Study on High-Repetition-Rate Diagnostics of Laser Ablation Plasma

Abstract

Plasma diagnostics of laser ablation plasmas have been widely conducted for utilization of the plasma to industrial and space propulsion applications. In this study, high-repetition-rate (200 kHz) diagnostics of laser ablation plasma were conducted to obtain temporal variations of space potentials, electron temperatures, and electron densities in vacuum environment. For the diagnostics, an emissive probe, on which high-repetition-rate rectangular pulse voltages were applied at 200 kHz, was utilized and installed in an arbitrary position downstream of a Cu target. From the results, it was shown that electron temperatures peaked up to 4.6 eV at 45 us after the induction of laser ablation plasma. In addition, electron densities peaked up to 7.3 × 108 cm^−3 at 20 us. Moreover, from the measurement, it was shown that space potentials of the plasma were about 1.0 V regardless of temporal points within the range of this measurement.