Improvement of accelerator of negative ion source on the Large Helical Device

M Kisaki; K Ikeda; M Osakabe; K Tsumori; H Nakano; S Geng; K Nagaoka; O Kaneko; Y Takeiri

doi:10.1063/1.4936249

Improvement of accelerator of negative ion source on the Large Helical Device

Rev Sci Instrum. 2016 Feb;87(2):02B321. doi: 10.1063/1.4936249.

Authors

M Kisaki¹, K Ikeda¹, M Osakabe¹, K Tsumori¹, H Nakano¹, S Geng², K Nagaoka¹, O Kaneko¹, Y Takeiri¹

Affiliations

¹ National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan.
² SOKENDAI (The Graduate University for Advanced Studies), 322-6 Oroshi, Toki, Gifu 509-5292, Japan.

PMID: 26932049
DOI: 10.1063/1.4936249

Abstract

To improve the performance of negative-ion based neutral beam injection on the Large Helical Device, the accelerator was modified on the basis of numerical investigations. A field limiting ring was installed on the upper side of a grounded grid (GG) support and a multi-slot GG was adopted instead of a multi-aperture GG. As a result, the voltage holding capability is improved and the heat load on the GG decreases by 40%. In addition, the arc efficiency is improved significantly only by replacing the GG.