RF-source development for ITER: Large area H− beam extraction, modifications for long pulse operation and design of a half size ITER source

With an extraction area of 152 cm2 a calorimetrically measured H− current density of 19.3 mA/cm2 has been achieved at 0.45 Pa with 90 kW RF power. With 306 cm2 the electrically measured H− current has reached up to 9.7 A corresponding to 32 mA/cm2 at 100 kW. The current on the calorimeter is limited by the extraction system. Down to 0.2 Pa only a weak dependence on the source pressure has been observed. The test bed will be upgraded to demonstrate cw operation with deuterium. Based on the tested prototype a half size ITER RF-source of 80 cm × 90 cm with 360 kW RF power has been designed.