Within this PhD project, key cases of interest will be identified and studied in detail for high-purity radioactive isotopes production through molecular sidebands formation. Specific attention will be paid to isotopes of refractory elements such as Os, which are not accessible with the current ISOL methods and to isotopes that show promise for pharmaceutical application.
Molecular sideband formation through interaction of reactive gases (oxygen, sulfur, halogens, …) with irradiated refractory targets (UCx, Ta, ...) will be first studied by theoretical methods. The complex chemical equilibria that result from these interactions will be studied by the Gibbs energy minimization technique coupled with databases of known thermochemical properties of refractories and their compounds. Ab initio calculations will be used to estimate specific thermochemical properties, in case these are missing. These theoretical studies will allow identifying chemically feasible systems and will put limits on target operating conditions, which is required input for basic experiments and further optimization studies. The theoretical studies will be benchmarked against previous successes of the molecular sidebands technique, such as the very recent production of germanium beams using sulfur gas.
Systems that proved to be chemically feasible will be validated in experiments with stable isotopes using the high temperature evaporation equipment at SCK-CEN. Target materials that contain the element of interest will need to be prepared. A system that is able to dose reactive gases to a high temperature evaporation chamber will be constructed. With such a setup, the release of the element of interest from the target can be characterized, either by off line detection methods (such as ICP-MS) or by on-line mass spectrometry. Target composition, morphology or dispersion may need to be varied in order to optimize the release.
The most promising systems will be tested under proton-beam irradiation. Such experiments will be performed in the frame of the BeamLab collaboration, which includes accelerator facilities such as ALTO, CERN, GANIL and INFN.