Special Article - New Tools and Techniques
A concept for the extraction of the most refractory elements at CERN-ISOLDE as carbonyl complex ions
Accelerator Systems Department, CERN, Geneva, Switzerland
2 Department of Chemistry - TRIGA Site, Johannes Gutenberg University, Mainz, Germany
3 GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
4 Helmholtz-Institut Mainz, Mainz, Germany
5 Department of Physics, Johannes Gutenberg University, Mainz, Germany
6 Laboratory of Powder Technology, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
7 Department of Physics, University of Gothenburg, Gothenburg, Sweden
8 FRIB, 640 S. Shaw Lane, 48824, East Lansing, MI, USA
9 SCK CEN, Boeretang 200, 2400, Mol, Belgium
Accepted: 17 April 2022
Published online: 17 May 2022
We introduce a novel thick-target concept tailored to the extraction of refractory 4d and 5d transition metal radionuclides of molybdenum, technetium, ruthenium and tungsten for radioactive ion beam production. Despite the more than 60-year old history of thick-target ISOL mass-separation facilities like ISOLDE, the extraction of these most refractory elements as radioactive ion beam has so far not been successful. In ordinary thick ISOL targets, their radioisotopes produced in the target are stopped within the condensed target material. Here, we present a concept which overcomes limitations associated with this method. We exploit the recoil momentum of nuclear reaction products for their release from the solid target material. They are thermalized in a carbon monoxide-containing atmosphere, in which volatile carbonyl complexes form readily at ambient temperature and pressure. This compound serves as volatile carrier for transport to the ion source. Excess carbon monoxide is removed by cryogenic gas separation to enable low pressures in the source region, in which the species are ionized and hence made available for radioactive ion beam formation. The setup is operated in batch mode. Initially, we investigate the feasibility of the approach with isotopes of more than 35s half-life. At the cost of reduced efficiency, the concept could also be applied to isotopes with half-lives of at least one to 10s. We report parameter studies of the key processes of the method, which validate this concept and which define the parameters for the setup. This would allow for the first time the extraction of radioactive molybdenum, tungsten and several other transition metals at thick-target ISOL facilities.
© The Author(s) 2022
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