Simulation of quasi-spherical shell implosions on Z for inertial confinement fusion

摘要

The magnetic implosion of a high-Z quasi-spherical shell filled with DT fuel by the 20-MA Z accelerator can heat the fuel to near-ignition temperature. The attainable implosion velocity on Z for an 8 mm diameter quasi-spherical shell, 13-cm/5s, is fast enough that thermal losses from the fuel to the shell are small. The fuel is initially heated by an ion acoustic wave to 200-eV after a convergence of 4. Thereafter the implosion is adiabatic and the temperature increases as the square of the convergence. To reach the ignition temperature of 5-keV an additional convergence of 5 is required. The implosion dynamics of the quasi-spherical implosion is modeled with the 2-D radiation hydrodynamic code LASNEX. LASNEX shows the main instability in the implosion to be surface mass flow from the higher latitudes to the equator that limits the convergence to 20. The LASNEX simulation shows an 8-mm diameter quasi-spherical tungsten shell weighing 20 mg on Z driving 6-atmospheres of DT fuel nearly to ignition at 3.5-keV with a convergence of 20. Simulations with MACH2 that determine the limits of convergence due to the Rayleigh-Taylor instability will be presented. Results of the simulations with LASNEX and proposals for experimental measurements will be presented.