2-D Numerical Investigation of the Formation of Z-Pinch-Driven Dynamic Hohlraum at 8-MA Current Level

Abstract

The newly developed code MULTI2D-Z is applied to simulate the formation process of a dynamic hohlraum driven by tungsten wire-array Z-pinch at 8-MA current level. In the initial phase, the foam is expanding due to the radiation heating from the imploding wire-array plasma. At the same time, this causes a compression-wave spreading inward in the foam, and in turn a challenge for the safety of capsule embedded in the center of the foam in the inertial confinement fusion ignition experiment. There is instability development during the collision of the expanding foam plasma and the imploding wire-array plasma. However, fortunately, this instability was then spontaneously restrained due to the subsequent snow-plow implosion. The formed wall-like high-Z plasma (shock wave), in which the radiation mean free path is about 10 $\mu \text{m}$ , compresses the foam, and plays a well role in trapping the radiation in the foam. When the foam has been compressed a little and the high-Z plasma temperature decreases, the dynamic hohlraum begins to form. While the thermal radiation wave in the foam is spreading toward the center axis, the radiation temperature profile becomes comparatively uniform, and almost equates to the plasma (matter) temperature except at the place of the shock wave. The radiation temperature in the hohlraum is above 100 eV. The simulated results also suggested that the radiation energy loss to the electrodes would be one of the main reasons for the nonuniformity in the radiation field and implosion instability development during hohlraum formation.