Isobar separation by time-of-flight mass spectrometry for low-energy radioactive ion beam facilities

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• 作者：Wolfgang R. Plaß ; Timo Dickel ; Ulrich Czok ; Hans Geissel ; Martin Petrick ; Katrin Reinheimer ; Christoph Scheidenberger ; Mikhail I.Yavor
• 关键词：Isobar separator ; Multiple-reflection time-of-flight mass spectrometer ; RF Ion trap ; Mass measurements ; Exotic nuclei
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2008
• 出版时间：October 2008
• 年：2008
• 卷：266
• 期：19-20
• 页码：4560-4564
• 全文大小：292 K

文摘

A multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) system for low-energy radioactive ion beam facilities has been developed, which can be used for (i) isobar separation and (ii) direct mass measurements of very short-lived nuclei with half-lives of about 1 ms or longer, and (iii) for identification and diagnosis of the ion beam by mass spectrometry. The system has been designed and simulated, and individual subsystems have been built and characterized experimentally. An injection trap for cooling and bunching of the ion beam has been developed, and cooling times of less than one millisecond have been achieved. The performance of the MR-TOF-MS was characterized using the isobaric doublet of carbon monoxide and nitrogen molecular ions. A mass resolving power of 10⁵ (FWHM) has been obtained even with an uncooled ion population. The separator capabilities of the MR-TOF-MS have been demonstrated by removing either carbon monoxide or nitrogen ions from the beam in a Bradbury-Nielsen Gate after a flight time of 320 μs. The separation power achieved is thus at least 7000 (FWHM) and increases for longer time-of-flight. An energy buncher stage has been designed that compresses the energy spread of the beam after the separation and facilitates efficient injection of the selected ions into an accumulation trap prior to transfer of the ions to experiments downstream of the MR-TOF-MS.