In-Flight Measurements of Capsule Shell Adiabats in Laser-Driven Implosions

We present the first x-ray Thomson scattering measurements of temperature and density from spherically imploding matter. The shape of the Compton downscattered spectrum provides a first-principles measurement of the electron velocity distribution function, dependent on $T_e$ and the Fermi temperature $T_F\sim n_e^{2/3}$. In-flight compressions of Be and CH targets reach 6–13 times solid density, with $T_e/T_F\sim 0.4–0.7$ and ${\Gamma }_{ii}\sim 5$, resulting in minimum adiabats of $\sim 1.6–2$. These measurements are consistent with low-entropy implosions and predictions by radiation-hydrodynamic modeling.