Roles of a plasma grid in a negative hydrogen ion source

Bacal, M.; Sasao, M.; Wada, M.; McAdams, R.

doi:10.1063/1.4916410

Cited by 13 publications

(7 citation statements)

References 21 publications

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“…The choice of Igor Stravinsky's work for large orchestra, The Rite of Spring , from 1913 was motivated by three reasons: (a) It contains a great variety of instrument combinations and playing techniques (e.g., pizzicato and flageolet); (b) it is available as a pre-edited MIDI file which is used by the VSL company for the demonstration of the OSL's capacity for high-quality sound [ 27 ]; (c) there is an up-to-date, high-quality recording of the piece [ 24 ]. The selected sections had a full orchestra sound and featured groups of instruments but no solo instruments.…”

Section: Methodsmentioning

confidence: 99%

Replacing the Orchestra? – The Discernibility of Sample Library and Live Orchestra Sounds

et al. 2016

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Recently, musical sounds from pre-recorded orchestra sample libraries (OSL) have become indispensable in music production for the stage or popular charts. Surprisingly, it is unknown whether human listeners can identify sounds as stemming from real orchestras or OSLs. Thus, an internet-based experiment was conducted to investigate whether a classic orchestral work, produced with sounds from a state-of-the-art OSL, could be reliably discerned from a live orchestra recording of the piece. It could be shown that the entire sample of listeners (N = 602) on average identified the correct sound source at 72.5%. This rate slightly exceeded Alan Turing's well-known upper threshold of 70% for a convincing, simulated performance. However, while sound experts tended to correctly identify the sound source, participants with lower listening expertise, who resembled the majority of music consumers, only achieved 68.6%. As non-expert listeners in the experiment were virtually unable to tell the real-life and OSL sounds apart, it is assumed that OSLs will become more common in music production for economic reasons.

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Section: Methodsmentioning

confidence: 99%

Replacing the Orchestra? – The Discernibility of Sample Library and Live Orchestra Sounds

et al. 2016

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“…103. The PE bias controls the current collected by the PE, the extracted negative ion and electron currents, and the potential drop across the magnetic filter.…”

Section: Role Of the Magnetic Filtermentioning

confidence: 99%

Negative hydrogen ion production mechanisms

Bacal

Wada

2015

Applied Physics Reviews

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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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“…This electrode separates the ion source extraction region from the extraction and acceleration structure; it is also called 'a plasma grid' when beams are extracted through multiapertures opened on this electrode. The roles of the plasma grid in negative ion sources [32] are: optimizing the extracted negative ion current, reducing the coextracted electron current, controlling the axial plasma potential profile, recycling the hydrogen or deuterium atoms to molecules, concentrating the negative ions near its surface. A function specific for surface production ion sources is the direct emission of negative ions under positive ion and neutral hydrogen or deuterium bombardment.…”

Section: Introductionmentioning

confidence: 99%

Negative ion source operation with deuterium

Bacal

Wada

2020

Plasma Sources Sci. Technol.

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When the working gas of a negative ion source is changed from hydrogen to its isotope, deuterium, an ‘isotope effect’ is observed; namely, several plasma characteristics such as the electron energy distribution, the atomic fraction and the spectra of rovibrationally excited molecules change. The understanding of the effect becomes more important, as research and development aiming at ITER power level operation is being challenged with feeding deuterium to the ion sources. As a historical review of the effort to develop hydrogen/deuterium negative ion sources, several types of negative ion sources designed for the neutral beam plasma heating are described: double charge exchange sources, volume sources and surface-plasma sources. The early results with volume sources operated with and without cesium are introduced. The characteristics of the source charged with deuterium are compared to those of the source charged with hydrogen. The isotope effect did not appear pronounced as the negative ion density was measured in a small source but became more pronounced when the plasma source size was enlarged and the discharge power density was increased to higher values. Surface plasma sources were optimized for deuterium operation but could not achieve the same performance as a source operated with hydrogen at the same power and pressure. The lower velocity of negative deuterium ions leaving the low work function surface seemed to limit the production efficiency. Fundamental processes causing these differences in negative ion source operation are summarized. After explaining the current status of negative ion source research and development, the acquired knowledge is utilized to the development of large negative ion sources for nuclear fusion research and to the development of compact negative ion sources for neutron source applications.

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Roles of a plasma grid in a negative hydrogen ion source

Cited by 13 publications

References 21 publications

Replacing the Orchestra? – The Discernibility of Sample Library and Live Orchestra Sounds

Replacing the Orchestra? – The Discernibility of Sample Library and Live Orchestra Sounds

Negative hydrogen ion production mechanisms

Negative ion source operation with deuterium

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