Demonstration of Geometric Effects and Resonant Scattering in the X-Ray Spectra of High-Energy-Density Plasmas

Abstract

In a plasma of sufficient size and density, photons emitted within the system have a probability of being re-absorbed and re-emitted multiple times - a phenomenon known in astrophysics as resonant scattering. This effect alters the ratio of optically-thick to optically thin lines, depending on the plasma geometry and viewing angle, and has significant implications for the spectra observed in a number of astrophysical scenarios, but has not previously been studied in a controlled laboratory plasma. We demonstrate the effect in the x-ray spectra emitted by cylindrical plasmas generated by high power laser irradiation, and the results confirm the geometrical interpretation of resonant scattering.