2001 Fiscal Year Final Research Report Summary
Measurement of distribution functions of hydrogen atoms and molecules in a negative hydrogen ion source
| Project/Area Number |
12680484
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
プラズマ理工学
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| Research Institution | DOSHISHA UNIVERSITY |
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Principal Investigator |
WADA Motoi Doshisha Univ. Faculty of Engineering Professor, 工学部, 教授 (30201263)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Negative ions / Time of flight / Velocity distribution functions / Gas temperature |
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| Research Abstract |
A device to analyze mass separated time of flight spectrum was assembled for the direct measurement of distribution functions for neutral particles in a negative hydrogen ion source. The velocity distribution function of neutral particles effusing out through a 3 mm diameter hole of a 6 cm diameter, 6 cm long compact ion source showed the evidence of an acceleration due to formation of static shock at ion source pressure greater than 0.6 Pa, and the measurement was made below this critical pressure. The data scattering made the determination of distribution function with enough accuracy, and the temperature was obtained by fitting the measured result to a Maxwellian distribution. By sustaining arc discharges filling deuterium, helium, and Ar gases keeping the discharge voltage constant at 63 V and changing the discharge current up to 5 A, gas heating coefficients of 1.7 Kcm^3/W, 0.6 Kcm^3/W, and 1.9 Kcm^3/W were obtained for the respective gas. Here, deuterium showed reduction in temperature against increase in discharge power after reaching the maximum temperature of 1200 K at 6 W/cm^3 discharge heating density. This is attributable to the reduction in high speed component of deuterium molecules by dissociation, which was confirmed through the reduction in deuterium flux.
Through the present measurement, the temperature of the molecules in actual ion sources can be assumed close to 1000 K. The temperature of atomic hydrogen has not been clarified yet due to a noise from residual hydrogen, but an attempt to measure it is still continued.
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