Design study of 500 keV H accelerator for ITER NB system

Kashiwagi, Mieko; Inoue, Takashi

In a neutral beam (NB) system for heating and current drive of ITER, detailed designs of a multi aperture five stage accelerator to produce 1 MeV 40 A D and 870 keV 46 A H ion beams are ongoing. However, it was expected that the shinethrough power from 870 keV H beam was above tolerable level for the maximum plasma density prior to any H mode. Therefore, it was required to reduce the beam energy to 500 keV with maintaining high beam current. The objective of this study is to identify necessary modifications from the original five stage accelerator to a three stage accelerator to produce 500 keV H ion beam. The physics design of the three stage accelerator was carried out based on a beam optics study in a 2D beam analysis, a beamlet steering design in a 3D multi beamlets analysis and gas density / stripping loss of negative ions in a 3D gas analysis. Finally, the items for necessary modification were summarized.