A high current volume H− ion source with multi-aperture extractor

Okumura, Y.; Horiike, Hiroshi; Inoue, Takashi; Kurashima, Toshio; Matsuda, Shinzaburo; Ohara, Y.; Tanaka, Shigeru

doi:10.1063/1.36544

Cited by 8 publications

(8 citation statements)

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“…At any rate, H-density has a tendency to be saturated with the increase of ne. This characteristic feature is confirmed experimentally by Okumura et a1 [4]. On the production of H,* (v"), the model considers not only the collisional excitation caused by ef, process (25), but also the production due to neutralisation of molecular ions, process (26).…”

Section: Dependence Of H-and He (U") Production On Plasma Parametersmentioning

confidence: 59%

Numerical studies on the optimisation of volume-produced H^-ions in the single-chamber system

Fukumasa

1989

J. Phys. D: Appl. Phys.

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Optimisation of volume-produced H- ions is studied by using a set of particle balance equations in a steady-state hydrogen plasma with a single-chamber system. The dependence of production of both H- ions and vibrationally excited hydrogen molecules H2* (vibrational level V") on plasma parameters (i.e. electron temperature Te, electron density ne, hydrogen gas pressure p, density ratio nfe/ne of fast primary electrons ef to slow plasma electrons e, energy of fast electron Efe, etc.) is explored because it is expected that H- ions are produced by the following two-step process, i.e. H2+ef to H2*(V")+Ef; H2*(V")+e to H-+H. Particular attention is also paid to wall effects, i.e. neutral particles-wall interaction, on H- production. So, a wall recombination coefficient gamma 1 for H and a wall de-excitation collision parameter gamma 2 for H2*(V") are treated as numerical parameters. It is confirmed that most H- ions are produced by the above-mentioned two-step process, and that the presence of ef with energies in excess of 40 eV is reasonable for H2*(V") production. With increasing Te (above 1 eV), H- yield decreases monotonically. Besides, ne, nfe/ne and p have some optimum values for H- production. However, the optimum condition for H- formation is not compatible with that for H2*(V") production. Another significant point is that the ion species ratios depend strongly on the wall parameters, i.e. gamma 1 and gamma 2. For H- production, the optimum condition is that gamma 1 approximately=1 and gamma 2<<1.

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Section: Dependence Of H-and He (U") Production On Plasma Parametersmentioning

confidence: 59%

Numerical studies on the optimisation of volume-produced H^-ions in the single-chamber system

Fukumasa

1989

J. Phys. D: Appl. Phys.

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“…60,61 Magnetic multicusp VPS for fusion applications have been developed in the US, 75 France, 76 UK, 77 and Japan. 78,79 A. The Penning volume negative ion source…”

Section: Volume Production H 2 Ion Sourcesmentioning

confidence: 99%

“…78,79 Soon after the experiments in LBNL and Ecole Polytechnique with the rod filter, high current negative ion beams were produced using a similar magnetic filter geometry by Okumura et al, 79 who demonstrated in 1986 that a high current H À ion beam of more than 1 A can be extracted from a volume ion source. Beams of H À ions formed by volume processes in a magnetically filtered multicusp plasma generator were extracted for 0.2 s through a multi-aperture extractor with a total extraction area of 133 cm 2 .…”

Section: Volume Negative Ion Sources For Fusion Applicationsmentioning

confidence: 99%

Negative hydrogen ion production mechanisms

Bacal

Wada

2015

Applied Physics Reviews

246

173

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International audienceNegative hydrogen/deuterium ions can be formed by processes occurring in the plasma volume and on surfaces facing the plasma. The principal mechanisms leading to the formation of these negative ions are dissociative electron attachment to ro-vibrationally excited hydrogen/deuterium molecules when the reaction takes place in the plasma volume, and the direct electron transfer from the low work function metal surface to the hydrogen/deuterium atoms when formation occurs on the surface. The existing theoretical models and reported experimental results on these two mechanisms are summarized. Performance of the negative hydrogen/deuterium ion sources that emerged from studies of these mechanisms is reviewed. Contemporary negative ion sources do not have negative ion production electrodes of original surface type sources but are operated with caesium with their structures nearly identical to volume production type sources. Reasons for enhanced negative ion current due to caesium addition to these sources are discussed. (31 pages, 265 refs

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“…However, the large electron to H" current ratio, as well as the high operating source pressure indicate that further development is needed in order to make this small negative ion source practical for producing high brightness H" beams for long pulse or steady-state operations. It has been reported by Okumura et al 25 that H" ion beams of 1.26 A were extracted at 21 keV for 0.2 s from the large multicusp source shown in …”

Section: Surface-produced H" Ion Sourcesmentioning

confidence: 99%

Development of high current and high brightness negative hydrogen ion sources

Leung

1989

Nuclear Instruments and Methods in Physics Research Section B:

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Negative hydrogen ions have found important applications in particle accelerators and in fusion research. These ions can be generated from two different types of ion sources -the surface conversion source and the volume production source. Recent experiments demonstrate that H" current exceeding 1 A can be obtained from both types of ion sources. Because of the lower H" ion temperature and the fact that they can be operated without cesium, volume H" sources are highly desired. However, further technology must be developed on the control of electrons and the reduction of gas flow i-IntroductionThe use of H" ions for accelerator applications was first proposed by Alvarez in 1951. 1 Since then, H" have found important applications in cyclotrons and tandem accelerators, in fueling storage rings of high energy accelerators, and in generating energetic neutral beams (E > 150 keV) for heating and for current drive in fusion plasmas. Negative hydrogen ions can be formed by double charge exchange processes or by direct extraction from a negative ion source. In general, two distinct types of H" ion sources can be identified: (1) surface conversion sources -in which the H" ions are generated by particle collisions with low work function surfaces, and (2) volume production sources -in which the negative ions are produced by electron-molecule and electron-ion collision processes in the volume of a discharge plasma. Because of the smaller beam omittance and the fact that they can be operated without cesium, volume H~ sources are now being developed by various high energy and fusion laboratories in the world. This article reviews the development and some of the latest technology of these two types of negative ion sources. It can be seen that in just twenty years, H" ion beams have been improved from several milli-ampere to more than 1 ampere. II. Surface-produced H" ion sourcesThere are two major types of surface conversion H" ion sources. One type uses a Penning discharge geometry (for example the planotron source)or an E x B discharge configuration (for example the magnetron source). The second type employs the multicusp plasma generator as the discharge chamber. This source was originally developed at Lawrence Berkeley Laboratory for neutral beam application. Recently, it has been used as an H" -2-source for particle accelerators at Los Alamos National Laboratory and at KEK in Japan.In 1972, the Novosibirsk group discovered that the yield of H" ions was increased from 5 to 20 mA by adding cesium to the hydrogen discharge in a planotron source. H" current density greater than 3 A/cm 2 has been achieved in milli-second pulses. 2 The function of the cesium is twofold: first, it acts as a sputtering agent, and second, it lowers the work function of the target surface so as to enhance the negative ion formation.In Novosibirsk, a multi-slit planotron source with one dimensional In normal operation, cesium is introduced into the discharge so as to lower the work function of the converter and consequently enhance the H"yiel...

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A high current volume H− ion source with multi-aperture extractor

Cited by 8 publications

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Numerical studies on the optimisation of volume-produced H^-ions in the single-chamber system

Numerical studies on the optimisation of volume-produced H^-ions in the single-chamber system

Negative hydrogen ion production mechanisms

Development of high current and high brightness negative hydrogen ion sources

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A high current volume H− ion source with multi-aperture extractor

Cited by 8 publications

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Numerical studies on the optimisation of volume-produced H-ions in the single-chamber system

Numerical studies on the optimisation of volume-produced H-ions in the single-chamber system

Negative hydrogen ion production mechanisms

Development of high current and high brightness negative hydrogen ion sources

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Product

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Numerical studies on the optimisation of volume-produced H^-ions in the single-chamber system

Numerical studies on the optimisation of volume-produced H^-ions in the single-chamber system