Development of Negative ION Based NBI System for JT-60U

Umeda, N.; Akino, N.; Ebisawa, N.; Grisham, L.; Hikita, S.; Honda, A.; Itoh, Takaò; Kawai, M.; Kazawa, M.; Kusaka, M.; Kusanagi, N.; Kuriyama, M.; Lee, P.; Mogaki, K.; Ohga, T.; Oohara, H.; Satoh, F.; Seki, Hiroshi; Seki, Norio; Tanai, Y.; Toyokawa, R.; Usui, K.; Yamazaki, H.

doi:10.13182/fst01-a11963398

Cited by 5 publications

(1 citation statement)

References 3 publications

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“…In these three years, we have also tried to improve the uniformity of negative ion production in the ion source [3], by tuning the input power of each filament group so as to change the arc power distribution in the chamber. Although a uniform arc power profile was achieved by filament tuning, a large non-uniformity in the profile of beams still remained, in particular, at the bottom of the chamber.…”

Section: Introductionmentioning

confidence: 99%

Improvement of beam performance in the negative-ion based NBI system for JT-60U

et al. 2003

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The injection performance of the negative-ion based NBI (N-NBI) system for JT-60U has been improved by correcting beamlet deflection and improving spatial uniformity of negative ion production. Beamlet deflection at the peripheral region of the grid segment due to the distorted electric field at the bottom of the extractor has been observed. This was corrected by modifying the surface geometry at the extractor to form a flat electric field. Moreover, beamlet deflection due to beamlet–beamlet repulsion caused by space charge was also compensated for by extruding the edge of the bottom extractor. This resulted in a reduction of the heat loading on the NBI port limiter. As a result of the improvement above, continuous injection of a 2.6 MW H0 beam at 355 keV has been achieved for 10 s. Thus, long pulse injection up to the nominal pulse duration of JT-60U was demonstrated. This has opened up the prospect of long pulse operation of the negative-ion based NBI system for a steady-state tokamak reactor. So far, a maximum injection power of 5.8 MW at 400 keV, with a deuterium beam, and 6.2 MW at 381 keV, with a hydrogen beam, have been achieved in the JT-60U N-NBI. Uniformity of negative ion production was improved by tuning the filament emission current so as to direct more arc power into the region where less negative ion current was extracted.

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Section: Introductionmentioning

confidence: 99%

Improvement of beam performance in the negative-ion based NBI system for JT-60U

et al. 2003

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Status of Negative-Ion-Based Neutral Beam Injectors in LHD

Kaneko¹,

Takeiri²,

Oka³

et al. 2005

AIP Conference Proceedings

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Recent progress in LHD N-NBI system is described. The system was designed to provide 15 MW of port-through beam power by three beam lines (BL-1 to BL-3) with 180 keV hydrogen for 10 sec. However, starting from 3.2 MW injection by two beam lines, the performance has not satisfied all its specifications at the same time yet. This is because several difficulties were found in large negative ion sources although the specifications were determined based on the R&D results of small ion sources. Hence, the continuous efforts have been done to improve the performance of negative ion source, and the injection power has been increased year by year, and in the latest LHD experimental campaign total port-through power of 13.1 MW was achieved, where R&D on the ion source of BL-1 has been succeeded. Two improvements have been done on the ion source of BL-1. One is the optimization of magnetic cusp structure by modifying the shape of plasma source, which increased the negative ion current. The other is the adoption of multi-slot aperture for the grounded grid, which reduces the conditioning time of the accelerator dramatically. As a result, the specifications of beam energy and port-through power were satisfied in BL-1. The remaining problem is a pulse length which is still limited due to high heat load on the grounded grid.

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The operational phase of negative ion beam systems on JT-60U and LHD

Grisham

2005

IEEE Trans. Plasma Sci.

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Development of Negative ION Based NBI System for JT-60U

Cited by 5 publications

References 3 publications

Improvement of beam performance in the negative-ion based NBI system for JT-60U

Improvement of beam performance in the negative-ion based NBI system for JT-60U

Status of Negative-Ion-Based Neutral Beam Injectors in LHD

The operational phase of negative ion beam systems on JT-60U and LHD

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