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报道了在北京大学新建成的5 Hz 200 TW飞秒激光加速器实验装置上利用68 TW(1.7 J,25 fs)的激光与混合气体(99%He掺杂1%N_2)进行激光电子加速的初步实验结果与理论分析.在实验中观测到了最大截止能量为290 MeV的连续电子能谱,并且最大输出能量在一定的聚焦范围内基本不变.二维particle-in-cell模拟表明:电离注入导致电子不断注入,使得纵向相空间在激光传播几个毫米后基本被电子填满;之后相空间中电子分布基本保持稳定,随着激光传播距离的增加,输出电子最大能量几乎不变,这与实验观察到的最大输出能量随激光聚焦位置在一定范围内不变的现象一致.实验与模拟结果揭示了在当前实验条件下连续电离注入对电子束品质的影响,为今后进一步优化电离注入电子品质提供了依据.
A preliminary report on the laser electron acceleration using a 68 TW (1.7 J, 25 fs) laser and a mixed gas (99% He doped with 1% N 2) at a newly constructed 5 Hz 200 TW femtosecond laser accelerator at Peking University Experimental results and theoretical analysis, the continuous electron spectroscopy with a maximum cut-off energy of 290 MeV was observed in the experiment, and the maximum output energy was basically unchanged within a certain range of focus.The two-dimensional particle-in-cell simulation showed that ionization implantation The electrons are continuously injected so that the longitudinal phase space is basically filled with electrons after the laser propagates a few millimeters. After that, the electron distribution in the phase space remains basically stable. As the distance traveled by the laser increases, the maximum output electron energy remains almost unchanged. The observed maximum output energy is consistent with the fact that the laser focus position does not change within a certain range.The experimental and simulation results reveal the effect of continuous ionization injection on the electron beam quality under the current experimental conditions and provide further optimization of the ionization injection electronic quality in the future The basis.