Online coupling and beam preparation for the TRIGA-SPEC experiment

Precise experimental data of the ground-state properties of short-lived nuclides are required to test the predictive power of nuclear mass models and to support nucleosythesis calculations of the astrophysical r-process. Besides the measurement of these properties with high precision, the creation and preparation of the nuclides of interest is one of the biggest challenges in this field of physics. So far, mostly the proton-rich side of the nuclear chart could be reached at various research facilities by bombarding a heavy target with light particles. For the TRIGA-SPEC experiment located at the TRIGA reactor in Mainz, nuclides of the neutron-rich side of the nuclear chart can be created by neutron-induced fission of an actinide target inside the reactor. The online coupling is going to be realized with an aerosol-loaded gas-jet system, an ion source, a separator magnet, and an RFQ quadrupole for ion beam cooling and bunching. The coupling of the already working mass spectrometer TRIGA-TRAP and laser-spectroscopy setup TRIGA-LASER to the reactor will be finished in the near future. An overview of the online coupling and the ion beam preparation as well as possible alternatives is presented. The TRIGA-TRAP mass spectrometer and the TRIGA-LASER laser spectroscopy setup, forming the TRIGA-SPEC experiment, were recently installed at the research reactor TRIGA Mainz in order to perform high-precision measurements of the ground state properties of short-lived neutron-rich radionuclides in the mass range 80<A<140. The radionuclides are produced by thermal neutron-induced fission in an actinide target inside the reactor, extracted by a gas-jet system, and ionized by an ECR ion source. The ions of interest will then be mass-separated in a 90 circle dipole magnet. An RFQ buncher is being installed to accumulate, cool and bunch the ion beam. It will reduce the ion beam's emittance using buffer gas cooling in Helium and accumulate bunches of up to 105 singly-charged ions. A following switchyard will then connect TRIGA-TRAP and TRIGA-LASER to the extraction part of the setup. The status of the implementation of the dipole magnet and the RFQ buncher is presented. TRIGA-TRAP is so far the only Penning-trap mass spectrometer installed at a nuclear research reactor worldwide. Its scientific goal is the high-precision mass measurement of neutron-rich fission products being prepared in the TRIGA reactor in Mainz. Precise experimental mass data in the region towards the island of stability of the nuclear chart are required to test nuclear mass models and to support the nucleosynthesis calculations of the astrophysical r-process. The production of the nuclides of interest is performed by thermal neutron-induced fission of an actinide target with rates of a few nuclides per second or less.