The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

345 / 2019-02-27 08:56:00

Measurement of Ionic Structure in Warm Dense Graphite from X-ray Thomson Scattering

Warm Dense Matter; X-ray Thomson Scattering; Ion Static Structure Factor.

Plenary track > Fundamental Physics at Extremes

As an intermediate state of matter between condense matter and plasma, warm dense matter (WDM) exists widely in the core of planets and the implosion phase of inertial confinement fusion (ICF).
In the past few decades, Xray Thomson scattering has been used extensively to obtain insight into the structure and properties of WDM. In this method, intense X-ray sources are applied to penetrate through WDM and probe its temperature, density and ionization state. Comparing with that of optical Thomson scattering, the probe light of X-ray Thomson scattering has a much shorter wavelength and hence are more suitable for investigating dense plasma with electron densities of solid and above.
In this talk, we will present non-collective spectrally resolved X-ray scattering measurements from isochorically heated graphite samples. The elastic and inelastic scattering spectra for titanium He-α x-ray line at 4.75keV yield characterization of the temperature and ionization state of the samples. It is found that the plasma theories employing a screened Coulomb potential fail to describe the ion structure of warm dense carbon plasmas and only the models accounting for the effects of electronic configuration show a good agreement with the experimental result. This agreement further suggests that the short-lived chemical bonds play an important role in determining the ion structure of warm dense graphite systems with temperature of several electron volts.