Weakly ionized plasma channel by accumulation effect of charged particles using high repetition rate excimer laser

Density of charged particles produced by KrF excimer laser with high repetition rate of kHz order has been measured. The charged particles whose process and effect of the accumulation were confirmed in the case of laser repetition rate of 1 kHz. Moreover, it is achieved that the plasma density order of 5 ∼1012 cm-3 when laser repetition rate is 1 kHz and number of pulses is 30. Key issue to success for laser triggered lightning is to make long plasma channel more than 100 m which requires plasma density of 1013 cm-3. A weakly ionized plasma channel produced by an ultra-violet laser has been adopted for the laser-triggered lightning. The weakly ionized plasma is excellent for guiding ability because of a long plasma channel. Triggering ability, however, is not expected so much because of low plasma density of 1010 ∼ 1011 cm-3. Therefore, the triggering ability was attempted to improve by an accumulation effect of charged particles, which leads to the enhancement of plasma density using a kHz high repetition rate of KrF excimer laser. In this experiment the accumulation effect was studied using the KrF excimer laser with high repetition rate. The effect of repetition rate did not appear in the data with burst frequency less than 1 kHz. Then we carried out the operation with 1 kHz and 1.5 kHz burst frequency and the density of charged particles is higher than that obtained under 1 kHz burst frequency. Besides, the voltage waveform in the case of 1 kHz burst frequency rose when number of pulses was increased. This waveform shows the process of the accumulation of charged particles.