Progress in the Development of an H- Ion Source for Cyclotrons

A multi-cusp DC H- ion source has been developed for cyclotrons in medical use. Beam optics of the ET ion beam is studied using a 21) beam trajectory code. The simulation results are compared with the experimental results obtained in the Mark I source, which has produced up to 16 mA H- ion beams. The optimum extraction voltages show good agreement between the calculation and the experimental results. A new ion source, Mark II source, is designed to achieve the next goal of producing an H- beam of 20 mA. The magnetic field configurations and the plasma electrode design are optimized for Cs-seeded operation. Primary electron trajectory simulation shows that primary electrons are confined well and the magnetic litter prevents the primary electrons from entering into the extraction region.