1991 Fiscal Year Final Research Report Summary
Basic Study for the Control of Lightning Using Laser-Induced Discharge and the Useful Method of Lightning Energy
| Project/Area Number |
02402030
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
電力工学
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| Research Institution | Kyushu Tokai University School of Engineering (1991)
Kumamoto University (1990) |
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Principal Investigator |
AKAZAKI Masanori Kyushu Tokai University School of Engineering, Professor, 工学部, 教授 (30037676)
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| Co-Investigator(Kenkyū-buntansha) |
HONDA Chikahisa Kyushu University, Graduate School of Engineering Sciences, Associate Professor, 総合理工学研究科, 助教授 (20037881)
IKEGAMI Tomoaki Kumamoto University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20136518)
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| Project Period (FY) |
1990 – 1991
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| Keywords | laser-induced discharge / lightning / 電放電 |
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| Research Abstract |
In this project we studied the basic process of laser-induced discharge under short and long gaps. Summary of research is as follows:
We measured the diffusing speed of the plasma induced in the air by CO_2 laser using Mach-Zender interferometer. According to our measurements, the plasma expands at the speed of 18 km/sec as a shock wave. expands at the speed of 18 km/sec as a shock wave.
We estimate that the plasma produced by laser acts as a conductor, because as the laser energy heats up, it expands and thins down the surrounding gas.
The absorption rate of laser energy by plasma is different depending upon the kind of laser. The absorption rate is 99.7%, 70 - 80% and 20 - 30% of the input energy in the case of the CO_2 laser, the YAG laser and the KgammaF excimer lasers respectively.
50% speak over voltages(V_<50>) decrease about one fourth by means of the plasma induced by laser in some conditions, but they gardly change in other conditions.
We observed in almost all experiments a long time-lag between plasma production and complete breakdown. This variation of time-lag depends on applied voltage and pressure rather than the kind of laser used or the laser energy.
In the range of our experiments, V_<50> are decreased to a minimum when the time-lag mentioned above is between several 10 mus and 100 mus.
When the electrode combination is plate vs. rod in the case of laser-induced discharge, we found that V_<50> are higher if plate electrode is negative than if it is positive. This characteristic is reversed when compared to normal 50% spark over voltages.
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