https://doi.org/10.1140/epjs/s11734-025-01605-z
Review
Technical design report for the cryogenic stopping cell of the Super-FRS at FAIR
1
II. Physikalisches Institut, Justus-Liebig-Universität Gießen, Gießen, Germany
2
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
3
University of Valencia, Valencia, Spain
4
University of Groningen, Groningen, The Netherlands
5
University of Edinburgh, Edinburgh, UK
6
Helmholtz Research Academy Hesse for FAIR (HFHF), GSI Helmholtz Center for Heavy Ion Research, Campus Gießen, Gießen, Germany
7
Extreme Light Infrastructure-Nuclear Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, Magurele, Romania
8
Department of Aerospace Sciences, Politehnica University of Bucharest, Bucharest, Romania
9
Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany
10
School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel
11
Soreq Nuclear Research Center, Yavne, Israel
12
University of Jyväskylä, Jyväskylä, Finland
13
Doctoral School in Engineering and Applications of Lasers and Accelerators, University Polytechnica of Bucharest, Bucharest, Romania
14
Institute for Analytical Instrumentation, Russian Academy of Sciences, St. Petersburg, Russia
15
PARTREC & Department of Radiation Oncology, University Medical Center Groningen, Groningen, The Netherlands
16
Department of Physics, Indian Institute of Technology (Indian School of Mines) Dhanbad, Jharkhand, India
Received:
31
December
2024
Accepted:
31
March
2025
Published online:
8
May
2025
Precision experiments with thermalized exotic nuclei will be possible at the super-conducting fragment separator Super-FRS at the Facility for Antiproton and Ion Research (FAIR). In the Early Science/First Science programs of FAIR, they will be performed at the focal plane FHF1 of the Super-FRS (in front of the High-Energy Branch) and, at a later stage during First Science++, also at the Low-Energy Branch. Exotic nuclei will be produced in flight and separated in the Super-FRS and their momentum spread will be reduced by energy-bunching. The ions will be further slowed down in a homogeneous degrader, thermalized in a gas-filled stopping cell, and extracted and transferred to the experimental setups. The stopping cell is, thus, a key device for experiments with thermalized exotic nuclei, and its performance characteristics will have a strong impact on the range of nuclides available and their yields, since its stopping and extraction efficiencies and extraction times strongly influence the rate of the extracted nuclei and put a limit on their lifetimes.
In combination with a multiple-reflection time-of-flight mass spectrometer, the stopping cell will enable the measurement of masses, branching ratios, e.g., -delayed (multi-)neutron emission probabilities, and lifetimes, as well as the in-cell production of exotic nuclei by multi-nucleon transfer with primary and secondary beams. Moreover, it will be a tool for the absolute calibration of the particle identification in the Super-FRS. Furthermore, using the combination of accurate mass determination with the PID of the Super-FRS on an event-by-event basis, completely new experimental possibilities will become available, such as the identification of millisecond isomers at the Super-FRS and the measurement of the dependence of the isomer-to-ground-state ratios on the production mechanism. These studies will be pursued in the context of the Super-FRS Experiment Collaboration.
At the Low-Energy Branch, high-accuracy mass measurements, in-trap conversion electron and alpha spectroscopy, and trap-assisted spectroscopy will be performed with MATS (Precision Measurements of very short-lived nuclei using an Advanced Trapping System for highly charged ions). Measurements of nuclear spins, magnetic dipole and electric quadrupole moments, and root-mean-square charge radii will be carried out using collinear laser spectroscopy on ions and atoms and beta-NMR experiments with LaSpec (Laser Spectroscopy of short-lived nuclei). These experiments will address a wide scientific field ranging from nuclear structure and nuclear astrophysics to tests of the weak interaction and of the Standard Model.
For the Super-FRS, a stopping cell with an areal density of is required, with a cross-section of the stopping volume of
, a high extraction efficiency that is element-independent, an extraction time on the order of 10 ms, and a rate capability of
ions/s up to a nuclear charge of Z=92. Furthermore, the stopping cell needs to deliver bunches of ions with high purity. No existing stopping cell is capable of reaching these performance characteristics simultaneously. To fulfill these requirements, a novel concept for gas-filled stopping cells has been developed. It is based on the cryogenic stopping cell of the FRS Ion Catcher, and, in addition, it implements the two-stage extraction of the thermalized ions in a direction orthogonal to the incoming ion beam (high-areal-density orthogonal-extraction cryogenic stopping cell, HADO-CSC). This will boost all performance characteristics of the stopping cell and thus remove the performance bottleneck of present stopping cells for the thermalization of exotic nuclei produced at relativistic energies.
This publication is an updated version of the Technical Report for the Design, Construction and Commissioning of the Cryogenic Stopping Cell of the Super-FRS, which was evaluated and approved previously by the Expert Committee Experiments of the Facility for Antiproton and Ion Research (FAIR).
© The Author(s) 2025
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