Numerical investigation on target implosions driven by radiation ablation and shock compression in dynamic hohlraums

Abstract

In a dynamic hohlraum driven inertial confinement fusion (ICF) configuration, the target may experience two different kinds of implosions. One is driven by hohlraum radiation ablation, which is approximately symmetric at the equator and poles. The second is caused by the radiating shock produced in Z-pinch dynamic hohlraums, only taking place at the equator. To gain a symmetrical target implosion driven by radiation ablation and avoid asymmetric shock compression is a crucial issue in driving ICF using dynamic hohlraums. It is known that when the target is heated by hohlraum radiation, the ablated plasma will expand outward. The pressure in the shocked converter plasma qualitatively varies linearly with the material temperature. However, the ablation pressure in the ablated plasma varies with 3.5 power of the hohlraum radiation temperature. Therefore, as the hohlraum temperature increases, the ablation pressure will eventually exceed the shock pressure, and the expansion of the ablated plasma will obviously weaken the shock propagation and decrease its velocity after propagating into the ablator plasma. Consequently, longer time duration is provided for the symmetrical target implosion driven by radiation ablation. In this paper these processes are numerically investigated by changing drive currents or varying load parameters. The simulation results show that a critical hohlraum radiation temperature is needed to provide a high enough ablation pressure to decelerate the shock, thus providing long enough time duration for the symmetric fuel compression driven by radiation ablation. V C 2015 AIP Publishing LLC.

Simulations on the multi-shell target ignition driven by radiation pulse in Z-pinch dynamic hohlraum*

“…However, when the plastic foam is covered with a metallic foam as the situation of type-B hohlraum, the preheat of plastic foam is well suppressed, and the shock S2 driven by the radiation ablation is eliminated. Xiao [38] proposed that the expansion of the ablated plasma will weaken the shock propagation and decrease its velocity with a critical hohlraum radiation temperature. The effects of the shock propagation transferring into the ablator plasma will be considered in future hohlraum design.…”

Preliminary investigation on electrothermal instabilities in early phases of cylindrical foil implosions on primary test stand facility

“…[1] Such an intense shot-pulse x-ray source can be employed to indirect drive inertial confinement fusion (ICF), like the dynamic hohlraum. [2] Meanwhile, the Z-pinch also shows the potential of direct drive ICF [1,[3][4][5][6][7] due to the huge magnetic pressure and the plenty of driven energy, such as the recent magnetized liner inertial fusion (MagLIF) concept. [6,8] Unfortunately, fast Z-pinches are inherently hydrodynamically unstable and are predominantly susceptible to the magneto-Rayleigh-Taylor (MRT) instability, [9][10][11] which occurs when a light fluid (driving magnetic pressure) is pushing against a heavy fluid (liner plasma) and seriously decreases the implosion quality.…”