Evaluation of laser-irradiated Ar clusters as a source for time-resolved x-ray studies

We have measured the absolute average photon flux, the spectral characteristics, and the time structure of x rays emitted from Ar clusters which were irradiated by a 100 fs laser with an intensity of 1017 W/cm2. The measured photon flux was 107 photons per shot in the Kα (at 3 keV) line in a 4π sr solid angle. The temporal structure was measured using a streak camera with a 10 ps time resolution. It was found that less than 1% of the photons were emitted within the 10 ps time-response function of the streak camera. The emission profile is roughly exponential with a time constant of 3 ns.