Effect of laser power density on self-generated magnetic field and electron thermal conduction
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摘要: 为了理解超强激光与等离子体相互作用中产生的自生磁场形成机制和电子热传导特性,采用相对论电磁粒子模拟程序,估算了不同激光功率密度下,在等离子体表面所形成的电磁不稳定性产生的自生磁场大小和空间分布,得到了超热电子和经典Spitzer-Harm理论描述的电子热流随激光功率密度的演化情形.结果表明,非Maxwell速度分布的等离子体,由于电子初始时刻的无规则热运动,在等离子体上激发电磁不稳定性,而不稳定性激发的强电磁场使电子束在非常短的距离内沉积能量,同时对在激光有质动力推开电子时形成的超热电子能量输运产生抑制作用.这一研究结果对更好理解惯性约束核聚变快点火过程中自生磁场的产生、电子热传导等方面有帮助的.Abstract: In order to understand the generation mechanism of self-generated magnetic field and electron thermal conduction characteristics in the process of the interaction between ultra-intense laser and plasma,the strength and spatial distribution of the self-generated magnetic field under different laser power density were estimated by means of electromagnetic relativistic particle-in cell program simulation.The electron-thermal evolvement phenomenon was observed as described by the Spitzer-Harm theory.It is shown that different from previous models,the initial non-Maxwell distributed plasma stimulates the electromagnetic instability in the plasma because of the random thermal motion of electrons.It is not the strong magnetic field excited by instability makes the electron beam deposit the energy within very short distance.Meanwhile,it restrains the electron thermo current to be formed when the laser ponderomotive force bursts through the electron.This result is helpful to the self-magnetic field generation and electron thermal conduction in fast ignition of inertial confinement fusion.
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