Current status of the MR-TOF-MS at the FRS ion catcher

The multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) is part of the FRS Ion Catcher, which is a test facility for the future Low-Energy Branch (LEB) of the Super-FRS at FAIR. At the FRS Ion Catcher, projectile and fission fragments are produced at relativistic energies, separated in-flight and range-focused at the FRS. Further they are slowed-down and thermalized in a cryogenic stopping cell (CSC) to kinetic energies of a few eV. In the MR-TOF-MS the ions are accumulated, cooled and ejected in bunches by a linear RF-trap. In the analyzer they are reflected multiple times to enlarge their flight path by orders of magnitude to enhance the resolution. The MR-TOF-MS can perform high precision mass measurements and in addition it can separate the ion of interest from isobaric contaminations for further experiments. It is a well suitable diagnostic device for operation of the CSC. The performance of the MR-TOF-MS has been enhanced by increasing the kinetic energy of the ions to 1300 eV and improving the stability of the voltages. In the recent experiment the mass resolving power has been increased to exceed 400.000 FWHM for several fission fragments.