Emittance and Brightness of Multiply-Charged Ion Beams from Duopigatron and Duoplasmatron Sources

The systematic study of the dependence of the charge state density distribution (CSDD) on the discharge parameters of both the duopigatron and the duoplasmatron sources has been conducted. The experimental data show that for both sources the optimum conditions for multiply-charged ion production correspond to the operation of the discharge at points between two different modes. In particular, the pressure must be matched to a minimum value (p=p*) corresponding to the arc starvation mode. Under this condition the discharge exhibits large level fluctuations which are correlated with enlarged ion energy spreads. However, the instability level can (particularly in the duopigatron) be minimized by a proper choice of the magnetic field shape and magnetic field strength (B=B*). In order to describe more completely the source performances, the emittance and brightness have been measured under optimum conditions for production of multiply-charged ions in our design. Solutions have been proposed to improve emittance and brightness by the adaptation of a plasma expansion cup. These solutions do not inversely affect the CSDD. The obtained performances are compared with other experiments.