Electron density measurement of cesium seeded negative ion source by surface wave probe

Kisaki, M.; Tsumori, K.; Nakano, H.; Ikeda, K.; Osakabe, M.; Nagaoka, K.; Shibuya, Masayuki; Sato, Mamoru; Sekiguchi, Hiroyuki; Komada, S.; Kondo, Tomoki; Hayashi, Hiroshi; Asano, E.; Takeiri, Y.; Kaneko, O.

doi:10.1063/1.3671745

Cited by 7 publications

(4 citation statements)

References 9 publications

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“…3 In this study, the electron density measurement was carried out by the SWP at various bias voltages in the pure-volume and Cs-seeded plasmas. We will discuss effects of the grid bias on electrons in the different negative ion production processes.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of plasma grid bias in large-scaled negative ion source

Kisaki

Tsumori

Ikeda

et al. 2014

Review of Scientific Instruments

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The electron density was measured at various bias voltages to understand how the plasma grid bias affects the electron near the plasma grid in large-scaled negative ion sources. It was found that the response of the electron to the bias voltage changes depending on negative ion production processes. The electron density remarkably decreases with increasing the bias voltage in the pure-volume plasma. On the other hand, the electron density depends on the bias voltage weakly in the Cs-seeded plasma. In addition, it was observed that the response of the co-extracted electron current to the bias voltage has similar trend to that of the electron density.

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Section: Introductionmentioning

confidence: 99%

Characteristics of plasma grid bias in large-scaled negative ion source

Kisaki

Tsumori

Ikeda

et al. 2014

Review of Scientific Instruments

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“…The latter also affects the electron temperature. This is predicted by numerical simulations [17,21] and demonstrated experimentally in other existing negative ion sources [10,27]. However, this is the first time that the effect of these parameters in a large source as SPIDER is studied.…”

Section: Plasma In the Expansion Regionmentioning

confidence: 61%

Correlation of source parameters and beam properties in the early operation of the full size ITER negative ion beam source

Ugoletti,

Agostini,

Poggi

et al. 2024

Nucl. Fusion

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One of the requirements of heating and current drive neutral beam injectors (HNB) for ITER is a beam homogeneity greater than 90%, to achieve an optimal beam transmission while keeping the heat load consistently low on the acceleration electrodes. The large size and complexity of ITER negative ion source play a key role in determining the homogeneity of the negative ion current of each of the 1280 beamlets and their divergence, and it is studied in the full-scale prototype source SPIDER.In this work the plasma properties are studied by spectroscopic and electrostatic measurements in the drivers, where the plasma is generated, and in the expansion region, where the plasma drifts and negative ions are produced, and they are correlated with the properties of the beam. The non-homogeneous plasma density profile is related to the non-homogeneous availability of negative ions along the beam vertical profile, with and without cesium evaporation. Visible tomography, a technique capable of characterizing isolated beamlet properties, is used to study the beam's dependence on plasma uniformity along the entire beam profile.Using these tools, it has been demonstrated how an increase in plasma density is linked to an improvement in beam homogeneity. The latter has been directly correlated with plasma homogeneity. The magnetic filter field and biases of the plasma grid and bias plate are responsible for the variation in plasma density and its homogeneity. Non-uniformities in the plasma’s top/bottom and left/right distributions have been studied and partially addressed experimentally. The first issue was resolved by adjusting the radio-frequency power supplied to the plasma in different vertical regions, while the second issue was addressed by reversing the direction of the magnetic filter field and increasing the plasma density.

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“…The electron density results obtained with the surface wave probe for Cs seeded conditions were one-to two-order of magnitude lower than those without Cs [83]. The surface wave probe results have also shown that the dependence of electron density upon the plasma electrode bias resembles the dependence of the electron drain current upon the plasma electrode bias [84]. Namely, the plasma electrons are the cause of coextracted electron current.…”

Section: Plasma Parametersmentioning

confidence: 99%