The objective of this proposed effort is to develop new ion beam target chamber technologies that will increase reliability while maintaining high yield capability for the production of PET radioisotopes (15O, 13N, 11C, 18F) obtained with the new lower cost, lower energy (3-4 MeV) accelerators now being developed for PET. Since target foil failure is a limiting factor in the performance of existing cyclotron-based PET radiopharmaceutical systems, the results of the proposed program will also be valuable in improving the performance of current PET systems. The new accelerators must operate at higher currents (up to 1 mA versus 50 muA with high energy cyclotrons) to achieve the 1-2 Curie saturated yields of these radioisotopes required for medical imaging applications. These high currents, in turn, require a factor of 40 times more cooling capacity for the ion beam transmission window (foil) which separates the evacuated accelerator beam line from the target chamber. The new target chamber technologies proposed for development in the effort include (1) conduction- cooled foils and foil support structures with a high-aspect-ratio geometry, (2) new methods of mounting these foils to reduce stress and extend foil life, (3) vortex controlled gas target material flow generators in insure more efficient and more uniform irradiation of the target material by the transmitted ion beam, and (4) a very thin liquid water target to reduce ion beam heating effects.
