was used to 9 deduce the parallel and perpendicular components of the unperturbed flow, taking into account the roundness of the collectors. The radial profile of the Mach numbers is shown in Figure 2.9. We note that the positive bias is not able to drive large sheared flows, which for both type of bias are larger around the limiter radius. The perpendicular Mach number behaves in opposite ways inside the LCFS and in the SOL region when bias is applied. We further note that the unbiased plasma exhibits a toroidal flow of about 0.2 throughout the measured region, being the direction the same as that of the toroidal field and plasma current. Furthermore, we note that the modification induced by biasing in the flows is maximum for negative bias and occurs in the region just inside the limiter for both parallel and perpendicular flows. Figure 2.9 - Radial traces of parallel and perpendicular Mach numbers. 2.6.4. Emissive probe measurements3 Detailed measurements of the edge quantities with high temporal and radial resolutions have been performed with a multi-pin array of emissive probes. The main aim of this work was to investigate the importance of temperature fluctuations in the turbulent transport estimation. Both the root mean square of the poloidal electric field and the fluctuation-induced particle flux were found to be significantly larger when measured with the emissive probes, indicating that temperature fluctuations are important for the particle flux determination. The flux distribution was also found to be more peaked and asymmetric when measured with the emissive probes (Figure 2.10). A clear reduction of the turbulent particle flux and an improvement of the plasma confinement are observed during the negative emissive electrode biasing. 3 Work carried out in collaboration with the Association EURATOM/OAW (University of Innsbruck). Contact Person: Roman Schrittwieser. Figure 2.10 - Probability distribution functions for the normalized turbulent particle flux at r = -8 mm inside LCFS. -20246 0.01 0.1 1 PDF (Γ) Γ / RMS( Γ ) cold emissive probes 11 3. PARTICIPATION IN THE USE OF THE JET FACILITIES BY THE EFDA ASSOCIATES F. Serra (Head), A. Figueiredo, A. Vannucci, B. Gonçalves1, C. Silva, C. Varandas, D. Alves, D. Borba2, F. Nabais, F. Salzedas, I. Nedzelski, I. Nunes, J. Sousa, L. Cupido, L. Fattorini, L. Meneses, N. Cruz, M.E. Manso, M.F. Nave, P. Belo, P. Varela, R. Coelho, S. Cortes, S. Hacquin3, T. Ribeiro, V. Plyusnin. 1 Member of the Close Support Unit. 2 Head of Office for the EFDA Associate Leader for JET 3 Secondee with JOC. 4 Work carried out in collaboration with the JET EFDA Contributers 3.1. INTRODUCTION The Association EURATOM/IST has proceeded with its participation in the collective use of the JET facilities, in the frame of the “European Fusion Development Agreement” (EFDA) through the “JET Operation Contract” and the “JET Implementing Agreement”. The main activities carried out during this year were related with: • Operation; • Scientific exploitation; • Performance enhancements; • Management. 3.2. OPERATION Two members of the IST/CFN staff have been working in the JET Operation Team:  One physicist belonged to the “Electron Kinetics Group”, being responsible by maintenance and data validation of the X-mode correlation reflectometer (KG8b) and the O-mode fluctuation reflectometer (KG3), as well as completing some shifts as “Diagnostic co-ordinator” (DCO) during the restart campaign;  The other physicist belonged to the “Operation Group”, being involved namely in the development of new plasma scenarios and configurations, in particular for the new divertor, and in the conceptual design of the tiles for all the main JET limiters and antenna (ICRH and LHCD) protections, and acting as first Session Leader in the restart of JET (during September/December 2005). 3.3. SCIENTIFIC EXPLOITATION4 3.3.1. Introduction The participation in the JET 2005 Work Programme had contributions from fifteen physicists who performed postanalysis of data from the experimental campaigns C13 - C14, and who were also involved in the preparation of the Campaigns C15-C17. The work was focused on code developments and physics studies related mainly with Task Forces M (with contributions to S1,S2, and T) , D and E. 3.3.2. Integration of transport and MHD codes (i) Implementation of sawtooth models into the transport code JETTO The so-called sawtooth crash is thought to start with the onset of the m/n=1/1 internal kink mode. During this crash a reconnection process results in the drop of the central temperature. The corresponding outward transport of energy defines an inversion radius that separates the central region, where energy is lost, from an outer region, where energy is deposited. Until recently the sawtooth physics available in the transport code JETTO was limited to a simple phenomenological model. At a user specified sawtooth crash time, the bulk plasma profiles of density and pressure were flattened within a user specified radius. No redistribution of the magnetic flux was included. In addition, the code could not be used for predictive sawtooth studies since no sawtooth trigger model was available. Following an assessment of available numerical modules, it has been proposed implementing into JETTO: (i) the NTCC Module KDSAW used in TRANSP; and (ii) the Porcelli’s sawtooth trigger model available in the BALDUR code. The first part of this work, the implementation of KDSAW into JETTO, has been carried out and completed (Figure 3.1). KDSAW is now fully integrated and tested. A new interface for JAMS has been written. WEB documentation has been prepared. The second part of the work, i.e. the work on the implementation of the Porcelli model was initiated. A test version of JETTO including the Porcelli model is now available. (ii) Testing JAMS interface for the equilibrium code HELENA and for the MHD code MISHKA5 The MHD codes MISHKA and HELENA have recently been integrated into JAMS. However, in order to simplify the JAMS input panels only a limited number of parameters were offered to the user, for the study of edge stability. Test runs of MISHKA and HELENA were 5 Work performed in collaboration with the Association EURATOM/UKAEA, Code Management Group. Contact Person: V. Parail 18 reconstruction and MISHKA-H and NOVA-K computations. The level of density fluctuations is then estimated by matching the phase perturbations evaluated experimentally (Figure 3.16) and those computed by WKB simulations. (ii) Turbulence studies H-mode access at very low plasma density has been studied on JET, providing valuable information on the physics of the edge transport barrier formation . In particular, a significant reduction of the turbulence level was observed after the L-H transition (Figure 3.17). This is exemplified on the figure below, which displays a clear reduction of the fluctuations of the reflectometer signal reflected in the edge plasma region. Figure 3.16 - Fluctuations of the reflectometry homodyne signal, of its amplitude and of its phase induced by the presence of an Alfvén cascade Figure 3.17 - Reduction of plasma turbulence at the L-H transition observed from a O-mode reflectometry signal at fixed frequency 34.1 GHz. From upper to lower parts: Raw reflected signal (b) Radial position of the cut-off layer (c) Averaged level of the reflected signal fluctuations (d) Spectrogram (sliding FFT) of the reflected signal 3.3.12. Turbulence experiments in reversed and standard-B field configurations in the JET tokamak In 2005 it was performed the analysis of the data collected by the fast reciprocating Langmuir probe system in the plasma boundary region during the campaigns of 2003/2004 with the aim to compare plasma turbulence in normal and reversed field configurations. Basic turbulence properties (e.g. level of fluctuations, ExB turbulent transport) are comparable in normal and reversed field configurations. It was observed that the SOL turbulence is less intermittent in REV-B discharges. The normalized Probability Distribution Function (PDF) shows that the distributions of fluctuations in the ion saturation current, Is and the floating potential, Vf are very similar in both magnetic field directions (Figure 3.18). It should also be noted that the PDF’s were obtained at different radial positions. Some differences in PDF shape are observed for the measurements from the far SOL (star points). The normalized PDFs of the turbulent flux are also remarkably similar (Figure 3.19). A reduction of the intermittence is observed in REV-B discharges (closed symbols) being this reduction more pronounced in inward intermittent flux events (ΓExB < -5 <ΓExB>, negative tail of the curve). This small difference is not reflected in the turbulent flux profiles because the contribution from intermittent events to the total flux is small. -4-202468 1E-4 1E-3 0.01 0.1 1 PDF Isat / IRMS sat -6 -4 -2 0 2 4 1E-4 1E-3 0.01 0.1 PDF Vfloating / VRMS floating Figure 3.18 - Probability Distribution function of Is (a)) and Vf (b)) normalized to the level of fluctuations a) b) 19 -20-100 102030 10-4 10-3 10-2 10-1 100 PDF ΓExB / <ΓExB> Forward B, old probe Forward B, new probe Reversed B, new probe -20 -10 0 10-4 10-3 10-2 PDF ΓExB / <ΓExB> -20-100 102030 10-4 10-3 10-2 10-1 100 PDF ΓExB / <ΓExB> Forward B, old probe Forward B, new probe Reversed B, new probe -20 -10 0 10-4 10-3 10-2 PDF ΓExB / <ΓExB> Figure 3.19 - a) PDF of the turbulent ExB flux. b) A detail of the tail of the distribution shows a reduction in the inward intermittent events for the reversed field discharges. 3.3.13. Analysis of generation and loss mechanisms of runaway electrons A comprehensive understanding of the trends of disruptiongenerated runaway electrons (REs) is needed to avoid their detrimental consequences on the materials of the plasma facing components (PFC) and vacuum chamber in large tokamaks and ITER. Comparison of experimental results and numerical modeling has allowed further contribution into development of the model for generation of runaway electrons during disruptions. Numerical modelling has been carried out in frame of a test particle model taking into account the evolution of the runaway beam geometry, which has been observed in experiments using soft-X diagnostics. A detailed scan on RE beam size shows that calculated current conversion efficiency can exceed the upper bound of the experimental values if the RE beam will occupy the whole plasma cross-section despite a significant decrease of the RE density (Figure 3.20 (a,b,c)). At some combinations of the disruption parameters the current conversion rate can achieve 100%, which never has been observed in experiments. Similar trends have been also predicted by other studies, where under certain conditions practically all the initial plasma current can be converted into runaways. Several mechanisms are considered as possible reasons for the observed in experiments a 60% upper bound for the current conversion rate: (i) REs are sensitive to magnetic fluctuations, which decrease the characteristic life-time of the runaways: τRE=apl/5.8Dr, where Dr≈ πqR0c(br/B0)2 is the coefficient of the radial diffusion caused by the presence of magnetic field perturbations with the magnitude br. Very large magnetic perturbations lead to the enhanced losses of fast particles and limit the energy and total amount of REs at the early stage of disruptions. However, with the increase of kinetic energy (Wkin) REs become less sensitive to the magnetic turbulence. (ii) Another loss mechanism can be understood from the analysis of the runaway orbit outward drift as the RE energy increases: dr=c/ωce (q/P||)(P|| 2+ P⊥ 2/2). From this expression one can obtain a condition for the energy of runaway electron, at which it will escape outside the confining region created after disruption: P⊥ 2=2(dr/q*ωce/c*P||-P|| 2) (Figure 3.21 (a)). So, that even under conditions of the perfect confinement the runaway electrons can produce intense photo-neutron emission interacting with PFC due to outward shift of the runaway orbit at certain values of the REs energy (Figure 3.21 (b)). beam radius nRE (10 16 m- 3 ) 00.25 0.5 0.75 1 1.25 1.5 0 2 4 6 8 10 beam radius Wkin (MeV) 00.2 0.4 0.6 0.8 1 1.2 0 15 30 45 60 75 beam radius IRE (MA) 00.2 0.4 0.6 0.8 1 1.2 0 0.5 1 1.5 2 Figure 3.20 - Dependence of the calculated RE density (a), maximal kinetic energy (b), and RE currents vs. dimensionless runaway beam radius. (a) (b) (c) 20 0 30 60 90 120 P|| 0 30 60 90 P⊥2 q =3 q =2 q =4 0 50 100 150 200 0 4 8 12 16 20 P⊥2 b/a=0.2 b/a=0.4 b/a=0.5 b/a=0.8 b/a= 1 P | | q=4 q=3 q=2 Figure 3.21 - (a) - Trajectories of the test electron in a momentum space at which its orbit outward shift becomes equal to the minor plasma radius (dr=a, for a=1 m) at different values of safety factor: q=2,q=3 and q=4. (b) - Evolution of the test runaway electron at different values of dimensionless runaway beam radius. Conditions for complete runaway electron diffusion from the confining region are presented by curves calculated at values q=2,3 and 4. 3.4. ENHANCEMENTS 3.4.1. Introduction The Association EURATOM/IST has been in charge with the following tasks carried out in the frame of the JET Enhanced Performance Project: • Mw access – Project management and implementation; • Development of a new fast sweep frequency reflectometer; • TOFOR – Project design and procurement activities; • Collaboration in the commissioning of TOFOR and MPRu; • RTP – Development of a real-time test facility; • PCU-VS – design of the PCU vertical stabilization; • DPDT4 – Real-time measurement & control diagnostics & infrastructure project; • Fast wave reflectometer. 3.4.2. Millimeter wave access (EFDA/01-625) The installation of both in-vessel and ex-vessel hardware, namely antennas and waveguides for both reflectometry and ECE, was completed. A quasi optical coupling arrangement to couple five different systems into a waveguide was developed. Calibration of the existing correlation reflectometrs to the expected performance within the new waveguides was done. Tests were performed, first with a mirror in-vessel and later with plasma. Figure 3.22 shows that significant improvements of the S/N ratio for the KG8b reflectometer signals have been reached. The increase of the raw signal amplitude by a factor of 50 suggests an improvement of at least 17 dB and a clear dynamic can now be observed on the signal spectrum. Figure 3.22 - Raw signal and corresponding spectrum from the KG8b 103 GHz channel before (on the left) and after (on the right) the installation of the new MWA 3.4.3. Development of a new fast swept frequency reflectometer (KG8a diagnostic). A new fast swept-frequency heterodyne reflectometer (KG8a diagnostic) dedicated to density profile measurement is being developed and should be operational for the next JET experimental campaigns in 2006. Providing routine measurement of the edge density profile with high spatial (< 1 cm) and temporal (< 30-50 µs) resolution, this diagnostic will be of the greatest importance for the pedestal studies on JET. In addition to the development of the routine for density profile inversion, some theoretical studies were carried out in order to estimate the spatial resolution of these measurements. The influence of the misalignment between the plasma magnetic axis and the probed region was especially assessed. As depicted in the figure below, a spatial resolution better than 1 cm is expected from the KG8a measurements in a large majority of the JET discharges. 3.4.4. TOFOR – Project design and procurement activities8 Five time digitizer boards (TDB) were assembled and delivered to JET after successfully tested at the Uppsala University. Since the TDB power needs require that no more than three boards coexist in the same computer, the control software was modified for three plus two boards in two computers, with an implementation of a TCP 8 Work carried out in collaboration with the Swedish Euratom Association Contact Person: J. Kelme 21 based synchronism server and a client. Better synchronization links were tested and found operative for the required length. Integration of the boards in the diagnostics was performed by the VR Association in close collaboration with IST/CFN. Figure 3.23 - Estimation of the spatial resolution of the KG8a reflectometer diagnostic as a function of the misalignment between the plasma and the reflectometry antenna mid-planes 3.4.5. RTP – Development of a real-time test facility The complete unit providing 32 waveform generator (WG) plus 8 transient recorder channels was assembled. Requirements compliance tests were performed at IST/CFN. Integration to CODAS and functional tests were performed at JET by the IST/CFN staff with success. Minor accuracy corrections on the WG outputs and additional software features allowing local unit control were incorporated. Software and hardware manuals have been finished. 3.4.6. PCU-VS – Design of the PCU vertical stabilization The implementation of a new vertical stabilization controller will require the increment of the number of input signals to over 50, while maintaining the control loop delay under 50 µs, and aiming to reducing it to fewer than 10 µs. The design of an ATCA-based hardware platform (Figure 3.24) for the low-latency controller was proposed aiming at: • Reducing the delays on the acquisition/generator endpoints and data interconnect links; • Providing high processing power near the acquisition/generator endpoints and on the system controller; • Providing the synchronism of all digitizer/generator endpoints; • Having an architecture designed for maintainability, upgradeability and scalability; • Targeting the specificities of the VS controller including low cost per channel; • Decreasing risks during implementation and testing. Figure 3.24 - Vertical stabilization controller 3.4.7. DPDT4 – Real-time measurement & control diagnostics & infrastructure project The essential aim of this project is to expand JET realtime diagnostics and control capabilities required to fulfil the programme objectives of JET in the proposed FP7 phase of operation dedicated to ITER preparation. In particular the objective is to optimize the control of the plasma during operation and to enable control schemes for the main plasma scenarios and in particular profile control. In response to the call for participation in the diagnostic enhancements, Associations IST, CEA and UKAEA declared interest in the project. IST offered to lead the project and proposed the workgroup organization chart of Figure 3.25. 3.5. Management The Association EURATOM/IST has collaborated on the management of the use of the JET facilities by the EFDA Associates in the following manner: • Dr. Duarte Borba, as Head of Office for the EFDA Associate Leader for JET, • Dr. Bruno Gonçalves as a member of the staff of the Close Support Unit to the EFDA Associate Leader for JET; • Prof. Horácio Fernandes and Dr. Paulo Varela as members of the Remote Participation Users Group. 22 Figure 3.25 – Organization of the DPDT4 project EDFA PROJECT BOARD ________ Project Sponsor Bernardo Carvalho Project Leader Robert Felton Co-Project Leader FIR Interferometer Project Manager Neutron Diagnostics Project Manager Emmanuel Joffrin FE Bremstrahlung Project Manager J. Sousa Network Infrastructure Project Manager RT Analysis Project Manager Optics design Mechanic Electronics Data Acquisition IST CEA UKAEA/JOC Associations Involved Data Acquisition Data Acquisition LH deposition profile codes q-profile analysis Test Methodology Evaluation Network JET OPERATOR Drawing Office Quality Assurance Installation & Commissioning Manager UKAEA 23 4. PARTICIPATION IN THE ASDEX UPGRADE PROGRAMME1 M.E. Manso (Head), F. Serra (Deputy Head), A. Combo, A. Ferreira, A. Silva, D. Borba, F. Salzedas, F. Silva, I. Nunes, J. Santos, L. Cupido, L. Fattorini, L. Guimarãis, L. Meneses, P. Varela, R. Coelho, S. Hacquin, S. Graça, T. Ribeiro 1 Work carried out in collaboration with the ASDEX-Upgrade Team. Contact Person: Dr. G. Conway. 4.1. INTRODUCTION The Portuguese participation in the ASDEX Upgrade2 (AUG) programme has been mainly focused in two research lines: • Microwave reflectometry; • MHD, turbulence and transport. 4.2. MICROWAVE REFLECTOMETRY 4.2.1. Introduction This research line included in 2005 activities on microwave systems and electronics, control and data acquisition, diagnostic developments, data processing, modelling and plasma physics studies. Concerning microwave systems and electronics, the V band LFS channel was tested and electronics had to be modified for homodyne detection due to the degradation of the mixer. After its repair it was changed back again to heterodyne. The main control switch board of the system was calibrated and a faulty optical coupler was replaced. The pig-back of the optical analogue signal transmitters was changed. V band/X-mode channel was tested and changed from heterodyne to homodyne detection. All the diagnostic channels were inspected and tested. Part of the transmission line of the Q/X-mode channel was disassembled, tested and calibrated after high losses that were found to be caused by metal peaces of soldering material inside one of the waveguides. The V/X-mode antenna was modified to correct a construction error. A new transmission line for the HFS channels is being studied in order to protect the diagnostic in AUG forthcoming experiments with increased ECRH power. Regarding control and data acquisition, the firmware of all of the eight control boards was upgraded to use a high level language, like the one used in the fluctuations monitor control system. This makes the communication more robust. Control software for a new “hopping” frequency system has being installed and tested. Also a new system has started to be developed. Concerning diagnostic developments, the new hopping diagnostic was completed and first turbulence results were obtained. Regarding data processing, a new algorithm was developed for the time-frequency analysis of broadband signals which allows the length of the analysis window of the spectrogram to be adapted to automatically to the local time-frequency characteristics of the signals while maintaining a good time-frequency resolution. Several upgrades were also made to the interactive data analysis tools for better efficiency and less computing time. Concerning modelling, dedicated tools were developed to simulate Doppler reflectometry. A code was developed for the analysis of turbulence and transport in the SOL. The plasma physics studies: were focused mainly in pellet experiments as well as MHD, turbulence and transport. The studies could be extended to higher densities with the W band channel in full operation. 4.2.2. Frequency calibration The frequency calibration system was upgraded with a delay line. The output of the detected signal resulting from interference between the non delayed and the delayed signal as well as the spikes from the frequency markers are shown in Figure 4.1. The interference data was used to obtain a continuous the frequency versus time characteristics of the oscillators in ultrafast swept operation. The instantaneous phase evolution of the signal shown in Figure 4.1a is obtained with an Hilbert Transform and the resulting frequency step is depicted in Figure 4.1b. The spectrogram of a signal reflected from a metallic mirror obtained with the frequency marker calibration shows significant deviations from a constant value corresponding to the distance between the antenna and the mirror (Figure 4.2a), whereas in the case of the delay line calibration an almost constant time delay is recovered (Figure 4.2b). The novel method greatly improved the accuracy of density profiles. 4.2.3. Control and data acquisition In order to exploit full diagnostic capabilities of the ASDEX Upgrade tokamak it is mandatory to upgrade the data acquisition and control system. This will cope with faster frequency sweep times and improved time resolution as well as accuracy allowing, for example, plasma position and shape measurements for control purposes, as it is foreseen for ITER. A new PCI-based 24 0 2 4 6 8 101214161820222426 -0.1 0.0 0.1 0.2 0.3 0.4 (c) Markers [V] t [µs] -0.4 -0.3 -0.2 -0.1 0.0 0.1 Interference [V] (a) 0 10 20 30 40 50 (b) ∆F [MHz] Figure 4.1 - a) Interference signal. b) Frequency step from the interference signal. c) Frequency markers signal. Figure 4.2– Spectrogram of a signal reflected from a metallic mirror: a) frequency marker calibration and b) delay line calibration. system (Figure 4.3) is being developed based on a digitizer card with 2 channels, 12-bit resolution and a waveform generator with one channel, 14-bit resolution. Both cards will have 512 Mbytes of memory, a Digital Signal Processor (DSP) for advanced processing modes and a Field Programmable Gate Array (FPGA) for real-time algorithms and complex trigger managing modes. The system will be able to support multiple cards (digitisers and signal generators) operating synchronously at a maximum speed of 210 MHz. The development of the fast digitizers and generators was started with the schematic and layout design of the PCI cards. 4.2.4. Numerical studies for plasma position The sensitivity and robustness of reflectometry to track plasma movements in a steady state ELMy H-mode scenario was studied aiming to fully demonstrate the use of reflectometry for control purposes as foreseen for ITER. Position curves after ELM removal were averaged using a window of 3 measurements or 26 ms, roughly equivalent to averaging three ITER individual measurements (at a 10 ms rate). To compensate the errors in the profile inversion due to the non probed plasma region with O-mode reflectometry, a dynamic initialization procedure was developed. Figure 4.3 - Current (A), new (B) data acquisition system and PCI module diagram. To track the separatrix position from reflectometry profiles two estimations for the density at the separatrix were used one from diagnostic XPTO and multiplying the average density by a factor α (with α Є [0.15, 0.65]). Position results obtained using the dynamic estimation for the ratio between the separatrix density and the average density after removing measurements performed during ELMs, were impressively good (Figure 4.4). In this case, shot #19701, the tracking of the separatrix position using 25 a fixed scaling of 30% of the average density to estimate the density at the separatrix would result in a match to the magnetic separatrix with a radial error of 2.5 mm and standard deviation of 2.5 mm both at HFS and LFS. Figure 4.4 - Position of density layers corresponding to esepe nn / _after removing during-ELM measurements and averaging during a 26 ms window (thick blue) and the corresponding distance to the magnetic separatrix, R ∆(red), in discharge #19701; sepee nn _ ,and corresponding ratio curve (top right plots); R ∆ and σ as a function of a static percentage of e n (bottom right plots). 4.2.5. Modelling2 The previously developed 2D code is being equipped with the tools to explore the possibilities of extracting information from reflectometry about thin velocity shear layers as those occurring, for example, in internal transport barriers and zonal flows. The numerical results can be applied to any reflectometry system, namely in ASDEX Upgrade or Tore Supra3. 2 Work carried out in collaboration with Dr. Stephan Heuraux (Université Poincaré, Nancy, France.) 3 Modelling analysis more focused on reflectometry for ITER is presented in section 8. The plasma is modelled with a generic density profile, across circular or elliptical iso-density lines (slab model corresponds to an infinitely elongated ellipsis). Turbulence is taken into account as a sum of modes with random phase. The density perturbation at each point obeys to, (, )cos () ( ) (, ) MM mm ij eTRB x y ij nAijkixkjyij δϕ ⎡ ⎤ =++ ⎣ ⎦ ∑∑ (1) The choice of the coefficients (, )Ai j is in agreement with the Tore Supra experimental data. The columns of the original turbulence matrix on the shear region are shifted poloidally, each column sliding at a speed given by the imposed velocity shear profile. Figure 4.5 shows the columns of the original turbulence matrix ne(r,t) (top left), as the simulation runs its course, slide with a velocity given by the shear profile. Its effect on the turbulence structure is shown on Figure 4.5 (bottom left). This model for velocity shear implies a modification of the wavenumber spectrum (k-spectrum) on the shear layer (both poloidal and radially). Figure 4.5 shows the original spectrum (top right) and the spectrum at iteration 50×103 (bottom left) are shown. They reveal the deformation of the density fluctuation spectrum in the shear zone reflecting the elongation of the turbulent structures along the poloidal direction and the radial squeezing as the matrix columns slide in the shear region. Figure 4.5 - Original turbulence matrix (top left) and the amplitude k-spectrum (top right). Matrix of turbulence at iteration 50 · 103 (bottom left) and the modified spectrum at the poloidal velocity shear region with a radial profile in the xdirection (bottom right). In classical reflectometry the code is usually run in a monostatic setup (same antenna used for emission and reception) and the signal is excited in the waveguide using a Unidirectional Transparent Source (UTS) allowing 26 unidirectional injection of a wave. Figure 4.6 (upper plot) presents a monostatic setup for a 2D H-plane horn with a half power beam width of 30◦ appears on top. The Doppler effects in this configuration appears due to lateral probing of the plasma through the relatively large antenna radiation pattern. The contribution to the frequency spectrum from the direct reflection on the plasma is stronger than the Doppler effects and the Doppler frequency shift arises on a wide frequency range according to the Bragg law at the turning point (oblique cut-off). The 2D code was adapted to typical Doppler reflectometry using an optical system (Figure 4.6 bottom plot). The use of a lens allows the emission of a quasi nondiverging beam with a planar wave front which will respond to a single wave number according to the injection angle chosen by the prism. The same impulsive response (IR) technique utilized to implement the UTS is used to eliminate the spurious reflection from the lens and prism. Figure 4.6 Classical reflectometry with a horn (top) and Doppler setup with a converging lens and prism to launch beams with high directivity. 4.2.6. Pedestal evolution in the presence of ELMs The study of the pedestal evolution in AUG discharge #1991, where four intrinsic type I ELMs and one pellet triggered ELM occurred, is presented in Figure 4.7, along with the time traces of the line average density obtained with the interferometer diagnostic, and the Hα radiation associated with the outward particles flux into the divertor plates. A further picture of edge profile dynamics under ELMs was obtained from the detailed profile evolution at the LFS (Figure 4.8). At the LFS the density time traces show clearly the two distinct regions separated by ~ 1cm around 2.17 m. This should be the position of the last closed flux surface, separating the pedestal (< 2.17 m) and the scrape of layer (SOL) (> 2.17 m). Transport during the ELM (period of enhanced Dα light emission) increases the SOL density during that period of time. Figure 4.7 – Time traces of: (a) line average density from interferometry (DCN H-1); (b) pedestal heigth from reflectometry (ne-ped); (c) H α radiation (ELM-H α ). Figure 4.8 – Density contour plots showing the time evolution of the edge density profile at the LFS. The bottom plot depicts the time trace of H α radiation (ELM-H α ). The high SOL density is maintained during the ELM, but is back to pre-ELMs values immediately after the end of the period of enhanced Dα light emission. This corresponds to a low confinement expected for the SOL and the higher density can only be maintained by the strong influx of particles to the SOL from the core during the ELM. The density in the pedestal also collapses very quickly, within 100 µs time scale, but recovers more slowly to the pre-ELM values taking ~ 10-20 ms, which is approximately the ELM repetition time. This means that the confinement in the pedestal is good between ELMs, allowing the profiles to recover, but poor during the ELMs. This is consistent with the expected picture of the density evolution in the pedestal and SOL regions during the ELM cycle. 4.2.7. Localization of TAE modes The new hopping reflectometer has the capability of probing several density cutoff layers (in the Q and V 27 bands at LFS) during each discharge. The position of density layers is determined using ne profiles from the broadband FM-CW reflectometry system. First results (Figure 4.9) show that in TAE experiments (AUG shot #20489), with low density (319 1025.3 − ×= mne), 5 MW of ICRH power and L- mode, the “hopping frequency system” allows the radial localization of modes at the edge as well as TAEs and sawteeth precursor in the core (ρpol = 0.6-0.35) clearly separated from the edge. These results are important to study the radial structure of TAEs modes. Figure 4.9 - Spectrogram of Q band “hopping frequency millimeter wave reflectometer” for TAE shot #20489 (a), the corresponding density profile from reflectometry for the localization of the density cutoff layers (b) and spectrogram from magnetics (c). 4.3. STUDIES ON MHD, TURBULENCE AND TRANSPORT 4.3.1. Introduction This research line included in 2005 code development for turbulence and transport analysis in the SOL of ASDEX- Upgrade. 4.3.2. Code development for turbulence and transport analysis in the SOL of ASDEX Upgrade The boundary of tokamak plasmas is characterised by electromagnetic interactions between wavelike and fluidlike motions on space scales down to the ion gyroradius. The two moment gyrofluid flux tube model GEM3 was used to investigate electromagnetic turbulence and the associated transport phenomena both in the edge and scrape-off layer (SOL) of such region of the plasma. The comparative study between edge and SOL conditions was concluded . The main results include the observation of the dominance of a convective cell mode (k⊥≠0 and k||=0) whenever the limiter was included, i.e., whenever the SOL boundary conditions were applied, in accordance with the experimental observations for the SOL region. The turbulent transport values were also found to increase in the latter situation, where the large scale interchange dynamics became dominant, due to the absence of the adiabatic response of the electrons in the convective cell mode. Conversely, with closed field lines boundary conditions, the field line connection of tokamak sheared magnetic fields suppresses the convective cell mode, when the flux surfaces are closed, leaving the drift wave character typical of the plasma edge, with the parallel electron dynamics keeping the electrostatic potential coupled to the electron pressure through parallel forces mediated by parallel currents. The study of the effect of the equilibrium magnetic field geometry of a tokamak (ASDEX Upgrade with diverted geometry) was continued, including the investigation of the issue of the spatial resolution of the simulations. This also included verifications made within the geometry code METRICS to check the consistency of the coordinates transformations made, and also the implementation of a Savitzky-Golay smoothing filter, constituting an improvement of the filtering that is necessary to apply to the curvature operators in the case of grids coming from the CARRE code. The results for closed flux surfaces regions showed a well spatially resolved system, even at the locations along the field lines where the grid cells are most severely deformed, due to the variations of the perpendicular (contravariant) metric components of the metric (Figure 4.10). When compared to the corresponding results obtained with the simplified geometry model (Figure 4.11), which retained only the poloidal dependence of the curvature operators, they revealed a reduction of the measured E × B turbulent transport, which brought the figures closer to experimentally measured values. This result supports the scenario whereby the local magnetic shear, that affects directly the polarisation dynamics (the main mechanism behind a fluid drift model) and is particularly strong close to the magnetic separatrix (Figure 4.11–left), facilitates the nonlinear decorrelation processes by twisting the turbulent perpendicular vortical structures, which are then torn apart to smaller scales. (a) (b) (c) 34 5.5. INFORMATION IST has proceeded with the divulgation of the ITER project to the general public, industry and research units. The following actions were performed in 2005:  Participation in the Fusion-Industry Workshop, held in Madrid, in 1 and 2 June. Prof. Carlos Varandas was the Co-chair of the working group on Industrial Policy Issues;  Publication of articles in the main Portuguese newspapers and participation in television programmes about ITER;  Organization of a Workshop in 24 November, at IST, for the divulgation of the ITER project to the Portuguese Industry and Research Units. This Workshop had about 114 participants;  Participation in the workshop “ITER: Opportunities for European Industry”, held in 13-14 December, in Barcelona, with a stand and 500 participants. 35 6. PARTICIPATION IN THE TJ-II PROGRAMME1 C. Varandas (Head), M. Manso (Deputy Head), A. Silva, C. Silva, I. Nedzelskij, L. Cupido, L. Pereira, Y. Tashchev. 6.1. INTRODUCTION The Portuguese participation in the TJ-II programme has been mainly focused in three research areas: • Microwave reflectometry; • Electrode biasing experiments; • Heavy ion beam diagnostic. 6.2. MICROWAVE REFLECTOMETRY2 CFN has developed in 2004 a fast frequency hopping reflectometer, operating in the Q-band (33-50 GHz), with wave propagation in X-mode. It can be tuned to any selected frequency, within a fraction of a ms, enabling to probe several plasma layers within a short time interval. This gives the possibility to study important characteristics of radial distribution of plasma turbulence. First results have been obtained in 2005 showing the formation of a velocity shear layer above a certain critical density and demonstrating the good spatial resolution of the reflectometry measurements. In view of the good results obtained with the diagnostic, a new system is being developed to study correlation properties of plasma turbulence. It uses basically the same design of the previous hopping system. The final design has been assessed and the procurement has been initiated. 6.3. ELECTRODE BIASING EXPERIMENTS3 Following earlier investigations on the effect of electrode bias on the TJ-II boundary plasma, a detailed comparison between positive and negative bias at densities above the threshold value to trigger the spontaneous development of ExB sheared flows has been performed. We found that at high densities negative voltages are easier to impose when compared with positive ones as the forced plasma rotation is in the same direction of the natural rotation. Figure 5.1 shows the time evolution of the main plasma parameters for discharge with negative bias. As the bias is applied, a strong reduction in the Hα emission is observed associated with an increase in the density up to the ECRH cut-off frequency. A stronger reduction of recycling is observed for negative bias, when compared with that observed for positive bias at similar plasma density, resulting therefore in a larger increase in the ratio n/Hα (~70%). These results are in agreement with observation in other devices where improvement in particle confinement is in general observed for both polarities, being larger with negative bias. -20 0 20 40 60 80 100 Bias Current (A) -100 0 100 200 300 400 Bias voltage (V) 11918 0.2 0.4 0.6 0.8 1.0 1.2 Density (10 19 m -3 ) 0.0 0.2 0.4 0.6 0.8 1.0 <Hα> (a.u.) -200 -150 -100 -50 0 50 Floating potential (V) -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 Phase velocity (km/s) r/a=0.8 0 1 2 3 4 Density/<Hα> (a.u.) -1 0 1 2 3 Particle flux (a.u.) 110 115 120 125 130 Time (ms) 0.0 0.2 0.4 0.6 0.8 RMS(Isat)/<Isat> 0 2 4 6 8 10 12 RMS(Eθ) (kV/m) Figure 6.1 – Time evolution of the main plasma parameters for a discharge with negative electrode bias (Vbias=200V, relec/a ≈ 0.9) at high density. 6.4. HEAVY ION BEAM DIAGNOSTIC3 6.4.1. Introduction This research line included in 2005 the improvement of the multiple cell array detector (MCAD), the revision of the conditioning electronics, the development and testing of a new control and data acquisition system and the beginning of the diagnostic operation. The revision of the multiple cell array detector was finished, including repair of the damaged contacts and cells, duplication of the contacts of the working cells and insulation of the MCAD housing and biasing grids from 1 Work carried out in collaboration with the Association EURATOM/Ciemat. Contact Person: J. Sanchez 2 Contact Person: J. Sanchez 3 Contact Person: C. Hidalgo 36 the TJ-II vacuum vessel. The cells have been modified and improved by insertion of tantalum “wire-balls” into Faraday cup matrix. Concerning the conditioning electronics eight preamplifiers and amplifiers have been repaired and tested. The preamplifier-connector part has been modified and included in a single box, aiming at decreasing the cable lengths and, therefore, the noise. A 24-channel control and data acquisition system has been developed, tested and pushed into operation. Regarding the diagnostic operation, the fist experimental campaigns have permitted clear observations of the primary ions at energies of 80 keV, 90 keV and 100 keV. 6.4.2. Control and data acquisition system 6.4.2.1. System Overview The new dedicated control and data acquisition system for the multiple cell array detector of the TJ-II heavy ion beam diagnostic (HIBD) is based on in-house designed VME modules and Linux. The hardware consists of: (i) a VME host running Linux; (ii) four CFN transient recorder boards; (iii) an analogue output board; and (iv) a commercial 32 bit TTL I/O M-Module mezzanine. The software for the active control of the primary and secondary beam lines has two major components: (i) a server daemon running on the VME host, receiving operation parameters and waveforms to be programmed and controlling board operation; (ii) client applications with graphical user interfaces running on the control room PC’s. The software for the MCAD acquisition system consists of a daemon controlling acquisition and writing data to the TJ-II database and a graphical application allowing easy configuration of acquisition parameters. 6.4.2.2. Multiple cell array detector Currently 32 channels are installed, provided by four inhouse designed transient recorder modules (VME8i125). Each VME8i125 transient recorder module has 8 channels with 12 bits resolution, 512 kSamples per channel of inboard memory and a sampling rate up to 1.25 MSPS. The end of acquisition signal is defined by a commercial 32 TTL I/O M-Module mezzanine, since the VME8i125 does not provide this information. The software of the MCAD data acquisition system has two major components (Figure 6.2): a daemon that runs on the VME host and a graphical application that is used to configure all acquisition parameters. The configuration application can be run in any computer (inside or outside the control room). The MCAD daemon: (i) reads the transient recorder module configuration (produced by the MCAD configuration editor application); (ii) programs and arms the transient recorder modules with the configuration provided by the user; and (iii) reads the acquired data from the board memory and writes it (along with configuration parameters) to the TJ-II database. Figure 6.2 - Block diagram of the software of the MCAD data acquisition system 6.4.2.3. Active beam control The active beam control software has two major components (Figure 6.3): a server daemon that receives the board configuration and waveforms and a pair of clients with graphical user interfaces. Both clients allow the user to configure the trigger type (external or internal), the update rate and the waveform. The main difference between the two clients is the way how the waveform is selected: one client has a set of predefined waveforms (sinus, triangular, sawtooth, and constant) and the other allows the user to interactively design a waveform with the mouse. The link between the clients and the server is achieved with an Ethernet connection. The communication is done using a custom protocol over TCP/IP. The daemon only accepts connections from specific computers in the control room. Additionally, at a given moment only one client is allowed to be connected to the server. To prevent the possibility of the VME8O board being loaded with garbage (due to waveform data corruption in the network transmission) all the waveform data passes through a software limiter in order to maintain the high voltage power supply within a safe voltage range. Figure 6.3 - Block diagram of the software for active beam control 37 7. PARTICIPATION IN THE TCV PROGRAMME C. Varandas (Head), A.P. Rodrigues P. Amorim, L.A. Pereira, T.I. Madeira 7.1. INTRODUCTION This project had in 2005 two research lines: • X-ray diagnostics • Advanced plasma control system (APCS) 7.2. X-RAY DIAGNOSTICS 7.2.1. Introduction This research line included in 2005 activities related with:  The operation and scientific exploitation of the horizontal pulse height analysis (PHA) diagnostic;  The commissioning, testing and implementation on TCV of the vertical PHA diagnostic;  The transformation of the vertical PHA diagnostic into a real-time system;  The commissioning and testing of the rotating crystal spectrometer. 7.2.2. Analysis of the data from the horizontal PHA diagnostic Since its commissioning, the horizontal PHA diagnostic has provided data which has contributed to many experimental studies particularly in the fields of impurity injection aided particle confinement and plasma heating scenarios: mild (Figure 7.1) to strong (Figure 7.2) deviations of the electron populations from a thermal distribution when additional heating is applied have been observed, and impurities resulting from the erosion of the plasma vessel walls during ECRH have been identified (Figure 7.3). The impurity identification is straightforward as long as the system calibration is known, but to determine the electron temperature, some situations have been treated by employing a single maxwellian fit (Figure 7.4), others are addressed by a bi-maxwellian model (Figure 7.1) in cases of strong non-Maxwellian behavior (Figure 7.2) the approximation of a Maxwellian distribution no longer holds and leads to erroneous results without physical meaning as there is no longer a correspondence between the observed photon energy and the electron energy. A qualitative interpretation of the experimental results is being investigated. Figure - 7.1 - Example of mild non-maxwellian behavior observed during ECRH Figure 7.2 - Example of strong non-maxwellian behavior observed during ECRH Figure 7.3 - Impurities resulting from erosion of the plasma vessel walls during ECRH. Figure 7.4 - Electron temperature measurement using single Maxwellian fit 7.2.3 Vertical PHA diagnostic The vertical PHA diagnostic is a modern upgrade of the “classical” horizontal PHA system that has been designed aiming at demonstrating an extremely low étendue X-ray 38 spectral measurement of a hot plasma with a regulated flux permitting real-time measurements of plasma parameters for a wide range of plasma conditions and real-time diagnostic feedback control. This diagnostic comprises a compact Silicon Drifted Detector (SDD) Peltier cooled diode and two independent systems for signal conditioning and processing: a commercial multiple-frame multichannel analyser (MCA3) with post acquisition analysis and a CFN designed VME hosted DSP card which will provide real-time analysis of the X-ray emission. Both system are designed to remote actuate the stepper motors whilst simultaneously regulating the system étendue to maintain an optimal throughput during a single discharge: the analogue system employs an integrator (sensor) together with a comparator that when the throughput limits are surpassed, gives out a signal that actuates the motors and change the position of the aperture. For the DSP system the pre-amplifier pulses are fed into a subsystem with a DAC that supplies the appropriate voltage to actuate the stepper motor. With a regulated input rate, a spectrum, with spectroscopic quality, may be obtained every 100 ms during a 2 s TCV discharge. Measurements of the central electron temperature have already been obtained with the MCA3 card for some TCV operation regimes (Figures 7.5), with an average throughput of 300 kHz. The DSP algorithms employed to make the histogram and calculate the electron temperature are still being essayed for performance during TCV operation. A set of beryllium filters of 50, 100 and 150 µm are also employed to reduce the dominant lower energy X-ray photon rate and a low power 55Fe source occupies one of the filter holder positions and can be used to diagnose and calibrate the system in situ. Figure 7.5 - Results obtained with the MCA3. (A) soft x-ray spectrum and (B) Electron temperature, temporal evolution. 7.2.4. Real-time diagnostic The research and theoretical development of the histograms construction algorithms were carried out. These algorithms, that give real-time results, were implemented using C language and the specific DSP Assembler. The debug and optimization were initially done using a simulation setup with data from the old PHA diagnostic and later with realtime data from the detector system in shot conditions. The synchronization of these algorithms with those that make the data acquisition and the electron temperature calculation has been also tested. The DSPs system in the TCV control was integrated with the data acquisition system and the detector system was connected with the DSPs module. The TCV trigger and timing system was also connected to the DSP module in order to get external synchronized triggers. These timing signals were programmed in the TCV main database and used to synchronize the real-time electron temperature calculation with the shot of the TCV. Implementation and test of the VME host CPU software were done. This software configures the DSPs module, gets the histograms and the electron temperature values, calculated during the shot. The control of the count rate in real-time is absolutely necessary in order to avoid saturation of the acquisition system and to maintain a minimum count rate that gives a minimum statistical error that enables the calculation of the electron temperature of the plasma in real-time. To overcome this need the development and implementation of the diaphragm real-time control algorithm which controls the X-ray count rate were done. The control algorithm must yet be tested in good shot conditions. This task should be concluded during 2006 when the shots of TCV will be stable. Then, the real-time electron temperature calculation can be achieved. 7.2.5. Rotating Crystal Spectrometer All parts of the diagnostic (the new microchannel plates, new pre-amplifiers and master/slave unit that actuates the stepper motor) have been assembled. The tests to the hardware have been initiated. First essays have shown that the pre-amplifiers were not working properly, their design had to be revised but every new adaptation did not succeed so far. The design of the holding structure at the horizontal port has started but had to be interrupted because the port was attributed to another device. No decisions have been taken so far in what concerns the new localization of the diagnostic. 7.3. ADVANCED PLASMA CONTROL SYSTEM After some preliminary tests, the main objective of the 2005 activity in this Project was the decrease of the control cycle. Aiming at having a transfer time in the DMBUS less then 10 µs, the control programming logic device (CPLD) that controls the DMBUS was replaced by a faster version. This change has originated the need of the reprogramming of the CPLD with another software tool and a different language. In parallel, a support library, a set of utilities and test scripts have been developed. 39 8. OTHER THEORY AND MODELLING STUDIES F. Serra (Head), J.P. Bizarro (Deputy Head), R.Coelho, J. Ferreira, F. Nave, P. Rodrigues. 8.1. INTRODUCTION This project included in 2004 three research lines: • Study of the role of magnetic reconnection processes in the dynamics and confinement of thermonuclear plasmas; • Modelling of Grad-Shafranov equilibria in tokamak plasmas. 8.2. ROLE OF MAGNETIC RECONNECTION PROCESSES IN THE DYNAMICS AND CONFINEMENT OF THERMONUCLEAR PLASMAS 8.2.1. Introduction This research line included in 2005 studies on:  The effect of sheared toroidal rotation on the stability of tearing modes;  Error field driven reconnection. 8.2.2. Effect of sheared toroidal rotation on the stability of tearing modes Magnetic reconnection events can degrade plasma confinement and limit fusion plasma performance. The physics of free reconnection, leading to the formation of magnetic island chains localised where the safety factor q(r) is rational, i.e. q=m/n, is a complex problem depending on many plasma figures of merit (collisionality, βp) and profiles (pressure, current density). For plasmas discharges with significant Neutral Beam Injection (NBI), toroidal rotation could have a strong effect on tearing mode stability. In fact, in a scenario with sheared toroidal plasma rotation, the toroidal component of plasma velocity perturbations (negligible in static plasmas) is no longer expected to be negligible and should be taken into account for inferring mode stability even in a large aspect ratio machine. Linear numerical MHD simulations in a cylindrical geometry with both perpendicular and parallel (to the equilibrium magnetic field) perturbations allow to conclude that plasma rotation in the equivalent toroidal direction can result both on the increase or decrease of the instability growth rate. A parabolic-like profile is considered for the toroidal rotation, vanishing at the plasma edge. Simulations were performed both for the single helicity model (that considers both parallel and perpendicular perturbations) and the conventional reduced MHD model (neglects parallel components of the perturbed quantities). Anomalous perpendicular plasma viscosity and plasma rotation shear at the modes’ rational surface play a key role on assessing the effect of shear flow. While destabilising for low viscosity plasmas (ratio of the resistive to viscous diffusion time scales τR/τV<<1) (Figure 8.1a), for viscous plasmas (τR/τV>1) shear flow reduces the growth rate, making possible mode stabilisation above a given rotation frequency (Figure 8.1b). Mode stabilisation is feasible owing to the considerable effect of the parallel component of the plasma velocity perturbations. 0 5000 10000 15000 20000 2.4 2.5 2.6 2.7 (a) x10 -5 x10 -4 SH γτ A V 0z (x=0) (Hz) 7.1 7.2 7.3 7.4 7.5 RM 0 5000 10000 15000 20000 -2 0 2 4 (b) SH RM x10 -5 γτ A V 0z (x=0) (Hz) Figure 8.1 – Sheared toroidal plasma rotation is destabilising in low-viscous plasmas for both the single helicity and reduced MHD models (a) and stabilising in viscous plasmas (b). When extrapolating to more reactor relevant operational conditions (higher Reynolds number S=τR/τA), one also notices that above a given threshold in the rotation shear (that decreases with increasing τR/τV) a tearing mode, unstable in the absence of rotation, can be stabilised (Figure 8.2). In addition, for the same ratio τR/τV, plasma rotation necessary for mode stabilisation decreases with increasing magnetic Reynolds number. 8.2.3. Error field driven reconnection studies The penetration and amplification of static external magnetic fields on rotating magnetically confined fusion plasmas imposes serious limitations on the plasma performance, degrading confinement and potentially leading to some disruptions. To gain further insight on the physical mechanisms involved during this penetration, a detailed investigation was carried out. Two distinct 40 10 6 10 7 10 8 50 100 150 200 250 Ga S Figure 8.2 – Threshold in Ga (= τ R/ τ V) for mode stabilisation as a function of the magnetic Reynolds number S for a rotating plasma with Vz0(x=0)=20kHz and aspect ratio A=R0/a=3.4. regimes are found, depending on the plasma rotation frequency with respect to the static external magnetic windings producing the “error-field”: a resistive-viscous regime, where plasma inertia plays a minor role in the reconnection; a viscous-ideal regime, where the reconnection layer is greatly affected by ideal MHD effects. The former regime is also known as Alfven Resonance regime (AR) since a resonance pair emerges at both sides of the q=m/n resonant tearing mode rational surface. These two resonances, spreading away from the q=m/n surface (q=2 in the simulations) as plasma rotation increases, play a significant role in the dynamics since they both shield magnetic reconnection at the q=m/n surface and are sinks for the transfer of angular momentum to the plasma. During the transition from a forced reconnection regime to an AR regime, the toroidal induced braking force is found to become an increasing function of plasma rotation frequency as a direct consequence of the emerging contributions at the AR locations, contrasting the decrease in the localised force at the q=2 surface (Figure 8.3). For a magnetic Reynolds number S=3x108, transition to the AR regime occurs at ~1.8kHz when the force becomes increasingly localised at the Alfven resonances. The threshold in plasma rotation for this regimes’ transition scales as 27.0 Athr S/1 τ∝ω and has a weak dependence on the anomalous plasma viscosity. It is conjectured that the lack of experimental evidence of an AR dominated regime in present tokamaks may be due either to an effective drag on plasma rotation caused by anomalous plasma viscosity or to the plasma collisionality regime (magnetic reconnection in a collisionless regime evolves on much faster time scales, implying a much larger threshold plasma rotation to enter the AR regime). 8.3. MODELLING OF GRAD-SHAFRANOV EQUILIBRIA IN TOKAMAK PLASMAS The studies on reversed Grad-Shafranov (GS) equilibria, with negative toroidal current density flowing in the core 10 7 10 8 1000 10000 b) 1/ τA S 0.27 Ga=0.005 Ga=2 Ga=20 1/ τA S 1/3 V z0,thresh (Hz) S ( τR / τA ) Figure 8.3 – Contour of the toroidal braking force exerted by static m=2,n=1 external magnetic fields on a rigid rotating plasma. Vertical axis indicates the radial direction and the plasma rotation lies on the x-axis (a). Rotation threshold for the transition between both regimes of reconnection (b). and overall positive plasma current, were continued both via numerical simulations in more demanding conditions and by further theoretical developments. In particular, numerical solutions were found for some profiles where the toroidal current density assumes negative values in a location sufficiently off-axis (Figure 8.4) which are strong enough in order to develop two distinct poloidal-field reversal (PFR) layers, where the poloidal magnetic field does vanish (Figure 8.5). Contrary to currently available GS solutions in toroidal-current reversal scenarios, the considered configuration does not yield a central channel containing the magnetic axis where the current flows in a direction opposite to the one in rest of the plasma. Instead, it results in an annular region of negative current enclosing a positive current channel and being surrounded by positive currents also. Toroidal current-density profiles of this type are usually found in nonlinear resistive MHD simulations of JET plasmas with strongly reversed magnetic shear, but no GS equilibria was yet available for them. Besides showing the robustness of the scheme previously proposed to solve the GS equation for equilibria with toroidal current reversal, these are 41 expected to help understand the physics behind the currenthole problem. Figure 8.4 - Zeroth-order profiles J φ 0(r) (solid line), ψ '0(r) (dashed line), and p(r)=p0(1+ α r) exp(- γ r) for α =5.55 and γ =10 (dot-dashed line), normalized to their maximum values. Following some previous work, a rigorous and consistent framework to describe the topological features of reversed equilibria (nested and non-nested) was developed by extending some fundamental concepts of Catastrophe Theory. This involved finding a suitable definition for nested equilibria, along with a systematic derivation of its most significant properties in current reversal scenarios. In general, these are extensions of results already established for isolated singularities of finite multiplicity, to manifolds of non-isolated singularities (such as the PFR layer) of infinite multiplicity. By rigorously showing that nested equilibria, on which most of the current knowledge is based, are non-typical and isolated elements, these results are expected to lead into a new paradigm when discussing GS solutions with toroidal current reversal. In addition, it was noted that non-static configurations with non-vanishing poloidal and toroidal plasma flow could, at least in principle, force the toroidal current-density profile to display negative values. This led to efforts aiming to include finite plasma-flow effects in GS equilibria computations in order to assess their role in leading to reversed configurations. Figure 8.5 - Flux surfaces for typical JET parameters and the profiles depicted in Figure 8.4. 43 9. OTHER ACTIVITIES ON CONTROL DATA ACQUISITION AND SIGNAL PROCESSING J. Sousa (Head), H. Fernandes, B.B. Carvalho, A. Batista, A. Combo, C. Correia, M. Correia, N. Cruz, R. Pereira, P. Ricardo. 9.1. INTRODUCTION This project concerns the activities on control, data acquisition and signal processing that are not included in the previous projects. The 2005 work programme has been essentially focused in four main working lines: • Development of a data acquisition system for the ETE tokamak; • Participation in the CASTOR programme on data acquisition; • Development of a low-cost, fully integrated, eventdriven real-time control and data acquisition system for fusion experiments; • Development of a time digitizer and transient recorder hybrid module for the enhanced neutron diagnostics data acquisition system Concerning the development of a complete data acquisition system for ETE1, the system architecture has been designed, including 64 transient recorder channels, a timing module and a CORBA based control and signal visualization software. Eight transient recorder modules were assembled and tested in 2005. The participation in the CASTOR2 programme on data acquisition has included the development of a complete data acquisition system, including 72 transient recorder channels as well as a CORBA based control and signal visualization software. Nine transient recorder modules, each one providing eight galvanic isolated channels, have been designed, assembled, mounted on an industry standard ATAC rack and functionally tested. The overall architecture of a low-cost, fully integrated, event-driven real-time control and data acquisition system for fusion experiments was planned. Regarding the time digitizer and transient recorder hybrid module for the enhanced neutron diagnostics data acquisition system, the module architecture has been defined accordingly to the specificities of the diagnostics, the acquisition module has been designed and the adequate software, firmware and hardware platforms have been identified. 1 ETE is a tokamak of the ‘Laboratório Associado de Plasma do Instituto Nacional de Pesquisas Espaciais’, de São José dos Campos, Brazil. 2 CASTOR is a tokamak of the Association Euratom/ IPP.CR (Institute of Plasma Physics), Prague. 9.2. PCI TRANSIENT RECORDER MODULE WITH GALVANIC ISOLATION This module (Figure 9.1) has eight differential acquisition channels, performing a sampling rate up to 2 MSPS with 14-bit resolution. Each channel is galvanicly isolated by means of a magneto-coupler device. The input dynamic range is settable to ±10V, ±5V, ±2.5V, ±2V, ±0.5V. Data from each channel is serialized by a local PLD. The main component of this module is its TMS320C6415TM DSP, which interfaces with the PCI bus, handles data processing tasks, and performs control of onboard memory. The use of state-of-the-art Field Programmable Gate Array (FPGA). (Xilinx Spartan 3 series) allows the implementation of data de-serialization, data synchronism and buffering and even the integration of digital data filters. A maximum storage of 512 MWords is available, in SDRAMM DIMM format. The module has both internal and external clock and trigger capabilities, configurable to either TTL or RS-485 standards. A dedicated bus permits the synchronization of a maximum of 8 units within the same host. 9.3. LOW-COST, FULLY INTEGRATED, EVENTDRIVEN REAL-TIME CONTROL AND DATA ACQUISITION SYSTEM The overall architecture of this system (Figure 9.2) was designed based on the PCI Express, Advanced Switching Interconnect (ASI) and Advanced Telecommunications Computer Architecture (ATCA) standards, to be scalable both in performance and number of input signals, to permit the transport of signals and events in real-time (< 1 µs), to have all nodes synchronized over the gigabit data interconnections (clock, time, triggers), include Ethernet, ATM, PCI-X bridges and to provide automatic recognition of each node features through a XML description for easy integration on existing platforms. Initially the following modules will be implemented: (i) an ATCA ix86-based controller; (ii) a digitizer/generator/processing card with 16 analogue input channels sampling at a rate up to 50 MSPS@12-bit, 4 analogue output channels, 8 digital IO channels and a state-of-the-art DSP and FPGA for real-time signal processing, and data flow control; (iii) a spectroscopy transient recorders with 4(2) channels sampling at a rate up to 200(400) MSPS@12-bit, 100(200) MSPS@14-bit and 1(2) GSPS@8-bit; and (iv) an ASI switch-fabric interconnection module and an ASI to ATM bridge. 44 Figure 9.1 – View of the TCA transient recorder module with galvanic isolation. ATM Gigabit Ethernet Processing Node (Power PC based) ATM Nodes Ethernet Nodes ASI ATM - ASI Ethernet - ASI PCIX - ASI ASI Nodes ASI - PCI Express Up to 4x 2.5 Gbit/s Up to 4x 2.5 Gbit/s Up to 4x 2.5 Gbit/s Up to 4x 2.5 Gbit/s Up to 4x 2.5 Gbit/s Up to 4x 2.5 Gbit/s SYNCHRONIZATION CTTS Signals PCI Express Up to 4x 2.5 Gbit/s Up to 4x 2.5 Gbit/s Up to 4x 2.5 Gbit/s 16x 2.5 Gbit/s Up to 4x 2.5 Gbit/s Non-Transparent Switch Card Controller (ATX Motherboard) NORTH BRIDGE DRAM DDR2 SOUTH BRIDGE Intel / AMD Ix86 Processor (Dual) Pentium4 / XEON ATHLON Gigabit Ethernet x16 PCIe slot x1 PCIe slot x1 PCIe slot 8.5 GB/s 8 GB/s PCIe 500 MB/s 500 MB/s 2 GB/s 10 GB/s dual chan. ADCs + FPGA ADCs + FPGA + DSP ASI - PCI Express DACs + FPGA Interface Eurocards Figure 9.2 - Overall architecture of the system and of one node. 9.4. TIME DIGITIZER AND TRANSIENT RECORDER HYBRID MODULE This module aims at: (i) implementing digital pulse processing (DPP) functions such as pulse height analysis (PHA) and pulse shape discrimination (PSD) for data reduction and real-time rough assessment of plasma parameters; (ii) fulfilling the requirements of the experiment diagnostics; (iii) having a high number of channels per board and consequently decreasing the cost per channel; and (iv) having an architecture designed for upgradeability and scalability. The module was designed for the ATAC bus with eight 12-bit resolution ADCs, providing eight analogue channels at 200 MSPS or, using a pair of digitizing channels shifted in phase (180º), four channels at 400 MSPS. Circuitry for using four ADCs to provide one channel at 800 MSPS is also included. The module contains two FPGAs, each controlling a memory bank of 1 GB and four acquisition channels and providing a gigabit communications interface, thereby reducing circuit complexity and cost by acting as a system-on-chip device, (Figure 9.3). 53 12. OTHER FUSION-RELATED ACTIVITIES 12.1. Collaboration with Brazilian Institutions IST/CFN has proceeded with the collaboration on nuclear fusion with two Brazilian Institutions: • Laboratório de Plasmas (LP), do Instituto de Física, da Universidade de São Paulo; • Laboratório Associado de Plasmas (LAP), do Instituto Nacional de Pesquisas Espaciais, de São José dos Campos. The 2005 working programme included the development of data acquisition boards for TCA/Br1 and ETE2, the design of a microwave reflectometer for TCA/Br, the development of a high spatial resolution Thomson scattering diagnostic for ETE and experiments on edge physics on TCA/Br. 12.2. Collaboration with IPP.CR IST starts in 2005 a new collaboration with Institute of Plasma Physics, (IPP.CR) related with the recommissioning in Prague of the COMPASS-D tokamak. The areas of joint work are control and data acquisition, microwave reflectometry and edge plasma diagnostics and physics. 12.3. Participation in the management of Fusion Programmes  Some members of the Association EURATOM/IST are delegates to Committees of the European Fusion Programme and of the European Fusion Development Agreement (Table 11.1).  Prof. Carlos Varandas is/was: - Chairman of the EFDA Steering Committee; - Member of the European Union Delegation to the ITER negotiations; - Member of the Steering Committees of the Bilateral Agreements of EURATOM with Russia, Japan and USA; - Member of the Ad-Hoc Group on ELE/EFEDO and related issues; - Chairman of the Ad-Hoc Group on the new European Fusion Development Agreement and the Contracts of Association.  Prof. Fernando Serra is/was a member of: - Ad-Hoc Group from STAC for the “Monitoring of W7-X Project”; - Member of the ITPA (International Tokamak Physics Activity) Topical Group on Diagnostics. 1 TCA/Br is a tokamak of the University of São Paulo 2 ETE is a tokamak of LAP.  Profª Maria Emília Manso was: - Member of the Programme Committee of the ASDEX-Upgrade Project; - Chairperson of the International Advisory Board on Reflectometry. 12.4. Organization of scientific meetings Two members of the CFN staff have been involved in the organization of scientific meetings: • Dr. Carlos Silva was member of the Programme Committee of the “Workshop on the Role of Electric Field in Plasma Confinement and Exhaust”. • Prof. Carlos Varandas was: - Chairman of the Organizing Committee of the Workshop on “Energies of the Present and Future”, Lisboa, 21 and 22 November 2005; - Member of the International Organizing Committee of the “XI Latin-American Workshop on Plasma Physics”, Mexico, 1-5 December 2005. 12.5. Collaboration with Portuguese Universities CFN has proceeded with the collaboration in graduation and post-graduation universitary programmes: • CFN has been responsible by experimental teaching in tokamak physics and engineering; • Seventh students have been performing Master and Ph.D. programmes at CFN in fusion plasma physics and engineering. 12.6. Public information CFN has proceeded with activities aiming at increasing the public understanding on fusion energy: • Six seminaries have been given in secondary schools; • A film about fusion and ITER has been translated to Portuguese; • Prof. Carlos Varandas has participated in television programmes about the ITER Project; • Several articles have been published in Portuguese newspapers with the direct or indirect participation of members of the IST/CFN staff. 54 Table 12.1 – Participation of members of the Association EURATOM/IST on the management of the European Fusion Programme and of the European Fusion Development Agreement Name Member of Carlos Varandas CCE-FU EFDA Steering Committee GoC3 CFI4 STC5 EFDA Technology Sub-Committee Maria Emília Manso CCE-FU EFDA Steering Committee EFDA Public Information Sub-Committee Fernando Serra STAC6 EFDA/PIG7 J.P. Bizarro STAC P. Silva STC EFDA Technology Sub-Committee Carlos Silva AFAC8 J.T. Mendonça IFEC9 3 GoC means “Group of Chairmen” 4 CFI means “Committee Fusion Industry” 5 STC means “Scientific and Technical Committee” 6 STAC means “Scientific and Technical Advisory Committee” 7 PIG means “Public Information Group” 8AFAC means “Administrative and Financial Advisory Committee” 9 IFEC means “Inertial Fusion Energy Committee” 55 13. THEORY AND SIMULATIONS ON HIGH ENERGY DENSITY SCIENCE AND ASTROPHYSICAL AND SPACE PLASMA PHYSICS J. T. Mendonça (Head), D. Resendes, L. O. Silva, J. Davies, J. M. Dias, M. Fajardo, R. A. Fonseca, A. Martins, Y. Omar, P. K. Shukla, G. Sorasio, P. T. Abreu, M. Fiore, L. Gargaté, M. Marti, I. Vieira, J. Vieira, B. Brandão, F. Fiúza, J. L. Martins, S. Martins, S. Mota, J. Santos 13.1. INTRODUCTION Research in theory and simulation at GoLP/CFP was focused on some of the outstanding problems in laserplasma interactions, basic plasma physics, exploring the connection between laboratory and astrophysical scenarios. The key aspects of research in 2005 dealt with: • Fast ignition and ICF physics, and laser-solid interactions; • Ultra intense laser plasma interactions and plasma based accelerators; • Development of simulation infrastructure for e- Science; • Relativistic Astrophysics and space plasma physics. 13.2. FAST IGNITION AND ICF PHYSICS, AND LASER-SOLID INTERACTIONS 13.2.1. A coupled two-step plasma instability in PW laser plasma interaction1 There is now a growing body of evidence for anomalous ion bulk heating in laser plasma interaction experiments, when the laser power approaches the Peta-Watt (PW) regime, both from experiments and from hybrid code simulations. We have proposed a possible explanation for the observed anomalous resistivity. Our model is based on the existence of two coupled processes. First, the fast electrons created by the laser pulse interact with the resulting return current and produce an intense electrostatic field, by means of a two stream instability. Second, the resulting electrostatic waves become modulationally unstable and decay resonantly into ion-acoustic waves. This mechanism is not efficient for electron heating but leads to an efficient ion heating which could explain the observations. 13.2.2. Laser-Solid Interactions and Fast Ignition Inertial Confinement Fusion The Vulcan TeraWatt and PetaWatt lasers have produced a vast quantity of data from laser-solid experiments using numerous diagnostics and target materials. We have been able to provide a coherent interpretation of much of this data based on our theoretical work on ion instabilities and magnetic field generation. Our work on magnetic field generation has been able to explain the increase in the divergence of the electrons accelerated into the target with 1 Work carried out in collaboration with R. Bingham, P. Norreys (RAL). increasing laser power and the associated appearance of a hollow plasma at the back of the target, in experiments with both the TeraWatt and PetaWatt lasers using both plastic and metal targets (Figure 13.1). We have also worked on magnetic inhibition of electron flow in layered targets. Figure 13.1 - Results from hybrid code modelling of experiments on the Vulcan 100 TW laser with solid, plastic targets (Mylar) that reproduces the electron beam hollowing. Figure 13.2 - "Finite width beam filamentation due to the Weibel instability" 56 13.2.3. Weibel instability in fast ignition of fusion targets2 Using relativistic kinetic theory, a theoretical model for the linear stage of the collisionless filamentation (Weibel) instability has been worked out, analyzing the coronal region of the fuel pellet in fast ignition. We have shown that only at the edge of the compressed pellet, the filamentation instability can develop even at large beam temperature with a small but not negligible growth rate. This is due to the ion presence, which cancels the space charge effects and allows for the instability to occur on the ion time scale. (i) Finite width beam filamentation due to the Weibel instability These aspects have been also numerically explored with a very large 2D simulation dealing with both the interaction of a picosecond-long ignition pulse with high-density (40 times critical density) pellet and the pulse driven electron beam propagation. Beam filamentation due to the Weibel instability as well as the role played by ions of neutralizing the space charge effects have been observed. The propagation of finite width beams through a background plasma has been studied numerically, performing 2D simulations (Figure 13.2). When the simulation plane is perpendicular to the propagation direction, the Weibel instability shows up, filamenting the beam. When the simulation plane is parallel to the propagation direction, evidences of the two-stream instability and the hosing instability have been observed. 13.2.4. Very High Mach-Number Electrostatic Shocks in Collisionless Plasmas The kinetic theory of collisionless electrostatic shocks resulting from the collision of plasma slabs with different temperatures and densities has been developed. The theoretical results are confirmed by self-consistent particlein-cell simulations, revealing the formation and stable propagation of electrostatic shocks with very high Mach numbers (M >>10), well above the predictions of the classical theories for electrostatic shocks. The theory demonstrates that the shock properties are strongly influenced by Θ, the ratio of the electron temperatures in the two slabs, and by Υ the ratio of the electron densities in the two slabs. The analysis shows that when the electron temperature of the downstream slab (R) is higher than the electron temperature of the upstream slab (L), the shock waves can have very large Mach numbers, which are otherwise not supported by isothermal plasmas. The model predicts that the maximum allowed Mach number increases with Θ, without an absolute upper limit. The theoretical results have been confirmed by onedimensional (1D) self-consistent particle-in-cell simulations, demonstrating the formation and the stable propagation of electrostatic shock waves with very large Mach numbers (M ~ 20) (Figure 13.3). 2 Work performed in collaboration with C. Ren (U. Rochester), M. Tzoufras, W B. Mori (UCLA). Figure 13.3 - Shock wave in the ion phase space p1x1. 13.2.5 White light parametric instabilities3 Parametric instabilities are pervasive in many fields of science with its importance stemming from their close connection to the onset of nonlinear and collective effects such as solitons, vortices, self-organization, and spontaneous ordering. We have employed a generalized photon kinetics formalism, directly inspired in the Wigner- Moyal formalism for Quantum Mechanics to establish the general dispersion relation for parametric instabilities driven by electromagnetic radiation, with arbitrary statistics, coupled to the electron collective dynamics in a unmagnetized plasma. The one-dimensional analysis for Stimulated Raman Scattering reveals a growth rate dependence with the coherence width σ of the radiation field scaling as 1/σ for backscattering, and 1/σ1/2 for forward scattering, and a significant dependence of the instability growth rate on the shape of the power spectrum of the radiation. The results open the way to a full multidimensional description of parametric instabilities driven by intense radiation sources, with arbitrary statistics, interacting with plasmas in laboratory and astrophysical scenarios. 13.3. ULTRA INTENSE LASER PLASMA INTERACTIONS AND PLASMA BASED ACCELERATORS 13.3.1 Shock shells driven by layered clusters and explosion of clusters driven by intense x-ray sources4 The interaction of ultra-short ultra-intense laser pulses with large deuterium clusters (>105 atoms) can lead to the removal of all (or most of) the electrons inducing a Coulomb explosion. During this phenomenon shock shells (multi-branch structures in the phase space) may be formed if ion overtaking occurs. However, significantly thick shock shells are hard to produce in homonuclear clusters with a single laser pulse. Instead, the use of heteronuclear layered clusters has been proposed as a means of driving shock shells. This method is based on the fact that the initial ion acceleration profile is a critical issue for the shock formation. Both the number density and the mass profiles can be chosen so as to 3 Work carried out in collaboration with R. Bingham (RAL) 4 Work performed in collaboration with F. Peano (Poli Torino) 57 produce the desired acceleration profile, the latter being used in this case. The explosion of layered clusters with light inner species and increasingly heavier species with radial distance was studied. PIC simulations of a three-layer cluster with step-like mass profile were performed with OSIRIS 2.0. It was found that ion overtaking of the outer heavy ions by the lighter inner ones occurs in both of the borders between the layers, even before the total removal of the electrons (Figure 13.4). Density peaks were observed where the overtaking occurs in an analogous manner to what is found in homonuclear clusters. As the core ions continued to expand the two density peaks eventually merged. However, the phase space structure observed in the case of the layered cluster differed from the homonuclear clusters shock shells in that only two branches appeared instead of the three branches seen in the latter. Figure 13.4 - Density peaks due to ion overtaking In this way, the proper selection of a mass profile offers a method for controlling the phase space of the cluster explosion to induce shock shell formation. The characteristics of this structure can be selected “a priori” by varying the widths, composition and number of layers of the cluster. The study of the possibility of producing shock shells in clusters in the x-ray regime was also initiated. Simulations were made of homonuclear clusters with two pairs of ion and electron populations. These electron populations were initiated at different times and with different energies, representing the two ionization stages expected if the cluster were to be irradiated by two x-ray laser pulses with distinct intensities and frequencies. It was observed that by choosing the laser parameters properly it was possible to induce ion overtaking with the appearance of shock shells in the phase space. 13.3.2 Blowout regime of the laser wakefield accelerator 5 Studies of electron acceleration in parabolic plasma channels have been carried out. Plasma is a very good medium for accelerating electrons, both injected 5 Work carried out in collaboration with W. Lu, M. Tzoufras, C. Joshi, W. B. Mori (UCLA) externally, or self injected from the plasma itself, since the accelerating gradients are orders of magnitude greater than in conventional accelerators. The primary focus of the work is focused on the plasma self injected electrons. There has been a considerate effort in achieving GeV electrons with this technique, as current experiments place the maximum energy gain of self-injected electrons on a few hundreds of MeV. These experiments operated in the blowout regime, where an intense laser pulse radially expels nearly all plasma electrons. An ion column is left behind the laser pulse and electrons are attracted inwards to the axis, forming an electron void cavity. This cavity is spherical and resembles a bubble that gave its name to the bucket (Figure 13.5). Figure 13.5 - Contour plot of the bubble excited by an ultraintense laser pulse. Blue contours are the plasma density. Red-Green contours are the laser pulse 13.3.3. Wigner diagnostic for photon acceleration6 A short intense laser pulse propagating through a gas can generate plasma waves, due to electron density modulation. This mechanism can upshift photons riding the waves, whether they are from a driver pulse or from a trailing low intensity pulse. Such phenomena provide important information about relativistic structures, as well as a novel way to tune radiation (Figure 13.6). Figure 13.6 - Wakefield generated by an ultra short intense laser pulse (laser pulse in red/green). 6 Work performed in collaboration with J. P. Bizarro, A. Figueiredo (CFN), R. Trines, and R. Bingham (RAL) 58 Several kinds of Wigner transforms were implemented to analyze photon acceleration. PIC simulations were preformed with OSIRIS 2.0, revealing that in 1D simulations, where the interaction length is comparable/longer than photon dephasing length in wake (regime achievable for very long Rayleigh lengths), different initial delays between the driver and probe pulses do not lead to different signatures in Wigner distribution (Figure 13.7). However, in 2D simulations, a tight focus leads to short interaction time with wake, thus different probe displacements lead to different final conditions. On the other hand, the FFT failed to reveal detailed internal dynamics of laser pulse. Figure 13.7 - Wigner transform of ultra short laser pulse riding a laser wakefield. 13.4. DEVELOPMENT OF THE SIMULATION INFRASTRUCTURE FOR E-SCIENCE 13.4.1 osiris 2.0 development7 The OSIRIS 2.0 framework is an integrated framework for particle-in-cell (PIC) simulations. This framework is based on a three-dimensional, fully relativistic, massively parallel, object oriented particle-in-cell code, that has successfully been applied to a number of problems, ranging from laser-plasma interaction and inertial fusion to plasma shell collisions in astrophysical scenarios. The main development milestone achieved in 2005 was the full implementation of the dynamic load balancing algorithm in OSIRIS. A binary tree algorithm for finding best problem partition solution was implemented to this end. During runtime, OSIRIS will dynamically analyze the load of each computing node, and reshape the parallel partition whenever needed to maintain an evenly balanced node. The OSIRIS code structure was also updated, with significant changes to the object hierarchy, and new current deposition modules are under development that will result in a significant performance boost. Standard PIC “collisions” occur between finite sized particles. It is an inherent property of the PIC algorithm that collisional effects therefore are not properly reproduced in a standard PIC algorithm, due to limitations 7 Work carried out in collaboration with F. Tsung and W. B. Mori (UCLA) in grid size possible with available computing power. In order to fully deal with collisional effects the standard PIC algorithm must be extended. Several extensions were proposed. For osiris, we follow the approach of binary collisions [Takizuka and Abe 1977, Nanbu 1997], generalized for the fully relativistic scenario. As is the rest of OSIRIS the implemented algorithm is fully relativistic. Osiris uses different weights for different particles. The collision algorithm is able to deal with this circumstance without violating any of the conservation laws (i.e. energy- and momentumconservation) [Nanbu and Yonemura 1998]. 13.4.2 dHybrid8 A hybrid code called dHybrid has been used in the study of space plasma interactions. Hybrid codes, due to the use of kinetic ions and fluid electrons, allow an intermediate step between full particle codes and fluid codes. The applicability of such codes ranges from low density plasmas like space plasmas to denser plasmas like the ones found in tokamaks. The first massively parallel version of dHybrid is now ready to completion. This code, originally written to study the solar wind interaction with an artificially created plasma cloud (AMPTE release experiments) has now new important features that broaden its applications (Figure 13.8). Studies such as solar wind interactions with artificial magnetospheres and coronal mass ejection interactions with the solar wind are now possible. Figure 13.8 - Magnetic field isosurfaces and field lines of the artificial magnetosphere at time 72 (simulation units). The solar wind flowing from the left exerts pressure on the system and creates asymmetry. The new version of the code allows better results due to improved statistics in these runs, which is possible only due to the use of massively parallel machines. New problems like the solar wind interaction with planetary exospheres (e.g. Mars, Venus) and planetary magnetospheres (eg. Earth) can now be considered. 8 In collaboration with R. Bingham (RAL) 59 13.4.3 Visualization infrastructure Visualization is an essential part of any numerical laboratory. The data being produced by our simulations is both large and complex, and requires an appropriate set of tools for the adequate understanding of the results obtained. We therefore developed a custom visualization and analysis infrastructure for our needs, that has been successfully used with several simulation and experimental data sources, most notably the OSIRIS code, the QUICKPIC code and the dHybrid code. The development of this infrastructure continued over 2005, and as a result of user feedback led to the development of new visualization tools, Significant work also went into the development of the new version of the visualization and data analysis routines, that will allow for better user-data interaction, and also provide a unified interface for representing data and metadata in encapsulated objects (Figure 13.9). Figure 13.9 - Simulation Browser. This simulation tools allows for quick access to multiple diagnostics for the same time step. The navigation tools (zoom/pan) for all the plots are linked. Different new visualization software for very large datasets was evaluated (VTK, OpenDX, SciRun), and finally VisIt was chosen (a visualization program from Lawrence Livermore National Laboratory, USA), because it was the only one to offer all the features needed: parallel data processing and rendering (distributed and shared memory), scriptable, expandable, high performance and scalability, multi platform, uses VTK and it is Open Source (Figure 13.10). A database plugin was developed for VisIt, that allows the full exploration and rendering, in parallel, of Osiris and dHybrid simulation results, in particular of very large datasets of 3D vectorial data (Figure 13.11). Research has been done in the development of general purpose algorithms for the modern graphics processor (GPGPU). Simulation algorithms can be accelerated by passing some of them to the shader unit of the GPU and taking advantage of its vectorial capabilities. A development system has been set up on the visualization cluster that allows for general research on this kind of algorithms and for research on parallel versions (distributed memory) of GPGPU. Figure 13.10 - Data visualization and users interface as seen in a web browser. Figure 13. 11 - Visualizing the inverse Faraday effect in VisIt. 13.5. ASTROPHYSICS AND SPACE PLASMA PHYSICS 13.5.1 Plasma thruster dynamics and charge exchange collisions With the goal of understanding the full kinetic dynamics of the charge exchange back flow originating from the plume injected from a spacecraft, and to understand how relevant the electron dynamics is in such scenario (in particular, to understand if a Boltzmann equilibrium for the electrons can be assumed in such configurations) several multidimensional particle in cell simulations have been performed in osiris 2.0 (Figure 13.12). In these scenarios charge exchange (cex) collisions play an important role, as they are responsible for the slowing down and thermalization of the fast ions originating from the thruster plume. Consequently a cex-module has been written and 60 tested for osiris 2.0. This module is an extension of the existent neutral module and allows for cex collisions to occur between multiple neutral and multiple charged species. Different models for the cross-section of interaction are available and fully parameterized. Proper accounting for the charge and mass transfer between the collision partners is conducted. Figure 13.12 - Xe+ ions originating from the thruster. The thruster plum pinches after a stage of free expansion leading to higher flow velocity. Densities [e ω03c3]: red 1, yellow 0.3 and green 0.1. 13.5.2 Development of Plasma Reflectometry for In- Flight Aerothermodynamic Research9 The reflectometry for in-flight aerothermodynamic research project is a new comprehensive project involving theory development, instrument design and prototype development. The principal objective of this project is the measurement of plasma density profiles surrounding a reentry vehicle as it comes into the atmosphere. Use of electromagnetic waves constitutes a powerful plasma diagnostic method. Due to the large electron to ion charge to mass ratio, it is primarily the electron properties of the plasma which can be obtained at microwave and higher frequencies. The physical parameters of relevance to plasma reflectometry in the shock layer of a re-entry vehicle, are the plasma density, neutral density and temperature. These are characterized on the basis of computational fluid dynamics (CFD), in order to define a reference environment and to set up an optimum measurement strategy. A typical case is the European Experimental Reentry Testbed (EXPERT) vehicle scenario. For this vehicle, the ionization shocked layer and the plasma sheath is thin, roughly at most 20 cm thick on the side and 1/3 of that in the nose region. The expected plasma frequencies for a 6.8 km/s re-entry speeds appears in the figure 13.13. The plasma distribution along a normal line to the vehicle surface is approximately parabolic. The electron density goes to zero at the surface, in the catalytic case, while it is 9 Work carried out in collaboration with G. Vecchi, V. Lancelloti, R. Maggiora (Poli Torino), M.E. Manso, and L. Cupido (CFN) the electron density gradient that goes to zero in the noncatalytic case. Plasma gradients can be very high with 1 GHz frequency change over a 1 cm distance fairly common. 2 3 6 7 4 5 x y 00.5 11.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Level FP 37 3.69358E+10 33 3.28501E+10 29 2.87645E+10 25 2.46789E+10 21 2.05932E+10 17 1.65076E+10 13 1.2422E+10 9 8.33635E+09 5 4.25071E+09 1 1.65082E+08 m=350kg, V=6km.s ea=-3.8o Mach 20 Altitude=68.1km Figure 13.13 - Predicted plasma characteristics for a 6 km/s reentry speed for EXPERT. 13.5.3 Magnetic field generation in clusters of galaxies10 Magnetic fields are ubiquitous in cosmic objects, from stars and galaxies, to galaxy clusters, the largest gravitationally bound objects in the Universe. The origin of these fields, observed to be as strong as a few micro- Gauss in a number of clusters, remains one of the outstanding problems of modern cosmology. Conventional explanations involve the amplification of a very weak seed field of possibly primordial origin by turbulence and gas compression during the formation of the cluster. However, the origin of the nano-Gauss seed field that is required remains a mystery. We have demonstrated that cluster magnetic fields could have been produced by shocks propagating through galaxy clusters and in the intercluster (ICM) medium during the formation of large-scale structure. We have performed three-dimensional particlein-cell simulations of a nonrelativistic shock in a electronproton plasma that show that such shocks generate a magnetic field via the counter-streaming (Weibel) instability (Figure 13.14). The strengths of the shockgenerated fields range from tens of nano-Gauss in the ICM through few micro-Gauss inside galaxy clusters. Thus, cluster magnetic fields may be explained without resorting to amplification of a primordial magnetic field. Figure 13.14 - The three-dimensional structure of the magnetic field generated at nonrelativistic collisionless shocks. 10 Work performed in collaboration with M. Medvedev and M. Kamionkowski (Caltech) 61 14. EXPERIMENTAL PHYSICS AND TECHNOLOGICAL DEVELOPMENTS ON ULTRA INTENSE LASERS, RADIATION SOURCES, PLASMA BASED ACCELERATORS AND BIOMEDICAL OPTICS J. T. Mendonça (Head), J. M. Dias, M. Fajardo, G. Figueira, N. Lopes, R. A. Fonseca, J. A. Rodrigues, L. O. Silva, L. Cardoso, J. Wemans, C. Leitão, N. Lemos, F. Wahaia, E. Abreu, N. Brites, R. Macedo, J. Sampaio, A. Smith, F. Viola 14.1. INTRODUCTION Research in experimental physics at GoLP/CFP covers fundamental and applied aspects of lasers, laser-plasma interactions, intense x-ray and vuv sources, biomedical optics, as well as technology developments for the support of these activities. A significant part of this work is associated with the activities of the Laboratory for Intense Lasers (L2I), the central experimental infrastructure maintained by GoLP. The key aspects of research in 2005 dealt with: • Laser physics and laser technology; • X-ray and VUV sources and their interaction with plasmas; • Plasma channels for laser-plasma accelerators; • Tunable radiation sources; • Biomedical optics 14.2. LASER PHYSICS AND LASER TECHNOLOGY 14.2.1 Mirrorless tilted-pulse-front single-shot autocorrelator Ultrashort pulses exhibiting angular dispersion have their pulse front tilted relative to the phase front. This leads to a serious degradation in the focused peak power, making the use of adequate diagnostics indispensable. We have developed an upgrade to a previously demonstrated autocorrelator for ultrashort laser pulsewidth measurements that extends its versatility, by making it suitable for detecting and correcting tilted pulse fronts. The device, called a tilted-pulse-front single-shot autocorrelator (TPF-SSAC) can be used to detect tilts in pulse fronts and perform pulse autocorrelation along any arbitrary direction. The principle of the TPF-SSAC is to decouple the measurements of the autocorrelation shape and the amount of pulse-front tilt: One of the replicas is flipped in both planes, and the tilt is detected in each direction at a time by correlating the replicas in the orthogonal direction. In this fashion, the presence of a tilt will result in an oblique autocorrelation, as shown in the figure below. Our modification consisted in introducing two orthogonal Dove prisms to provide horizontal and vertical flipping, converting this autocorrelator into a TPF-SSAC. The figure 14.1 shows this experimental arrangement. We have used this modified TPF-SSAC to optimize the alignment of the grating compressor of our terawatt CPA laser. We found that initially there was a small pulse-front tilt present in our compressed pulse, which was easy to correct with the aid of this diagnostic. The resulting autocorrelation trace is shown in Figure 14.1. Figure 14.1 – Schematic of tilted pulse front autocorrelator geometry. To illustrate the capability of the device, we have also acquired a trace of the autocorrelation for a large front tilt, introduced by deliberately deviating the grating pair from parallelism and correcting for the resulting change in their separation in order to obtain the shortest autocorrelation, also shown in the Figure 14.2. From this, we can appreciate that the actual trace width does not change significantly from the corrected version, which illustrates the necessity of using this kind of autocorrelator. Figure 14.2 - Autocorrelation traces of corrected (solid line) and tilted (dashed line) pulse fronts 14.2.2 OPCPA at GoLP Optical parametric processes are not new, but their application in laser amplification, especially in high power pulses, is quite recent. Optical parametric amplification can combine a very high gain per pass, tunability and a 62 broad bandwidth. Adding to it the chirped pulse amplification technique to avoid the inconvenience of excessive peak power inside the laser system, and we have a versatile and relatively efficient way to achieve short, high power laser pulses. Due to the short path needed inside the amplifying media (Figure 14.3), femtosecond pulses suffer little distortions and lengthening, enabling petawatt range pulses to be raised out of the energy of mere terawatt range pump beams. Figure 14.3 - BBO non-linear crystal: the amplifying media where the green pump beam transfers its energy to the infrared signal beam. Presently we want to demonstrate we can master this promising technique by running mid power amplifiers and comparing the experimental against the expected theoretical results. The equipment in the current setup is likely to become part of some future secondary/probe beam, provided a new pump beam is made available. Concurrently, there are plans to use OPCPA as an “upgrade” to L2I’s multi terawatt laser system, whose beam, the whole or in part, would be used as a pump for a possible petawatt range system. 14.2.3 Ultra Broadband OPCPA – from the theory to the demonstration The creation of a 3D compatible simulation code for the better understanding of the OPA process provided the conditions to find a new geometry allowing the amplification of ultra broadband pulses. Usually both signal and pump are input in the crystal propagating at given fixed directions which, in general, allows a quite limited gain bandwidth. But the optimum input angle actually varies rather smoothly and predictably with the signal wavelength. It is then possible to angularly disperse the broadband signal, with a grating for example, to interact with the pump beam at close to the optimum angle over a large bandwidth. To demonstrate this concept we use a slightly modified version of our first OPCPA setup, but we also need to get a broadband signal. That is being arranged by a photonic crystal fibre tailored to generate white light supercontinuum out of our sub-20 nm wide, ~100 fs oscillator. This technique will enable the simultaneous amplification of wavelengths spanning for almost one octave (Figure 14.4). This will allow the construction of tuneless amplifiers for tunable narrow band oscillators or, exploring its full potential, the support of sub-10 fs pulses with excellent contrast. Figure 14.4 - Spectral gain profile (λS/nm) vs. reference signal wavelength (λ0/nm), when signal angular dispersion is optimised for the broadest bandwidth in BBO pumped with 532 nm. 14.2.4 Characterization of the dynamical behavior of diode pumping induced thermal lens on a Yb:phosphate glass1 We measured the characteristic focal length of the thermal lens effect induced in a Yb:phosphate glass pumped by a high intensity diode laser pulse (Figure 14.5). Because the glass is the active material of a laser amplifier setup its was necessary to define some special characteristics of the thermal effect: the ideal amplification section in the glass where the thermal lens effect is constant; the temporal dynamics of the effect during a single pump pulse and through the first warm-up pump cycles; the dependence of the effect with the pump intensity. The overall goal of the study was to provide vital information about the thermal effects that can be applied in improving the performance of laser amplifiers based on this active medium and pump setup. Figure 14.5 - 3D visualization of the wavefront distortion induce to the laser beam during one pass trough the glass at full pump. 1 Work carried out collaboration with the Polaris group in the Institut für Optik und Quantenelektronik, Jena 70 growth associated with the identified linear instabilities. To pursue this goal, we are assessing the possibility of adapting a numerical kinetic (particle in cell) code developed in Kyoto University (Kempo1) to simulate the proposed model underlying the emissions and thus follow the nonlinear regime of the instabilities. 15.3. LARGE AMPLITUDE WAVES AND INSTABILITIES 15.3.1. Introduction2 Electrostatic ion-acoustic instabilities have been observed in space environments (e.g., in the solar wind) where both the nature of the free energy source and the inexistence of the condition for small Landau damping (Te >> Tp ) are not encountered and thus defy the standard theory of these instabilities. 15.3.2 Research results To contribute to the interpretation of the above observations, we looked into the generation of electrostatic waves by parametric decays of large-amplitude left-hand and right-hand waves propagating in the direction of the background magnetic field. It is shown that the forward propagating ion acoustic waves involved in the parametric decay of the circularly polarized waves experience negligible Landau damping and can thus account for the puzzling observations of electrostatic ion-acoustic wave activity. 2 This research line has been carried out in collaboration with Prof. Luis Gomberoff, Physics Department, University of Chile at Santiago, and partially funded by FONDECYT (Chilean Institute). 15.4. NONLINEAR WAVE EQUATIONS 15.4.1 Introduction The study of nonlinear wave equations is a problem of considerable theoretical importance and with applications to several branches of Physics. In the case of Plasma Physics, it is relevant to the study of the interaction of pulsars and high power laser radiation with plasmas. It is the purpose of this research to give a contribution to the theoretical understanding of such waves. We address the question of integrability and the construction of exact solutions, in particular solitons, of certain nonlinear wave equations. 15.4.2 Ongoing research We resort to the Painlevé method (for determining the type of movable singularities of the solutions) and the Hirota method (for determining if multisoliton solutions exist) to investigate the integrability of the following nonlinear equations: (i) the system of four partial differential equations that describe the evolution in time and one space dimension of the complex amplitudes of four waves constituting two resonant triplets; (ii) the partial differential equation in l+1 dimensions that appears in the analysis of the consistency error of the second-order Runge-Kutta method for the numerical integration of ordinary differential equations. 71 16. ENVIRONMENTAL ENGINEERING PLASMA LABORATORY C. M. Ferreira (Head), F. M. Dias (Deputy Head), E. Tatarova, J. Henriques 16. 1. INTRODUCTION The research work carried out by this team in 2005 falls into the following main fields of investigation: • Spatial structure and radiation of microwave plasma sources; • Surface wave induced N2 – Ar plasma torch; • Flowing N2 and N2-O2 discharges and postdischarges; • Improved Langmuir Probe Techniques for Plasma Diagnostics. 16.2. SPATIAL STRUCTURE OF MICROWAVE N2- AR PLASMA SOURCE1 A theoretical model for a large-scale, slot-antenna excited surface wave plasma source operating in N2-Ar mixtures was developed. The model incorporates the description of both the discharge plasma, sustained by a pure TM140 surface mode, and the remote “electric field free” plasma. Maxwell’s equations and the rate balance equations for the most important species – vibrationally ),(N 1 2v g + ΣΧ , (16.1) electronically excited molecules u) ´ w,Πa,Σa´,ΠC,ΠB,Σ(AN g 1 u 1 u 3 g 3 u 3 2∆ −+ , (16.2) Ar(3p54s) and Ar(3p54p) atomic states, +++++ 242 Ar,Ar,N,N,N (16.3) ions, and nitrogen atoms N(4S,2P,2D) are consistently solved to yield the species spatial distributions. The model further determines the three-dimensional discharge structure, i.e., the radial, azimuthal and axial variations of the main plasma quantities. Strong correlation is shown to exist between the density distributions of plasma electrons and electronically excited states of molecules and atoms and the electric field intensity distribution in the discharge zone of the source. This indicates that electron driven processes play a dominant role in the discharge workings. The transition from the source discharge to the remote plasma was analysed in detail. The pumping of the higher vth levels as a result of near-resonant V-V energyexchanges between vibrationally excited ),(N 1 2v g + ΣΧ was shown to be very effective, and to influence strongly the remote plasma kinetics. In fact, the pumping of the vibrational distribution function “tail” strongly influences the axial evolution of the EEDF and the number density of 1 Colaborators: Prof. H. Sugai and Dr. I. Ganachev (Nagoya University, Japan) electrons and electronically excited states of molecules in the remote plasma zone. Collisions of ),(N 1 2v g + ΣΧ (16.4) molecules in highly vibrational levels with ground N(4S) atoms are responsible for the formation of )Σa´,ΠC,ΠB,Σ(AN u 1 u 3 g 3 u 3 2−+ (16.5) electronically excited states. As a result, the number densities of electrons and electronically excited states )Σa´,ΠC,ΠB,Σ(AN u 1 u 3 g 3 u 3 2−+ (16.6) increase in the “late” remote plasma zone, at axial distances ∆z > 35 cm (Figure 16.1). An experimental validation of the model predictions was achieved using optical emission spectroscopy. The spatial variations of the emission intensities of the lines belonging to the 1st negative and 2nd positive systems of nitrogen have been detected and compared with the theoretical results. The agreement obtained between experimental and theoretical results is satisfactory, taking into account the numerous uncertainties in collisional data still existing. The results obtained clearly demonstrate that the remote “electric field free” plasma zone of the present source is a big reservoir of excited species in metastable and vibrational states and of charged particles. By changing the mixture composition, and thus the dissociation degree of N2 molecules, it is possible to control the processes of excited species production in the remote plasma zone of this microwave source. Figure 16.1 - Axial variation of the vibrational distribution function (80%N2 – 20% Ar, p = 0.9 mbar, r = cm, ϕ = 162). 72 16.3. HYDROGEN BALMER LINE BROADENIBNG IN A MICROWAVE PLASMA SOURCE2 Emission spectroscopy (Doppler broadening technique and molecular rotational bands measurements) was used for the diagnostic of gas particle temperatures in a large-scale, slot-antenna excited microwave plasma source operating in pure hydrogen, helium-hydrogen and argon-hydrogen mixtures at low-pressures (p = 0.3 Torr). The measured profiles of Hα and Hβ lines are well fitted by a Gaussian profile, (Figure 16.4 (a,b)). For the purposes of comparison, the normalized profiles of the 6678.8 Aº helium line [transition 31D →21P] (shifted along the scale of wavelengths) are also shown (Figure 16.2). The helium line profiles are also well fitted by a Gaussian one. The emission profile of the Balmer-α line shows larger broadening than that of the Balmer-β and helium singlet line at 6678.8 Aº [transition 31D →21P]. The line profiles do not present wings and we could not find any evidence of fast hydrogen atoms in the discharge zone of the plasma source. The Doppler temperatures corresponding to the helium singlet line at 6678.8 Aº (400 – 900 K) are close to the rotational temperatures (300 – 800 K) calculated from the Q-branch of the Fulcher-α band [d3Πu (v=0) → a3Σg + (v=0)] under the same conditions. Therefore these temperatures can be assumed to be indicative of the gas temperature. The measured Doppler temperatures of hydrogen atoms range from 3100 K to 3700 K (Figure 16.5b) in a 95% He-5% H2 mixture (P = 900 W) and from 2700 K to 3600 K in a 95% Ar- 5% H2 mixture (P = 600 W) while in pure hydrogen (P = 600 W) the minimum and maximum temperatures are 2500 K and 3400 K, respectively. Thus, there is a “separation” of the excited hydrogen atom temperature from the gas temperature. The reason for such “separation” are connected to the processes leading to the creation of excited atoms such as electron impact dissociation and ion conversion. Figure 16.2 - H α (a) and H β (b) profiles compared with 6678 A He line profile. 16.4. SURFACE WAVE INDUCED N2 – AR PLASMA TORCH3 Theoretical investigation on surface wave driven N2-Ar microwave plasma torch at atmospheric pressure 2 Work carried out in collaboration with Dr. N. Puac (Belgrade University, Serbia) and Dr. A. Ricard (CPAT, Université Paul Sabatier, France) 3 Work performed in collaboration with Prof. Dr. B. Gordiets (Institute of Physics, Academy of Sciencies, Russia). conditions is presented. The main plasma and wave characteristics are obtained in the framework of selfconsistent 1D theoretical model which describes the axial structure, including overdense discharge plasma sustained by an azimuthally symmetric TM surface mode and postdischarge plasma arising due to the axial gas transport. The system of equations (in the framework of fluid approach) considered to describe the plasma source includes: Maxwell´s equations; The rate balance equations for the vibrationally excited states of electronic ground state molecules ),(N 1 2v g + ΣΧ ; u) ´ w,Πa,Σa´,ΠC,ΠB,Σ(AN g 1 u 1 u 3 g 3 u 3 2∆ −+ and Ar(3p54s), Ar(3p54p) excited states of molecules and atoms, positive +++++ 2 Ar,Ar,N, 4 N, 2 N ions and electrons, ground state N(4S) and excited N(2P, 2D) atoms. Further on, the gas thermal balance equation and the equation of mass conservation for the fluid as a whole are incorporated in the model. The results show high values of the gas temperature (up to 12 000 and very strong population in vibrational levels of the electronic ground state ),(N 1 2v g + ΣΧ molecules in the discharge part of the, close to the microwave source (Figure 16.3). Figure 16.3 - Axial variation of Tg at different Ar percentages (P=2000 W, Q=1000 sccm). 16.5. EXPERIMENTAL AND THEORETICAL STUDY OF FLOWING N2 AND N2-O2 DISCHARGES AND POST-DISCHARGES4 A complex experimental and theoretical investigation on a strong afterglow formed in the post-discharge region of a microwave plasma source is performed (Figure 16.4). The objective of this work was to investigate the concentration of various active species, such as O and N – atoms, N2 + ions, and N2(A3Su +) and NO(A2Su +) molecules, as a function of the spatial position and the mixture composition. Emission spectroscopy was used to measure 4 Work carried out in collaboration with André Ricard (CPAT, Université Paul Sabatier, France) 73 the N2(1+,2+,1) and NO(g,b) band intensities in the discharge and in early post-discharge (see pictures below). The densities of N and O – atoms were measured using an actinometry method in the plasma region and NO titration in the post-discharge. The titration technique that provides absolute densities was used to calibrate the actinometry method in the early post-discharge, close to the discharge end. The experimental results are interpreted using kinetic theory in the discharge and in the late afterglow. The postdischarge region is of particular interest due to the formation of a strong afterglow and this extended “field free region” is rich in active species such as nitrogen and oxygen atoms, vibrationally and electronically excited nitrogen molecules and ions as the results show. The obtained results have direct application for cold plasma sterilization of surgical material and other medical devices. Figure 16.4 - Experimental setup showing the discharge and post-discharge reactor. 16.6. IMPROVED LANGMUIR PROBE TECHNIQUES FOR PLASMA DIAGNOSTICS5 16.6.1. Restoration of Time-averaged Probe Characteristics We developed three simple methods that enable restoring time-averaged Langmuir probe characteristics measured under time-varying plasmas, in the sense that plasma parameters, i.e., electron density and average energy, electron energy distribution function (EEDF), and plasma 5 Work carried out in collaboration with Tsv. Popov, and M. Dimitrova (St. Kliment Ohridski University of Sofia, Faculty of Physics, Bulgaria) potential, are deduced more accurately than what otherwise could be retrieved from averaged data. The first method (SAM) is based on analytic expressions of the first and second derivatives of the probe characteristic, and only requires the standard deviation of the measured current, i.e., the probe characteristic itself is not needed. The other two methods assume that the probe characteristic experiences either an anamorphic deformation (ADM) or a linear deformation of the lowenergy part of the EEDF (BDM), which from our experience are the most simple, acceptable assumptions (Figure 16.5). Although our motivation were probe diagnostics, the above techniques are of general interest since all kinds of data acquisition have to deal with the problem of a finite integration time, and the output is always the result of some kind of average. Figure 16.5 - Model test of the three restoration methods (Maxwellian EEDF) 16.6.2 Improved Probe Differentiation Techniques A combination of the harmonic and numerical differentiation techniques is being developed in order to measure the electron energy distribution function (EEDF) with an error of the order of the 8th derivative instead of the order of the 4th derivative, which is typical in standard methods. In addition to the increased accuracy, instrument functions are adaptively adjusted in such a way that the error and the noise levels are continuously kept at similar levels, which is possible because the overall system has the ability to evaluate the noise as well as the error levels of the differentiators at measuring time. The superior differentiation performance is achieved using a redundant approach, which enables keeping the noise from individual differentiators uncorrelated, and signals are combined in such a way that the resulting signal-to-noise ratio is the maximum possible. -2 -1 0 1 2 3 4 5 10-3 10-2 10-1 100 Maxwellian SAM ϕ = π ADM ϕ = π ADM ϕ = 0 BDM ϕ = π BDM ϕ = 0 Second derivative (a.u.) Probe bias (V) 75 17. NONEQUILIBRIUM KINETICS AND SIMULATION OF DISCHARGES, AFTERGLOW PLASMAS AND HIGH-SPEED PLANETARY ENTRIES C.M. Ferreira (Head), J. Loureiro (Deputy Head), V. Guerra, P. A. Sá, C. D. Pintassilgo, M. L. Silva and K. Kutasi 17.1. INTRODUCTION The research work carried out by this team in 2005 falls into the following main fields of investigation: • Kinetics of the nitrogen afterglow; • Plasma sterilization at reduced gas pressure and low temperature; • Nonequilibrium processes and plasma radiation in high-speed spacecraft planetary entries; • Microwave discharges in N2-CH4 for metal nitrocarburizing and chemistry studies of Titan’s atmosphere; • Modeling of surface atomic recombination 17.2. KINETICS OF THE NITROGEN AFTERGLOW1 The study of the electron and heavy-particle kinetics in nitrogen post-discharges has been continued. The theoretical study involves two separate modules, one for the discharge (I) and another for the post-discharge (II). The stationary solutions from I are the initial conditions for module II. The electron energy distribution function (EEDF), the vibrational distribution function (VDF) of ground-state N2(X,v) molecules, and the concentrations of the most important neutral and ionic species are obtained from the coupled solutions to the electron Boltzmann equation and a system of rate-balance equations for the heavy-particles. The purpose of this investigation is to understand the behavior of the pink afterglow, characterized by a raise in the emission of the first negative system bands, corresponding to transitions between the ionic states N2+(B→X), after a dark zone downstream from the end of a flowing discharge. The concentration of several other species, both radiative and metastable, exhibit a similar profile. In particular, it is very striking to verify an increase in the population of N2(A) and N2(a) metastables, taking place in the field-free post-discharge. It has been shown that an equilibrium between the vibrational distribution of ground-stated N2(X,v) molecules is established and that collisions of highly vibrationally excited molecules with N atoms are in the origin of a maximum in the electron density, occurring downstream from the discharge. It is concluded that there must be a local production of N2(A) molecules, which has been shown to be due to near resonant vibration-vibration (V-V) energy exchanges, followed by electronic-vibration (V-E) 1 Work carried out in collaboration with Université des Sciences et Technologies de Lille (France) and Université Joseph Fourier de Grenoble (France). exchanges. The later can be induced by collisions of highly vibrationally excited N2(X,v) molecules with both N atoms and electrons. Once the N2(A) state is created, it starts transferring energy to other states and to ionization. Therefore, many other excited states, as well as electrons and positive ions, have a similar profile during the afterglow (Figure 17.1). In spite of the general good agreement between the available experimental results and the theoretical predictions, a global explanation for the ionization processes taking place in the nitrogen afterglow is still missing. As a matter of fact, recent experiments made in Grenoble, France, show that the role of singlet metastables in the ionization during the afterglow has been overestimated. That being so, the present-day description of the afterglow underestimates ionization, and new ionization mechanisms have to be investigated. Figure 17.1 - Time evolution of the EEDF in the nitrogen afterglow. 17.3. PLASMA STERILIZATION AT REDUCED GAS PRESSURE AND LOW TEMPERATURE2 Gas plasma sterilization in hospitals has appeared a very promising alternative to conventional sterilization processes. Because of materials that are thermosensitive are increasingly being used in the composition of medical 2 Work performed in collaboration with the Physics Department of the University of Montreal (Canada), the Laboratoire de Science et Génie des Surfaces de l’ École des Mines de Nancy (France), the Department of Physical Electronics of the Faculty of Science of the Masaryk University of Brno (Czech Republic), and Prof. P.J. Coelho (Department of Mechanical Engineering, IST). 76 and dental devices, the possibility of the various active species created in a plasma medium may be used for sterilization has been considered. Further, this possibility should be also explored due to the necessity of inactivating new types of pathogenic agents. Plasma sterilization reactors operating in the afterglow of a gas discharge is the most interesting new device to be used, since it fulfill the two conditions of much lower gas temperature than in the discharge itself and the absence of charged species which could damage the material to be sterilized. Investigations realized by the group of Plasma Physics in the Physics Department of the University of Montreal has shown that almost total inactivation of an initial prion spore population can be achieved using the afterglow of a microwave N2-O2 discharge, with small O2 addition of the order of 0.2-2%, as a result of a synergistic effect between UV photons emitted by NO(B2Π) molecules and O(3P) atoms. With the aim of giving an insight into the the kinetics of a low pressure microwave flowing postdischarge in N2-O2, and thus determining the optimal operating conditions, investigations have been conducted in CFP by developing a fully self-consistent model for the kinetics of electrons and heavy-neutral and charged species in a flowing microwave discharge. Once the concentrations of active species produced in the discharge are determined, the afterglow is modeled by considering both a short-lived afterglow, at the end of the discharge, and the long-lived afterglow in the sterilization vessel of much larger dimension, where the objects to be sterilized will be placed. In the afterglow a complex interplay kinetics between active neutral species still continues to take place leading to the creation of some species and to the destruction of others. Work has been performed on the kinetics of charged and heavy-species in a N2-O2 microwave discharge, with a model for the short-lived afterglow downstream from the discharge tube. Furthermore, a comparison between measured and predicted populations in the afterglow of a N2-O2 microwave discharge was also conducted. This work has been pursued by considering a 3-D Navier-Stokes model for the post-discharge chamber, based on the coupled solutions to the set of equations for mass conservation of different species, total mass conservation, momentum transfer, and energy conservation. With this hydrodynamic model the concentrations of the various species, such as the molecules responsible by UV emission and oxygen atoms, may be followed up to the farthest remote zones of the reactor (Figure 17.2). Finally, the study of O2 and O2-N2 microwave discharges and post-discharges has been also conducted with the purpose of application to surface treatments, namely in the study of the oxygen plasma surface interaction in treatments of polyolefines and of the modification of hexatriacontane by O2-N2 microwave postdischarges (Figure 17.3). Figure 17.2 - The post-discharge chamber used in the modulation is shown in this figure. The active species created in a N2-O2 flowing microwave discharge after passing through a short afterglow region are introduced into the large vessel. The entrance and the outlet have a length and width of 2.6 cm and are situated in the middle of the planes giving symmetry to the chamber. Figure 17.3 - Distribution of velocity (a), temperature (b, c), relative mass density of NO(B2Π) molecules (d, e, f) and of O(3P) atoms (g, h, i), in the entrance plane y = 0.125 m (figures a, b, d, e, g, h) and in the x-y plane at z = 0.1 m height (figures c, f, i). The results are presented for two discharge conditions: (i) p = 8 Torr, f = 915 MHz (figures a, b, c, d, g); and (ii) p = 2 Torr, f = 2.45 GHz (figures e, f, h, i). Here, the results are for a N2-2%O2 mixture composition and gas flow of 2×103 sccm but the influence of these parameters is investigated. The gas temperature at the inlet and in the wall is assumed to be 500 K and 300 K, respectively. 17.4. NONEQUILIBRIUM PROCESSES AND PLASMA RADIATION IN HIGH-SPEED SPACECRAFT PLANETARY ENTRIES During an atmospheric entry of a space vehicle at hypersonic speeds (>5 km/s), a strong shock-wave is created in front of the spacecraft forebody. Immediately behind the shock-wave, the translational temperature of the flow reaches temperatures usually in large excess of 10,000 K. For interplanetary missions, the flight pattern is hyperbolic, and the entry velocities and translational temperatures may exceed 10 km/s and 100,000 K 77 respectively. After the excitation of the flow translational mode through the shock front, excitation of vibrational levels of the gas then follows through redistribution of energy from the translational mode to the vibrational mode. Dissociation and ionization of the gas species then follow until a plasma state is reached. Two issues arise in this case. The dissociation and ionization channels need to be known, in order to accurately describe the evolution of the flow macroscopic parameters (species concentrations and temperatures). This has a large impact on the determination of the convective heat transfer endured by the spacecraft thermal protections. Moreover, nonequilibrium excitation processes of neutral and ionised flow species need to be accurately known in order to determine the radiation from the plasma and to evaluate the radiative fluxes endured by the spacecraft thermal protections. 17.4.1. Analysis of shock-induced dissociation processes A numerical model based on the Forced Harmonic Oscillator (FHO) theory has been developed for the simulation of atom-diatom and diatom-diatom Vibration- Translation (V-T) processes. This model is advantageous compared to First Order Perturbation Theory (SSH models) as it allows the simulation of multiquantum transitions and provides accurate results at very high temperatures (up to 100,000 K). Good agreement has been reached between this model and quasi-classical calculations for N2 and O2 molecules. The influence of multiquantum transitions on the global dissociation rates of molecular nitrogen has also been evidenced. Currently, the influence of molecular rotation on V-T processes is being studied through the development of additional models. Vibration-Electronic (V-E) transfer processes are scheduled to being studied shortly. Future studies will also focus on ionization processes such as associative ionization (A+B→ AB+ +e-) or Penning ionization (AB*+AB*→ AB+ +e-). Long term objectives include the development of a full collisonal-radiative model for Earth, Mars and Titan high speed atmospheric entries. Figure 17.4 - Dissociation times for different post-shock translational temperatures, at a 76 km altitude, and for a preshock temperature of 195 K. A collaboration program has also been established with the Université de Provence in Marseilles, France, where the shock-tube TCM2 is located. This facility is operated in the frame of the ESA-sponsored AURORA program for the simulation of shock-waves typical of Earth, Mars, and Titan atmospheric entries. The established working plan has scheduled a series of visits from researchers from the two institutions, in order to carry an interpretation and a numerical reproduction of spectra measured in Titan and Martian-type mixtures. 17.4.2. Analysis of atmospheric entry radiative processes A detailed investigation of the high temperature radiative processes encountered during an atmospheric entry is also carried in the research group. Currently, two different numerical tools have been developed and made available to the atmospheric entry research community: i) The line-by-line code SPARTAN (Simulation of Plasma Radiation in ThermodynAmic Nonequilibrium) for the simulation of plasma radiation from air and CO2-N2 plasmas has been developped and is freely made available to the general scientific community. The numerical code is capable of simulating over 50 different bound, bound-free, and free transitions (Figure 17.5). More informations on the numerical code can be found in the following electronic adress: http://cfp.ist.utl.pt/geg/radiation/SPARTAN/. Currently, the code is being used by three different european research teams (two in France and one in Italy). ii) An electronic database gathering factual information on radiative transitions of diatomic molecules of interest for planetary atmospheric entries has been developed and put online at the following electronic adress: http://cfp.ist.utl.pt/geg/radiation/GPRD/. Future versions of this database are scheduled to be added to the electronic databases provided by the European Space Agency, acting as the database of reference for providing spectral coefficients for the calculation of atmospheric entries radiation. Figure 17.5 - Sample calculation of the spectral-dependent absorption coefficient for a 97% CO2 – 3% N2 plasma at 1bar, 5000K, and in thermodynamic equilibrium 78 The group maintains a collaboration with the Laboratoire Arc Electrique et Plasmas Thermiques in Clermont-Ferrand, France. An analysis of the thermodynamics and radiative properties of a Martian-type CO2-N2 plasma produced in a Inductively Coupled Plasma torch at atmospheric pressure is being carried in the scope of this collaboration. Also, the group is currently involved in the expertise and further development of the ESA lineby-line code PARADE (Fluid Gravity Eng. Contract with M. Dudeck, U. Paris VI). 17.4.3. Analysis of Born-Oppenheimer hypothesis in polyatomic molecules A working group has been recently set-up to focus on the Born-Oppenheimer hypothesis breakdown and it’s impact on aerothermodynamics. We are participating in this working group whose task is to meet at regular schedules and to analyse the consequences of using the Born- Oppenheimer hypothesis in the majority of all the classical to quantum molecular models developped by the scientific community. The working group task also includes examining the possibility of developping further methods who do not require this assumption, and defining a roadmap for future investigations. . 17.5. MICROWAVE DISCHARGES IN N2-CH4 FOR METAL NITROCARBURIZING AND CHEMISTRY STUDIES OF TITAN’S ATMOSPHERE3 The study of a N2-CH4 afterglow has an actual interest due to the large number of applications in different fields, such as the detoxification of gases, metal surface nitrocarburizing and the study of the atmospheric chemistry of Titan. In the case nitrocarburizing, the afterglow resulting from a nitrogen-methane flowing microwave discharge can be very efficient in metal surface treatments, due to the importance of the presence of N and C atoms in the formation of carbonitrides ε-Fe2-3 (C, N) and γ-Fe4(C,N) in metal nitrocarburizing processes. Further, this treatment can be improved with the presence of H atoms. Two situations have been investigated in a flowing N2- CH4 afterglow of a microwave discharge: i) methane is added to N2 in the downstream afterglow; ii) methane is added to the discharge. In both cases the CH4 addition is always smaller than ~ 0.5-1%. The discharge is produced using a surfatron device connected to a microwave generator at 2.45 GHz and the post-discharge is analysed at about 200 mm downstream from the discharge. Optical Emission Spectroscopy (OES) is carried out in the postdischarge. The densities of N and C atoms in the late postdischarge can be inferred from OES measurements of the first positive system of N2 , emission of the N2(B3Πg,11) → 3 Work carried out in collaboration with the Laboratoire de Science et Génie des Surfaces de l’ École des Mines de Nancy (France) and the Service d’ Aéronomie de l’ Université de Paris VII and Versailles/Saint Quentin (France). N2(A3Σu+,7) transition, and of the CN violet band CN(B²Σ ,7) → CN(X²Σ,7), respectively, by assuming simple kinetic models for the long-lived afterglow, and using absolute calibration by NO titration. On the other hand, the kinetic model considers the self-consistent determination of the active species concentrations in the discharge and consequent time-relaxation in the afterglow. In situation i), where a small methane percentage is introduced into the post-discharge at 250 mm downstream from the end of the discharge, methane dissociation (CH3, CH2, etc.) occurs in the afterglow in the presence of active nitrogen, together with several other reactions leading to formation of HCN, CN(X²Σ), CN(B²Σ), etc. The C atoms are then formed as a result of a complex kinetics. Discharges in N2-CH4 have been also studied with the aim of understanding the organic chemistry of Titan’s atmosphere, in particular the conditions for formation of organic aerosols, also termed “tholins”, that are observed in Titan. 17.6. MODELING OF SURFACE ATOMIC RECOMBINATION: The study of the surface kinetics of atomic species, such as N and O atoms, and in particular of the elementary processes leading to heterogeneous recombination, is nowadays an important subject of research in various problems of rarefied gas dynamics, such as the aerodynamics of space vehicles moving in rarefied gases. On the other hand, many of the characteristics of plasma reactors are in practice controlled by wall reactions. Therefore, there is a need to address the questions of the role of surface processes in the overall behavior of different gas discharges. Many theoretical works have been done recently in order to investigate surface recombination of atoms. For instance, phenomenological models and Monte Carlo models have been developed. All these models provide important physical insight into the various elementary mechanisms occurring at the surface and, particularly for the case of the Monte Carlo, allow to perform quite complete and detailed simulations. The purpose of the present investigation is to follow a different approach, by obtaining asymptotic analytic solutions for the recombination probability. It is shown that the approximate analytic solutions describe the system with very high accuracy (Figure 17.6). Thus, for the system under analysis, the recombination probability can be readily evaluated from a simple expression, with no need for any numeric treatment. As a consequence, the dependence of the recombination probability on different surface parameters, such as the activation energies of the various processes and the wall temperature, can be fully understood. The probability for surface atomic recombination of a single gas is theoretically investigated, for a system that takes into account atomic adsorption in physisorption and chemisorption sites, surface desorption, surface diffusion, 79 and both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) recombination mechanisms. Figure 17.6 - Numerical (blue circles) and asymptotic analytical solutions (full line) for the recombination probability of nitrogen in silica. The contribution of L-H (dashed line) and E-R (dotted line) recombination mechanisms to the total recombination probability is also shown. 81 18. MODELLING OF PLASMA REACTORS C.M. Ferreira (Head), L. L. Alves (Deputy Head), R. Alvarez, L. Marques, S. Letout 18. 1. INTRODUCTION The research activity in 2005 was fully focused onto the modeling of several configurations of Plasma Reactors (PR), used in different types of industrial chains with electronics, photovoltaic, optics, food industry, or surface modification. The main objective with this research program is the development of sophisticated simulation tools, to optimize the operation conditions of different PRs, according to the specific needs with each application. The validation of such tools requires a strong interplay between modeling and experiment, without which it is not possible to improve the understanding of the main mechanisms controlling discharge operation. Several projects have been initiated, pursued or concluded, in the following main fields of investigation: • Inductively-coupled plasma reactors; • Microwave plasmas sustained by an Axial Injection Torch; • Microwave plasma reactor with coaxial geometry at 2.45GHz frequency in argon; • Capacitively-coupled radio-frequency discharges in hydrogen. 18.2. INDUCTIVELY-COUPLED PLASMA REACTOR FOR THE ETCHING OF METAL OXIDES1 We have started the modeling of an inductively-coupled plasma reactor (ICP-R), for the etching of metal oxides by fluorocarbon plasmas. Standard fabrication techniques of CMOS-base electronic devices generally apply deep etching processes to silicon oxide (with low-dielectric constant). Usually, this plasma processing technique is carried out within ICP- R’s, which present the advantage of operating at very low pressures (~mTorr) and high plasma densities (~1013 cm-3), thus ensuring both the effectiveness of the etching mechanism and a reduced contamination. The full description of etching processes within an ICP-R can significantly contribute to their control and optimization. However, the development of such a global simulation program constitutes a very hard task due to the complex and diverse nature of the phenomena involved: electromagnetic, chemical (either in gas or in surface phases) and transport. The development of such a simulation tool will bring together complementary competences in the domains of Plasma Physics and 1 Work carried out in collaboration with the Laboratoire des Plasmas et des Couches Minces (LPCM) of the Institut des Matériaux de Nantes (IMN, Nantes, France). Engineering, Surface Physics and Material Science. We intend to develop a multi-scale model of an ICP-R (Figure 18.1) for the etching of metal oxides, by fluorocarbon plasmas. In 2005, we have concentrated onto the description of the excitation source part of the reactor, by developing a two-dimensional simulation tool that calculates the electromagnetic field distribution therein. Figure 18.1 - ICP reactor with the LPCM (Nantes, France) 18.3. MICROWAVE PLASMAS SUSTAINED BY AN AXIAL INJECTION TORCH (TORCHE À INJECTION AXIALE, TIA)2 The disposal of pollutants produced by industrial processes is a mandatory task to ensure an environmental protection within a sustained development framework. Recently, a microwave plasma torch was applied in waste treatment, to the destruction of dangerous chemical compounds (such as Volatile Organic Compounds (VOCs) and BEXT aromatic hydrocarbons), with great success. Results show that this is a non-expensive and efficient way of neutralizing dangerous products, yielding destruction rates above 99,999% when applied to trichloroethylene and carbon tetrachloride. The microwave plasma under study is produced by a TIA inside a cylindrical reactor (5.5 cm radius and 15 cm high) – Spanish patents P200201328 and P200302980. The 2.45 GHz discharge runs in atomic (Ar, He) or molecular (N2, air) gases at atmospheric pressure, for powers ranging from 300 to 3000 W and gas flow-rates between 0.5 and 13 L/min, which shows the versatility of the plasma. The 2 Work performed in collaboration with the Physics Department of the University of Cordoba (Cordoba, Spain). 88 • "The JET-enhanced performance programme: more heating power and diagnostic capabilities in preparation for ITER" Lioure A., A. Kaye, A. Murari, J. Sanchez, T. Todd, C. Damiani, J. Pamela and JET-EFDA Contributors. Fusion Engineering and Design, 74, 141, 2005 • “Fast ion distribution driven by polychromatic ICRF waves on JET” Mantsinen, M.J., V. Kiptily, M. Laxaback, A. Salmi, Yu Baranov, R. Barnsley, P. Beaumont, S. Conroy, P. de Vries, C. Giroud, C. Gowers, T. Hellsten, L.C. Ingesson, T. Johnson, H. Leggate, M-L Mayoral, I. Monakhov, J-M Noterdaeme, S. Podda, S. Sharapov, A.A. Tuccillo, D. Van Eester and EFDA JET Contributers Plasma Physics and Controlled Fusion, 47, (9), 1439, 2005 • “Active control of MHD instabilities by ECCD in ASDEX Upgrade” Maraschek, M., G. Gantenbein, T.P. Goodman, S. Günter, D.F. Howell, F. Leuterer, A. Mück, O. Sauter, H. Zohm, contributers to the EFDA-JET workprogramme and the ASDEX Upgrade Team Nuclear Fusion, 45, (11), 1369, 2005 • “Additional evidence for the universality of the probability distribution of turbulent fluctuations and fluxes in the scrapeoff layer region of fusion plasmas” Milligen, B. Ph. Van., R. Sánchez, B.A. Carreras, V.E. Lynch, B. LaBombard, M.A. Pedrosa, C. Hidalgo, B. Gonçalves, R. Balbín and the W7-AS Team. Physics of Plasmas, 12, (5), 052507, 2005 • “Impurity-seeded ELMy H-modes in JET, with high density and reduced heat load” Monier-Garbet, P., Ph. Andrew, P. Belo, G. Bonheure, Y. Corre, K. Crombe, P. Dumortier, T. Eich, R. Felton, J. Harling, J. Hogan, A. Huber, S. Jachmich, E. Joffrin, H.R. Koslowski, A. Kreter, G. Maddison, G.F. Matthews, A. Messiaen, M.F. Nave, J. Ongena, V. Parail, M.E. Puiatti, J. Rapp, R. Sartori, J. Stober, M.Z. Tokar, B. Unterberg, M. Valisa, I. Voitsekhovitch, M. von Hellermann and JETEFDA contributers. Nuclear Fusion, 45, (11), 1404, 2005 • “Sawtooth control experiments on ASDEX Upgrade” Mück, A., T.P. Goodman, M. Maraschek, G. Pereverzev, F. Ryter, H. Zohm and ASDEX Upgrade Team Plasma Physics and Controlled Fusion, 47, (10), 1633, 2005 • “New developments in JET neutron, γ -ray and particle diagnostics with relevance to ITER” Murari, A., L. Bertalot, S. Conroy, G. Ericsson, V. Kiptily, S. Popovichev, H. Schuhmacher, J.M. Adams, V. Afanasyiev, M. Angelone, G. Bonheure, B. Esposito, J. Källne, M. Mironov, M. Pillon, M. Reginatto, D. Stork, A. Zimbal and JET-EFDA Contributers Nuclear Fusion, 45, (10), S195, 2005 • “Fishbones in Joint European Torus plasmas with high ioncyclotron-resonance-heated fast ions energy content” Nabais, F., D. Borba, M. Mantsinen, M. F. F. Nave and S. E. Sharapov Physics of Plasmas, 12, 10, 102509, 2005 • “Efficiency of plasma biasing by movable localized limiter in tokamak ISTTOK” Nedzelskiy, I.S., C. Silva, H. Figueiredo, C.A.F. Varandas, J.A. Cabral, Chechoslovak Journal of Physics, 55, 3, 361, 2005. • “Tungsten: an option for divertor and main chamber plasma facing components in future fusion devices” Neu, R., R. Dux, A. Kallenbach, T. Pütterich, M. Balden, J.C. Fuchs, A. Herrmann, C.F. Maggi, M.O’Mullane, R. Pugno, I. Radivojevic, V. Rohde, A.C.C. Sips, W. Suttrop, A. Whiteford and the ASDEX Upgrade team. Nuclear Fusion, 45, (3) 209, 2005 • “Experimental studies of toroidal momentum transport in ASDEX Upgrade” Nishijima, D., A. Kallenbach, S. Günter, M. Kaufmann, K. Lackner, C.F. Maggi, A.G. Peeters, G.V. Pereverzev, B. Zaniol and the ASDEX Upgrade Team. Plasma Physics and Controlled Fusion, 47, (1), 89, 2005 • "Matching to ELMy plasmas in the ICRF domain" Noterdaeme, J.-M., V.V. Bobkov, S. Brémond, A. Parisot, I. Monakhov, B. Beaumont, Ph. Lamalle, F. Durodié, M. Nightingale, the ASDEX Upgrade Team, the Tore Supra Team, and the JET-EFDA contributers. Fusion Engineering and Design, 74, 191, 2005 • “Density profile analysis during an ELM event in ASDEX Upgrade H-modes” Nunes, I., M. Manso, F. Serra, L.D. Horton, G.D. Conway, A. Loarte and the ASDEX Upgrade CFN Reflectometry Teams Nuclear Fusion, 45, (12), 1550, 2005 • “Overview of JET results” Pamela, J., J. Ongena and JET EFDA Contributers Nuclear Fusion, 45, (10), S63, 2005 • "Overview of recent JET results in preparation for ITER operation: interplay between technical and scientific progress" Pamela, J., J. Ongena, D. Borba, R. Buttery, G. Counsell, R. Felton, E. Joffrin, P. Lomas, A. Murari, J.-M. Noterdaeme, G. Piazza, V. Riccardo, R. Pitts, S. Rosanvallon, D. Stork, K.-D. Zastrow and JET-EFDA Contributors. Fusion Engineering and Design, 74, 17, 2005 • ”Microstructural Characterization on Eurofer/ODS RAFM Steel in the Normalized and Tempered Condition and after Thermal Aging in Simulated Fusion Conditions” Paúl, A., E. Alves, L.C. Alves, C. Marques, R. Lindau, J.A. Odriozola, Fusion Engineering and Design, 75-79 (2005) 1061-1065. • “Threshold for sheared flow and turbulence development in the TJ-II stellarator” Pedrosa, M.A., C. Hidalgo, E. Calderón, T. Estrada, A. Fernández, J. Herranz, I. Pastor and the TJ-II team 89 Plasma Physics and Controlled Fusion, 47, (6), 777, 2005 • “Linear gyrokinetic stability calculations of electron heat dominated plasmas in ASDEX Upgrade” Peeters, A.G., C. Angioni, M. Apostoliceanu, F. Jenko, F. Ryter and the ASDEX Upgrade Team. Physics of Plasmas, 12, (2), 022505, 2005 • “Linear gyrokinetic calculations of toroidal momentum transport in a tokamak due to the ion temperature gradient mode” Peeters, A.G., C. Angioni and the ASDEX Upgrade Team. Physics of Plasmas, 12, (7), 072515, 2005 • “Understanding of the density profile shape, electron heat transport and internal transport barriers observed in ASDEX Upgrade” Peeters, A.G., C. Angioni, M. Apostoliceanu, G.V. Pereverzev, E. Quigley, F. Ryter, D. Strintzi, F. Jenko, U. Fahrbach, C. Fuchs, O. Gehre, J. Hobirk, B. Kurzan, C.F. Maggi, A. Manini, P.J. McCarthy, H. Meister, J. Schweinzer, J. Stober, W. Suttrop, G. Tardini and the ASDEX Upgrade Team. Nuclear Fusion, 45, (9), 1140, 2005 • “Edge and divertor physics with reversed toroidal field in JET” Pitts, R.A., P. Andrew, X. Bonnin, A.V. Chankin, Y.Corre, G. Corrigan, D. Coster, I. Duran, T. Eich, S.K. Erents, W. Fundamenski, G. Kirnev, P.J. Lomas, A. Loate, G.F. Matthews, C. Silva, M.F. Stamp, J. Strachan, Journal of Nuclear Materials, 337-339, 146, 2005 • “Bright spots generated by lower hybrid waves on JET” Rantamäki, K.M., V. Petrzilka, P. Andrew, I. Coffey, A. Ekedahl, K. Erents, V. Fuchs, M Goniche, G. Granucci, E. Joffrin, S.J. Karttunen, P. Lomas, J. Mailloux, M. Mantsinen, M-L Mayoral, D.C. McDonald, J-M Noterdaeme, V. Parail, A.A. Tuccillo, F. Zacek and Contributers to the EFDA – JET Workprogramme Plasma Physics and Controlled Fusion, 47, (7), 1101, 2005 • “Tokamak turbulence computations on closed and open magnetic flux surfaces” Ribeiro, T.T., B. Scott Plasma Physics and Controlled Fusion, 47, (10), 1657, 2005 • “Timescale and magnitude of plasma thermal energy loss before and during disruptions in JET” Riccardo, V., A. Loarte and the JET EFDA Contributers Nuclear Fusion, 45, (11), 1427, 2005 • “Development of internal transport barrier scenarios at ITER-relevant high triangularity in JET” Rimini, F.G., M. Bécoulet, E. Giovannozzi, P.J. Lomas, O. Tudisco, B. Alper, F. Crisanti, M. de Baar, E. de La Luna, P. de Vries, A. Ekedahl, N. Hawkes, G. Huysmans, X. Litaudon, V. Parail, G. Saibene, A.A. Tuccillo, K.D. Zastrow and EFDA-JET Workprogramme Contributers Nuclear Fusion, 45, (12), 1481, 2005 • "Grad-Shafranov equilibria with negative core toroidal current in tokamak plasmas" Rodrigues, P. and J. P. S. Bizarro Phys. Rev. Lett., 95, 015001, 2005 • “MHD stability analysis of diagnostic optimized configuration shots in JET” Saarelma, S., V. Parail, Y. Andrew, E de la Luna, A. Kallenbach, M. Kempenaars, A. Korotkov, A. Loarte, J. Lonnroth, P. Monier-Garbet, J. Stober, W. Suttrop and Contributers to the EFDA-JET Workprogramme Plasma Physics and Controlled Fusion, 47, (5), 713, 2005 • “On the energy transfer between flows and turbulence in the plasma boundary of fusion devices” Sánchez, E., C. Hidalgo, B. Gonçalves, C. Silva, M.A. Pedrosa, M. Hron, K. Erents, Journal of Nuclear Materials, 337-339, 296, 2005 • "Probe methods for direct measurements of the plasma potential" Schrittwieser, R., C. Ioniţă, P.C. Balan, C.A.F. Varandas, H.F.C. Figueiredo, C. Silva, H. Fernandes, J. Stöckel, J. Adámek, M. Hron, J. Ryszawy, M. Tichý, E. Martines, G. Van Oost, T. Klinger, R. Madani, R.M.O. Galvão, Romanian Journal of Physics, 50, No.7-8, 2005 • “Experimental studies of instabilities and confinement of energetic particles on JET and MAST” Sharapov, S.E., B. Alper, F. Andersson, Yu.F. Baranov, H.L. Berk, L. Bertalot, D. Borba, C. Boswell, B.N. Breizman, R. Buttery, C.D. Challis, M. de Baar, P. de Vries, L.-G. Eriksson, A. Fasoli, R. Galvão, V. Goloborod’ko, M.P. Gryaznevich, R.J. Hastie, N.C. Hawkes, P. Helander, V.G. Kiptily, G.J. Kramer, P.J. Lomas, J. Mailloux, M.J. Mantsinen, R. Martin, F. Nabais, M.F. Nave, R. Nazikian, J.-M. Noterdaeme, M.S. Pekker, S.D. Pinches, T. Pinfold, S.V. Popovichev, P. Sandquist, D. Stork, D. Testa, A. Tuccillo, I. Voitsekhovich, V. Yavorskij, N.P. Young, F. Zonca, JET-EFDA Contributers and the MAST Team Nuclear Fusion, 45, (9), 1168, 2005 • “Determination of the particle and energy fluxes in the JET far SOL during ELMs using the reciprocating probe diagnostic” Silva, C., B. Gonçalves, C. Hidalgo, K. Erents, A. Loarte, G. Matthews, M. Pedrosa Journal of Nuclear Materials, 337-339, 722, 2005 • “Comparison of limiter and emissive electrode bias on the tokamak ISTTOK” Silva, C., I. Nedzelskiy, H. Figueiredo, R.M.O. Galvão, J.A.C. Cabral, C.A.F. Varandas Journal of Nuclear Materials, 337-339, 415, 2005 • “Transport and fluctuations during electrode biasing on TJII” Silva, C., M.A. Pedrosa, C. Hidalgo, K. McCarthy, E. Calderón, B. Gonçalves, J. Herranz, I. Pastor, O. Orozco, Czechoslovak Journal of Physics, 55, 1589, 2005 90 • "Unidirectional transparent signal injection in finitedifference time-domain electromagnetic codes – application to reflectometry simulations" Silva, F. da, S. Heuraux, S. Hacquin and M. Manso Journal of Computational Physics, 203, 2, 467, 2005 • “Small ELM regimes with good confinement on JET and comparison to those on ASDEX Upgrade, Alcator C-mod and JT-60U” Stober, J., P.J. Lomas, G. Saibene, Y. Andrew, P. Belo, G.D. Conway, A. Herrmann, L.D. Horton, M. Kempenaars, H.-R. Koslowski, A. Loarte, G.P. Maddison, M. Maraschek, D.C. McDonald, A.G. Meigs, P. Monier-Garbet, D.A. Mossessian, M.F.F. Nave, N. Oyama, V. Parail, Ch. P. Perez, F. Rimini, R. Sartori, A.C.C. Sips, P.R. Thomas, Contributers to the EFDA-JET workprogramme and the ASDEX Upgrade Team Nuclear Fusion, 45, (11), 1213, 2005 • “Overview of transport, fast particle and heating and current drive physics using tritium in JET plasmas” Stork, D. Yu. Baranov, P. Belo, L. Bertalot, D. Borba, J.H. Brzozowski, C.D. Challis, D. Ciric, S. Conroy, M. de Baar, P. de Vries, P. Dumortier, L. Garzotti, N.C. Hawkes, T.C. Hender, E. Joffrin, T.T.C. Jones, V. Kiptily, P. Lamalle, J. Mailloux, M. Mantsinen, D.C. McDonald, M.F.F. Nave, R. Neu, M.O’Mullane, J. Ongena, R.J. Pearce, S. Popovichev, S.E. Sharapov, M. Stamp, J. Stober, E. Surrey, M. Valovic, I. Voitsekhovitch, H. Weisen, A.D. Whiteford, L. Worth, V. Yavorskij, K.-D. Zastrow and JET EFDA contributers. Nuclear Fusion, 45, (10), S181, 2005 • “Studies of the 'Quiescent H-mode' regime in ASDEX Upgrade and JET” Suttrop, W., V. Hynönen, T. Kurki-Suonio, P.T. Lang, M. Maraschek, R. Neu, A. Stäbler, G.D. Conway, S. Hacquin, M. Kempenaars, P.J. Lomas, M.F.F. Nave, R.A. Pitts, K.-D. Zastrow, the ASDEX Upgrade team and contributors to the JET-EFDA workprogramme Nuclear Fusion 45, 7, 721-730, 2005 • “Predictive transport simulations of real-time profile control in JET advanced tokamak plasmas” Tala, T., L. Laborde, D. Mazon, D. Moreau, G. Corrigan, F. Crisanti, X. Garbet, D. Heading, E. Joffrin, X, Litaudon, V. Parail, A. Salmi and contributers to the EFDA-JET workprogramme Nuclear Fusion, 45, (9), 1027, 2005 • “Current losses induced by edge localized modes in JET tokamak plasmas” Testa, D., M. Bigi and JET-EFDA contributers Plasma Physics and Controlled Fusion, 47, (6), 733, 2005 • “Position dependence of the unstable vertical movement of JET plasmas triggered by ELMs” Villone, F., V. Riccardo, F. Sartori and contributers to the EFDA-JET workprogramme Nuclear Fusion, 45, (11), 1328, 2005 • “Effect of sawtooth activity on tritium and beam deuterium evolution in trace tritium experiments on JET” Voitsekhovitch, I., K-D Zastrow, B. Alper, G. Bonheure, X. Garbet, V. Kiptily, E de la Luna, D.C. McDonald, S. Popovichev, S.E. Sharapov, D. Stork and JET EFDA Contributers Plasma Physics and Controlled Fusion, 47, (11), 1877, 2005 • “Density dependence of trace tritium transport in H-mode Joint European Torus plasma” Voitsekhovitch I., X. Garbet, D.C. McDonald, K.-D. Zastrow, M. Adams, Yu. Baranov, P. Belo, L. Bertalot, R. Budny, S. Conroy, J.G. Cordey, L. Garzotti, P. Mantica, D. McCune, J. Ongena, V. Parail, S. Popovichev, D. Stork, A.D. Whiteford and JET EFDA contributers Physics of Plasmas, 12, (5), 052508, 2005 • “Simulation of environment effects on retroreflectors in ITER” Voitsenya, V.S., A.J.H. Donné, A. F. Bardamid, A.I. Belyaeva, V.L. Berezhnyj, A.A. Galuza, Ch. Gil, V.G. Konovalov, M. Lipa, A. Malaquias, D.I. Naidenkova, V.I. Ryzhkov, B. Schunke, S.I. Solodovchenko and A.N. Topkov. Review of Scientific Instruments, 76, (8), 83502, 2005 • “Effects of temperature ratio on JET transport in hot ion and hot electron regimes” Weiland, J., E. Asp, X. Garbet, P. Mantica, V. Parail, P. Thomas, W. Suttrop, T. Tala and the EFDA-JET Contributors. Plasma Physics and Controlled Fusion, 47, (3), 441, 2005 • “Collisionality and shear dependences of density peaking in JET and extrapolation to ITER” Weisen, H., A. Zabolotsky, C. Angioni, I. Furno, X. Garbet, C. Giroud, H. Leggate, P. Mantica, D. Mazon, J. Weiland, L. Zabeo, K.-D Zastrow and JET-EFDA contributors. Nuclear Fusion, 45, (2) L1, 2005 • “Edge stability of the ELM-free quiescent H-mode on DIII- D” West, W.P., K.H. Burrell, T.A. Casper, E.J. Doyle, P.B. Snyder, P. Gohil, L.L. Lao, C.J. Lasnier, A.W. Leonard, M.F.F. Nave, T.H. Osborne, D.M. Thomas, G. Wang and L. Zeng Nuclear Fusion 45, 12, 1708-1714, 2005 • “A cross-tokamak neural network disruption predictor for the JET and ASDEX Upgrade tokamaks” Windsor, C.G., G. Pautasso, C. Tichmann, R.J. Buttery, T.C. Hender, JET EFDA Contributers and the ASDEX Upgrade Team Nuclear Fusion, 45, (5) 337, 2005 • “Feedback and rotational stabilization of resistive wall modes in ITER” Yueqiang Liu, A. Bondeson, M.S. Chu, J.-Y. Favez, Y. Gribov, M Gryaznevich, T.C. Hender, D.F. Howell, R.J. La Haye, J.B. Lister, P. de Vries and EFDA JET Contributers. Nuclear Fusion, 45, (9), 1131, 2005 • “Helium exhaust experiments on JET with type I ELMs in H-mode and with Type III ELMs in ITB discharges” Zastrow, K.-D., S.J. Cox, M.G. von Hellermann, 91 M.G.O’Mullane, D. Stork, M Brix, C.D. Callis, I.H. Coffey, R. Dux, K.H. Finken, C. Giroud, D. Hillis, J.T. Hogan, K.D. Lawson, T. Loarer, A.G. Meigs, P.D. Morgan, M.F. Stamp, A.D. Whiteford and JET-EFDA contributors. Nuclear Fusion, 45, (3) 163, 2005 19.1.3. Papers in international conferences - Second IAEA Technical Meeting on the Theory of Plasma Instabilities: Transport, Stability and their Interaction, 2-4 de March, Trieste, Italy • “Effect of Sheared Equilibrium Plasma Rotation on the Stability of Tearing Modes” Coelho, R. - 32nd Annual IoP Plasma Physics Group Conference, 21-24 of March, Oxford, England • Reflectometry for Density Profile and Turbulence Measurement in Fusion Plasmas Hacquin, S., on behalf of the “Electron Kinetics” Group, the JET Task Force D and the EFDA-JET Contributors - US-European transport task force Workshop, Napa, USA, April 6-9 2005 • “n=0 Energetic Particle Driven Oscillations in JET” Berk, H.L., C. Boswell, T. Johnson, , M.F.F. Nave, S.D. Pinches, S.E. Sharapov, L. Zakharov and contributors to the EFDA-JET workprogramme • "Recent progress in diagnostics of energetic particle driven modes: new opportunities and challenges" Sharapov, S., B. Alper, H. Berk, D. Borba, C. Boswell, B. Breizman, E. de la Luna, J. Fessey, S. Hacquin, G. Kramer, R. Nazikian, S. Pinches, J. Rapp, D. Testa, N. Young and JET-EFDA Contributors - 7th International Reflectometry Workshop for Fusion Plasma Diagnostics, 9-12 of May, Garching, Germany • “Profile Reflectometry on MAST” Cunningham, G., T. Edlington, A. Silva and L. Meneses • “Frequency Hopping Millimeter-wave Reflectometry in ASDEX Upgrade” Cupido, L., S. Graça, L. Meneses, J. Santos, M. Manso and F. Serra • “Identification of Local Alfvén Wave Resonances with Reflectometry as a Diagnostic Tool in Tokamaks” Elfimov, A.G., R. M.O. Galvão, L. F. Ruchko, M.E.C.Manso and A.A.Ivanov • “Fluctuation Measurements in TJ-II using a Broadband Fast Frequency Hopping Reflectometer” Estrada, T., E. Blanco, L. Cupido, M.E. Manso and J. Sánchez • “A New Spectral Analysis to Study Pellet Triggered ELMs from Broadband Reflectometry at ASDEX Upgrade” Fattorini, L., M. E. Manso, P. T. Lang and the ASDEX Upgrade Team • “Nonlinear Effects in the Doppler Reflectometry (Analytical Theory and Numerical Simulations)” Gusakov, E.Z., S. Heuraux, F. da Silva and A.V. Surkov • “Further Development of Reflectometry Diagnostics for Measurement of Alfvén Cascades on the JET Tokamak” Hacquin, S., S. Sharapov, B. Alper, D. Borba, C. Boswell, J. Fessey, L. Meneses, M. Walsh and the JET EFDA Contributors • “Radial Behaviour of Density Fluctuations Deduced from FM-CW Tore Supra Reflectometry Data” Heuraux, S., L. Vermare, F. Clairet, G. Leclert and F. da Silva • “JET Density Profile Reflectometer, New Design” Meneses, L., L.Cupido, A.A. Ferreira, M. Manso and L. Guimarãis • “Experimental Studies of the Registration of Alfvén Wave Resonances in the TCABR Tokamak by the Frequency Scanning Reflectometry” Ruchko, L. F., R. M. O. Galvão, A. G. Elfimov, J. I. Elizondo, E. Sanada, Yu. K. Kuznetsov, A. M. M. Fonseca, V. Bellintani Jr, A. N. Fagundes, I.C. Nascimento, W. P. de Sá, C.A.F. Varandas, M. Manso, P. Varela and A. Silva • “Doppler Reflectometry Spectra Simulations with Velocity Shear Layer” Silva, F. da, S. Heuraux and M. Manso • “Automatic Electron Density Measurements with Microwave Reflectometry During High-Density H-mode Discharges on ASDEX Upgrade” Silva, A., P. Varela, L. Cupido, M. Manso, L. Meneses, L.Guimarães, G. Conway, F. Serra and the ASDEX Upgrade Team • “Adaptive Window Calculation for Automatic Spectrogram Analysis of Broadband Reflectometry Data” Varela, P., A. Silva, M. Manso and the ASDEX Upgrade Team • “Status and Plans for Reflectometry in ITER” Vayakis, G., and C. Walker for the ITER International Team and Participant Teams with contributions from F. Clairet, R. Sabot, V. Tribaldos, T. Estrada, E. Blanco, J. Sánchez, G.G. Denisov, V.I. Belousov, F. Da Silva, P. Varela, M. E. Manso, L. Cupido, João Dias, Nuno Valverde, V.A. Vershkov, D.A. Shelukhin, S.V. Soldatov, A.O. Urazbaev, E.Yu. Frolov and S. Heuraux - 14th IEEE-NPSS Real Time Conference, 4-11 of June, Stockholm, Sweden - “A FPGA-Based Multi-Rate Interpolar with Real-Time Rate Change for a JET Test-Bench System” Batista, A. J. N., D. Alves, N. Cruz, J. Sousa, C. A. F. Varandas, E. Joffrin, R. Felton, J. Farthing and JET-EFDA Contributors 92 • “Upgrade of the Data Acquisition and Control System of the ASDEX Upgrade Microwave Reflectometer” Combo, A., A. Silva, P. Varela, M. Manso, J. Sousa, C. Correia and C.A.F. Varandas • “Digital Control System for the TCV Tokamak” Duval, B.P., J-M. Moret, A.P. Rodrigues, L.A. Pereira, C.A.F. Varandas • “A Cooperative JAVA Web-Start Environment for Shared Multi-User Remote Operation” Neto, A., H. Fernandes, B. B. Carvalho, J. Sousa and C. A. F. Varandas • “Real-Time Multi-DSP Based VME System for Feedback Control on the TCV Tokamak” Rodrigues, A.P., L. Pereira, T.I. Madeira, P. Amorim, C.A.F. Varandas and B. Duval • “Fast Feedback Control for Plasma Positioning with a PCI hybrid DSP/FPGA Board” Valcárcel, D. F., I. S. Carvalho, B. B. Carvalho, H. Fernandes, J. Sousa and C. A. F. Varandas - 32nd EPS Conference on Plasma Physics and Controlled Fusion, 27 of June to 1 of July of 2005, Tarragona, Spain • "H-mode access in the low density regime on JET" Andrew Y, Sartori R, Righi E, de la Luna E, Hacquin S, Hawkes N C, Horton L D, Huber A, Korotkov A, O'Mullane M G, JET-EFDA contributors • “Numerical Simulation of Impurity Screening in the SOL of JET Plasma by Localised Deuterium Gas Puffing” Belo, P., V. Parail, G Corrigan, J Hogan, D. Heading, J. Spence, C. Giroud and JET EFDA contributors • “Experimental Observations of n = 0 Mode Driven by Energetic Particles on JET” Boswell,C., H.L. Berk, T. Johnson, M.F.F. Nave, S.D. Pinches, S.E. Sharapov, L. Zakharov and EFDA-JET contributors • “Effect of Alfvén Resonances on the Penetration of Error Fields on a Rotating Viscous Plasma” Coelho, R. and E. Lazzaro • “High Spatial and Temporal Resolution FM-CW Reflectometry to Study Pellet Triggered ELMs at ASDEX Upgrade” Fattorini, L., P. T. Lang, M. E. Manso, S. Kalvin, G. Kocsis and the ASDEX Upgrade Team • “A tool for the Parallel Calculation and Ready Visualization of the Choi–Williams Distribution: Application to Fusion Plasma Signals” Figueiredo, A.C.A., J.S. Ferreira, B.B. Carvalho and M.F.F. Nave • “Study of edge flows and transport during emissive electrode biased discharges on ISTTOK” Figueiredo, H., C. Silva, I. Nedzelsky, B. Gonçalves, H. Fernandes, C.A.F. Varandas, • “Turbulence Experiments in Reversed and Standard-B Field Configurations in the JET Tokamak” Gonçalves, B., C. Hidalgo, C. Silva, M.A. Pedrosa, M. Hron and JET EFDA contributors • “Sawtooth control in fusion plasmas” Graves, J. P., R. V. Budny, R. J. Buttery, S. Coda, L.-G. Eriksson, C. G. Gimblett, R. J. Hastie, H. R. Koslowski, M. J. Mantsinen, M.-L. Mayoral, A. Mueck, M. F. F. Nave, O. Sauter, and JET-EFDA Contributors • “Electron transport barriers, rationals and fluctuations in the TJ-II” Krupnik, L., J.A. Alonso, A. Cappa, A.A. Chmuga, N.B. Dreval, L. Eliseev, T. Estrada, A. Fernandez, C. Fuentes, C. Hidalgo, S.M. Khrebtov, A.D. Komarov, A.S. Kozachok, A.V. Melnikov, I.S. Nedzelskiy, M. Liniers, J.L. de Pablos, M.A. Pedrosa, Yu. Tashchev, V. Tereshin, E. Sanchez • “ELM mitigation by externally induced ELMs - Physics and Prospects” Lang, P.T., J.Bucalossi, L.Fattorini, K.Gal, L.D.Horton, A.Kallenbach, J.Lister, S.Kalvin, G.Kocsis, M.E.Mansoy, M.Maraschek, Y.Martin, V.Mertens, R.Neu, J.Neuhauser, T.Pütterich, A.C.C.Sips, W.Suttrop, G.Veres and ASDEX Upgrade Team • “First Results Obtained with the Real-Time PHA Diagnostic on TCV” Madeira, T.I., P.Amorim, B.P.Duval, A.P.Rodrigues, L.Pereira and C.A.F.Varandas • “Spatial Asymmetries in ELM induced Pedestal Density Collapse in ASDEX Upgrade H-modes” Nunes, I., M. Manso, F. Serra, L. D. Horton, G. D. Conway, A. Loarte and the ASDEX Upgrade and CFN Reflectometry Teams • “Effect of the Plasmas Geometry Evolution on Runaway Electron Generation in Tokamak Disruptions” Plyusnin, V.V. • “Gyrofluid Turbulence Computations in the Edge and SOL Regions of Tokamak Plasmas using Realistic Magnetic Field Geometry” Ribeiro, T.T., B. Scott, D. Coster and F. Serra • “On the Momentum Re-distribution via Fluctuations in Fusion Plasmas” Sanchez, E., C. Silva, M.A. Pedrosa, C. Hidalgo, K. McCarthy, E. Calderón, B. Gonçalves, J. Herranz, I. Pastor and O. Orozco • “Transport and fluctuations during electrode biasing on TJ-II” Silva, C., M.A. Pedrosa, C. Hidalgo, K. McCarthy, E. Calderón, B. Gonçalves, J. Herranz, I. Pastor, O. Orozco, • “Relaxation phenomena during edge plasma biasing in the CASTOR tokamak” Spolaore, M., J. Brotánková, P. Peleman, P. Devynck, H. Figueiredo, G. Kirnev, E. Martines, J. Stöckel, G. Van 93 Oost, J. Adamek, E. Dufková, I. Duran, M. Hron, V. Weinzettl - 17th International Conference on Ion Beam Analysis, Sevilla, Spain, June 26 - July 1 2005 • “Ion Beam Characterisation of ODS Steel Samples after Long Term Annealing Conditions” Alves, L. C., E. Alves, A. Paúl, M. R. da Silva, J. A. Odriozola - 8th Workshop on the Electric Field, Structures and Relaxation in Edge Plasmas, 3-4 of July of 2005, Tarragona, Spain • “Study of pellet triggered ELMs using high spatial and temporal resolution FM-CW reflectometry at ASDEX Upgrade” Fattorini, L., P. T. Lang, M. E. Manso, S. Kalvin, G. Kocsis and the ASDEX Upgrade Team. • “Local 3D Perturbation Experiments for Probing the SLM stability” Lang, P.T., J. Neuhauser, J. Bucalossi, L. Fattorini, L.D. Horton, S. Kalvin, G. Kocsis, M.E. Manso, M. Maraschek, G. Veres and the ASDEX Upgrade Team - 5th IAEA Technical Meeting on Control, Data Acquisition and Remote Participation for Fusion Research, 12-15 of July of 2005, Budapest, Hungary • “JET Real Time Project Test-Bench Software Structure” Cruz, N., A.J.N. Batista, D. Alves, J. Sousa, C.A.F. Varandas, E. Joffrin, R. Felton, J.W. Farthing and JET-EFDA Contributors • "Efficient use of VME modules in TCABR" Fagundes, A.N., B.B. Carvalho, M. Correia , J. Sousa • “A Generic Remote Method Invocation for Intensive Data Processing” Neto, A., D. Alves, H. Fernandes, J. S. Ferreira and C.A.F. Varandas • “Control and Data Acquisition System for the Multiple Cell Array Detector of the TJ-II Heavy Ion Beam Diagnostic” Pereira, L., I.S. Nedzelskiy, B. Gonçalves, J.L. de Pablos, A. Alonso, C. Hidalgo and C.A.F. Varandas • “The Software for the Real-Time DSP-Based VME System for Feedback Control on TCV using a PHA X-ray Diagnostic” Pereira, L., A.P. Rodrigues, T.I. Madeira, P. Amorim, B. P. Duval and C.A.F.Varandas • “Enhanced Neutron Diagnostics Data Acquisition System based on a Time Digitizer and Transient Recorder Hybrid Module” Pereira, R. C., A.Combo, N.Cruz, Jorge Sousa, C. Correia, C. Varandas, S. Conroy and J. Källne • “Real-Time Data Transfer in the TCV Advanced Plasma Control System” Rodrigues, A.P., L. Pereira, J-M. Moret, B. P. Duval and C. A. F. Varandas • “A Unified Real-Time Control and Data Acquisition Hardware Platform” Sousa, J., A. J. N. Batista, R. C. Pereira and C. Varandas - 19th International Conference On Numerical Simulation of Plasmas, 12-15 of July of 2005, Nara, Japan • “On the Computation of Tokamak Equilibria with Negative Core Toroidal Current” Rodrigues, Paulo and João P. S. Bizarro • “Developments on Reflectometry Simulations for Fusion Plasmas: Application to ITER Position Reflectometers” Silva, da F. S. Heuraux and M. Manso - 6th International Workshop “Strong Microwaves in Plasmas”, July 25 – August 1 of 2005, Nizhny Novgorod – Saint Petersburg, Russia • “JET Passive Active Multijunction Lower Hybrid Launcher” Bibet, Ph., Belo, J., Bertrand, B., Bizarro, J.P.S., Cesario, R., Kaye, A.,Leguern, F.,Lioure, A.,Mailloux, J., Mirizzi, F., Portafaix, C., Testoni, P., Tuccillo, A.A., Vallet, J.C., Walton, B., - 10th IAEA Technical Meeting on H–mode Physics and Transport Barriers, St. Petersburg (Russia), September 2005. • “The quiescent H-mode regime in ASDEX Upgrade” Suttrop, W., V. Hynönen, T. Kurki-Suonio, G. D. Conway, L. Fattorini, P. T. Lang, M. Maraschek, R. Neu, J. Schirmer, A. Stäbler and ASDEX Upgrade Team. - RIVA V - 5th Iberian Vacuum Meeting, 18-21 of September of 2005, Guimarães, Portugal • “Redesign of the tokamak ISTTOK hydrogen injection system” Correia, J. Nunes, A. Soares, H. Fernandes • “Aluminium Vacuum Deposition Coatings for Dielectric Substrate Microwave Antennas Production” Figueiredo, J., H. Fernandes and C.A.F. Varandas - 21st IEEE/NPSS Symposium on Fusion Engineering, September 26-29 of 2005, Knoxville, USA. • “ITER LHCD plans and design” Bibet, Ph., Beaumont, B., Belo, J.H., Bizarro, J.P.S., Delpech, L., Ekedahl, A., Granucci, G., Kazarian, F., Kuzikov, S., Litaudon, X., Mailloux, J., Mirizzi, F., Pericoli, V., Prou, M., Rantamäki, K., Tuccillo, A.A - 47thAnnual Meeting of the Division of Plasma Physics, 24- 28 of October of 2005, Denver, USA • "Detection of Alfvén cascades in advanced JET plasmas" Alper, B., S. Sharapov, S. Hacquin, D. Borba, C. Boswell, S. Pinches and JET-EFDA Contributors • “Testing the Porcelli Sawtooth Trigger Module” Bateman, G., A. H. Kritz, M.F.F.Nave, V. Parail 94 • “Axisymmetric Phase Space Structures Driven by Fast Ions in JET” Berk, H. L., C. J. Boswell, Mit-PSFC, S. E. Sharapov, T. Johnson, M. F. F. Nave, S. D. Pinches • “Edge Stability Analysis of JET Quiescent H-mode Experiments” Nave, M.F.F., G. Huysmans, J-S. Lonnroth, V. Parail, M. Marascheck, W. Suttrop and EFDA-JET Contributors - 6th Int. Workshop Electrical Probes in Magnetized Plasmas (IWEP 2005), Seoul, Korea, 2005 • "Overview of electrical probe measurements on ISTTOK" Varandas, C.A.F., C. Silva, I. Nedzelsky, H. Figueiredo, H. Fernandes, R. Schrittwieser, C. Ioniţă, P. Balan - Int. Conf. Nuclear Energy for New Europe 2005 (Bled, Slovenia, Sept. 5-8, 2005) • "Probe Diagnostics for Edge Plasmas in Fusion Experiments" Ioniţă, C., R. Schrittwieser, P.C. Balan, J. Stöckel, J. Adámek, M. Hron, C.A.F. Varandas, H.F.C. Figueiredo, C. Silva, M. Tichý, E. Martines, G. Van Oost, J.P. Gunn, T. Klinger • "Edge Plasma Fluctuations Measurements in Fusion Experiments" Oral presentation Schrittwieser, R., C. Ioniţă, P.C. Balan, C.A.F. Varandas, H.F.C. Figueiredo, C. Silva, J. Stöckel, J. Adámek, M. Hron, M. Tichý, C. Hidalgo, M.A. Pedrosa, E. Calderón, E. Martines, G. Van Oost, J.P. Gunn, T. Klinger - 9th IAEA TCM on Energetic Particles, Takayama, Japan, November 9-11, 2005 • “Axisymmetric Phase Space Structures Driven by Fast Ions in JET” Berk, H. L., C. J. Boswell, D. Borba, T. Johnson, M. F. F. Nave, S. D. Pinches, S. E. Sharapov, and JET EFDA contributors • “Fishbones Activity in JET Low Density Plasmas” Nabais, F., D. N. Borba, M. J. Mantsinen, S. E. Sharapov and JET-EFDA contributors • "Alfvén cascades in JET discharges with NBI-heating" Sharapov, S., B. Alper, Y. Baranov, H. Berk, D. Borba, C. Boswell, B. Breizman, C. Challis, M. de Baar, E. de la Luna, E. Evangelidis, S. Hacquin, N. Hawkes, V. Kiptily, S. Pinches, P. Sandquist, I. Voitsekhovitch, N. Young and JET-EFDA Contributors - 7th IEA Workshop International workshop on Beryllium Technology for Fusion, Santa Barbara, USA, 29 Nov. - 2 Dec. 2005 • “Structural and oxidation studies of titanium beryllides” Alves, E., L.C. Alves, N. Franco, M.R. da Silva, A. Paúl • “Beeeryllium breeder blankets-status of the European R&D” Moeslang, A., E. Alves, L.V. Bocaccini, J.B.J. Hegeman, P. Kurinsky, et al. - 12th International Conference on Fusion Reactor Material, Santa Barbara, USA, 5-10 December 2005 • “Oxidation and stability studies of Beryllium Titanate” Alves, E., L. C. Alves, N. Franco, M.R. da Silva, A. Paúl • “Microstructural characterisation of reduced activation EUROFER ODS alloy after long-term annealing” Paúl, A., L. C. Alves, E. Alves, J. A. Odrizola - XI Latin-American Workshop on Plasma Physics, Mexico, 5-9 December 2005 • " ELMy Studies in ITER Relevant Regimes in ASDEX Upgrade Broadband FM-CW Reflectometry Techniques” (Oral presentation) Manso, M.E., A. Silva, P. Varela, D. Borba, P. Lang, L. Cupido, I. Nunes, G. Conway and the ASDEX Upgrade Team. • "Real time plasma control tools for advanced tokamak operation" (Invited talk) Varandas, C.A.F., J. Sousa, A.P. Rodrigues, B.B. Carvalho, H. Fernandes, A.J. Batista, N. Cruz, A. Combo and the CFN Control and Data Acquisition Group - 55th Annual Meeting of the Austrian Phys. Soc. (Vienna, Austria, 2005) • "Measurements of edge plasma fluctuations in toroidal plasmas with probes" Ioniţă, C., P.C. Balan, R. Schrittwieser, J. Stöckel, J. Adámek, M. Hron, M. Tichý, E. Martines, G. Van Oost, C.A.F. Varandas, H.F.C. Figueiredo, C. Silva, J.J. Rasmussen, V. Naulin - 6th International Balkan Workshop on Applied Physics (Constanţa, Romania, 2005) • "Edge plasma fluctuations in magnetized plasmas", invited lecture Balan, P., C. Ioniţă, R. Schrittwieser, J. Stöckel, J. Adámek, M. Hron, M. Tichý, E. Martines, G. Van Oost, H.F.C. Figueiredo, J.A. Cabral, C. Varandas, C. Silva, M.A. Pedrosa, C. Hidalgo 19.1.4. Papers in nacional conferences - 14ª Conferência Nacional de Física 2005, Dezembro 1-3, Porto • “Computação de turbulência na periferia de plasmas de tokamaks”. Ribeiro, T. T., B. Scott, D. Coster e F. Serra Druyts F and E. Alves • “O papel do tokamak ISTTOK no programa europeu de fusão” Silva, C., H. Fernandes, B.B. Carvalho, I. Carvalho, P. Carvalho, R. Coelho, J. Ferreira, H. Figueiredo, J. Figueiredo, J. Fortunato, R. Gomes, I. Nedzelskij, A. Neto, T. Pereira, V. Plyusnin, A. Soares, D.F. Valcárcel, C.A.F. Varandas 95 - As Energias do Presente e do Futuro, Lisboa, 21-22 Novembro, 2005 • “Fusão nuclear: uma opção energética para o futuro” Manso, M.E., (Oral presentation) • "O Sistema de Controlo em Tempo-Real do Tokamak ISTTOK" Valcárcel, D.F., I.S. Carvalho, A. Neto, P. Ricardo, J. Fortunato, A.S. Duarte, A.J.N. Batista, B.B. Carvalho, C. Silva, H. Fernandes, J. Sousa, C.A.F. Varandas • “Energia nuclear: uma opção para o futuro” Varandas, C.A.F. (Invited talk) 19.1.5. Articles in newspapers • “Um marco importante para a energia de fusão nuclear” Carlos Varandas Público, 29 June 2005 • “ITER: oportunidade de trabalho para as Empresas e Unidades de Investigação Portuguesas” Carlos Varandas Diário Económico, 22 November 2005 19.1.6. Laboratorial Prototypes • “Retarding Field Energy Analyzer” Nedzelskij, I., C. Silva and H. Fernandes • “Multi-pin array of emissive probes” Silva, C. and H. Figueiredo • “Real-time test facility” Batista, A. and J. Sousa • “PCI transient recorder module with galvanic isolation” Correia, M. and J. Sousa 1.9.1.7. Prizes and Awards • Bruno Gonçalves received the Ph.D Research Award for an outstanding Doctoral Thesis, given by the Plasma Physics Division of the European Physical Society, in June 2005 • Prof. C. Varandas was awarded the degree of “Grande Oficial da Ordem do Infante D. Henrique” for his contributions to Physics in Portugal by the President of the Portuguese Republic in November 2005 19.2. TECHNOLOGIES OF PLASMAS AND LASERS 19.2.1. Ph.D thesis • “Coulomb explosion of large clusters” Fabio Peano Politecnico di Torino, March 2005 19.2.2. Book chapters • Guerra,V., P. A. Sá, and J. Loureiro, Kinetic modeling of the nitrogen afterglow, in V. Haubrecht e J. Bartl (editores) 16th Symposium on Physics of Switching Arc, Brno University of Technology, Brno-Letohrad, Czech Republic, 2005. 19.2.3. Articles in scientific journals • “The effect of the gas flow-rate on the radial structure of a torch-like helium plasma” Álvarez, R., M.C. Quintero and A. Rodero IEEE Trans. Plas. Sci. 33(2), 422–423, 2005 • “Radial description of excitation processes of molecular and atomic species in a high-pressure helium microwave plasma torch” Álvarez, R., M.C. Quintero and A. Rodero J. Phys. D: App Phys. 38(20), 3768-3777, 2005 • “Thermal inequilibrium of atmospheric helium microwave plasma produced by an axial injection torch” Álvarez, R., A. Rodero, M. C. Quintero, A. Sola, A. Gamero and D. Ortega J. Appl. Phys. 98, 093304, 2005 • “Oxygen plasma surface interaction in treatments of polyolefines” Belmonte, T., C.D. Pintassilgo, T. Czerwiec, G. Henrion, V. Hody, J.M. Thiebaut, and J. Loureiro Surface and Coatings Technology 200, 26-30, 2005 • “Wave kinetic treatment of forward four-wave stimulated scattering instabilities” Bingham, R., L. O. Silva, R. M. G. M. Trines, J. T. Mendonça, P. K. Shukla, W. B. Mori, R. A. Cairns Journal of Plasma Physics 71, 899, 2005 • "Broadband amplification in non linear crystals using controlled angular dispersion of signal beam" Cardoso, L., G. Figueira Optics Communications 251, 405, 2005. • “Bandwidth increase by controlled angular dispersion of signal beam in optical parametric amplification” Cardoso, L., G. Figueira, N. Lopes, J. Wemans, J. T. Mendonça, Proc. SPIE Vol. 5777, 775, 2005. • “Exact orbital motion theory of the shielding potential around an emitting, spherical body” Delzanno, G. L., A. Bruno, G. Sorasio, G. Lapenta, Phys. Plasmas 12, 062102, 2005 • “Effects of Landau quantization on the equation of state (EOS) in intense laser plasma interactions with strong magnetic fields” Eliezer, S., P. Norreys, J. T. Mendonca, K. Lancaster, Phys. Plasmas 12, 052115, 2005 • “A new diagnostic for very high magnetic fields in expanding plasmas” Eliezer, S., J. T. Mendonca, R. Bingham, P. Norreys Physics Letters A 336, 390, 2005 • “Mirrorless tilted pulse front single-shot autocorrelator” Figueira, G., L. Cardoso, N. Lopes, J. Wemans, Journal of the Optical Society of America B 22, 2709, 2005 96 • "Performance and characterization of a 2.8 TW Ti:sapphire- Nd:glass chirped pulse amplification laser system" Figueira, G., et al. Proc. SPIE Vol. 5777, 636, 2005. • “Densities of N and O – atoms in N2-O2 flowing glow discharges by actinometry” Henriques, J., S. Villeger, J. Levaton, J. Nagai, S. Santana, J. Aamorin AND A. Ricard, Surface and Coating Tech. 200, 814 (2005). • “Ion acoustic instability triggered by finite amplitude polarized waves in the solar wind” Gomberoff, L., J. Hoyos and A.L. Brinca, J. Geophys. Res.109, A06101, 2005; • “Self-confinement of a fast pulsed electron beam generated in a double discharge” Goktas, H., M. Udrea, G. Oke, A. Alacakir, A. Demir, and J. Loureiro, Journal of Physics D: Applied Physics 38, 2793-2797, 2005 • “New mechanism of vacuum radiation from non-accelerated moving boundaries” Guerreiro, A., J. T. Mendonça, A. M. Martins, J. Optics B: Quantum and Semiclassical Optics 7, S69, 2005 • “Characterization of a surface-wave sustained plasma discharge in a coaxial structure” Letout, S., L.L. Alves, C. Boisse-Laporte and P. Leprince, J. Optoelectronics and Advanced Materials Vol. 7, No. 5, 2005 • “Creation and expansion of a magnetized plasma bubble for plasma propulsion” Loureiro, J., J. T. Mendonça, A. L. Brinca, R. Fonseca, L. O. Silva, I. Vieira Journal of Atmospheric and Solar-Terrestrial Physics 67, 1315, 2005 • “Double Sheaths in RF Discharges” Marques, L., G. Gousset and L.L. Alves IEEE Trans.Plasma Sci. - Special Issue on Images In Plasma Science 33, 358-359, 2005 • “Three-dimensional wakes driven by intense relativistic beams in gas targets” Martins, S. F., R. A. Fonseca, L. O. Silva, F. S. Tsung, W. B. Mori, S. Deng, T. Katsouleas IEEE Transactions on Plasma Science 33, 558, 2005 • “Long-time evolution of magnetic fields in relativistic GRB shocks” Medvedev, M., M. Fiore, R. A. Fonseca, L. O. Silva and W. B. Mori The Astrophysical Journal Letters, 618, L75, 2005 • “Micrometeoroid flight in the upper atmosphere: Electron emission and charging” Mendis, D. A., Wai-Ho Wong, M. Rosenberg, and G. Sorasio, J. Atmos. Sol.-Terr. Phys. 67, 1178, 2005 • “Physical problems of artificial magnetospheric propulsion” Mendonça, J. T., A. L. Brinca, R. Fonseca, J. Loureiro, L. O. Silva, I. Vieira Journal of Plasma Physics 71, 495, 2005 • “A coupled two-step plasma instability in PW laser plasma interactions” Mendonça, J T, P Norreys, R Bingham and J R Davies Plasma Phys. Control. Fusion 47 B799, 2005 • “Beam Instabilities in Laser-Plasma Interaction: Relevance to Preferential Ion Heating” Mendonça, J. T., P. A. Norreys, R. Bingham, and J. R. Davies Phys. Rev. Lett. 94, 245002, 2005 • “Wakefield of Bose-Einstein condensates in a background thermal plasma” Mendonça, J. T., P. K. Shukla, R. Bingham, Physics Letters A 340, 355, 2005 • “Parametric excitation of neutrino pairs by electron plasma waves” Mendonça, J. T., A. Serbeto, R. Bingham, P. K. Shukla, J. Plasma Physics 71, 119, 2005 • “A kinetic approach to Bose-Einstein condensates: selfphase modulation and Bogoliubov oscillations” Mendonça, J.T., R. Bingham and P.K. Shukla, Journal of Experimental and Theoretical Physics (JETP) 101, 942-948, 2005 • “Time refraction and the quantum properties of vacuum” Mendonça, J.T. and A. Guerreiro, Physical Review A 72, 044512, 2005 • “Absolute Time-Resolved X-Ray Laser Gain Measurement” Mocek, T., S. Sebban, G. Maynard, Ph. Zeitoun, G. Faivre, S. Hallou, M. Fajardo, S. Kazamias, B. Cros, J. P. Rousseau, and J. Dubau Phys. Rev. Lett. 95, 173902, 2005 • “Observation of ion temperatures exceeding background electron temperatures in petawatt laser-solid experiments” Norreys, P. A., K. L. Lancaster, H. Habara, J. R. Davies, J. T. Mendonça, R. J. Clarke, B. Dromey, A. Gopal, S. Karsch, R. Kodama, K. Krushelnick, S. D. Moustaizis, C. Stoeckl, M. Tatarakis, M. Tampo, N. Vakakis, M. S. Wei and M. Zepf Plasma Phys. Control. Fusion 47, L49, 2005 • “Particle Statistics in quantum information processing” Omar, Y. Int. J. Quantum Information 3, 201, 2005 • “Characterization and crystal structure of the bimetallic cyano-bridged [(eta 5-C5H5) (PPh3)(2) Ru (mu-CN) Ru (PPh3)2(eta(5)-C5H5)][PF6], Synthesis, Inorganica Chimica” 97 Ornelas, C., C. Candum, J. Mesquita, J. Rodrigues, M. H. Garcia, N. C. Lopes, M. P. Robalo, K. Nattinen, K. Rissanen, Acta 358 (8) 2482-2488, May, 2005. • “Dynamics and control of shock shells in the Coulomb explosion of very large deuterium clusters” Peano, F., R. A. Fonseca, L. O. Silva, Physical Review Letters 94, 033401, 2005; also in Virtual Journal of Ultrafast Science 4, issue 2, 2005 • “Modelling of a N2-O2 flowing afterglow for plasma sterilization” Pintassilgo, C.D., J. Loureiro, and V. Guerra, Journal of Physics D: Applied Physics 38, 417-430, 2005 • “Pair production by a strong wakefield excited by intense neutrino bursts in plasmas” Rios, L. A., A. Serbeto, J. T. Mendonça, P. K. Shukla, R. Bingham, Physics Letters B 606, 79, 2005 • “Wigner-Moyal description of free variable mass Klein- Gordon fields” Santos, J. P., and L. O. Silva, Journal of Mathematical Physics 46, 102901, 2005 • “Periodic structures on an ionic-plasma-vacuum interface” Shukla, P. K., and L. Stenflo, Physics of Plasmas 12, 044503, 2005 • “Molecular Dissociation in N2-H2 Microwave Discharge” Tatarova, E., F. M. Dias, B. Gordiets and C. M. Ferreira Plasma Sources and Science Technology 14 19-31, 2005. • “A Large scale Ar Plasma Source Excited by a TM33 mode” Tatarova, E., F. M. Dias, J Henriques and C. M. Ferreira, IEEE Transactions on Plasma Science 33 866-875, 2005 • “A quasi-particle approach to modulational instabilities in wave-plasma interactions” Trines, R., R. Bingham, L. O. Silva, J. T. Mendonça, P. K. Shukla, and W. B. Mori, Physica Scripta T116, 75, 2005 • “Quasi-particle approach to the modulational instability of drift waves coupling to zonal flows” Trines, R., R. Bingham, L. O. Silva, J. T. Mendonça, P. K. Shukla, and W. B. Mori, Physical Review Letters 94, 165002, 2005 • “An update of argon inelastic cross-sections for plasma discharges” Yanguas, A., J. Cotrino and L.L. Alves J. Phys. D: Appl. Phys. 38, 1588-1598, 2005 • “Characterisation and optimisation of a multiterawatt CPA laser system using SPIDER” Wemans, J., G. Figueira, N. Lopes, L. Cardoso, Proc. SPIE Vol. 5777, 642, 2005. 19.2.4. Papers in conference proceedings • “Modelo hidrodinâmico de difusão-convexão em grelha adaptativa, para plasmas de descarga micro-ondas em geometria coaxial” Alves, L.L. Congreso de Métodos Numéricos en Ingeniería (CMNI-05), Granada, Spain 2005. • “New features on surface-wave discharges: boundary phenomena and power deposition” Alves, L.L. XIth Conference on Plasma Physics and Applications, Iasi, Rumania 2005. • “Bandwidth increase by controlled angular dispersion of signal beam in optical parametric amplification” Cardoso, L., G. Figueira, N. Lopes, J. Wemans, J. T. Mendonça, Proc. SPIE Vol. 5777, 775 (2005) • “On the possibility to restore time-averaged Langmuir probe characteristics” Dias, F. M. Tsv. K. Popov FLTPD VI "Frontiers in Low Temperature Plasma Diagnostics VI", Les Houches, France, 2005, 56 • “Precise Determination of the Electron Density in Intermediate Pressure Gas Discharges Using Langmuir Probe Measurements” Dimitrova, M., Tsv. K. Popov, F. M. Dias, FLTPD VI "Frontiers in Low Temperature Plasma Diagnostics VI", Les Houches, France, 2005, 47 • “Performance and characterization of a 2.8 TW Ti:sapphire-Nd:glass chirped pulse amplification laser system” Figueira, G., N. Lopes, L. Cardoso, J. Wemans, J. Dias, M. Fajardo, C. Leitão, T. Mendonça, Proc. SPIE Vol. 5777, 636, 2005 • “Simulation of plasma radiation in Earth and Mars atmospheric entries” Silva, M. Lino da, V. Guerra, J. Loureiro, and M. Dudeck, 4th International Symposium on Atmospheric Reentry Vehicles and Systems, Arcachon (France) 2005. • “Kinetics of Particles in Relativistic Collisionless Shocks, in Particle Acceleration in Astrophysical Plasmas: Geospace and Beyond” Mikhail V. Medvedev, Luis O. Silva, Ricardo A. Fonseca, J. W. Tonge, and Warren B. Mori Edited by D. Gallagher, J. Horwitz, J. Perez, R. Preece, and J. Quenby, Geophysical Monograph Series, Volume 156, 2005 • “Experimental study and modelling of the afterglow of an N2-O2 microwave discharge” Pintassilgo, C.D., M. Mrázková, P. Vašina, V. Kudrle, V. Guerra and A. Tálský, 27th International Conference on Phenomena in Ionized Gases (ICPIG), Eindhoven (The Netherlands) 2005.