Tooley M P, Ersfeld B, Yoffe S R, Noble A, Brunetti E, Sheng Z M, Islam M R, Jaroszynski D A
Department of Physics, SUPA and University of Strathclyde, Glasgow G4 0NG, United Kingdom.
Laboratory for Laser Plasmas and Department of Physics and Astronomy, Shanghai 200240, China.
Phys Rev Lett. 2017 Jul 28;119(4):044801. doi: 10.1103/PhysRevLett.119.044801. Epub 2017 Jul 26.
Self-injection in a laser-plasma wakefield accelerator is usually achieved by increasing the laser intensity until the threshold for injection is exceeded. Alternatively, the velocity of the bubble accelerating structure can be controlled using plasma density ramps, reducing the electron velocity required for injection. We present a model describing self-injection in the short-bunch regime for arbitrary changes in the plasma density. We derive the threshold condition for injection due to a plasma density gradient, which is confirmed using particle-in-cell simulations that demonstrate injection of subfemtosecond bunches. It is shown that the bunch charge, bunch length, and separation of bunches in a bunch train can be controlled by tailoring the plasma density profile.
在激光等离子体尾场加速器中，自注入通常是通过提高激光强度直至超过注入阈值来实现的。或者，也可以使用等离子体密度斜坡来控制泡状加速结构的速度，从而降低注入所需的电子速度。我们提出了一个模型，用于描述在等离子体密度任意变化的短脉冲串 regime 中的自注入。我们推导了由于等离子体密度梯度导致的注入阈值条件，这一条件通过粒子模拟得到了证实，该模拟展示了亚飞秒脉冲串的注入。结果表明，通过调整等离子体密度分布，可以控制脉冲串的电荷量、脉冲串长度以及脉冲串列中脉冲串之间的间隔。
