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Fundamental Study due to Quantitative Measurement of Light Emission from Induced Discharge in Cloud

云中感应放电光发射定量测量的基础研究

基本信息

批准号：
04650239
负责人：
ARAI Kenji
金额：
$ 0.26万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

The purpose of this project is to clarify various characteristics of laser produced plasma to trigger lightning in cloud. The results are as follows.The experiment is performed by using water vapor as a target for the plasma production. The threshold laser energy for plasma production is reduced by 1/3 in this conditon. Using the optical image processing system for discharge light measurements, which consists of an image converter camera and a CCD camera, the spatial distributions of light emission from laser produced plasma and their temporal developments are successfully measured. The analyzing programs for these experimental data are newly coded on the usual personal computers and the engineering work station. The expansion and decay phases are quantitatively evaluated by the result of analysis. On one hand, the numerical analysis, in which the shock wave induced by a point explosion is treated, is performed to clarify the physical mechanism. The calculated results are well agree with the experimental results. The behavior of the plasma in the phase after the laser energy deposition can be described by the characteristics of shock wave propagation.The experiment is developed to spectrum analysis of the light emission. The absolute intensity of light is measured in two dimensional space of time and wavelength. The calibration experiments of the measurement system are carried out to short-gap discharge in air SF_6, which show the effectiveness of the system. The measurement is applied to the laser produced plasma, and its density and temperature are estimated. The estimated values are similar with a report by other groups.The further experiments, the measurement of induced current in the weak electric field, are already started. The more detailed and reliable knowledge will be obtained by the synthetic analysis with the result of this project.

本项目的目的是阐明激光产生的等离子体在云中触发闪电的各种特性。实验结果如下：实验采用水蒸气作为等离子体产生的靶标。在此条件下，产生等离子体的激光阈值能量降低了1/3。利用光学图像处理系统，成功地测量了激光等离子体光发射的空间分布及其时间发展。这些实验数据的分析程序是在普通的个人计算机和工程工作站上新编写的。根据分析结果，对膨胀相和衰变相进行了定量评价。一方面，对点爆炸产生的冲击波进行了数值分析，阐明了其物理机制。计算结果与实验结果吻合较好。激光能量沉积后等离子体的行为可以用冲击波的传播特性来描述，实验发展到光发射的光谱分析。光的绝对强度是在时间和波长的二维空间中测量的。对该测量系统进行了SF6气体中短间隙放电的标定实验，验证了该系统的有效性。对激光产生的等离子体进行了测量，估算了等离子体的密度和温度。估计的数值与其他小组的报告类似。进一步的实验--测量微弱电场中的感应电流--已经开始。通过与本项目成果的综合分析，将获得更详细、更可靠的认识。