2002 Fiscal Year Final Research Report Summary
TOF Measurement of Low Energy Hydrogen Atoms Reflected on Solid Surface
| Project/Area Number |
12480125
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear fusion studies
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TAKAGI Ikuji Kyoto University, Department of Nuclear Engineering, Associate Professor, 工学研究科, 助教授 (20206717)
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| Co-Investigator(Kenkyū-buntansha) |
FUJITA Haruyuki Kyoto University, Department of Nuclear Engineering, Assistant Professor, 工学研究科, 助手 (90026039)
HIGASHI Kunio Kyoto University, Department of Nuclear Engineering, Professor, 工学研究科, 教授 (30026017)
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| Project Period (FY) |
2000 – 2002
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| Keywords | plasmas-facing walls / hydrogen recycling / particle reflection / atomic hydrogen / time-of-flight / energy reflection / velocity distribution / surface coverage |
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| Research Abstract |
For estimation of the hydrogen recycling in fusion devices, the velocity distribution of atomic hydrogen flying from rf plasma and that after reflected on metal surface were measured by use of the time-of-flight (TOF) method. The start pulse for the TOF measurement was obtained from a rotating blade with a small pinhole, with which hydrogen particles were bunched. The stop pulse was obtained from a quadrupole mass analyzer with a secondary electron multiplier, which could distinguish atomic hydrogen from other particles such as molecular hydrogen and residual gases.
The TOF measurement of atomic hydrogen ions from the rf plasma showed that the velocity distribution was expressed by the Maxwell-Boltzmann distribution with a temperature of 10,000 K when the mean free path of hydrogen in the plasma was larger than the characteristic length of the plasma The TOF measurement of atomic hydrogen ions after reflected on stainless steel showed that the energy reflection coefficient was around 80% for most hydrogen atoms and some hydrogen atoms were thermalized to room temperature.
The results of the present work are the followings; (l) The velocity distribution of atomic hydrogen from the rf plasma, generally difficult to be known, was quantitatively measured. (2) The energy reflection coefficient of 80% suggested that atomic hydrogen was not reflected with a binary collision but interacted with effective mass of some atoms existing on surface. (3) The probability of neutralization of atomic hydrogen ions was found to be larger than that to be expected from the data at higher energy regions.
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