Impact of load variations on the stagnation of nested stainless steel and copper z pinches

Summary form only given. A variety of wire array experiments in the last few years at the 20 MA Z accelerator have been performed to assess the impact of initial load mass, initial load diameter, and variations of the nested array configuration on the K-shell output. Nominally, optimized configurations have been identified, with optimization determined by the highest K-shell output with the fastest rising, narrowest X-ray pulse. Experimental and computational work has suggested that other load configurations may continue to improve the output. For example, experiments with W arrays have found that closure of the radial anode-cathode (RAK) gap may be reducing the radiated output achievable and wire number studies with single arravs have indicated that higher wire number loads could further increase output. Additionally, the impact of wire orientation on the large (> 1 mm) interwire gap nested loads has not been assessed. In this paper, the results of experiments performed to evaluate these configuration changes are presented. For stainless steel wire arrays (K-shell emission 5.6-7.7 keV), increasing the wire number on the nested arrays resulted in increased K-shell yield and K-shell power. Increasing the RAK gap, however, from 6 mm to 10 mm did not impact the K-shell emission, although changes were observed in the soft X-ray emission. The orientation of the wires on the inner and outer arrays of Cu wire arrays was not observed to impact the radiated output, although calculations suggest that the effect of wire orientation will be overwhelmed by magnetic field asymmetries induced by the wire location relative to the openings in the return current can. Stagnated plasma conditions from these experiments are discussed and compared with the conditions observed from previous experiments. Computational results for these configurations are also presented.