Kαfluorescence measurement of relativistic electron transport in the context of fast ignition

Abstract

Electron transport within solid targets, irradiated by a high-intensity short-pulse laser, has been measured by imaging $K_{\alpha }$ radiation from high-$Z$ layers (Cu, Ti) buried in low-$Z$ (CH, Al) foils. Although the laser spot is $\sim 10\mu \mathrm{m}$ [full width at half maximum (FWHM)], the electron beam spreads to $⩾70\mu \mathrm{m}$ FWHM within $<20\mu \mathrm{m}$ of penetration into an Al target then, at depths $>100\mu \mathrm{m}$, diverges with a $40°$ spreading angle. Monte Carlo and analytic models are compared to our data. We find that a Monte Carlo model with a heuristic model for the electron injection gives a reasonable fit with our data.