Characteristics of extracted ion beam from a cesium-free negative ion source using sheet plasma

Kaminaga, Hiroki; Takimoto, Toshikio; Tonegawa, Akira; Sato, Kohnosuke

doi:10.1063/5.0013364

Cited by 4 publications

(3 citation statements)

References 19 publications

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“…The experiment was performed using the Cs-free negativeion source TPDsheet-U apparatus, which is schematically illustrated in figure 1 [10][11][12][13][14][15]. TPDsheet-U is divided into two regions: the sheet plasma source and extraction regions.…”

Section: Cs-free Negative-ion Source Tpdsheet-umentioning

confidence: 99%

“…The volume production of negative hydrogen ions in the produced magnetized sheet plasma is proposed to be developed as a negative-ion source using test plasma produced by direct current for sheet plasma upgrade (TPDsheet-U) [10][11][12][13][14][15]. High-density magnetized sheet plasmas are suitable for producing H − ions in dissociative attachment (DA) processes because of the narrow space (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…An electron fence (EF) was installed on the extraction grid (PG). Because of the fence, the co-extracted electron current was reduced without reducing the H − ion current density because the height of EF is similar to the gyro-radius of H − and is much larger than that of electrons [14]. The ratio of the extracted electron current I EG (e) to the H − current (I EG (H − ), I EG (e)/I c (H − )), decreases from 8.0 to 2.0 with an increase in the height of EF (H EF ) from 0 mm to 8 mm, which prevents electron diffusion.…”

Section: Introductionmentioning

confidence: 99%

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Characteristics of the extracted negative-ion beam in a cesium-free negative-ion source using TPDsheet-U

Tonegawa¹,

Kaminaga²,

Hanai³

et al. 2021

Nucl. Fusion

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The progress toward realizing a high-performance cesium (Cs)-free negative-ion source based on volume production in a magnetized sheet plasma device (TPDsheet-U) is reported. In the experiments, H− ions were successfully extracted from sheet plasma using single-/multi-aperture grids. The experimental results of the single-aperture grid show that the negative hydrogen ion current density (J C(H−)) performance of Cs-free H− ion beams in TPDsheet-U is about one-fourth that of Cs-containing H− ion sources in the ITER negative-ion neutral-beam injector (NNBI). (i) The J C(H−) was ∼7.5 mA cm−2 at an extraction voltage of 10 kV, a discharge current I d of 90 A, and a gas pressure of 0.3 Pa. (ii) The electron current J EG(e) with this soft magnetic filter (SMF) was only ∼10% of the electron current without the SMF; The J EG(e)/J C(H−) ratio was reduced below 0.4 at y < 18 mm for a single-aperture grid with the SMF at I d = 50 A and external magnetic field strength of 38 mT.

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