Factors controlling the x-ray pulse emission from an intense femtosecond laser-heated solid

The evolution and radiation of strongly heated and ionized solid density material is calculated for conditions which are produced by an intense, femtosecond laser pulse. It is found that the spectrally integrated radiation emitted in the frequency range hν>kT_e, where T_e is the initial peak plasma temperature, can be as short in duration as ∼100 fs if kT_e is in an optimum range, set by the target material chosen. For temperatures in this range, the radiation pulse duration is controlled primarily by hydrodynamic expansion. Low x-ray yields can be attributed to suppression of high-ion-stage populations by the high rate of three-body recombination in solid density plasma.