Principal Hugoniot measurements of CH using Refraction Enhanced Radiography on the Gbar platform at the National Ignition Facility*

We have implemented Refractive Enhanced Radiography (RER) [1] for the Gbar platform [2] at the National Ignition Facility (NIF), which allows to obtain the principal Hugoniot over a range of pressures by measuring shock compression of spherically converging shock waves in indirect drive implosion experiments. Here, we present the results of a proof of principle experiment, which repeated a previous experiment using a solid plastic sphere [1] at 30 – 50 Mbar with 4x better spatial and temporal resolution. The trajectory of the shock wave was recorded using x-ray backlighting at 8.4 keV generated by a Cu tube passing a 5 µm wide slit, which defines the spatial resolution and is sufficiently small to generate refraction fringes at the shock front.  Fringe amplitude and integral provide an independent measurement of shock compression in addition to the nominal absorption contrast at the shock front, which is independent of ionization and hence opacity in the sample.

[1] Dewald et al. HEDP 36, 100795 (2020)

[2] Doeppner et al. Phys. Rev. Lett. 121, 025001 (2018)