Plasma and Fusion Research

Volume 2, S1047 (2007)

Regular Articles

Observation of Hydrogen and Cesium Spectra in a Negative Ion Source for a Neutral Beam Injector using a Multi-Channel Spectrometer

K. IKEDA, U. FANTZ¹⁾, K. NAGAOKA, Y. TAKEIRI, M. OSAKABE, K. TSUMORI, O. KANEKO and Y. OKA

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
1): Max-Planck-Institut fuer Plasmaphysik, Boltzmannstrasse 2 D-85748, Garching, Germany

(Received 4 December 2006 / Accepted 2 April 2007 / Published 20 November 2007)

Abstract

Effective production of hydrogen negative ions (H^-) is one of the important issues in high power neutral beam injection (NBI) for fusion experimental devices. Cesium (Cs) vapor is seeded in the H^- sources to enhance the H^- production rate, which depends strongly on the amount of Cs inside the source. On the other hand, oxygen and water attenuate the production rate. In order to investigate the states of those species inside ion source, we have installed two multi-channel spectrometer systems with different spectral resolution. Hydrogen emissions, Cs emissions and oxygen emission are clearly observed with the time resolution of several handled milliseconds. Most of evaporated Cs atoms ionize in arc discharge plasma, and the emission increases strongly due to the ion back streaming with beam extraction. Oxygen neutral emission increases at the beginning of the beam conditioning, and its evaporation depends on the condition of the grid system.

Keywords

negative ion source, spectroscopy, hydrogen, cesium, oxygen

DOI: 10.1585/pfr.2.S1047

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This paper may be cited as follows:

K. IKEDA, U. FANTZ, K. NAGAOKA, Y. TAKEIRI, M. OSAKABE, K. TSUMORI, O. KANEKO and Y. OKA, Plasma Fusion Res. 2, S1047 (2007).