Computational studies on a primary electron collisions and lifetime in a bucket-type ion source

In our recent simulations to trace three-dimensional primary electron orbits in a bucket-type ion source, collision processes between primary electrons and neutral gas atoms have been included. In the code with collisions, the distribution of ionization points and the actual lifetime of primary electrons emitted from filaments are examined. The results of primary electron lifetime show the performance of an ion source, that is, ionization efficiency or primary electron confinement in a source. Design problems of filament length and magnet disposition are studied. (author)