Thomson scattering in dense plasmas with density and temperature gradients

TL;DR

This paper investigates how inhomogeneities in density and temperature affect X-ray Thomson scattering spectra in dense plasmas, revealing significant discrepancies from homogeneous assumptions.

Contribution

It provides a detailed analysis of the impact of plasma inhomogeneities on Thomson scattering diagnostics in dense, laser-generated hydrogen plasmas.

Findings

Discrepancies over 10% between mean and effective density.

Discrepancies over 10% between mean and effective temperature.

Inhomogeneities significantly influence scattering spectra interpretations.

Abstract

Collective X-ray Thomson scattering has become a versatile tool for the diagnostics of dense plasmas. Assuming homogeneous density and temperature throughout the target sample, these parameters can be determined directly from the plasmon dispersion and the ratio of plasmon amplitudes via detailed balance. In inhomogeneous media, the scattering signal is an average of the density and temperature dependent scattering cross-section weighted with the density and temperature profiles. We analyse Thomson scattering spectra in the XUV range from near solid density hydrogen targets generated by free electron laser radiation.The influence of plasma inhomogeneities on the scattering spectrum is investigated by comparing density and temperature averaged scattering signals to calculations assuming homogeneous targets. We found discrepancies larger than 10% between the mean electron density and the effective density as well as between the mean temperature and the effective temperature.