Recent progress in R&D for long pulse and ultra-high voltage components for the ITER HNB

Abstract

Toward ITER, the long-pulse acceleration of MeV-class negative ion beams has been successfully demonstrated and R&Ds and the procurement of high-voltage components of 1MV power supply system have been progressed. In the accelerator development after the production of 1MeV beams, an extraction grid, where a water cooling is reinforced and the beam is steered by aperture offset to suppress grid heat loads, has been newly developed to extend the pulse duration of the MeV-class beams. As the result, a total grid heat load has been reduced from 20% to 10% of the total beam power. The beam pulse was successfully increased from 0.4s to 60s at 0.68MeV, 100A/m2 and 12s at 0.89MeV, 156A/m2 beams. As for the procurement of the 1MV power supply system, 1MV insulating transformer as the critical component has been developed. In the mock-up, a dc 1.2MV for 1h with the margin of 20% was stably sustained. Through the R&Ds of the critical components, design of five power supplies procured by JAEA has been finalized, and out of which a testing power supply has been completed in June 2014.