相对论强度下laser -物质相互作用中存在预等离子体时超高能电子源的确定
Identifying the source of super-high energetic electrons in the presence of pre-plasma in laser-matter interaction at relativistic intensities
摘要：
在一维平板近似下，采用粒子模拟方法研究了相对论强度激光与物质相互作用中预等离子体对超高能电子产生的影响。研究了$1\ μ\text{m}$、$5\ μ\text{m}$、$10\ μ\text{m}$和$15\ μ\text{m}$的不同前等离子体尺度长度，发现随着前等离子体尺度长度的增加，电子的粒子数和截止动能都增加，截止动能大大超过相应的激光有质动力能.提出了一个两阶段的电子加速模型来解释基本物理。第一阶段是纵向电场和激光脉冲的协同加速，其加速效率取决于等离子体尺度长度。这些在第一阶段预加速的电子可以建立一个强烈的静电势垒，其最大值是初始电子动能的几倍。部分高能电子在静电势垒的反射作用下被进一步加速，最终的动能明显高于第一阶段的预加速值。
英文摘要：
The generation of super-high energetic electrons influenced by pre-plasma at relativistic intensity laser-matter interaction is studied in a one-dimensional slab approximation with particle-in-cell simulations. Different pre-plasma scale-lengths of $1\ μ\text{m}$, $5\ μ\text{m}$, $10\ μ\text{m}$ and $15\ μ\text{m}$ are considered, showing an increase in both particle number and cut-off kinetic energy of electrons with the increase of pre-plasma scale-length, and the cut-off kinetic energy greatly exceeding the corresponding laser ponderomotive energy. A two-stage electron acceleration model is proposed to explain the underlying physics. The first stage is attributed to the synergetic acceleration by longitudinal electric field and laser pulse, with its efficiency depending on the pre-plasma scale-length. These electrons pre-accelerated in the first stage could build up an intense electrostatic potential barrier with its maximal value several times as large of the initial electron kinetic energy. Part of energetic electrons could be further accelerated by the reflection off the electrostatic potential barrier, with their finial kinetic energies significantly higher than the values pre-accelerated in the first stage.
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