Fig. 1. Schematic of vacuum-plasma boundary injection in laser wakefield acceleration真空等离子体边界激光尾波电子注入示意图

Fig. 2. Distributions of plasma density and injected electrons after 500T₀ propagation when the boundary slant angle is 0°: (a) Injected electrons; (b) electrons in the second bubble 倾斜角为0°时激光传播500T₀后等离子体密度与注入电子(γ ≥ 15)的位置分布　(a)注入电子的分布; (b)放大后第二个空泡中的电子分布

Fig. 3. Average energy growth with time: (a) Average gamma factor of electrons in the first bubble; (b) average gamma factor of electrons in the second bubble激光传播过程中不同角度下的电子平均能量增长的情况　(a)第一个空泡内电子平均相对论因子γ的变化; (b) 第二个空泡内电子平均相对论因子γ的变化

Fig. 4. Electrons statistics after same acceleration length: (a) Average energy; (b) total acceleration charge (normalized to pC/μm).不同角度下电子注入后经过相同加速距离后的加速情况对比　(a)被加速电子的平均能量; (b)被加速电子的总电量(单位归一化到 pC/μm)

Fig. 5. Trajectories of electrons in the first bubble (red) and second bubble (blue): (a) 0°; (b) 45°. Ten electrons’ trajectories have been selected for clearer view不同倾斜角度下的第一个空泡(红色)和第二个空泡(蓝色)中注入电子的轨迹(为了显示清晰, 对两种倾角情形, 各自只选取了10个典型的电子)　(a) 0°; (b) 45°

Fig. 6. (a) Average transverse momentum of electrons in the first bubble (red) and second bubble (blue) when the boundary slant angle is 0°; (b) average transverse momentum of electrons in the first bubble (red) and second bubble (blue) when the boundary slant angle is 45°(a) 0°倾斜边界角时注入空泡1 (红)和空泡2上下两侧注入电子(蓝)的平均动量; (b) 45°倾斜边界角时注入空泡1和空泡2电子的平均动量

Fig. 7. Electrons’ injection trajectories when the boundary slant angle is 0°: (a) T/T₀ = 20; (b) T/T₀ = 40; (c) T/T₀ = 60; (d) T/T₀ = 90. Here the background color bar represents the plasma density, we have selected 3 particles with equally separation along the transverse direction. The blue and red lines represent the injection trajectories and the circles represent the particles’ positions at that time 倾斜边界角为0°时的电子注入过程(等横向间距选取了3个粒子作为示意, 背景为等离子体密度, 线条代表粒子的真实轨迹, 圆圈代表粒子在该时刻的位置)　(a) T/T₀ = 20; (b) T/T₀ = 40; (c) T/T₀ = 60; (d) T/T₀ = 90

Fig. 8. Electrons injection at 45° incidence: (a) T/T₀ = 40; (b) T/T₀ = 60; (c) T/T₀ = 80; (d) T/T₀ = 110 45°入射下边界面产生电子注入的过程　(a) T/T₀ = 40; (b) T/T₀ = 60; (c) T/T₀ = 80; (d) T/T₀ = 110

Fig. 9. (a) Original positions of the trapped electrons when the boundary slant angle is 0°; (b) original positions of the trapped electrons when the boundary slant angle is 45°(a)倾斜边界为0°情况下第一个空泡和第二个空泡内注入电子的起始位置; (b) 倾斜边界为45°入射下第一个空泡和第二个空泡内注入电子的起始位置