Radiation losses from high Z, 10.6 μm laser-irradiated microballoons

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Abstract
The radiation emitted from CO2 laser-irradiated (λ = 10.6 μm), gold-coated microballoons has been measured absolutely in the photon energy range from 30 eV to 6 keV. Incident laser intensity varied from 1.6×1014 W/cm2 to 9.5×1015 W/cm2 with a 1 nsec FWHM pulse. Multi-channel x- ray diode data were statistically tested against assumed spectral forms, finding the best parameter fit corresponding to the minimum variance, chi square. The spectra were established to be blackbody with color temperatures ranging from 66 to 134 eV and with the fraction of incident energy radiated decreasing from 15% to 2.3% as laser intensity was increased across the above- mentioned range. Associated diagnostics confirmed these results. An analytical model is presented in which radiated emission from hot electron energy deposition is calculated. The calculations agree well with the measured data.