Capsule design for charged-particle stopping power measurements using simultaneous gamma-ray, particle, and x-ray observations of implosions*

We plan to measure the stopping power $\Delta E$/$\rho \Delta x$ of nonthermal charged particles in ICF plasmas, using an imploded capsule containing DT$^{3}$He. We will measure (1) ablator areal density $\rho \Delta $\textit{x via} $^{12}$C(n,n'$\gamma )$ gamma-ray detection, using the Gamma Reaction History diagnostic, where the gamma rays are generated by 14.1-MeV DT neutrons; and (2) proton energy downshift $\Delta E$ \textit{via} spectrometry of 14.7-MeV D$^{3}$He protons, through collaboration with the MIT PSFC group. To measure $\Delta E$/$\rho \Delta x$ with a given accuracy imposes requirements on the accuracy of the separate measurements of $\Delta E$ and $\rho \Delta x$, and in turn on the yields of DT and D$^{3}$He reactions and $\rho \Delta x$ of the capsule. Other requirements include optimizing the shell to have shallow gradients of temperature $T_{e}$ and density $n_{e}$ so that most of the particle slowing occurs at well defined conditions. Further major necessities are: the ability to diagnose $T_{e}$ and $n_{e}$ in the shell \textit{via} x-ray spectra; and minimizing shell perturbation growth and anisotropy of particle emission.