Study of the beam extraction system of a negative ion source with a C12A7 electride plasma electrode

Key issues to fabricate a beam extraction system of a H− source with a plasma electrode (PE) made from C12A7 electride which has low work function were studied. Preliminary study of the H− extraction using a compact ECR ion source reveals, that high H− current can be extracted from a source without PE bias of high voltage. A bucket type with ECR source is being designed. Beam simulation for the extraction through the designed electrodes has been carried out using the OPERA code. It predicts that the optimum perveance is 0.6 mA/kV1.5, optimum acceleration to extraction voltage ratio Vacc/Vext is 4, with the minimum beam divergence of 9 mrad, which are enough to demonstrate the capability to produce a high H− current density.