Radiation Transport in Laser-Matter Interactions.

X-ray emission and transport in laser-irradiated aluminum targets was studied both numerically and experimentally. The temporal evolution of the K-shell photoabsorption edge of shock compressed aluminum was measured with an x-ray streak camera. The experimental results were found to be in reasonable agreement with the predictions of one -dimensional hydrocode (HYRAD) which includes detailed calculation of radiation emission and transport. The effects of a finite focal spot on the K-edge profile were also assessed using a simplified two-dimensional hydrocode. The results suggest that the measured edge broadening is a consequence of non-uniform target conditions. Further numerical simulations using HYRAD verified the importance of K_ alpha emission spectrum in studying the effects of radiation transport. However, these predictions were found to be in significant disagreement with our experimental measurements of the time resolved K_alpha emission spectrum. One possible explanation for this discrepancy is an underestimate of the K_ alpha fluorescent yield for certain ion species of aluminum. The reason for this is the generation of excited states which can not decay through the Auger process. Nevertheless, the experimental results still show characteristics of the radiatively heated zone predicted by the hydrocode.