Thomson scattering from near-solid density plasmas using soft X-ray free electron lasers

We discuss a collective Thomson scattering experiment at the VUV free electron laser facility at DESY (FLASH) to diagnose warm dense matter at near-solid density. The plasma region of interest marks the transition from an ideal plasma to a correlated and degenerate many-particle system and is of current interest, e.g., in ICF experiments or laboratory astrophysics. Plasma diagnosis of such plasmas is a longstanding issue which is addressed here using a pump–probe scattering experiment to reveal the collective electron plasma mode (plasmon) using the high-brilliance radiation to probe the plasma. Distinctive scattering features allow one to infer basic plasma properties. For plasmas in thermal equilibrium the electron density and temperature are determined from scattering off the plasmon mode.