Development of large scale negative ion source for LHD-NBI

In this paper we report the first results on a prototype negative ion source for LHD-NBI. The ion source with a multi-cusp configuration consists of the external magnetic filter and has an inner volume of 140 cm in height ×35 cm in width ×25 cm in depth. Two cesium lines are installed to seed cesium vapor into arc plasma for enhancement of H− current. The H− ion beam was extracted from an area of 120 cm×25 cm and was accelerated via single-stage accelerator. An H− current of about 4 A with the energy of 73 keV was obtained at the arc power of 250 kW for a duration of 0.3 sec.