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Title: Stability of High Power Beam Injection in Negative-Ion-Based LHD-NBI

Abstract

We describe the characteristic of stable beam injection in a neutral beam injector (NBI) for Large Helical Device (LHD) in high injection power of more than 6 MW. In the NBI, it takes a week after starting Cs seeding to finish the pre-injection conditioning. The injection starts with the beam power {approx}6.2 MW, and the maximum power reaches {approx}7 MW. The Cs-seeding rate affects the beam stability in such high power injections. By optimizing the rate to 0.65 mg/shot, the success ratio, which is defined as a ratio of actual pulse duration to setting one, increases to 85-90% in the power and energy range of more than 6.2 MW and 185 keV, respectively. The weights of Cs adsorbed on several surfaces in the ion sources of the NBI are measured by means of Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), and averaged surface densities are calculated by dividing with the several surface areas. The seeded Cs of 99.5% is condensed in the plasma generator, and very tiny amount of Cs reaches the surfaces of the accelerator grids. This very low amount of Cs on the grids is interpreted that most of the Cs atom evaporated from the inner walls is ionizedmore » during the arc discharges, and repelled to the source plasmas by the electrostatic field for H- extraction.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ;  [1]
  1. National Institute for Fusion Science, 322-6 Oroshi Toki Gifu 509-5292 (Japan)
Publication Date:
OSTI Identifier:
21611698
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 1390; Journal Issue: 1; Conference: 2. international symposium on negative ions, beams and sources, Takayama City (Japan), 16-19 Nov 2010; Other Information: DOI: 10.1063/1.3637423; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 43 PARTICLE ACCELERATORS; ANIONS; AUGER ELECTRON SPECTROSCOPY; BEAM EXTRACTION; BEAM INJECTION HEATING; CESIUM; ELECTROSTATIC ACCELERATORS; EMISSION SPECTROSCOPY; ION SOURCES; KEV RANGE; LHD DEVICE; NEUTRAL ATOM BEAM INJECTION; PLASMA; PLASMA BEAM INJECTION; SURFACE AREA; ACCELERATORS; ALKALI METALS; BEAM INJECTION; CHARGED PARTICLES; CLOSED PLASMA DEVICES; ELECTRON SPECTROSCOPY; ELEMENTS; ENERGY RANGE; HEATING; IONS; METALS; PLASMA HEATING; SPECTROSCOPY; SURFACE PROPERTIES; THERMONUCLEAR DEVICES

Citation Formats

Tsumori, K., Kaneko, O., Takeiri, Y., Osakabe, M., Ikeda, K., Nagaoka, K., Nakano, H., Shibuya, M., Asano, E., Kondo, T., Sato, M., Komada, S., and Sekiguchi, H. Stability of High Power Beam Injection in Negative-Ion-Based LHD-NBI. United States: N. p., 2011. Web. doi:10.1063/1.3637423.
Tsumori, K., Kaneko, O., Takeiri, Y., Osakabe, M., Ikeda, K., Nagaoka, K., Nakano, H., Shibuya, M., Asano, E., Kondo, T., Sato, M., Komada, S., & Sekiguchi, H. Stability of High Power Beam Injection in Negative-Ion-Based LHD-NBI. United States. doi:10.1063/1.3637423.
Tsumori, K., Kaneko, O., Takeiri, Y., Osakabe, M., Ikeda, K., Nagaoka, K., Nakano, H., Shibuya, M., Asano, E., Kondo, T., Sato, M., Komada, S., and Sekiguchi, H. Mon . "Stability of High Power Beam Injection in Negative-Ion-Based LHD-NBI". United States. doi:10.1063/1.3637423.
@article{osti_21611698,
title = {Stability of High Power Beam Injection in Negative-Ion-Based LHD-NBI},
author = {Tsumori, K. and Kaneko, O. and Takeiri, Y. and Osakabe, M. and Ikeda, K. and Nagaoka, K. and Nakano, H. and Shibuya, M. and Asano, E. and Kondo, T. and Sato, M. and Komada, S. and Sekiguchi, H.},
abstractNote = {We describe the characteristic of stable beam injection in a neutral beam injector (NBI) for Large Helical Device (LHD) in high injection power of more than 6 MW. In the NBI, it takes a week after starting Cs seeding to finish the pre-injection conditioning. The injection starts with the beam power {approx}6.2 MW, and the maximum power reaches {approx}7 MW. The Cs-seeding rate affects the beam stability in such high power injections. By optimizing the rate to 0.65 mg/shot, the success ratio, which is defined as a ratio of actual pulse duration to setting one, increases to 85-90% in the power and energy range of more than 6.2 MW and 185 keV, respectively. The weights of Cs adsorbed on several surfaces in the ion sources of the NBI are measured by means of Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), and averaged surface densities are calculated by dividing with the several surface areas. The seeded Cs of 99.5% is condensed in the plasma generator, and very tiny amount of Cs reaches the surfaces of the accelerator grids. This very low amount of Cs on the grids is interpreted that most of the Cs atom evaporated from the inner walls is ionized during the arc discharges, and repelled to the source plasmas by the electrostatic field for H- extraction.},
doi = {10.1063/1.3637423},
journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 1390,
place = {United States},
year = {2011},
month = {9}
}