Investigation of argon gas as a potential shock attenuator in Z-IFE chambers using Alegra

The Z-IFE (inertial fusion energy) plant is a unique, inertial confined, fusion energy concept in which high yield targets will be ignited to fusion, yielding brief energy bursts in the 3 to 20-gigajoule range. The fusion reaction yields an energetic burst that consists principally of neutrons, X rays, and charged particles. The X rays rapidly attenuate in matter, causing the material to expand rapidly, thus generating a strong shock wave. This shock wave must be mitigated if the Z-IFE chamber is to last for a period of 30 to 50 years. ALEGRA simulations were conducted for a hypothetical Z-IFE chamber filled with argon gas and ionized by an X ray source. The calculations employed a set of sophisticated models, including Saha ionization, XSN and CDF opacities, bremsstrahlung radiation, linearized diffusion of X ray photons for a blackbody, fully-coupled magnetohydrodynamic models, electron thermal conduction, Spitzer thermal conductivity with cold material interpolation, and Mie-Gruneisen EOS. In order to obtain confidence in the results, a laser experiment from UCSD was simulated. In the experiment, laser photons were used to ionize argon gas. The simulations showed that ALEGRA quite successfully calculated the measured temperature, level of ionization, and spatial evolution of the argon plasma.