Analysis of Connection Process among Plural Number of Laser Produced Plasma Clusters for Laser Induced Lightning

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This project treats a connection process among plural number of laser produced plasma clusters for laser induced lightning. Analytical studies has been carried out for two years, and the following results are obtained.1. Air ionization process by ultra-violet laser irradiatiorn was investigated. The fourth-harmonic wave of YAG laser and a charged particle detection scheme due to an external electric field application were used. The density of ionized particles produced seemed to saturate in higher laser intensity region. The precise evaluation of the ionized region, however revealed that the density increased up to in the order of 10 to the 18th per cubic meter. The use of the second-harmonic wave with higher energy was also tried, but higher ionization was not obtained.2. The fourth-harmonic wave of YAG laser was irradiated and superposed on the irradiation of carbon di-oxide laser, and the probability of plasma production was examined. The most dominant factor of the plasma production was a time difference between both laser pulses.3. A dynamics of sheath of laser produced plasma on an external electric field application was numerically studied. By introducing a spatial variation of neutral particle density, a natural boundary condition was realized. The accumulation of electrons at the boundary of the higher potential side was confirmed. The potential dip, however, was not found in the calculations.We cannot achieve the final goal of the project in this two years. The project is still continuing, and more clear results will be obtained in the near future.