Formation and Dynamics of the Current Sheath in the Plasma Shell of a Z-Pinch in the Microsecond Implosion Regime

Abstract

The structure and characteristics of the current sheath formed in a metal-puff with an external plasma shell were studied with a current flowing up to 2.5 MA in amplitude with a microsecond rise time. It is shown that in the system used, a compact and uniform in azimuth current sheath is formed already in the early stage of implosion, which stabilizes the process of compression of the liner from large diameters in the microsecond regime. The thickness of the current sheath decreases as it moves toward the center, and the average current density increases and amounts to tens of kA/cm2. According to B-dot data, the velocity of the current sheath exceeds the speed of sound in the liner plasma, leading to the appearance of a shock wave and compression of the plasma on the axis. A stable shell with a high current density, together with a density profile formed in the Z-pinch configuration, ensures stable liner implosion from an initial diameter of 32 cm to a pinch with a diameter of several mm.