TALIF at H− ion sources for the determination of the density and EDF of atomic hydrogen
Abstract The production of H − ions in negative ion sources relevant for particle accelerator facilities and neutral beam injection systems is based predominantly on the surface conversion of H atoms at a low work function surface covered with caesium (the plasma grid (PG)). Therefore, the H atom de...
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Published in | Journal of physics. D, Applied physics Vol. 56; no. 15; pp. 155201 - 155210 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
IOP Publishing
13.04.2023
|
Subjects | |
Online Access | Get full text |
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Summary: | Abstract
The production of H
−
ions in negative ion sources relevant for particle accelerator facilities and neutral beam injection systems is based predominantly on the surface conversion of H atoms at a low work function surface covered with caesium (the plasma grid (PG)). Therefore, the H atom density
n
H
and energy distribution function (EDF) close to the PG determine the amount of surface produced H
−
ions. As a direct method for the density and EDF determination, two-photon absorption laser induced fluorescence (TALIF) on H atoms was implemented at the ion source of the teststand BATMAN Upgrade (BUG) being the first time that this was accomplished at an H
−
ion source. Several challenges had to be overcome concerning the application of the diagnostic at the complex facility and the evaluation of the fluorescence signals against a bright H
α
background. The observed line profiles suggest a Maxwellian EDF with an H atom temperature of
(
2000
±
500
)
K. The presence of highly energetic H atoms (measured by optical emission spectroscopy, (OES)) could not be resolved by the TALIF system due to the insufficient signal-to-noise ratio. Atomic densities were measured for H
2
and D
2
plasmas for varying ion source parameters at BUG resulting in values between
3
×
10
18
m
−3
and
1.1
×
10
19
m
−3
for hydrogen. For the operation with deuterium,
30
%
higher atomic densities are observed for similar ion source parameters which agree well with the previous results obtained with OES. |
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Bibliography: | JPhysD-133101.R1 |
ISSN: | 0022-3727 1361-6463 |
DOI: | 10.1088/1361-6463/acc07c |