Multi-phase ionization dynamics of carbon thin film irradiated by high power short pulse laser
Multi-phase ionization dynamics of carbon thin film irradiated by high power short pulse laser
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DOI：
10.1063/1.4986034
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发表时间：
2017-10-01
影响因子：
2.2
通讯作者：
Kishimoto, Yasuaki
中科院分区：
文献类型：
--
作者：
Kawahito, Daiki;Kishimoto, Yasuaki
用扩展的粒子积分程序（EPIC）研究了碳薄膜在10（19-20）W/cm（2）强短脉冲激光辐照下的电离动力学。两种类型的电离动力学表现出不同的时空结构被发现占主导地位的调节过程，并出现依赖于激光振幅。第一个是一个快速的对流传播的电荷状态C4+，这保持了陡峭的电离前沿。波前的速度大约是光速。前沿的形成是由局部纵向静电场和相关的场电离引起的，场电离又在薄膜内部传播。当激光场变得足够高，使得由激光有质动力加速的电子聚束达到相对论能量并穿过表面进入膜内时，就会触发这种对流传播。第二个动力学是一个快速的非扩散传播的电离，显示了一个长的等离子体密度尺度长度为C5+和C6+。该过程主要由激光连续产生的高能电子束团的电子碰撞电离引起。这些电子聚束还激发在膜内传播的尾场，并有助于将膜电离到更高的电荷状态，即，C5+和C6+，特别是靠近前表面。场电离损失的影响，这敏感地影响电离动力学在相对较低的激光功率制度，也进行了讨论。由AIP出版社出版。
he ionization dynamics of a carbon thin film irradiated by a high power short pulse laser in the range of 10(19-20) W/cm(2) are studied using the extended particle-based integrated code (EPIC), which includes atomic and collisional processes. Two types of ionization dynamics exhibiting different spatio-temporal structures are found to predominantly regulate the process, and arise depending on the laser amplitude. The first is a fast convective propagation for charge states up to C4+, which keeps a steep ionization front. The velocity of the front is of the order of the speed of light. The front formation results from the localized longitudinal electrostatic field and associated field ionization, which in turn propagates inside the film. This convective propagation is triggered when the laser field becomes high enough that electron bunches accelerated by the laser ponderomotive force reach relativistic energies and penetrate inside the film across the surface. The second dynamics is a fast non-diffusive propagation of ionization showing a long plasma density scale length for C5+ and C6+. This process results predominantly from electron impact ionization by high energy electron bunches successively produced by the laser. These electron bunches also excite wake fields that propagate inside the film and contribute to ionizing the film to higher charge states, i.e., C5+ and C6+, especially near the front surface. The effect of field ionization loss, which sensitively influences the ionization dynamics in the relatively low laser power regime, is also discussed. Published by AIP Publishing.