Experimental study of intense proton beam transport through plastic foam using 2-D hybrid-PIC simulations with a unique proton source model*

Laser-accelerated proton beams have proven useful in many ways, including proton radiography and fast heating of solids to warm dense regimes. For applications requiring high current density, such as Fast Ignition Inertial Confinement Fusion, transport behaviors of the proton beam have not been well-studied. We report on an experimental study, done on the Omega EP laser, of intense (~10⁹ A/cm²) proton beam transport through plastic foam targets (380 mg/cm³) of length 0.55 mm or 1.0 mm. Copper foils were placed on the foams’ rear faces, and a spherical crystal imager tuned to Cu-Kα photon energies revealed proton- and electron-induced emission images, showing minimal beam break-up at both depths. 2-D hybrid fluid-PIC simulations implementing a unique proton-energy-dependent beam divergence showed that the foam could be heated to temperatures of several keV, and good agreement was found between the experimental and simulated Cu-Kα emission profiles.