The FRS Ion Catcher - A facility for high-precision experiments with stopped projectile and fission fragments

详细信息    查看全文

• 作者：W.R. Pla脽 ; T. Dickel ; S. Purushothaman ; P. Dendooven ; H. Geissel ; J. Ebert ; E. Haettner ; C. Jesch ; M. Ranjan ; M.P. Reiter ; H. Weick ; F. Amjad ; S. Ayet ; M. Diwisch ; A. Estrade ; F. Farinon ; F. Greiner ; N. Kalantar-Nayestanaki ; R. Kn枚bel ; J. Kurcewicz ; et al.
• 关键词：Cryogenic gas-filled stopping cell ; Extraction time ; Multiple-reflection time-of-flight mass spectrometer ; Direct mass measurement ; Projectile fragmentation ; Exotic nuclei
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：15 December, 2013
• 年：2013
• 卷：317
• 期：part_PB
• 页码：457-462
• 全文大小：1266 K

文摘

At the FRS Ion Catcher at GSI, projectile and fission fragments are produced at relativistic energies, separated in-flight, range-focused, slowed down and thermalized in a cryogenic stopping cell. A multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) is used to perform direct mass measurements and to provide an isobarically clean beam for further experiments, such as mass-selected decay spectroscopy. A versatile RF quadrupole transport and diagnostics unit guides the ions from the stopping cell to the MR-TOF-MS, provides differential pumping, ion identification and includes reference ion sources. The FRS Ion Catcher serves as a test facility for the Low-Energy Branch of the Super-FRS at the Facility for Antiproton and Ion Research (FAIR), where the cryogenic stopping cell and the MR-TOF-MS will be key devices for the research with stopped projectile and fission fragments that will be performed with the experiments MATS and LaSpec. Off-line tests of the stopping cell yield a combined ion survival and extraction efficiency for ²¹⁹Rn ions of about 30% and an extraction time of about 25 ms. The stopping cell and the MR-TOF-MS were commissioned on-line as part of the FRS Ion Catcher. For the first time, a stopping cell for exotic nuclei was operated on-line at cryogenic temperatures. Using a gas density almost two times higher than ever reached before for a stopping cell with RF ion repelling structures, various ²³⁸U projectile fragments were thermalized and extracted with very high efficiency. Direct mass measurements of projectile fragments were performed with the MR-TOF-MS, among them the nuclide ²¹³Rn with a half-life of 19.5 ms only.