Role of a biased electrode in the production of highly charged ions using the DECRIS 14-3 ion source

ECR ion sources are used for the production of highly charged ions in various accelerator facilities. In most of them biased electrodes are normally used to increase the ion yield. Physical processes in the plasma of an ion source are quite complicated and the role of a biased electrode is not clear. To investigate the effect of a biased electrode on the intensity of extracted highly charged ions, an axially movable electrode was placed into the plasma chamber of the DECRIS 14-3 ion source. It was found that the intensity of Ar ions depends on the position of the biased electrode and negative bias voltage. The optimal position of the biased electrode was found near the maximum of the magnetic field. Experiments with a pulsed biased electrode were also carried out. The influence of the negative pulse on the ion yield depends on the ion charge state.