The propagation of a plasma shock wave generated from an Al target surface ablated by a nanosecond Nd：YAG laser operating at 355 nm in air is investigated at the different focusing positions of the laser beam by usin...The propagation of a plasma shock wave generated from an Al target surface ablated by a nanosecond Nd：YAG laser operating at 355 nm in air is investigated at the different focusing positions of the laser beam by using a time-resolved shadowgraph imaging technique. The results show that in the case of a target surface set at the off-focus position, the condition of the focal point behind or in front of the target surface greatly influences the evolution of an Al plasma shock wave, and an ionization channel forms in the case of the focal point set in front of the target surface. Moreover, it is found that the shadowgraph with the evolution time around 100 ns shows that a protrusion appears at the front tip of the shock wave if the focal point is at the target surface. In addition, the calculated results of the expanding velocity of the shock wave front, the mass density, and pressure just behind the shock wave front are presented based on the shadowgraphs.展开更多
基金Project supported by the National Key Basic Research Program,China(Grant No.2013CB922404)the National Natural Science Foundation of China(Grant Nos.61178022,11074027,11274053,and 11211120156)+1 种基金the Funds from Science and Technology Department of Jilin Province,China(Grant Nos.20111812 and 20130522149JH)the Research Fund for the Doctoral Program of Higher Education of China(Grant Nos.20122216120009,20122216110007,and 20112216120006)
文摘The propagation of a plasma shock wave generated from an Al target surface ablated by a nanosecond Nd：YAG laser operating at 355 nm in air is investigated at the different focusing positions of the laser beam by using a time-resolved shadowgraph imaging technique. The results show that in the case of a target surface set at the off-focus position, the condition of the focal point behind or in front of the target surface greatly influences the evolution of an Al plasma shock wave, and an ionization channel forms in the case of the focal point set in front of the target surface. Moreover, it is found that the shadowgraph with the evolution time around 100 ns shows that a protrusion appears at the front tip of the shock wave if the focal point is at the target surface. In addition, the calculated results of the expanding velocity of the shock wave front, the mass density, and pressure just behind the shock wave front are presented based on the shadowgraphs.
