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

Abstract

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>${\mathit{kT}}_{\mathit{e}}$, where ${\mathit{T}}_{\mathit{e}}$ is the initial peak plasma temperature, can be as short in duration as ∼100 fs if ${\mathit{kT}}_{\mathit{e}}$ 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.