Measurement of Fast-Electron Energy Spectra and Preheating in Laser-Irradiated Targets

Fast electrons produced by the irradiation of plane-layered targets with 20-J, 100-ps, ${10}^{15}$-W.${\mathrm{cm}}^{-2\mathrm{}}$, neodymium-laser pulses have been diagnosed by the $K\alpha$ emission which they cause at various depths in the targets. The fast-electron energy spectrum and absolute energy deposition (target preheat) are measured.