Time-resolved high-energy x-ray spectra of laser-irradiated targets

Temporally resolved x-ray spectra in the range of 1-20 keV have been obtained from laser-irradiated high-Z disk targets. We obtain the first time-resolved direct observation of the suprathermal x-ray tail resulting from hot-electron generation due to collective processes. The measurements indicated that the suprathermal temperature theta/sub H/ has a temporal behavior which essentially follows the laser pulse of intensity I, implying a relation theta/sub H/ approx. I/sup n/,n > or approx. = 1, an unexpected result.