Abstract

At the FRS Ion Catcher (FRS-IC), projectile and fission fragments are produced at relativistic energies, separated in-flight, energy-bunched, slowed down, and thermalized in the ultra-pure helium gas-filled cryogenic stopping cell (CSC). Thermalized nuclei are extracted from the CSC using a combination of DC and RF electric fields and gas flow. This CSC also serves as the prototype for the CSC of the Super-FRS, where exotic nuclei will be produced at unprecedented rates making it possible to go towards the extremes of the nuclear chart. Therefore, it is essential to efficiently extract thermalized exotic nuclei from the CSC under high beam rate conditions, in order to use the rare exotic nuclei, which come as cocktail beams. The dependence of the extraction efficiency on the intensity of the impinging beam into the CSC was studied with a primary beam of 238U and its fragments. Tests were done with two different versions of the DC electrode structure inside the cryogenic chamber, the standard 1 m long and a short 0.5 m long DC electrode systems. In contrast to the rate capability of 104 ions/s with the long DC electrode system, results show no extraction efficiency loss up to the rate of 2 × 105 ions/s with the new short DC electrode. This order of magnitude increase of the rate capability paves the way for new experiments at the FRS-IC, including studies of exotic nuclei with in-cell multi-nucleon transfer reactions. The results further validate the design concept of the CSC of the Super-FRS, which was developed to effectively manage beams of even higher intensities.

Funding

FundersFunder number
GSI Helmholtzzentrum fuer Schwerionenphysik
HMWK
OCPC20191034
Office of China Postdoctoral Council
Polish Minister of Science and Higher Education2022–2024, Nr 5237/GSI-FAIR/2022/0
Romanian Ministry of Research, Innovation and Digitalization
Helmholtz Graduate School for Hadron and Ion ResearchPN 23.21.01.06
Helmholtz Graduate School for Hadron and Ion Research
Bundesministerium für Bildung und Forschung05P21RGFN1, 05P19RGFN1, 05P16RGFN1
Bundesministerium für Bildung und Forschung
Hessisches Ministerium für Wissenschaft und Kunst
Ludwig-Maximilians-Universität MünchenLMTHI2023
Ludwig-Maximilians-Universität München
ExtreMe Matter Institute, GSI Helmholtzzentrum für Schwerionenforschung

    Keywords

    • Cryogenic stopping cell
    • Exotic nuclei
    • Extraction efficiency
    • Gas cell
    • Rate capability

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