为了掌握激光点火中烧蚀和等离子体的特性, 采用平行电极板法研究了脉冲Nd∶YAG激光对硼-硝酸钾点火时的激光烧蚀等离子体导电特性和特征参数值。实验获得了B-KNO3(m(B)∶m(KNO3)=40∶60)和B-KNO3-酚醛树脂(m(B)∶m(KNO3)∶m(phenolic resin)=40∶60∶0.5)的等离子体形成的临界能量密度值分别为34.07±8.06 J/cm2和28.56±2.62 J/cm2, 电荷通量值和平均动能值分别为1.82×10-5 C/(mm2·s), 10.85×103 eV(62.05 J/cm2)和2.29×10-5 C/(mm2·s), 13.61×103 eV (60.80 J/cm2)。激光形成等离子体的点火延迟时间随着激光能量密度的增大而呈指数衰减, 在较低能量密度下掺杂酚醛树脂的B-KNO3的点火延迟时间比无酚醛树脂的B-KNO3长, 但是当能量密度达到35 J/cm2时两者相同。研究表明,酚醛树脂有助于B-KNO3的烧蚀, 并且形成的可反应性烧蚀产物具有较高离子浓度和动能。

Electric conductivity of laser plasma and its characteristic parameters were studied by parallel-plate electrode method for pulsed Nd∶YAG laser ignition of boron-potassium nitrate. The ignition threshold values of laser plasma of B-KNO3 (40/60 mass fraction) and B-KNO3-phenolic resin (40/60/0.5 mass fraction) are 34.07±8.06 J/cm2 and 28.56±2.62 J/cm2, and their ionic charge flux and average kinetic energy are 1.82×10-5 C/(mm2·s), 10.85×103 eV (at 62.05 J/cm2) and 2.29×10-5 C/(mm2·s), 13.61×103 eV (at 60.80 J/cm2) respectively. The ignition delay time of plasma depends on laser energy density in exponential decay, and the delay time of B-KNO3 doped phenolic resin is larger than that of B-KNO3 under a relatively low laser energy density, but same over 35 J/cm2. The results shown that phenolic resin accelerates the ablation of B-KNO3, and plays an important role to produce higher ionic concentration and kinetic energy of reactivity ablation products.