Design study on a 1MeV, 12.5MW neutral beam injector module for ITER

摘要

A high energy neutral beam injector has been designed for the International Thermo-nuclear Experimental Reactor(ITER). Two types of designs are proposed; a short beamline option and a long beamline option. The short beamline option is characterized by a very short neutralizer, which makes it possible to integrate all the beamline components within the cryostat of ITER. The long beamline option has a conventional layout, where the beamline is installed outside the cryostat. In both cases, the system is more compact and more reactor-relevant than the ITER-CDA(Conceptual Design Activity) design, since the present design is based on the recent progress on the negative ion beam development. In the design, 25A D-ion beam is produced by a cesium-seeded volume negative ion source and accelerated to 1MeV by a multi-stage electrostatic accelerator. The beam is neutralized in a gas cell and 12.5MW (1MeV, 12.5A) neutral beam is injected into each injection port. Using 4 NBI modules and 4 ports, 50MW is to be injected into the plasma in ITER. A special emphasis is laid on the radiation shielding and the radiation effects in the beamline components, which was considered to be a serious problem in applying a neutral beam system for ITER. We found that the irradiation dose rate in the beamline components including the ion source/accelerator can be suppressed to a moderate value and no serious damage on these components is expected. (author).