# The 18th International Conference on Ion Sources

1-6 September 2019
Lanzhou
Asia/Shanghai timezone
The deadline for the ICIS 2019 manuscript submission is extended to September 30. All oral presentations have been uploaded on the page of 'timetable'.

## Extension of High Power Deuterium Operation of Negative Ion Based Neutral Beam Injector in LHD

4 Sep 2019, 14:30
20m
Lanzhou

#### Lanzhou

No. 1 Beibinhe East Road, Chengguan District, Lanzhou
Contributed oral

### Speaker

Dr Katsunori Ikeda (National Institute for Fusion Science)

### Description

Deuterium operation of negative ion based neutral beam injector (N-NBI) was initiated in 2017 in the Large Helical Device (LHD). Negative ion sources and their accelerator were optimized for hydrogen operation. The specification of the H$^–$ current and the beam energy are 80 A and 180 keV, respectively. Total injection power was 16 MW for hydrogen operation by three beam lines. In the first deuterium beam operation, the D$^–$ current of 46.2A was generated with the averaged current density of 190 A/m$^2$ for the electron ion current ratio of $I_e/I_{D^-}$ = 0.39 by only changing operation gas using the same accelerator. In the second deuterium beam operation in 2018, the electron and ion current ratio decreases to $I_e/I_{D^-}$ = 0.31 using the short extraction gap distance of 7 mm between the plasma grid and the extraction grid. Thermal load on the extraction grid for deuterium operation is as low as that for hydrogen operation. The volume of negative ion rich region between the plasma grid and EDM(electron deflection magnetic) field lobe is considered to be increasing in the vicinity of PG surface. The reduction of the electron current made it possible to operate a high power arc discharge and beam extraction. Then the deuterium negative ion current increases to 55.4 A and the averaged current density of 233 A/m$^2$. The injection beam power increases from 2.3 MW to 2.9 MW in one beam line, and the total beam injection power increases from 5.3 MW to 7 MW by three beam lines in the second deuterium campaign.

Category of your contribution Ion sources for fusion

### Primary author

Dr Katsunori Ikeda (National Institute for Fusion Science)

### Co-authors

Prof. Katsuyoshi Tsumori (National Institute for Fusion Science) Prof. Kenichi Nagaoka (National Institute for Fusion Science) Dr Haruhisa Nakano (National Institute for Fusion Science) Dr Masashi Kisaki (National Institute for Fusion Science) Dr Yutaka Fujiwara (National Institute for Fusion Science) Dr Shuji Kamio (National Institute for Fusion Science) Mr Yasuaki Haba (Nagoya University) Mr Shingo Masaki (SOKENDAI) Prof. Masaki Osakabe (National Institute for Fusion Science)

### Presentation Materials

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