电致伸缩效应下水中电子输运特性

Electron transport characteristics in water under electrostrictive effect

水中快脉冲(脉宽数ns甚至ps级)放电过程中,快脉冲在电极附近引起电致伸缩效应导致电极附近形成空化区.电子在空化区内积累能量并高速进入水体,电子在水中的输运特性是水中脉冲放电起始与发展的关键因素.本文构建了考虑弹性与非弹性碰撞截面的水中电子输运物理模型,采用蒙特卡罗方法研究不同能量电子的透射与散射径迹结构特征,研究了弹性碰撞、电离与激发碰撞频次随电子初始能量的变化以及水中电子能量损失特征.结果表明,较低能量的电子(约20 eV)受水分子散射影响能量损失较大,透射能力较弱,随着电子初始能量的增高,电子受水分子散射作用的影响逐渐减小,具有更强的液体穿透能力;弹性碰撞次数远大于激发与电离碰撞,导致电子散射距离与透射深度相当,电离碰撞和激发碰撞次数随电子能量升高显著增加;电子入射能量越高,其能损越大,随运动距离增加,能损急剧下降,与电子的平均电离能量损失W变化趋势一致.本研究可为探究快脉冲放电机理提供重要数据基础.

The transport characteristics of electrons are crucial for the initiation and development of pulse discharge in water.In this work,we develop a physical model of electron transport that consides elastic and inelastic collision cross sections.The purpose of this study is to investigate frequency variations of elastic collisions,ionization and excitation collisions with different initial electron energy values,and to explore the characteristic of electron energy loss in water.The Monte Carlo method is employed to track structure characteristics of electron transmission and scattering under varying energy values.The results show that the electrons of lower energy(~20 eV)are significantly impacted by the water molecule scattering,hence their transmission capacities are weakened.When the incident energy of electron reaches 100 eV,the scattering deviation distance is roughly equivalent to the transmission depth,about 6-8 nm,and the maximum deviation angleθshift~60°.When the electron incident energy is in a range of 10-1000 eV,the number of elastic collisions is much greater than the number of excitation and ionization collisions,and the number of ionization collisions and excitation collisions increases significantly with the increase of electron energy.The higher the electron incident energy,the greater the energy loss is.However,the energy loss decreases sharply with the extension of penetration distance.For the ionization collision,the average ionization energy loss,W,decreases rapidly with the increase of electron energy,and ultimately maintains at a level of 20-30 eV,which is consistent with the experimental results reported.