First quantitative measurements of charged-particle stopping and its dependence on electron temperature and density in Inertial-Confinement-Fusion plasmas

We report on the first quantitative measurements of charged-particle stopping in Inertial-Confinement-Fusion (ICF) plasmas at various conditions. In these experiments, four charged fusion products from the DD and D$^{3}$He reactions in D$^{3}$He gas-filled filled implosions were used to determine the stopping power of ICF plasmas at electron temperatures ($T_{e})$, ion temperatures ($T_{i})$, and areal densities ($\rho R)$ in the range of 0.6-4.0 keV, 3-14 keV and 2-10 mg/cm$^{2}$, respectively. The resulting data, in the form of measured energy downshift of the charged fusion products, clearly indicate that the stopping-power function depends strongly on $T_{e}$. It was also observed that the stopping-power function change in characteristics for higher-density implosions in which ions and electrons equilibrate faster, resulting in higher $T_{e}$ relative to $T_{i}$ and higher $\rho R$s. These results will be modelled by Landau-Spitzer theory and contrasted to different stopping-power models. This work was partially supported by the US DOE, NLUF, LLE, and GA.