Comparison of Implosions in Low Wire Number Cylindrical, Nested, and Linear Loads in the Zebra Generator

Summary form only given. Dynamics of the implosion stages in cylindrical, nested, and linear wire arrays were compared in the 1-MA Zebra generator. Using multi-frame laser probing and gated X-ray imaging in wire array Z-pinches, measurements of the microscopic origins of mass flow instabilities and current distribution were performed. In cylindrical wire arrays, plasma bubbles bring material to the axis of the array with a speed 200-500 km/s and produce a shock during collision with the precursor plasma column. A bubble-like mass transport is observed in all types of wire arrays (cylindrical, nested, linear, etc). In linear wire arrays, ablation and implosion begins on the outermost wires. Imploding plasma moves to the center of the array cascading from wire to wire. Nested arrays with the equal wire length were tested. Two-step implosions were observed in double nested arrays. Implosion begins on the outer array. The plasma bubbles then hit the plasma columns at the locations of the inner array wires, which then collapses to the center. Rescaling of plasma perturbations was observed in linear and nested arrays. This rescaling was also observed in Al nested double and triple wire arrays. In Al triple wire arrays, smoothing of plasma instabilities was observed in the last phase of the implosion.