We report systematic studies of laser-driven proton beams produced with micrometer-thick solid targets made of aluminum and plastic, respectively. Distinct effects of the target materials are found on the total charge, cutoff energy, and beam spot of protons in the experiments, and these are described well by two-dimensional particle-in-cell simulations incorporating intrinsic material properties. It is found that with a laser intensity of 8 × 1019 W/cm2, target normal sheath acceleration is the dominant mechanism for both types of target. For a plastic target, the higher charge and cutoff energy of the protons are due to the greater energy coupling efficiencies from the intense laser beams, and the larger divergence angle of the protons is due to the deflection of hot electrons during transport in the targets. We also find that the energy loss of hot electrons in targets of different thickness has a significant effect on the proton cutoff energy. The consistent results obtained here further narrow the gap between simulations and experiments.

中文翻译：

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来自强烈激光-固体相互作用的质子束：目标材料的影响

我们报告了分别由铝和塑料制成的微米厚固体靶产生的激光驱动质子束的系统研究。在实验中发现目标材料对质子的总电荷、截止能量和束斑有不同的影响，这些都通过结合固有材料特性的二维粒子在细胞模拟中得到了很好的描述。结果表明，在 8 × 1019 W/cm2 的激光强度下，目标法向鞘加速是两种目标的主要机制。对于塑料靶，质子的较高电荷和截止能量是由于来自强激光束的能量耦合效率较高，而质子较大的发散角是由于热电子在靶中传输过程中的偏转。我们还发现，不同厚度靶材中热电子的能量损失对质子截止能量有显着影响。这里获得的一致结果进一步缩小了模拟和实验之间的差距。