Hot Electron Confinement in High Intensity Laser-Matter Interactions

High-intensity ($>$10$^{18}$ W/cm$^{2})$ lasers can produce relativistic electrons ($\sim $MeV) when focused onto solid density targets. We present measurements of escaped relativistic electron lifetimes in short pulse laser-irradiated solid experiments. Electron durations measured were significantly longer than the laser pulse length, suggesting the presence of phenomena which confine high energy electrons within the target-plasma volume. Investigating the confinement time of high energy electrons exceeds the limits of any simple plasma expansion models. Utilizing the implicit hybrid particle-in-cell code LSP [D. R. Welch \textit{et al.}, Phys. Plasmas \textbf{13}, 063105 (2006)], experimental conditions were simulated to explore the physics of hot electron confinement in laser-irradiated materials. *This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.