Control of fast electron propagation in plastic foam by doping high-Z elements

Fast electron propagation in foam target is studied by a newly developed hybrid particle-in-cell (PIC)/fluid simulation code named HEETS. The code employs an explicit time-stepping approach, treats the fast electrons by a standard, relativistic PIC method (including scattering and drag by the background plasmas), and models the background plasma as a collisional fluid.

A scheme of doping high-Z elements (like bromine (Br)) into low-Z target (polystyrene foam) in order to confine ultraintense laser-driven fast electron propagation in target is proposed. It is found that fast electrons can be confined better in doped target compared to that in pure low-Z target, attributing to its increasing resistivity and density, which induce an intenser resistive magnetic field to collimate the fast electron propagation. The increase of energy deposition in targets is slightly for doped targets, suggesting that it is suitable for long propagation of fast electrons. The scheme is also effective for fast electrons driven by higher laser intensities, like intensity required by fast ignition (I = 10²⁰W/cm²). The results here should be helpful for the applications of ultraintense laser-driven fast electrons.