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

本计画针对雷射诱发闪电，探讨复数个雷射产生电浆团簇间的连结过程。分析研究已经进行了两年，并获得了以下结果.研究了紫外激光辐照空气电离过程。四次谐波的YAG激光和带电粒子检测计划，由于外部电场的应用程序。在较高的激光强度区域，产生的电离粒子密度趋于饱和。然而，对电离区域的精确评估显示，密度增加到每立方米10的18次方。还尝试了使用能量较高的二次谐波，但未能获得较高的电离度.将YAG激光的四次谐波与CO2激光的四次谐波进行叠加照射，考察了产生等离子体的可能性。等离子体产生的最主要因素是两个激光脉冲之间的时间差.对激光等离子体鞘层在外加电场作用下的动力学行为进行了数值研究。通过引入中性粒子密度的空间变化，实现了自然边界条件。确认了电子在高电位侧的边界处的累积。然而，在计算中并没有发现潜在的下降，我们无法在这两年内实现该项目的最终目标。该项目仍在继续，在不久的将来将取得更明确的结果。

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.