Superhot-x-ray and -electron transport in high-intensityCO2-laser–plasma interactions

A comprehensive investigation of the high-energy [(70–400)-keV] x-ray emission from ${\mathrm{CO}}_2$-laser-produced plasmas at intensities up to 3×${10}^{14}$ W/${\mathrm{cm}}^2$ has revealed the presence of a ‘‘superhot’’ component. The intensity of this component scales very strongly with incident laser intensity. It is expected that for intensities ?5×${10}^{15}$ W/${\mathrm{cm}}^2$ energy balance in ${\mathrm{CO}}_2$-laser-produced plasmas would be dominated by the energetic electrons responsible for this high-energy x-ray emission.