填充预等离子体通道靶激光电子加速研究

Laser electron acceleration in pre-plasma-filled channel targets

采用紧聚焦的超强短脉冲激光与固体通道靶相互作用是获得大电量、高准直相对论电子束的一种有效方式。实验中由于激光预脉冲烧蚀靶壁产生预等离子体会膨胀、填充到真空通道中,从而导致电子束品质发生变化。采用二维PIC粒子模拟程序研究了通道靶中填充预等离子体的电子加速过程。模拟结果显示,在功率密度为5.0×10^(20W/cm^(2))的超强短脉冲激光条件下,通道中填充一定密度的等离子体时激光场优先与低密度等离子体相互作用,激光脉冲与通道壁的相互作用减弱,电子加速机制由纵向场主导的真空电子加速转变为横向电场主导的等离子体电子加速,产生电子束具有更大的电荷量,但能量降低,发散角增大。

Two-dimensional PIC(Particle-in-Cell)simulation is used to investigate the electron acceleration process when a vacuum channel is filled with pre-plasma.Using a tightly focused ultra-intense short-pulse laser to interact with a hollow plasma channel is an effective way to obtain a relativistic electron beam with high power and high collimation.In the experiment,the pre-plasma generated by the laser pre-pulse ablation of the target wall will expand and fill the vacuum channel,resulting in changes in the quality of the electron beam.The simulation results show that under the condition of short-pulse laser with a power density of 5.0×10^(20W/cm^(2)),the laser field preferentially interacts with the low-density plasma when the channel is filled with plasmas.The laser pulse interacts with the low-density plasma and the interaction of the channel wall is weakened.The electron acceleration mechanism is transformed from the vacuum electron acceleration dominated by the longitudinal field to the plasma electron acceleration dominated by the transverse electric field,resulting in an electron beam with a larger amount of charge,but with a lower energy and an increased divergence angle.