电子-离子碰撞对超热电子影响的PIC模拟计算

PIC SIMULATION OF THE ELECTRON-ION COLLISION EFFECTS ON SUPRATHERMAL ELECTRONS

超热电子 离子的产生和输运在传统的ICF方案和“快点火”方案中都是很重要的问题 .讨论了电子 离子碰撞对参量不稳定性产生超热电子的过程和超热电子输运过程的影响 .指出电子 离子弱碰撞项的加入增强了碰撞吸收 ,提高了热电子温度 ,降低了静电波破裂时的场能 .这些改变了超热电子的总能量和分布 ,使之更集中于静电波的相速 ;电子 离子碰撞的存在还增强了自洽电场 ,阻碍了超热电子的输运 ,同样也是超热电子能量下降的原因之一 .同时 ,为确保计算结果的可靠 ,讨论了初条件对PIC模拟计算的影响 ,指出空间位置随机热启动容易引入非物理因素 。

The generation and transportation of suprathermal electrons are important to both traditional ICF scheme and “Fast Ignition” scheme. This paper discusses the effects of electronion collision on the generation and transportation of the suprathermal electrons by parametric instability. It indicates that the weak electron\|ion term in the PIC simulation results in the enhancement of the collisional absorption and increase of the hot electron temperature and reduction in the maximum electrostatic field amplitude while wave breaking. Therefore the energy and distribution of the supratermal electrons are changed. They are distributed more close to the phase velocity of the electrostatic wave than the case without electron\|ion collision term. The electron\|ion collision enhances the self\|consistent field and impedes the suprathermal electron transportation. These factors also reduce the supratermal electron energy. In addition, we discuss the effect of initial condition on PIC simulation to ensure that the results are correct.