Towards Model-free Temperature Diagnostics of Warm Dense Matter from Multiple Scattering Angles

TL;DR

This paper introduces a model-free method for diagnosing the temperature of warm dense matter using multiple scattering angles in x-ray Thomson scattering data, improving the robustness of temperature measurements.

Contribution

It presents a novel model-free analysis approach for XRTS measurements at multiple angles, applied to heated graphite, highlighting potential for better EOS measurements.

Findings

Good consistency in temperature extraction across angles

Possible non-equilibrium signatures are masked by source function

Method suggests improved experimental setups for EOS and relaxation times

Abstract

Warm dense matter (WDM) plays an important role in astrophysical objects and technological applications, but the rigorous diagnostics of corresponding experiments is notoriously difficult. In this work, we present a model-free analysis of x-ray Thomson scattering (XRTS) measurements at multiple scattering angles. Specifically, we analyze scattering data that have been collected for isochorically heated graphite at the Linac Coherent Light Source (LCLS). Overall, we find good consistency in the extracted temperature between small and large scattering angles, whereas possible signatures of non-equilibrium may be hidden by the source function, and by the available dynamic spectral range. The present proof-of-principle study directly points to improved experimental set-ups for equation-of-state measurements and for the model-free study of relaxation times.