Rate capability of a cryogenic stopping cell for uranium projectile fragments produced at 1000 MeV/u

详细信息    查看全文

• 作者：M.P. Reiter^a ; A.-K. Rink^a ; ¹ ; T. Dickel^a ; ^b ; E. Haettner^a ; ^b ; F. Heiß ; e^a ; ^b ; ^c ; W.R. Plaß ; ^a ; ^b ; ^{Wolfgang.R.Plass@exp2.physik.uni-giessen.de" class="auth_mail" title="E-mail the corresponding author} ; S. Purushothaman^b ; F. Amjad^b ; S. Ayet San André ; s^a ; ^b ; J. Bergmann^a ; D. Blum^b ; P. Dendooven^d ; M. Diwisch^a ; J. Ebert^a ; H. Geissel^a ; ^b ; F. Greiner^a ; C. Hornung^a ; C. Jesch^a ; N. Kalantar-Nayestanaki^d ; R. Knö ; bel^a ; ^b ; J. Lang^a ; W. Lippert^a ; I. Miskun^a ; ^b ; I.D. Moore^e ; C. Nociforo^b ; M. Petrick^a ; S. Pietri^b ; M. Pfü ; tzner^b ; ^f ; I. Pohjalainen^e ; A. Prochazka^b ; C. Scheidenberger^a ; ^b ; M. Takechi^b ; Y.K. Tanaka^b ; H. Weick^b ; J.S. Winfield^b ; X. Xu^a ; ^b
• 关键词：Cryogenic gas-filled stopping cell ; Rate capability ; Space charge ; Extraction efficiency ; Extraction time
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2016
• 出版时间：1 June 2016
• 年：2016
• 卷：376
• 期：Complete
• 页码：240-245
• 全文大小：1031 K

文摘

At the Low-Energy Branch (LEB) of the Super-FRS at FAIR, projectile and fission fragments will be produced at relativistic energies, separated in-flight, energy-bunched, slowed down and thermalized in a cryogenic stopping cell (CSC) filled with ultra-pure He gas. The fragments are extracted from the stopping cell using a combination of DC and RF electric fields and gas flow. A prototype CSC for the LEB has been developed and successfully commissioned at the FRS Ion Catcher at GSI. Ionization of He buffer gas atoms during the stopping of energetic ions creates a region of high space charge in the stopping cell. The space charge decreases the extraction efficiency of stopping cells since the high amount of charge distorts the applied DC electric drag fields. Thus the understanding of space charge effects is of great importance to make full use of the high yields at future RIB facilities such as the Super-FRS at FAIR. For this purpose a detailed study of space charge effects in the CSC was performed using experiments and simulations. The dependence of the extraction efficiency, the extraction time and the temporal ion extraction profile on the intensity of the impinging beam and the electric field strength was studied for two different ²³⁸${}^{238}$U projectile fragments produced at 1000 MeV/u and separated with the FRS. Good agreement between experiments and simulations was found.