Electric field measurements in plasma based on electric field induced second harmonic generation (E-FISH) with nanosecond/picosecond laser

摘要

Electric field distribution is critically important for quantitative insights into the physics of non-equilibrium plasma in high voltage engineering. A promising non-intrusive optical technique namely electric field induced second harmonic generation (E-FISH), which has been set up to measure the steady state and transient fields with sub-nanosecond resolution based on nanosecond and picosecond Nd: YAG laser. The measuring system with picosecond laser has a sensitivity on the order of 0.5 kV/cm with a spatial resolution of several mm. Then we investigated the steady state electric field distribution under DC corona discharges with nanosecond pulse laser beams. The electric field distribution is obtained. By comparing the measurements with the results predicted by the ion flow model for negative corona discharge, we estimated the ion mobility and verified the Kaptzov assumption upon the surface electric field. Then we successfully conducted the sub-nanosecond (0.5 ns) resolution transient electric field under dielectric barrier discharge between 2-mm air gap parallel plates covered with ceramics in atmospheric air with picosecond laser. The measured results are compared to the kinetic model showing good agreements.