The dependence of the laser-driven ion acceleration from thin titanium foils in the Target Normal Sheath Acceleration (TNSA) regime on target and laser parameters is explored using two dimensional particle-in-cell simulations. The oblique incidence (${\theta }_L=45°$) and large focal spot size ($w_0=40\mu \mathrm{m}$) are chosen to take an advantage of quasi one-dimensional geometry of sheath fields and effective electron heating. This interaction setup also reveals low and achromatic angular divergence of a proton beam. It is shown that the hot electron temperature deviates from the ponderomotive scaling for short laser pulses and small pre-plasmas. This deviation is mainly due to the laser sweeping, as the short duration laser pulse each moment in time effectively heats only a fraction of a focal spot on the foil. This instantaneous partial heating results in an electron temperature deviation from the ponderomotive scaling and, thus, lower maximum proton energies than it could have been expected from the TNSA theory.

中文翻译：

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具有大激光焦距的目标正常护套加速度

使用二维粒子模拟，探索了目标常规鞘层加速（TNSA）方案中薄钛箔的激光驱动离子加速度对靶标和激光参数的依赖性。斜入射${\theta }_{\mathrm{大号}}=45°$）和较大的焦点尺寸（$w_0=40\mu \mathrm{米}$选择）是为了利用鞘场的准一维几何形状和有效的电子加热的优势。这种相互作用的设置还揭示了质子束的低和消色差角发散。结果表明，对于短的激光脉冲和小的等离子等离子体，热电子温度偏离了重势定标。这种偏差主要是由于激光扫掠造成的，因为每个时间的短时脉冲激光仅有效地加热了箔片上焦点的一小部分。这种瞬时局部加热导致电子温度偏离了磁势标度，因此，最大质子能量比TNSA理论所期望的低。