Preparations for Parasitic Production of Biomedically Useful Positron-Emitters

The long-time rebuilding of the old GWI-machine into a sector-focussing synchrocyclotron will hopefully be completed within 1985. External beams of protons, deuterons, Helium-3, alpha-particles and heavier ions will be available for physics and biomedical research, and also for direct radionuclide production (e.g. 40 ¿A of protons 45-110 MeV, less for higher energy protons, cf. Table 1). This being the principal Swedish accelerator undertaking of the eighties, we foresee, however, some difficulties in getting enough and regular beamtime for an increasing demand of cyclotron-produced `medical´ radionuclides (for PET-work etc.). Possibilities for parasitic production are therefore investigated. One example is given by the 11C-production by protons in the cooling water of planned spallation neutron sources and targets for the production of thermal neutrons (reaction: (p, 3p3n) on oxygen1). The extraction of 11C from cooling water was successfully tested at the thermal neutron facility of TRIUMF2. These experiences are used in the construction of water beam dumps with provisions for extraction of medically useful, positronemitting radionuclides during for instance (n,p)-experiments.