A collisional radiative model for caesium and its application to an RF source for negative hydrogen ions

Journal Article · Wed Apr 08 04:00:00 EDT 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4916415· OSTI ID:22391397

Wimmer, C. ^[1]; Friedl, R. ^[2]

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1. Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany)
2. AG Experimentelle Plasmaphysik, Universität Augsburg, 86135 Augsburg (Germany)

A collisional radiative (CR) model for caesium atoms in low-temperature, low-pressure hydrogen-caesium plasmas is introduced. This model includes the caesium ground state, 14 excited states, the singly charged caesium ion and the negative hydrogen ion. The reaction probabilities needed as input are based on data from the literature, using some scaling and extrapolations. Additionally, new cross sections for electron collision ionization and three-body recombination have been calculated. The relevance of mutual neutralization of positive caesium ions and negative hydrogen ions is highlighted: depending on the densities of the involved particle species, this excitation channel can have a significant influence on the population densities of excited states in the caesium atom. This strong influence is successfully verified by optical emission spectroscopy measurements performed at the IPP prototype negative hydrogen ion source for ITER NBI. As a consequence, population models for caesium in electronegative low-temperature, low-pressure hydrogen-caesium plasmas need to take into account the mutual neutralization process. The present CR model is an example for such models and represents an important prerequisite for deducing the total caesium density in surface production based negative hydrogen ion sources.

• OSTI ID: 22391397
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1655; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CESIUM
CESIUM IONS
CROSS SECTIONS
ELECTRON COLLISIONS
EMISSION SPECTROSCOPY
EXCITATION
EXCITED STATES
GROUND STATES
HYDROGEN IONS 1 MINUS
ION SOURCES
IONIZATION
ITER TOKAMAK
PLASMA
POPULATION DENSITY
RECOMBINATION
THREE-BODY PROBLEM