X-ray observations of tungsten wire array Z-pinch implosions on QiangGuang-1 facility

Z-pinch experiments with two arrays consisting, respectively, of 324-μm- and 6-μm-diameter tungsten wires have been carried out onQiangGuang-1 facility with a current rising up to 1.5MA in 80ns. At earlytime of implosion, x-ray framing images show that the initial emission comesfrom the central part of arrays, and double clear emission rings, driftingto the anode and the cathode at 5×10⁶cm/s and 2.4×10⁷cm/s respectively, are often produced near the electrodes. Later,in a 4-μm-diameter tungsten wire array, filamentation caused by ohmicheating is prominent, and more than ten filaments have been observed. Aradial inward shift of arrays starts at about 30,ns earlier than theoccurrence of the x-ray peak power for both kinds of arrays, and theshrinkage rate of emission region is as high as 1.7×10⁷cm/s ina 4-μm-diameter tungsten wire array, which is two times higher thanthat in a 6-μm one. Emission from precursor plasmas is observed inimplosion of 6-μm-diameter tungsten wire arrays, but not in implosionof a 4-μm-diameter tungsten wire array. Whereas, in a 4-μm-diameter tungsten wire array, the soft x-ray emission shows the growth ofm=1 instability in the plasma column, which is caused by current. Thereasons for the discrepancy between implosions of 4-μm- and 6-μm-diameter tungsten wire arrays are explained.