Integrated simulation of the generation and transport of proton beams from laser-target interaction

High current, energetic protons are produced by irradiating thin metal foils with intense lasers. Here, the laser plasma interaction produces relativistic electrons at the critical surface. These electrons propagate through the foil and create a space-charge cloud that accelerates proton contaminants on the back side. Self-consistent electromagnetic simulations of this process using a hybrid particle-in-cell code show the importance of detailed modeling of the electron production and transport, as well as the distributed acceleration and spatial distribution of the protons well off the foil surface. The protons become neutralized by energetic electrons resupplied by the expanding plume of the back surface, not by energetic electrons thermalizing within the proton cloud. Details of the laser-plasma interaction simulation techniques and implications for ion-driven fast ignition are also discussed.