A high-performance multiple-reflection time-of-flight mass spectrometer and isobar separator for the research with exotic nuclei T. Dickel a,b , W.R Plaß a,b,n , A. Becker a , U. Czok a , H. Geissel a,b , E. Haettner a,b , C. Jesch a , W. Kinsel a,b , M. Petrick a , C. Scheidenberger a,b , A. Simon a , M.I. Yavor c Q1 a II. Physikalisches Institut, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany b GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany c Institute for Analytical Instrumentation, Russian Academy of Sciences, St. Petersburg, Russia article info Article history: Received 11 September 2014 Received in revised form 23 December 2014 Accepted 23 December 2014 Keywords: Time-of-flight mass spectrometer Multiple reflection Isobar separator Direct mass measurement Exotic nuclei abstract A novel multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) and isobar separator for the research with exotic nuclides at low-energy rare isotope beam facilities has been developed, commis- sioned and characterized. It can be used (i) as broadband mass spectrometer with medium resolution, (ii) as highly accurate mass spectrometer for direct mass measurements and (iii) as high-resolution mass separator. The device features a worldwide unique combination of performance characteristics: a mass resolving power of 600,000 (FWHM), a mass measurement accuracy of  10  7 , large ion capacities in excess of 10 6 ions per second, a transmission efficiency of up to 70%, single-ion sensitivity, and cycle frequencies of up to 400 Hz have been achieved. The spatial separation of close-lying isobars with an intensity ratio of 200:1 and a binding energy difference as small as 4 MeV have been demonstrated. The MR-TOF-MS is ideally suited for experiments with rare and very short-lived nuclei at present and future in-flight, ISOL or IGISOL facilities, such as the FRS Ion-Catcher and SHIP/SHIPTRAP at GSI, TITAN at TRIUMF, IGISOL at the University of Jyväskylä and the Low-Energy Branch of the Super-FRS at FAIR. & 2014 Elsevier B.V. All rights reserved. 1. Introduction In recent years much progress has been made in the research with exotic nuclei [1,2]. Experiments with exotic nuclei yield key information about nuclear structure and about the origin of the chemical elements in the universe. Further advances, such as closer access to nuclides along the nucleosynthesis pathways, will be achieved at next-generation accelerator facilities, which are presently under construction (such as the Facility for Antiproton and Ion Research FAIR in Darmstadt, Germany, SPIRAL2 at GANIL, France and the Facility for Rare Isotopes FRIB at Michigan State University, USA) or already in operation (RI-beam factory RIBF at RIKEN, Japan). It is difficult to produce very exotic nuclei in sufficient amounts and purity and to study their properties. Even existing facilities face serious challenges for experiments with exotic nuclei in the form of life time limitations caused by the cycle time of the experiments and the overwhelming amount of con- taminants produced together with the nuclides of interest. These challenges will intensify at future facilities, as the primary beam intensities are increased and more exotic species can be produced. A new approach to precision experiments with exotic nuclei is the production and in-flight separation of the nuclei and their subsequent slowing-down and thermalization in gas-filled stop- ping cells [3]. It enables precision experiments with ions almost at rest, including mass measurements in ion traps, high-resolution decay spectroscopy, and laser spectroscopy, while retaining the advantages of the in-flight method of fast and universal produc- tion. Alternatively, exotic nuclei can be made available with low kinetic energies at conventional ISOL or at IGISOL facilities. At all these low-energy rare isotope beam (RIB) facilities the fast, universal, sensitive and broadband identification of ions is an additional challenge, which must be met in order to efficiently perform and optimize experiments. Time-of-flight mass spectrometry (TOF-MS) allows for fast and broadband measurements as well as for high transmission effi- ciency and single-ion sensitivity. It is hence an ideal tool to address these issues. However, hitherto the mass resolving power obtained by TOF-MS has been limited to a few ten thousand, which is not sufficient for the resolution of most atomic isobars. The most important limitation is the turn-around time [4] caused by the initial, viz. thermal, velocity spread of the ions prior to accelera- tion. It leads to different flight times even for otherwise identical 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A http://dx.doi.org/10.1016/j.nima.2014.12.094 0168-9002/& 2014 Elsevier B.V. All rights reserved. n Corresponding author at: II. Physikalisches Institut, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany. Tel.: þ49 641 99 33253. E-mail address: Wolfgang.R.Plass@exp2.physik.uni-giessen.de (W. Plaß). Please cite this article as: T. Dickel, et al., Nuclear Instruments & Methods in Physics Research A (2015), http://dx.doi.org/10.1016/j. nima.2014.12.094i Nuclear Instruments and Methods in Physics Research A ∎ (∎∎∎∎) ∎∎∎–∎∎∎