激光等离子体和烧蚀对含能材料的激光点火过程的影响

通过测试激光点火的延迟时间、等离子体电荷通量和等离子体对激光的吸收能力，研究了激光等离子体和烧蚀对激光点火过程的影响。实验采用的含能材料为B／KNO3(m(B)：m(KNO3)=40：60)，外加5％的酚醛树脂，激光器为脉冲宽度为680μs的Nd：YAG固体激光器。实验结果表明等离子体密度随激光能量的提高而增大，而且激光等离子体的电荷通量大于燃烧流的电荷通量。当激光能量密度低于某一临界值时，点火延迟时间随激光能量密度的提高而线性变短，然而激光能量密度超过该临界值后，激光点火延迟时间保持恒定。在实验条件下，激光等离子体几乎不吸收入射的激光能量，但是点火延迟时间的变化规律表明了烧蚀会阻碍激光能量向含能材料注入。

Effects of Plasma and Ablation on Ignition Processes of Energetic Materials under Pulsed Laser

The charge flux of plasma, the delay time of laser ignition and the absorbability of laser by plasma were tested to study the effects of plasma and ablation on laser ignition processes of energetic materials. Tested energetic material is B/KNO3 (m(B)∶m(KNO3)=40∶60)+additional 5% phenolic resin, 20 mg, under 37.92 MPa pressure. Laser set is a Nd∶YAG laser with 680 μs pulsed width. The density of plasma rises with increase of laser energy, and the charge flux of plasma is larger than that of combustion flow. The delay time of ignition is shorted with the rise of the energy density of laser linearly, but when the energy density increases over a critical value, the delay time keeps constant. The plasma do not almost absorb incident laser beam in the testing conditions, but experimental results of the delay time of ignition show that the ablation of laser prevents laser energy from depositing in energetic materials.