Xray Thomson Scattering and Emission Spectroscopy as a Measurement of Non-thermal Electrons in Hot Dense Plasmas

When intense x-rays, such as those produced by an x-ray FEL, interact with a solid target to produce a plasma [1,2], electrons are excited into the continuum via photo-excitation and Auger decay, providing a controlled source of electrons that are well-defined in energy, being a function of the atomic properties of the target and the energy of the FEL beam.  Owing to the dense nature of the system, these electrons rapidly thermalise due to collisional effects [3,4], yet during the FEL pulse itself, a non-thermal component of the electron distribution function will persist.  In principle, information concerning the collisional dynamics and the evolution of the electron distribution function could be gleaned from a diagnosis of this non-thermal component, providing important insight into several aspects of the physics of dense plasmas.  We present here an analysis of how such measurement might be obtained via the use of a combination of x-ray Thomson scattering and emission spectroscopy.  Initial results are compared with simulations from the CCFLY code, and appear promising for further studies.