Description
Laser-driven proton acceleration (LPA) is a promising route to compact proton sources for high-energy-density science and related applications. The target normal sheath acceleration (TNSA) is the commonly used accelerating scheme via a thin foil target. To enhance the cutoff energy, the microstructure is fabricated on the target. Recently, foam targets are considered as a potential target for laser-driven ion acceleration. By controlling the averaged density with its porous structure, the near critical density for LPA can be implemented.
There were several LPA experiments with foam targets and the uniform density distribution with the averaged density is usually assumed to compare the experimental data with the 2D/3D PIC simulation results. However, the porous structure should have a significant impact on the proton accelerations. Hence, we are motivated to constructed the foam target structure instead of using a uniform averaged density.
We construct synthetic foams using three-dimensional Voronoi Diagram (VD) to form statistically isotropic cellular networks. A VD partitions space into cells such that each cell contains all points closest to a given seed point. This geometry is ubiquitous in nature, appearing in cellular tissues, foams, polycrystalline grains, and many other packing and growth patterns. Its importance is that it provides a simple and statistically controlled way to generate realistic microstructures for systematic modeling and parameter scans.
Each realization is parameterized by the averaged pore size and the prescribed averaged density, which self-consistently determine the solid filling fraction and implied fiber thickness. This enables controlled parameter scans while preserving the target’s average density. The generated morphologies are benchmarked against scanning electron microscopy images and reproduce key pore-scale geometric features.
In this paper, we compare the foam target and uniform density target by full 3D PIC simulations. Moreover, we also systematically study the influence of the pore size and the averaged density on the proton acceleration.