Optimisation of highly charged ion currents and efficiency in ECR ion sources

Abstract

The charge state distribution (CSD) of an electron cyclotron resonance (ECR) ion source in a good vacuum regime is here expressed in two closed forms; solution parameters a and b are related to quantities, here tabulated for some elements, expressing the trends of ionization cross sections with the charge state i and the plasma electron temperature Th. Difference of this CSD from a maxwellian distribution and its relation to the double exponential distribution are noted. The momenta and the generating function of the charge distribution are computed, so that ionization and thermal balance can be computed and many element effects can be studied; optimal element mixing can be derived. Simple relation between the charge state and the efficiency of the ECR charge breeders are also obtained.