Abstract
We report on the characteristics of the electronegative plasma in a large-scale hydrogen negative ion (H-) source. The measurement has been made with a time-resolved Langmuir probe installed in the beam extraction region. The H- density is monitored with a cavity ring-down system to identify the electrons in the negative charges. The electron-saturation current decreases rapidly after starting to seed Cs, and ion-ion plasma is observed in the extraction region. The H- density steps down during the beam extraction and the electron density jumps up correspondingly. The time integral of the decreasing H- charge density agrees well with the electron charge collected with the probe. The agreement of the charges is interpreted to indicate that the H- density decreasing at the beam extraction is compensated by the electrons diffusing from the driver region. In the plasmas with very low electron density, the pre-sheath of the extraction field penetrates deeply inside the plasmas. That is because the shielding length in those plasmas is longer than that in the usual electron-ion plasmas, and furthermore the electrons are suppressed to diffuse to the extraction region due to the strong magnetic field.
| Original language | English |
|---|---|
| Article number | 02B116 |
| Journal | Review of Scientific Instruments |
| Volume | 83 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 2012 |
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ASJC Scopus subject areas
- Instrumentation
Cite this
Spatial distribution of the charged particles and potentials during beam extraction in a negative-ion source. / Tsumori, K.; Nakano, H.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Shibuya, M.; Asano, E.; Kondo, T.; Sato, M.; Komada, S.; Sekiguchi, H.; Kameyama, N.; Fukuyama, T.; Wada, S.; Hatayama, Akiyoshi.
In: Review of Scientific Instruments, Vol. 83, No. 2, 02B116, 2012.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Spatial distribution of the charged particles and potentials during beam extraction in a negative-ion source
AU - Tsumori, K.
AU - Nakano, H.
AU - Kisaki, M.
AU - Ikeda, K.
AU - Nagaoka, K.
AU - Osakabe, M.
AU - Takeiri, Y.
AU - Kaneko, O.
AU - Shibuya, M.
AU - Asano, E.
AU - Kondo, T.
AU - Sato, M.
AU - Komada, S.
AU - Sekiguchi, H.
AU - Kameyama, N.
AU - Fukuyama, T.
AU - Wada, S.
AU - Hatayama, Akiyoshi
PY - 2012
Y1 - 2012
N2 - We report on the characteristics of the electronegative plasma in a large-scale hydrogen negative ion (H-) source. The measurement has been made with a time-resolved Langmuir probe installed in the beam extraction region. The H- density is monitored with a cavity ring-down system to identify the electrons in the negative charges. The electron-saturation current decreases rapidly after starting to seed Cs, and ion-ion plasma is observed in the extraction region. The H- density steps down during the beam extraction and the electron density jumps up correspondingly. The time integral of the decreasing H- charge density agrees well with the electron charge collected with the probe. The agreement of the charges is interpreted to indicate that the H- density decreasing at the beam extraction is compensated by the electrons diffusing from the driver region. In the plasmas with very low electron density, the pre-sheath of the extraction field penetrates deeply inside the plasmas. That is because the shielding length in those plasmas is longer than that in the usual electron-ion plasmas, and furthermore the electrons are suppressed to diffuse to the extraction region due to the strong magnetic field.
AB - We report on the characteristics of the electronegative plasma in a large-scale hydrogen negative ion (H-) source. The measurement has been made with a time-resolved Langmuir probe installed in the beam extraction region. The H- density is monitored with a cavity ring-down system to identify the electrons in the negative charges. The electron-saturation current decreases rapidly after starting to seed Cs, and ion-ion plasma is observed in the extraction region. The H- density steps down during the beam extraction and the electron density jumps up correspondingly. The time integral of the decreasing H- charge density agrees well with the electron charge collected with the probe. The agreement of the charges is interpreted to indicate that the H- density decreasing at the beam extraction is compensated by the electrons diffusing from the driver region. In the plasmas with very low electron density, the pre-sheath of the extraction field penetrates deeply inside the plasmas. That is because the shielding length in those plasmas is longer than that in the usual electron-ion plasmas, and furthermore the electrons are suppressed to diffuse to the extraction region due to the strong magnetic field.
UR - http://www.scopus.com/inward/record.url?scp=84857828280&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84857828280&partnerID=8YFLogxK
U2 - 10.1063/1.3672116
DO - 10.1063/1.3672116
M3 - Article
C2 - 22380273
AN - SCOPUS:84857828280
VL - 83
JO - Review of Scientific Instruments
JF - Review of Scientific Instruments
SN - 0034-6748
IS - 2
M1 - 02B116
ER -