皮秒脉冲机制下近临界密度等离子体中的高效激光离子加速
Efficient laser ion acceleration in near-critical density plasmas in the picosecond pulse regime
- Cornell University（康奈尔大学）
- Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
针对皮秒脉冲激光与近临界密度等离子体作用，提出扩展TNSA的解析模型，通过激光穿透加热电子鞘层提升离子能量与转换效率，预测最大效率37%，并经PIC模拟和实验验证。
AI中文摘要：
千焦耳级短脉冲（<10皮秒）激光器是产生相对论性离子束的优良工具，但实现高激光-离子转换效率仍是一个悬而未决的挑战。最近的实验表明，当利用平均等离子体密度接近相对论临界极限的目标时，转换效率显著提高。我们提出了一个解析模型来解释这一提高，该模型将靶法向鞘层加速（TNSA）理论扩展到包含激光对相对论临界密度目标的穿透，从而通过加热膨胀的电子鞘层将能量传递至离子前沿。这一物理过程增强了鞘层场强度，并相对于经典TNSA显著提高了离子截止能量和激光-离子转换效率。该模型通过优化激光透射和目标面密度，预测最大离子转换效率为37%。模型的关键标度与粒子网格（PIC）模拟及已发表的实验数据一致。一系列针对碳氢等离子体的二维和三维模拟证实了加速过程的稳健性，展示了利用相对论临界密度目标最大化离子产额的路径。
英文摘要：
Kilojoule-class short-pulse (< 10 ps) lasers are excellent tools for generating relativistic ion beams, but achieving high laser-to-ion conversion efficiency remains an open challenge. Recent experiments show a significant increase in conversion efficiency when leveraging targets with an average plasma density approaching the relativistic-critical limit. We present an analytical model that explains this increase by extending the theory of target-normal sheath acceleration (TNSA) to include laser penetration of relativistic-critical density targets, enabling energy transfer to the ion front by heating the expanding electron sheath. This physical process increases the sheath field strength and significantly improves ion cutoff energy and laser-to-ion conversion efficiency relative to classical TNSA. The model predicts a maximum ion conversion efficiency of 37% by optimizing laser transmission and target areal density. Key scalings of the model agree with particle-in-cell (PIC) simulations and published experimental data. A series of 2D and 3D simulations of hydrocarbon plasmas confirm the robustness of the acceleration process, demonstrating a path for maximizing ion yields using relativistic-critical targets.
