激光诱导等离子体中聚焦程度对真空开关真空度检测的影响

Vacuum circuit breaker, as a kind of pollution-free circuit breaker, is expected to replace SF6 circuit breaker in high voltage and ultra high voltage power systems. On-line monitoring of vacuum switch vacuum degree is still an international problem. The vacuum detection method of vacuum switch based on laser-induced plasma is expected to realize the online detection of vacuum degree of vacuum switch. However, the formation process of laser-plasma is complicated, and the laser focusing degree directly affects the formation of laser-plasma. Therefore, the influence of laser focusing degree on laser-plasma needs further study. Firstly, the imaging of laser-plasma generated by different focal spots is studied. The results show that decreasing the focusing distance and increasing the beam waist radius can reduce the focal spot size and enhance the laser-plasma. In coaxial imaging, decreasing the focusing distance can increase the laser-plasma radiation intensity by 77.5% and decrease the coefficient of variation by 93.1%. Increasing the waist radius of the laser beam before focusing can increase the intensity by 32.9% and decrease the coefficient of variation by 73.5%. Secondly, the results of side imaging show that decreasing the focusing distance is better than increasing the waist radius before focusing, and the laser-plasma radiation is stronger. Finally, the stability analysis of laser-plasma shows that, the smaller the focal spot is, the more stable the laser plasma will be, and the accuracy of vacuum degree detection can be improved by increasing the laser power density.