Development of an ECR ion source for the mass separation of xenon radioisotopes

The electron cyclotron resonance (ECR) principle has been studied for mass separation applications. The main features of ECR ion sources make them ideally suited for online mass separation. For this reason a single stage 6.4 GHz test source for the separation of 123Xe/125Xe was built at the Paul Scherrer Institute (PSI). This report describes design, construction and testing of the source in detail. Use was made of basic design ideas of the experimentally successfull Karlsruhe source of Bechtold and Sheikh. Due to their fundamental simplicity, almost all single stage sources show the same main features: a set of Helmholtz-coils to induce the axial magnetic field, radial microwave injection, a Sm2Co17-hexapole inside a multimode cavity, two concentric quartz tubes as vacuum and plasma volumes. The source development took place at a scandinavian type mass separator equipped with a 55o-doublefocusing magnet. About 1200 h of operation were accumulated and experimental data was collected reliably. A screening experimental design was used to identify the most important parameters. The effect of these parameters was investigated qualitatively as well as quantitatively and optimal ranges for source pressure, microwave power and axial magnetic field were determined. Under these operating conditions, an efficiency of 57% was achieved for singly charged Xe with H2 as support gas. Optimal parameter ranges were verified running various tracer and support gases. H2 turned out to be the most efficient support gas, but due to cluster formation, Helium should be used for the separation of neighbour masses (M/z) and ((M+1)/z). In runs with radioactive 127Xe, a total efficiency of 40% was determined under non-optimal conditions. These trials showed clearly the difficulties associated with batch-separation of radioisotopes which especially occur when handling very small amounts of material. (author) 32 figs., 16 tabs., 65 refs