Plasma plume characteristics of an aluminum target irradiated by a nanosecond pulsed laser with oblique incidence

The incidence angle of the pulsed laser has a significant influence on the performance of laser propulsion. To further reveal the impulse coupling mechanism when the pulsed laser is obliquely incident irradiated, a plume observation system with high spatial and temporal resolution and a plasma plume emission spectrometry system were designed and built. In this paper, time-resolved images and the plasma emission spectrum were investigated for pulsed laser irradiation of aluminum targets at 0°, 15°, 30°, 45°, 60°, and 75° in a vacuum environment. The results of the study show that the plasma plume is always ejected along with the normal phase of the target surface. Additionally, the electron number density, the plume radiation intensity, and the plasma temperature weaken as the angle of incidence increases. Besides, a high-precision three-dimensional spectral collection platform was built to finely study the two-dimensional spatial distribution of the plasma parameters in the flow field. The results show that the electron number density decreases rapidly with increasing distance from the target surface. In conclusion, the foundation is established for the analysis of the impulse coupling mechanism of pulsed laser oblique incidence.