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HK: Fachverband Physik der Hadronen und Kerne

HK 81: Instrumentation

HK 81.1: Gruppenbericht

Donnerstag, 7. März 2013, 16:45–17:15, WIL-A221

On-Line Commissioning of the Cryogenic Stopping Cell for the (Super-)FRS at the FRS Ion Catcher — •Moritz Pascal Reiter — II. Physikalisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany

At the FRS projectile and fission fragments are produced at relativistic energies, separated in-flight, range-bunched, slowed-down and thermalized in the FRS Ion Catcher, a cryogenic stopping cell (CSC), from which they are extracted with kinetic energies of a few eV. A multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) is used as a diagnostic tool for the extracted ions, to remove isobaric contaminants and to perform direct mass measurements of the projectile and fission fragments. The achieved clean beam may be delivered to further experiments, for example mass-selected decay spectroscopy. The FRS Ion Catcher serves as a test facility for the Low-Energy-Branch of the Super-FRS at FAIR, where the CSC and the MR-TOF-MS will be key devices for experiments with very neutron rich fission fragments.
In October 2011 and July/August 2012, the CSC and the MR-TOF-MS were commissioned on-line at the FRS Ion Catcher at GSI. 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 projectile fragments were thermalized and extracted with high efficiencies and short extraction times. For the first time, direct mass measurements of short-lived nuclei were performed with an MR-TOF-MS, among them the nuclide 213Rn with a half-life of only 20 ms.