Status of the ion trap project at IGISOL

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY 4.0 https://creativecommons.org/licenses/by/4.0/ Status of the ion trap project at IGISOL © the Authors, 2001. Published version Szerypo, Jerzy; Jokinen, Ari; Kolhinen, Veli; Nieminen, A.; Rinta-Antila, Sami; Äystö, J. Szerypo, J., Jokinen, A., Kolhinen, V., Nieminen, A., Rinta-Antila, S., & Äystö, J. (2001). Status of the ion trap project at IGISOL. Acta Physica Polonica B, 32(3), 985. http://www.actaphys.uj.edu.pl/fulltext?series=Reg&vol=32&page=985 2001 Vol. 32 (2001) ACTA PHYSICA POLONICA B No 3 STATUS OF THE ION TRAP PROJECT AT IGISOL  J. Szerypo, A. Jokinen, V.S. Kolhinen, A. Nieminen S. Rinta-Antila Department of Physis, University of Jyväskylä P.O. Box 35 (Y5), FIN-40351 Jyväskylä, Finland and J. Äystö CERN, CH-1211 Geneva 23, Switzerland (Reeived November 2, 2000) The IGISOL faility at the Department of Physis of the University of Jyväskylä (JYFL) is delivering radioative b eams of short-lived exoti nulei, in partiular the neutron-rih isotop es from the ssion reation. These nulei are studied with the nulear sp etrosopy methods. In order to substantially inrease the quality and sensitivity of suh studies the b eam should undergo b eam handling: o oling, bunhing and isobari puriation. The rst two pro esses are p erformed with the use of an RFQ o oler/bunher. The isobari puriation will b e made by a Penning trap plaed after the RF-o oler element. This ontribution desrib es the urrent status of the ion trap pro jet and its future prosp ets. The latter omprise the preise nulear mass measurements, nulear spetrosopy in the Penning trap interior as well as the laser sp etrosopy on the extrated b eams. PACS numbers: 39.10.+j 1. Intro dution A pro jet for improving the quality of radioative ion b eams pro dued at IGISOL [1℄ has b een started in 1997 [2, 3℄. Basi parameters of a radioative b eam at IGISOL presently are: b eam energy spread  E  80 eV, transverse emittane   10  mm mrad and mass resolving p ower R = M =  M = 2001000. In order to enhane the quality of exp eriments at IGISOL it was neessary to improve the radioative b eam quality. The goal was to obtain:  Presented at the XXXV Zakopane Sho ol of Physis Trends in Nulear Physis, Zakopane, Poland, September 513, 2000. (985) 986 J. Szerypo et al.  E  1 eV,   1  mm mrad and R = 10 5 . The latter means a p ossibility of rejeting even isobari ontaminants, obtaining a pure monoisotopi b eam. This improvement will b e ahieved due to radioative b eam handling, whih onsists of three steps: b eam o oling (whih improves b oth  E and  ), bunhing and puriation (due to high R ). The rst two steps are done with use of an RFQ o oler/bunher (see [4℄). The b eam puriation is p erformed with the use of a ylindrial Penning trap similar to the one desrib ed in Ref. [5℄. 2. Pro jet desription The RFQ o oler/bunher [4℄ exists at JYFL already. Its p erformane as follows:  E = 0 : 6 eV,   1 2  mm mrad, transmission TR > 60 % and o oling time around 1 ms. Bunhing p ossibility was also demonstrated. In the Penning trap ase, mass-seletive buer gas o oling tehnique [6℄ will b e used for puriation. In order that the puriation ould take plae, the trap interior has to b e lled with a buer gas at low pressure (10  3 10  4 mbar), usually helium. A low-energy (of the order of 100 eV) ion b eam oming from the RFQ o oler/bunher is aptured in the trap enter and then the buer gas o oling an start. For this purp ose, the entral ring eletro de is segmented azimuthally into 4 segments. The segments are supplied with an osillating RF-p otential so that an osillating quadrup ole eld in the azimuthal plane is reated. The RF-frequeny is hosen so that it is equal to the ylotron frequeny of the ions of interest, whih are usually mixed with other, ontaminating ions. The joint ation of the RF-eld and the buer gas is o oling and entering the ions of interest on the trap axis, whereas ontaminants are not entered. The ions of interest are then ejeted through a small hole in the endap of the trap. This pro ess an have a high mass resolving p ower, of the order of 10 5 , whih p ermits to rejet even isobari ontaminants [5℄. This is partiularly imp ortant for the exp erimental program at IGISOL, whih in future will b e entered on exoti neutron-rih nulei, pro dued in ssion. The isobari puriation will allow for rejeting of all unwanted memb ers of the isobari hain, leaving only a sp eies of interest. This will signiantly improve signal-to-bakground ratio, sensitivity and preision of the exp eriments, and will extend the range of the isotop es investigated. The task of the puriation Penning trap at IGISOL is to p erform the isobari puriation and to deliver lean, monoisotopi b eams for nulear and laser sp etrosopy as well as preise nulear mass measurements. In order to ahieve this goal, it is planned to plae the Penning trap inside a B = 7 T sup eronduting magnet. This magnet was delivered already by Magnex Sienti Ltd. and installed at the IGISOL area in Novemb er Status of the Ion Trap Projet at IGISOL 987 1999 (see Fig. 1). It is a solenoid with two homogeneous magneti eld regions (inhomogeneities within 1 m 3 volume b elow 10  6 and 10  7 , resp e- tively). The isobari puriation of radioative b eam will b e p erformed in the ylindrial Penning trap p ositioned in the rst region. As mentioned, it will substantially enhane the sensitivity and preision of ollinear laser and nulear sp etrosopy exp eriments. The former will prot already of the presene of the RFQ o oler/bunher, delivering a bunhed b eam with very go o d emittane [4℄. Fig. 1. The 7 T sup eronduting solenoid. The seond step of the ion trap development will onsist of building a se- ond Penning trap for the preise nulear mass measurements of radioative ions. It will b e plaed diretly after the puriation trap in the same sup eronduting magnet, in the seond homogeneous magneti eld region. A trap of a ylindrial typ e will b e used, whih should assure the measurement auray of 10  6 10  7 . It will enable mass measurements of many neutronrih isotop es not reahable anywhere else ( e.g. of refratory elements) and will signiantly broaden exp erimental program at IGISOL. In the third step of Penning trap development, nulear sp etrosopy in a Penning trap interior is foreseen. This means plaing the detetors of a needed typ e diretly inside the trap and p ositioning the radioative sample in 988 J. Szerypo et al. front of them. Suh a sheme has ertain advantages over onventional sp e- trosopy, like very go o d quality radioative soure (very thin, small size, no baking, free of intensity attenuation, energy degradation and baksattering problems), minimization (in a given detetor) bakground ontribution from other typ es of radiation, and an eient passive shielding for bakground radiation with the magnet ryostat. It is planned to install and test the puriation trap in the year 2000. A part of the neessary vauum omp onents ( e.g. turb o-pumps) has b een delivered already. The eletronis and ontrol system (LabVIEW based) are under development. The Penning trap system is done in lose ollab oration with GSI Darmstadt, where a similar trap pro jet SHIPTRAP aiming at exp eriments with transuranium isotop es [7℄ is in preparation. The ion trap development at IGISOL is done in a ollab oration with other nulear physis lab oratories group ed in a Europ ean network EXOTRAPS (JYFL is a o ordinator of this network). Within this ollab oration, IGISOL group has partiipated (Novemb er 1999) in preise nulear mass measurements with the ISOLTRAP Penning trap set-up at ISOLDE, CERN [8℄. Then, the mass of 33 Ar (auray of 10  7 ) with T 1 = 2 = 174 ms was measured (see [9℄). Thus, the nulei with half-lives of the order of 0.1 s should also b e available in the future for preise nulear mass measurements at IGISOL. This work was supp orted by the Aademy of Finland under the Finnish Centre of Exellene Program 2000-2005 (Pro jet No. 44875, Nulear and Condensed Matter Program at JYFL) and by the EXOTRAPS pro jet in the EU LSF-RTD program under ontrat no. ERBFMGECT980099. REFERENCES [1℄ P. Dendo oven, Nul. Instrum. Methods Phys. Res. B126 , 182 (1997). [2℄ A. Jokinen et al. , JYFL Annual Rep ort 15 , (1997). [3℄ A. Nieminen et al. , JYFL Annual Rep ort 16 , (1998). [4℄ A. Nieminen et al. , JYFL Annual Rep ort 17 , (1999). [5℄ H. Raimbault-Hartmann et al., Nul. Instrum. Methods Phys. Res. B126 , 378 (1997). [6℄ G. Savard et al., Phys. Lett. A158 , 247 (1991). [7℄ J. Dilling et al., Hyperne Interat. 127 , 491 (2000). [8℄ G. Bollen et al., Nul. Instrum. Methods Phys. Res. A368 , 675 (1996). [9℄ F. Herfurth et al., Phys. Rev. Lett. , to b e published.