Design study of isochoric compression of DT capsules for ignition-scale proton fast ignition experiments

In the fast ignitor scheme, the assembly of a high-density inertial fusion target and the subsequent heating of a small "ignition spark" region are separated. The former being driven by a spherically distributed configuration of nanosecond-scale laser beams while the latter derives from a high-intensity, picosecond-scale laser which accelerates either electrons or protons that subsequently deposit their energy into the ignition spark region temporally near peak compression. With the compression and heating phases separated, the symmetry and thermodynamic requirements associated with producing an isobaric central hot spot are eliminated, opening the door for more opportunistic compression schemes centered solely on the maximization of density and areal density. One such example is isochoric compression. Isochoric compression involves compressing the inertial fusion target to uniform density and, ideally, low and uniform entropy. This uniform density profile results in comparatively higher areal densities than equivalent isobaric compression schemes by a factor of the hot spot aspect ratio to the two-thirds power. We present initial design studies of isochoric compression simulations at ignition scale using the one-dimensional radiation-hydrodynamics code, MULTI-IFE along with SESAME equation of state tables using both a multistage shock driver approach and a compression wave driver approach. The basis for this design follows the work of Guderley, Lazarus, and Clark utilizing self-similar flow variables as attractor solutions to the collapsing cavity problem.