Plasma evolution and modulated structures along the wire within aluminum z-pinch/x-pinch loads on QG-I facility

Summary form only given. Experimental results on imploding dynamics of aluminum wire array z-pinch and x-pinch loads driven by QG-I facility are presented. The generator, mainly consisting of a linear transformer driver (240 kJ, 2.4 MV, 1 μs) and three sections of water coaxial lines, can deliver a 1.6 MA peak current, 60-70 ns 10%-90% rise time main pulse, with a pre-pulse of 100 kA amplitude, 200 ns duration, to z-pinch like loads. The prepulse may explode the wires to form core-coronal plasma columns with much larger diameters than the initial values, before the arrival of the main pulse.Cylindrical (CWA) and double planar wire arrays (DPWA) consisting of 20-50 micron diameter aluminum wires, and 2 4 wire x-pinches loads consisting of 50-200 micron diameter wires, have been tested to check the variation of plasma dynamics under different global magnetic field topologies. Time-gated x-ray images reveal similar features for both 8-16-wire CWA and two-wire x-pinch loads, i.e., formation of plasma streams perpendicular to the wire and quasi-periodically modulated structures along the wire with a wavelength of ~1 mm. In the CWA configuration, spots and gaps formed al ternately on different wires seem to be azimuthally correlated in many shots, although the interwire gaps are several millimeter large. While in the two-wire x-pinch configuration, plasma streams ablated from the wires form extremely intense axial jets, which interact with both A-K electrodes and lead to other rapidly expanding plasmas towards the crosspoint. This structural evolution causes collapse of the initial "X" shape and formation of more distributed plasma loads. Implosions of DPWA appear to be dominated by fast moving spots on the outer wires, resulting in axial modulation and trailing mass distribution, as the case of CWA loads. These observations, as well as characteristics of K-shell X-ray production, will be compared to reported results from other 1 -MA facilities which provide diff- rent dr iven pulses.