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

Journal Article · Mon Sep 26 04:00:00 EDT 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3637423· OSTI ID:21611698

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 ^[1]

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1. National Institute for Fusion Science, 322-6 Oroshi Toki Gifu 509-5292 (Japan)

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.

• OSTI ID: 21611698
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1390; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCELERATORS
ALKALI METALS
ANIONS
AUGER ELECTRON SPECTROSCOPY
BEAM EXTRACTION
BEAM INJECTION
BEAM INJECTION HEATING
CESIUM
CHARGED PARTICLES
CLOSED PLASMA DEVICES
ELECTRON SPECTROSCOPY
ELECTROSTATIC ACCELERATORS
ELEMENTS
EMISSION SPECTROSCOPY
ENERGY RANGE
HEATING
ION SOURCES
IONS
KEV RANGE
LHD DEVICE
METALS
NEUTRAL ATOM BEAM INJECTION
PLASMA
PLASMA BEAM INJECTION
PLASMA HEATING
SPECTROSCOPY
SURFACE AREA
SURFACE PROPERTIES
THERMONUCLEAR DEVICES