Negative hydrogen ion production mechanisms

Negative 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 th...

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Bibliographic Details
Published in:Applied physics reviews 2015-06, Vol.2 (2), p.21305
Main Authors: Bacal, M., Wada, M.
Format: Article
Language:English
Subjects:
ANIONS
ATOMIC AND MOLECULAR PHYSICS
ATOMS
CESIUM
CESIUM ADDITIONS
DEUTERIUM
DEUTERIUM IONS
ELECTRIC CURRENTS
ELECTRODES
ELECTRON ATTACHMENT
ELECTRON TRANSFER
HYDROGEN
HYDROGEN IONS
MOLECULES
Physics
PLASMA
Plasma Physics
SURFACES
WORK FUNCTIONS
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Summary:Negative 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)
ISSN:1931-9401
1931-9401
DOI:10.1063/1.4921298