Elementary Study on Pulsed CO_2 Laser Induced Electrical Discharge through Plasma Produced by Linear Focused Beam Method in Atmospheric Air

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§1.Introduction From the view point of understanding elementary knowledge about the laser induced lightning method, we focused on the dependences of laser power density (LPD) at focused points and aerosol particles on laser induced electrical discharges (LIED) with non-uniform DC electric filed in an atmospheric air. We studied on experimentally (1) inner plasma energy and (2) characteristics of LIED by using of the LPD difference between point-focused and linear-focused methods with aerosol conditions.§2.Study on the behavior of pulsed laser produced plasma (PLPP) We measured electron temperature (T_e) and ion densitie (n_i) of a PLPP by a triple probe method of three ring chips with same surface area and high responsiveness-1μs. As the results, T_e was 4.4 eV and n_i was 〜10^<21> m^<-3> an illuminative PLPP at a point-focused position, and the plasma state was maintained more than 100μs without illuminating.§3.Study on the characteristics of LIED with aerosol particles We studied on experimentally the characteristics of LIED with non-uniform DC electric filed in an atmospheric air with aerosol particles simulated by incense smog. The density distribution of simulated aerosol particles in a discharge gap was observed to be nearly uniform by a laser scattering method. The relative increased density was 6x10^5. As the results, the LIED occurred even though the laser power density was 1/700 compared with the threshold of air breakdown in a simulated aerosol condition, and the discharge path of LIED was nearly linear.