Selective microwave mode excitation and charge state distribution on the first stage of tandem type ECRIS

摘要

A new concept on magnetic field of plasma production and confinement has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure. We make this source a part of new tandem type ion source for the first stage. We are also constructing the large bore second stage for synthesizing, extracting and analyzing ions. Both ECR plasmas are necessary to be available to coexist and to be operated individually with different plasma parameters. In the first stage, we optimize the ion beam current and ion saturation current by a mobile plate tuner. They change by the position of the plate tuner for single and multi-frequencies microwaves. The peak positions of them are close to the position where the microwave mode forms standing wave between the plate tuner and the extractor. We show a new guiding principle, which the number of efficiently azimuthal microwave mode should be selected to fit to that of multipole of comb-shaped magnets. We obtained the excitation of selective modes using new mobile plate tuner to enhance ECR efficiency. Furthermore we first obtained charge state distributions of ion beams extracted from the first stage after constructing the second stage and its beam line.