Laser-driven ion sources are interesting for many potential applications, from nuclear medicine to material science. A promising strategy to enhance both ion energy and number is given by Double-Layer Targets (DLTs), i.e. micrometric foils coated by a near-critical density layer. Optimization of DLT parameters for a given laser setup requires a deep and thorough understanding of the physics at play. In this work, we investigate the acceleration process with DLTs by combining analytical modeling of pulse propagation and hot electron generation together with Particle-In-Cell (PIC) simulations in two and three dimensions. Model results and predictions are confirmed by PIC simulations—which also provide numerical values to the free model parameters—and compared to experimental findings from the literature. Finally, we analytically find the optimal values for near-critical layer thickness and density as a function of laser parameters; this result should provide useful insights for the design of experiments involving DLTs.

激光驱动离子源对于从核医学到材料科学的许多潜在应用都很有趣。双层靶（DLT）给出了一种提高离子能量和离子数量的有前途的策略，即通过近临界密度层涂覆的微米级箔。对于给定的激光设置，优化DLT参数需要深入而透彻地了解物理原理。在这项工作中，我们通过将脉冲传播和热电子生成的分析模型与二维和三维中的单元内粒子（PIC）仿真相结合，研究了DLT的加速过程。模型结果和预测已通过PIC仿真得到了证实，该仿真还为自由模型参数提供了数值，并与文献中的实验结果进行了比较。最后，我们通过分析找到了作为激光参数函数的近临界层厚度和密度的最佳值；该结果应为涉及DLT的实验设计提供有用的见识。