Implosion time circuit optimization study of ICF wire array loads for Sandia ZR facility

Summary form only given. We have conducted a theoretical study to optimize the performance of a Z-pinch-driven hohlraum powered by the future ZR accelerator. The Z-pinch system is being developed for inertial-confinement fusion (ICF) applications. The radiation source for the hohlraum consists of two co-linear 20-mm-diameter tungsten-wire-array pinches. Each of these will be either in a single- or nested-array configuration. Recent experiments on Z show that conventional 100 ns implosions are not necessarily optimal, with shorter implosions times on the order of 60 to 80 ns giving higher peak X-ray powers. This and other experimental evidence appears to validate the heuristic scaling of Stygar et al., which suggests that peak power is proportional to (I/sub p///spl tau//sub i/)/sup 3/2/, where I/sub p/ and /spl tau//sub i/ are the peak load current and implosion time, respectively. Using this heuristic scaling relationship we performed a system study for ZR, utilizing the NRL transmission code BERTHA. The wire load is modeled taking into account the influence of wire discreteness on the load inductance, and the wire ablation model introduced by Sergei Lebedev and collaborators in Imperial College, London UK. The importance of considering wire ablation is that this process affects the load inductance time history and thus the peak current and to a lesser extent the implosion time.