JET Diagnostic Enhancements Testing and Commissioning in Preparation for DT Scientific Campaigns

REVIEW OF SCIENTIFIC INSTRUMENTS 89, 10K119 (2018) JET diagnos ic enhancemen s es ing and commissioning in p epa a ion o DT scien i ic campaigns J. Figuei edo,1,2,a) A. Mu a i,1,3 C. Pe ez Von Thun,1,4 D. Ma occo,5M. Ta docchi,6F. Belli,5 M. Ga c´ ıa Mu˜ noz,7A. Sil a,2T. C aciunescu,8P. Blancha d,9I. Balboa,10 N. Hawkes,10 I. S. Ca alho,2B. Tal,11 J. Be na do,2,12 I. Zycho ,13 and JET Con ibu o sb) EURO usion Conso ium, JET, Culham Science Cen e, Abingdon OX14 3DB, Uni ed Kingdom 1EURO usion P og amme Managemen Uni , Culham Science Cen e, Abingdon, Uni ed Kingdom 2Ins i u o de Plasmas e Fus˜ ao Nuclea , Ins i u o Supe io T´ ecnico, Uni e sidade de Lisboa, Lisboa, Po ugal 3Conso zio RFX (CNR, ENEA, INFN, Uni e si a’ di Pado a, Acciaie ie Vene e SpA), Pado a, I aly 4Fo schungszen um J¨ ulich GmbH, Ins i u ¨ u Ene gie- und Klima o schung—Plasmaphysik, Ge many 5Uni ` a Tecnica Fusione, ENEA C. R. F asca i, Via E. Fe mi 45, 00044 F asca i, Roma, I aly 6IFP-CNR, Via R. Cozzi 53, 20125 Milano, I aly 7Uni e sidad de Se illa, Se illa, Spain 8The Na ional Ins i u e o Lase , Plasma and Radia ion Physics, Magu ele, Bucha es , Romania 9Ecole Poly echnique F´ ed´ e ale de Lausanne (EPFL), CRPP, CH-1015 Lausanne, Swi ze land 10CCFE, Culham Science Cen e, Abingdon, Oxon OX14 3DB, Uni ed Kingdom 11Wigne Resea ch Cen e o Physics, P.O. Box 49, H-1525 Budapes , Hunga y 12JET Exploi a ion Uni , Culham Science Cen e, Culham OX14 3DB, Uni ed Kingdom 13Na odowe Cen um Bada´ n Ja˛d owych (NCBJ), 05-400 O wock-Swie k, Poland (P esen ed 17 Ap il 2018; ecei ed 3 May 2018; accep ed 29 June 2018; published online 24 Oc obe 2018) In o de o op imize he scien i ic exploi a ion o JET (Join Eu opean To us) du ing he upcom- ing deu e ium- i ium expe imen s, a se o diagnos ic sys ems is being enhanced. These upg ades ocus mainly on he expe imen al and ope a ional condi ions expec ed du ing i ium campaigns. I should be s essed ha measu emen s ele an o bu ning plasmas a e speci ically a ge ed. P e i- ously non-a ailable capabili ies, such as a cu en measu emen sys em ully co e ing all poloidal ield ci cui s, a e desc ibed in de ail. Ins umen desc ip ions, pe o mance p edic ion, es ing, and ini ial commissioning esul s o hese sys ems a e p esen ed. h ps://doi.o g/10.1063/1.5038548 I. INTRODUCTION The upcoming JET deu e ium- i ium (DT) campaign, DTE2, is scheduled o ake place be o e he end o 2020. Fo many yea s, JET diagnos ics ha e been upg aded in o de o p o ide adequa e suppo o scien i ic exploi a ion, wi h pa - icula a en ion o he expe imen al and ope a ional condi ions expec ed du ing deu e ium- i ium campaigns.1–3Diagnos ic capabili ies ele an o bu ning plasmas condi ions ha e been speci ically a ge ed. II. DIAGNOSTICS UPGRADE FOR OPERATION The cu en s lowing in he 9 poloidal ield ci cui s (P1, PFX (Poloidal Field o X poin o ma ion), P4, Imbalance, Shaping, and D1–D4) a e cu en ly measu ed by h ee di e en echnologies.4Cu en measu emen d i s ha e appea ed o e he yea s and no p ope ly ecalib a ed, o igina ing a disc ep- ancy be ween wo simila measu emen s o abou 6%. E en wi h a p ope calib a ion, some diagnos ics such as “shun s” and Rogowski coils (in he in eg a o pa ) su e , o exam- ple, om empe a u e sensi i i y, which can change s ongly du ing he campaigns. I he measu emen s a e inaccu a e No e: Pape published as pa o he P oceedings o he 22nd Topical Con e - ence on High-Tempe a u e Plasma Diagnos ics, San Diego, Cali o nia, Ap il 2018. a)Elec onic mail: [email p o ec ed]g. b)See he au ho s lis o “X. Li audon e al., Nucl. Fusion 57, 102001 (2017).” (o se s), he e is con lic ing in o ma ion (be ween cu en and magne ic measu emen s) o he e alua ion o he plasma cu en p o ile, which leads o inconsis encies be ween he EFIT (Equilib ium Fi ing code)5 econs uc ed poloidal ield cu en s and he poloidal ield cu en s measu ed du ing he discha ge. Rega ding he poloidal ield cu en s acquisi ion sys em, i would be use ul o ha e a be e empo al esolu- ion since a s ong coupling be ween he plasma and P1 coil means ha high cu en s can be induced du ing a dis up ion. The ea ly phase o he cu en quench las s less han 10 ms a JET and sees he ise o elec omagne ic o ces as well as un- away elec on beams. A be e ime esolu ion o P1 cu en measu emen would imp o e unde s anding o he condi ions in which unaway elec ons a e c ea ed. Ano he impo an mo i a ion o acqui e he poloidal ield powe supplies cu en , wi h high p ecision and good empo al esolu ion (>2.5 kHz), is o unde s and how he cen al solenoid and he o he poloidal ield cu en s d i e he eco e y o he plasma cu en be ween ELMs and possibly o unde s and be e how he plasma cu - en suddenly changes as a consequence o an ELM (Edge Localized Modes). These measu emen s would p o ide a be - e e alua ion o plasma s o ed ene gy in e -ELM (Wp/Wdia) and he quan i ica ion o i s d op a e an ELM. To add ess hese issues, open-loop, open-pa h, Hall e ec cu en measu emen senso s will be ins alled ully co e ing all poloidal ield ci cui s. Imaging capabili ies ha e become an impo an ool bo h ope a ionally and o he p o ec ion 0034-6748/2018/89(10)/10K119/5/$30.00 89, 10K119-1 27 May 2025 12:51:58 10K119-2 Figuei edo e al. Re . Sci. Ins um. 89, 10K119 (2018) FIG. 1. JET isible wide angle and di e o iews acqui ed h ough op ical elay. o plasma acing componen s. An op ical elay sys em has now been pu in place, and ini ial da a (Fig. 1), o bo h he wide angle6and di e o 7 ields o iew, ha e been ob ained du ing sys em commissioning, gua an eeing ope abili y p io o plasma ope a ions. The equipmen o he co e ac i e cha ge exchange diag- nos ic sys em, essen ial o a quali y inc ease o he ion empe a u e measu emen s, has now been pu in place.8 III. DIAGNOSTIC UPGRADES FOR NEUTRON DETECTION A 12-pixel Single C ys al Diamond (SCD) ma ix has been de eloped and ins alled in he JET oo labo a o y ( adial line o sigh ).9The SCD neu on spec ome e has been de eloped o 14 MeV neu on measu emen s in DT plasmas whe e i o e s e y high ene gy esolu ion (abou 1% FWHM) combined wi h a high coun ing a e capabili y (>1 MHz). Measu emen s o 2.5 MeV neu ons om DD (Deu e ium-Deu e ium) eac ions ha e shown ha basic neu- on spec oscopy can be pe o med also o he 2.5 MeV neu ons. A single pixel SCD was ins alled ea lie in he beam dump o a neu on spec ome e 10 (wi h an oblique line o sigh ). Following his ins alla ion, good 2.5 MeV da a we e collec ed which ha e p o en ha he SCD can p o- ide use ul in o ma ion on he neu on spec um. In pa icula , he diagnos ic can p o ide in o ma ion on non- he mal neu- on emission caused by Ion Cyclo on Resonance Hea ing (ICRH). This will comple e he in o ma ion p o ided by he spec ome e s ins alled wi h a adial line o iew [TOFOR (Time-O -Fligh neu on spec ome e a Op imized Ra e), dia- mond ma ix and NE21311,12] and an oblique iew (NE213), which is impo an in o de o measu e he aniso opici y in he dis ibu ion unc ion o he hea ed uel ions. SCD spec om- e e s obse ing he neu on emissions om di e en lines o sigh in u u e D, TT (T i ium-T i ium), and DT campaigns will allow o be e sepa a ion o he neu on spec al componen s [due o he mal Neu al Beam Injec ion (NBI) and ICRH]. In DT plasmas, he SCD neu on spec ome e s will p o ide in o ma ion on he mal/non- he mal neu on emission, ICRH as ion ails, and possible ion empe a u e. The ins alla ion o a emo e con ollable high ol age powe supply and a digi- ize capable o eal ime analysis o he pulses will p o ide he capabili ies needed o ope a ions in he coming high powe FIG. 2. Expec ed neu on spec a wi h di e en componen s du ing he JET DT campaign o he SCD in oblique line o sigh . D, TT, and DT campaign. The expec ed neu on spec a o a SCD in his posi ion a e shown in Fig. 2. SCD has shown o ha e good esolu ion (Fig. 3) and spec- al capabili ies able o dis inguish sou ce composi ion. The esul s shown on Fig. 4a e measu emen s ob ained wi h a SCD o moni o he gene a o used o 14 MeV neu on calib a ion a JET. ToFu is a ully digi al upg ade o he da a acquisi ion sys em (DAS) o he TOFOR neu on spec ome e 13 a JET. The ToFu sys em o e s conside able simpli ica ion and FIG. 3. Single c ys al diamond spec ome e esolu ion. 27 May 2025 12:51:58 10K119-3 Figuei edo e al. Re . Sci. Ins um. 89, 10K119 (2018) FIG. 4. DT spec al capabili ies o single c ys al diamond. enhancemen s o he pe o mance o he spec ome e , wi h highe da a quali y and imp o ed physics analysis. The imp o ed physics possibili ies include imp o ed backg ound supp ession ha makes he spec ome e sensi i e o e en weake emission componen s in he spec um, he eby imp o - ing he possibili ies o s udies o ICRH and MHD physics, as well as exo ic neu on p oduc ion channels. The sha pe esponse unc ion opens up o simul aneous measu emen s o he weak DD emission in DT domina ed plasmas. Thus, in es- iga ion o ITER- ele an me hods o uel ion densi y a io de e mina ion will be possible, along wi h he po en ial o dis- en angle he beha io D and T sub-popula ions in DT plasmas. Implemen a ion o new on-line da a acquisi ion and educ ion modes, in pa icula in DT, could inc ease conside ably he o al numbe o e en s pe sho ha he sys em can s o e, hus imp o ing he s a is ical accu acy o he measu emen s. A p esen , he ToFu sys em is limi ed o 20 acquisi ion channels wi h some o he 37 de ec o s o he TOFOR spec ome e ha - ing o sha e channels. Fu he mo e, i is dependen on con ol signals supplied om he TOFOR DAS sys em. The e o e he ToFu sys em will be expanded o equip e e y de ec o wi h i s own acquisi ion channel while in eg a ing i in o JET da a acquisi ion and con ol sys ems. This will make he sys em uly independen o he TOFOR DAS, da a will become com- monly a ailable, and sys em o e all eliabili y will inc ease. The simula ed esponse unc ions o TOFOR and ully digi al (ToFu) acquisi ion sys ems a e shown in Fig. 5. The long ails cha ac e is ic o TOFOR o bo h 2.5 and 14 MeV neu ons a e ackled by ToFu. FIG. 5. Simula ed esponse unc ions o TOFOR and ully digi al (ToFu) acquisi ion sys ems. FIG. 6. Bic on BC418 i on bu n up expe imen al signal da a added h ough se o pulses. Ini ial da a ob ained wi h he Bic on BC418 de ec o s14 o he neu on came as, a e ins alla ion o he new digi al acqui- si ion sys em, show he i on bu n up signal added h ough a se o pulses o s a is ical pu poses (Fig. 6). IV. DIAGNOSTIC UPGRADES FOR ALPHA PARTICLES JET has an excellen se o con ined alpha-pa icle diag- nos ics, which comp ise gamma- ay spec ome e s, KM6S-1 ( e ical iew), KM6S-2 ( e ical iew), and KM6T (quasi- angen ial iew) o measu ing ene gy dis ibu ion o as ions and a 2D neu on/gamma- ay came a o omog aphic econ- s uc ion o he alpha-pa icle sou ce and he empo al e o- lu ion o i s spa ial emissi i y.15 The easibili y o alpha- ay measu emen s depends on e iciency o he neu on supp es- sion. Also, i is impo an o a oid ca bon-con aining ma e ials in he neu on a enua o because he inelas ic sca e ing o neu ons wi h ene gy exceeding 5 MeV, 12C(n,n’gamma)12C, leads o he unwelcome backg ound o 4.44-MeV gamma ays. The bes neu on a enua o is 6LiH, bu LiH wi h a na u al Li composi ion could be used as well. I is compac , e ec- i e, and well anspa en o MeV gamma- ays. I does no p oduce in e e ing gamma- ays in he high-ene gy ange. A 30-cm sample o he 6LiH- il e educes he 2.5-MeV neu- on lux ≈900 imes and he 15-MeV neu on lux ≈30 imes. The a enua o has been es ed in JET expe imen s wi h deu- e ium plasmas. Assessmen s o he gamma- ay backg ound 27 May 2025 12:51:58 10K119-4 Figuei edo e al. Re . Sci. Ins um. 89, 10K119 (2018) educ ion in he ene gy ange below 3 MeV ga e a ac o o 100. A small educ ion o he spec a ( ac o o 2) was ound in he ene gy ange abo e 3 MeV, due o he Gamma- ay ans- pa ency o he 6LiH-a enua o . The KM6S-1 de ec o (JET Oc an 8) wi h a LaB 3(Ce) scin illa o is iewing he plasma cen e e ically h ough 2-m collima o s. A simila de ec o , KM6S-2 (JET Oc an 5), is pe manen ly eco ding he spec a iewing he plasma cen e h ough a 30-cm 6LiH a enua o . Fo he DT ope a ion, an addi ional 30-45 cm LiH a enua o is needed o alpha-pa icle measu emen s in DTE2. A new LiH a enua o will be ins alled inside he exis ing S ainless S eel (SS) collima o (a e sui able modi ica ions). In Fig. 7, he posi ion o he de ec o and a enua o ela i e o he JET essel is shown. The gamma came a16–18 esul s ha e been ob ained o gammas gene a ed by unaway beams (Fig. 8). This has been done wi h he CeB 3p o o ype de ec o s ( he inal de ec o s use LaB 3c ys als) ha we e ins alled be o e he beginning o he las expe imen al campaigns. This p o ides suppo o upcoming s udies bo h a JET and in e na ionally.19–21 FIG. 7. Gamma ay de ec o and a enua o posi ion ela i e o JET. FIG. 8. Measu emen s o gamma ays gene a ed by unaway elec ons.22 FIG. 9. Gamma came a calib a ion spec a.23 FIG. 10. Recons uc ed pulse heigh spec um o he LaB 3in insic ac i i y. All he CsI de ec o s ha e now been eplaced wi h LaB 3. The inc eased capabili ies o he sys em now allow measu ing calib a ion sou ces ha we e p e iously no de ec ed (see Ba peaks in Fig. 9). CeB 3and LaB 3p o ed o ha e e y simila cha ac e - is ics wi h he decision o choose LaB 3being mainly due o he in insic ac i i y his c ys al has. This ac can be use ul o calib a ion pu poses. The ob ained spec a o he LaB 3 in insic ac i i y is show on Fig. 10. V. INSTABILITIES DIAGNOSTIC UPGRADES A JET, he edge elec on densi y p o ile can be mea- su ed by a Li beam diagnos ic (schema ic o he sys em in 27 May 2025 12:51:58 10K119-5 Figuei edo e al. Re . Sci. Ins um. 89, 10K119 (2018) FIG. 11. Schema ic o he Li Beam diagnos ic sys em a JET. Fig. 11) along a e ical line (R = 3.252 m) in oc an 7 ×24 spa ial channels wi h esolu ion o 1 cm (mapped on o he midplane). The educ ion in he exis ing Li beam cu en wobbling, by emo ing he ing ans o me om he so i on shield and e-a anging he hea ing cables, will be essen ial o blob in es- iga ion by educing an in ense equency peak in he spec al egion o in e es o such s udies and allow a as e and sa e eplacemen o he ion gun, which could be pe o med in ½ h a he han 2 h. In his way, educing he exposu e o s a o high ac i a ion a e high le el NBI discha ges and T expe - imen s would minimize he impac on JET ope a ion ime, educe he powe losses in he ans o me chain, and p o ide inc eased ope a ional space o he hea ing, which would ex end he use ul ope a ion ime o he ion gun. Fu he mo e, ELMs can ha e a signi ican impac on he de ec ed backg ound ligh le els. Thus, his should be moni o ed, i.e., beam chopping is needed o backg ound measu emen s on ime scales o in e - es . Fo JET, pedes al analysis in e ELM p o iles a e ypically eques ed. Conside ing he maximum epe i ion equency o ELMs (e.g., in he case o high gas injec ion), beam chop- ping should be ca ied ou wi h 10 kHz equency (a p esen , his can only be pe o med up o 100 Hz). The inc ease in he cu en ou pu o ≈100 mA will be achie ed by wo new powe supplies and u he sligh modi ica ions o he sys em will allow chopping wi h 10 kHz equency and wi h only mic osecond long ise ime. O he upg aded diagnos ics such as he TAE (To oidal Al ´ en Eigenmodes),24 he Fas Los Ion De ec o 25 and e lec ome y sys ems26 ha e al eady ob ained expe imen al esul s du ing he las campaigns. ACKNOWLEDGMENTS Wi h his se o diagnos ics, JET is in he p ocess o concluding an enhancemen s p og amme ha has p epa ed his de ice o upcoming DT campaigns. This wo k has been ca ied ou wi hin he amewo k o he EURO usion Con- so ium and has ecei ed unding om he Eu a om esea ch and aining p og amme 2014-2018 unde G an Ag eemen No. 633053. 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