An Weiming, Lu Wei, Huang Chengkun, Xu Xinlu, Hogan Mark J, Joshi Chan, Mori Warren B
Department of Electrical Engineering, University of California Los Angeles, Los Angeles, California 90095, USA.
Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
Phys Rev Lett. 2017 Jun 16;118(24):244801. doi: 10.1103/PhysRevLett.118.244801. Epub 2017 Jun 14.
Plasma-based acceleration is being considered as the basis for building a future linear collider. Nonlinear plasma wakefields have ideal properties for accelerating and focusing electron beams. Preservation of the emittance of nano-Coulomb beams with nanometer scale matched spot sizes in these wakefields remains a critical issue due to ion motion caused by their large space charge forces. We use fully resolved quasistatic particle-in-cell simulations of electron beams in hydrogen and lithium plasmas, including when the accelerated beam has different emittances in the two transverse planes. The projected emittance initially grows and rapidly saturates with a maximum emittance growth of less than 80% in hydrogen and 20% in lithium. The use of overfocused beams is found to dramatically reduce the emittance growth. The underlying physics that leads to the lower than expected emittance growth is elucidated.
基于等离子体的加速被视为构建未来直线对撞机的基础。非线性等离子体尾场在加速和聚焦电子束方面具有理想的特性。由于纳米库仑束的大空间电荷力引起的离子运动，在这些尾场中保持具有纳米尺度匹配光斑尺寸的纳米库仑束的发射度仍然是一个关键问题。我们使用对氢和锂等离子体中的电子束进行完全解析的准静态粒子模拟，包括加速束在两个横向平面具有不同发射度的情况。预计发射度最初会增长并迅速饱和，在氢等离子体中最大发射度增长小于80%，在锂等离子体中小于20%。发现使用过聚焦束可显著降低发射度增长。阐明了导致发射度增长低于预期的潜在物理机制。
