Neutral beams for ITER (invited)a)

Hemsworth, R.; Feist, J.‐H.; Hanada, M.; Heinemann, B.; Inoue, Takashi; Küssel, E.; Krylov, A.; Lotte, P.; Miyamoto, K.; Miyamoto, Naoki; Murdoch, D.; Nagase, A.; Ohara, Y.; Okumura, Y.; Paméla, J.; Panasenkov, A. A.; Shibata, Kozo; Tanii, Masahiro; Watson, M.

doi:10.1063/1.1146852

Cited by 80 publications

(19 citation statements)

References 3 publications

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“…It has been pointed out that the profile of negative ion beam consists of two Gaussian parts, namely a beam core with good a beam optics and a beam halo with a poor beam optics. 3 The beam halo appears directly as the beam profile, [4][5][6] or indirectly as a component of the heat loads in the accelerator grids. 7,8 It is crucial to suppress the beam halo since the beam halo can contribute to reduce the beam transmission and increase the heat loads even at the optimum perveance for minimizing the divergence of the beam core.…”

Section: Introductionmentioning

confidence: 99%

Effect of basic physical parameters to control plasma meniscus and beam halo formation in negative ion sources

Miyamoto

Okuda

Nishioka

et al. 2013

Journal of Applied Physics

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Our previous study shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources: the negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. In this article, the detail physics of the plasma meniscus and beam halo formation is investigated with two-dimensional particle-in-cell simulation. It is shown that the basic physical parameters such as the H− extraction voltage and the effective electron confinement time significantly affect the formation of the plasma meniscus and the resultant beam halo since the penetration of electric field for negative ion extraction depends on these physical parameters. Especially, the electron confinement time depends on the characteristic time of electron escape along the magnetic field as well as the characteristic time of electron diffusion across the magnetic field. The plasma meniscus penetrates deeply into the source plasma region when the effective electron confinement time is short. In this case, the curvature of the plasma meniscus becomes large, and consequently the fraction of the beam halo increases.

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Section: Introductionmentioning

confidence: 99%

Effect of basic physical parameters to control plasma meniscus and beam halo formation in negative ion sources

Miyamoto

Okuda

Nishioka

et al. 2013

Journal of Applied Physics

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“…1), now under construction, useful for code validation and for testing of advanced beam diagnostic, and a fast emittance scanner (FES). The development of Neutral Beam Injectors (NBI) for the ITER project [1] and the large beam test facilities planned to be built at Consorzio RFX (Padova, Italy) described elsewhere [2] are a strong motivation to further improve the negative ion sources (NIS [3,4,5,6]) and the understanding of their beam extraction, also in the perspective of fusion reactors beyond ITER.…”

Section: Introductionmentioning

confidence: 99%

Status of NIO1 construction

Cavenago¹,

Fagotti²,

Poggi³

et al. 2011

AIP Conference Proceedings

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The NIO1 (Negative Ion Optimization phase 1) project consists of a multiaperture negative ion source mounted on a 60 kV accelerating column; up to 9 beamlets (15 mA H − each one) arranged in 3 x 3 matrix with 14 mm spacing can be extracted. The moderate size and the modular concept make some relative rotation of the source magnetic filter and the electrodes possible, so that the effect of crossed and aligned field can be easily compared. Other goals of source experimental program are emittance (and beam profile) measurement at several distances (for simulation code validation), testing of diagnostic components and of radiofrequency coupling. A full set of construction drawing was completed; also the Fast Emittance Scanner (FES) and its vacuum chambers were built (four mounting positions are reserved to FES). Some low power rf matching boxes were developed for a test plasma, approximately half the source size. A cesium oven compatible with NIO1 is being also developed; by using some industrial standard 100 W heaters (with a proper driver) a careful control of temperature is planned.

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“…In international thermonuclear experimental reactor ͑ITER͒, e.g., the ion source/accelerator is designed to produce a 40 A, 1 MeV D Ϫ beam for more than 1000 s. 1 In accelerating such a high power negative ion beam for a long time duration, one of the critical issues is a power loading of acceleration grids. To reduce the grid power loading in a negative ion accelerator, acceleration of electrons should be suppressed since electrons have the same charge and easily accelerated with ions.…”

Section: Introductionmentioning

confidence: 99%