R. Ferrer

TRIGA-SPEC: A setup for mass spectrometry and laser spectroscopy at the research reactor TRIGA Mainz

Abstract The research reactor TRIGA Mainz is an ideal facility to provide neutron-rich nuclides with production rates sufficiently large for mass spectrometric and laser spectroscopic studies. Within the TRIGA-SPEC project, a Penning trap as well as a beamline for collinear laser spectroscopy are being installed. Several new developments will ensure high sensitivity of the trap setup enabling mass measurements even on a single ion. Besides neutron-rich fission products produced in the reactor, also heavy nuclides such as 235 U or 252 Cf can be investigated for the first time with an off-line ion source. The data provided by the mass measurements will be of interest for astrophysical calculations on the rapid neutron-capture process as well as for tests of mass models in the heavy-mass region. The laser spectroscopic measurements will yield model-independent information on nuclear ground-state properties such as nuclear moments and charge radii of neutron-rich nuclei of refractory elements far from stability. TRIGA-SPEC also serves as a test facility for mass and laser spectroscopic experiments at SHIPTRAP and the low-energy branch of the future GSI facility FAIR. This publication describes the experimental setup as well as its present status.

Precise mass measurements of exotic nuclei—the SHIPTRAP Penning trap mass spectrometer

The SHIPTRAP Penning trap mass spectrometer has been designed and constructed to measure the mass of short‐lived, radioactive nuclei. The radioactive nuclei are produced in fusion‐evaporation reactions and separated in flight with the velocity filter SHIP at GSI in Darmstadt. They are captured in a gas cell and transfered to a double Penning trap mass spectrometer. There, the cyclotron frequencies of the radioactive ions are determined and yield mass values with uncertainties ⩾4.5⋅10−8. More than 50 nuclei have been investigated so far with the present overall efficiency of about 0.5 to 2%.

Mass measurements of exotic nuclides at SHIPTRAP

The Penning trap mass spectrometer SHIPTRAP is installed behind the velocity‐filter SHIP at GSI for high‐precision mass measurements of fusion‐evaporation residues. To facilitate an efficient stopping of the reaction products a buffer gas stopping cell is utilized. In an investigation of neutron‐deficient nuclides in the terbium‐to‐thulium region around A ≈ 146, 18 new or improved mass values have been obtained, resulting in a more accurate determination of the proton drip line for holmium and thulium. With the present performance of SHIPTRAP, a first direct mass measurement of transuranium elements in the nobelium region is within reach.