We investigated the effect of a plasma charge separation field on radiation reaction (RR) in laser–plasma interactions. By implementing the plasma field equation developed in one-dimension into the classical Landau–Lifshitz formula, our numerical test-particle modeling revealed distinctive plasma electron dynamics in three regimes: the low density underdense regime, the near-critical density (NCD) regime and the highly overdense one. It is discovered from the electron trajectories and gamma-ray emission that the RR effect is mostly significant at near-critical plasma densities. The underlying mechanism is well interpreted by the theoretical analysis from the perspective of the potential contained in the charge separation field and demonstrated in two dimensional particle-in-cell simulations using the quantum electro-dynamic photon emission approach. Our findings indicate that the NCD plasma is the most efficient medium to leverage RR and generate high-energy and low-divergence gamma-photons.
我研究了激光-等离子体相互作用中等离子体电荷分离场对辐射反作用（RR）的影响。通过将一维中发展的等离子体场方程纳入经典Landau-Lifshitz公式，我们的数值测试粒子模型揭示了三种密度区域中独特的等离子体动力学：低密度欠稠密区域、近临界密度（NCD）区域和高度过稠密区域。从电子轨迹和伽马射线发射中发现，RR效应在近临界密度等离子体中最为显著。其潜在机制通过理论分析从电荷分离场中所含势能的角度得到了很好的解释，并在使用量子电动力学光子发射方法的二维粒子模拟中得到了验证。我们的研究结果表明，NCD等离子体是利用RR产生高能量、低发散度伽马光子的最有效介质。