A multi-sheath model for highly nonlinear plasma wakefields
A multi-sheath model for highly nonlinear plasma wakefields
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DOI：
10.1063/5.0051282
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发表时间：
2021-06-01
影响因子：
2.2
通讯作者：
Mori, W. B.
中科院分区：
文献类型：
--
作者：
Dalichaouch, T. N.;Xu, X. L.;Mori, W. B.
提出了一种改进的描述非线性等离子体尾流场的相速度接近光速，并与完全动力学粒子模拟进行了比较。这些尾场由强粒子束或激光激发，将等离子体电子径向向外推动，产生由电子鞘包围的离子泡，其特征在于源项S = -1/en（p）（rho-J（z）/c），其中rho和J（z）分别是电荷和轴向电流密度。以前，鞘源项被描述为唯象的正定函数，导致在一个正定的尾流电位。实际上，尾流电势在离子柱的后部是负的，这对于自注入和精确的束流加载模型是重要的。为了解释这一点，我们引入了一个多鞘模型，其中的源项，S，等离子体尾可以是负的离子泡以外的区域。利用这个模型，我们得到了一个新的表达式的尾流势和一个修正的微分方程的气泡半径。从这些方程得到的数值结果进行了验证，对卸载和加载尾流的粒子在细胞模拟。新的模型提供了准确的预测的形状和持续时间的拖尾束流轮廓，扁平等离子体尾场。它也被用来设计一个所需的纵向变化加载韦克菲尔德的拖尾束。我们提出了激光尾流场的光束加载结果，并讨论了如何在未来的工作中可以改善激光驱动器的模型。最后，我们讨论的多鞘和单鞘模型的预测梁加载之间的差异。由AIP Publishing独家授权出版。
An improved description for nonlinear plasma wakefields with phase velocities near the speed of light is presented and compared against fully kinetic particle-in-cell simulations. These wakefields are excited by intense particle beams or lasers pushing plasma electrons radially outward, creating an ion bubble surrounded by a sheath of electrons characterized by the source term S = -1/en(p) (rho - J(z)/c), where rho and J(z) are the charge and axial current densities, respectively. Previously, the sheath source term was described phenomenologically with a positivedefinite function, resulting in a positive definite wake potential. In reality, the wake potential is negative at the rear of the ion column which is important for self-injection and accurate beam loading models. To account for this, we introduce a multi-sheath model in which the source term, S, of the plasma wake can be negative in regions outside the ion bubble. Using this model, we obtain a new expression for the wake potential and a modified differential equation for the bubble radius. Numerical results obtained from these equations are validated against particle-in-cell simulations for unloaded and loaded wakes. The new model provides accurate predictions of the shape and duration of trailing bunch current profiles that flatten plasma wakefields. It is also used to design a trailing bunch for a desired longitudinally varying loaded wakefield. We present beam loading results for laser wakefields and discuss how the model can be improved for laser drivers in future work. Finally, we discuss differences between the predictions of the multi- and single-sheath models for beam loading. Published under an exclusive license by AIP Publishing.