Plasma flow control in the ablation and implosion phases in nested cylindrical and star wire array Z-pinches

Wire array Z-pinches are the most powerful laboratory x-ray sources, and the optimization of the x-ray radiation output requires the understanding of diverse phenomena. During the wire array implosion in such arrays, the jxB forces ablate plasma from the wires to the center, before the whole array mass implodes. We studied the ablation and implosion dynamics in nested cylindrical and star wire array Z-pinches. The two implosion modes of nested arrays were simulated by Al star wire arrays with "gates". Arrays with regular-length gate wires imploded in the "nontransparent regime". Arrays with long, higher-Z gate wires imploded in the "transparent" regime. A two-frame end-on UV laser probing diagnostics was developed for the Zebra generator.;Modified nested cylindrical arrays, called closely spaced arrays, were designed to implode without a precursor. Low-wire number arrays imploded accordingly. Precursor plasma was observed in higher wire-number arrays, despite outward jxB forces on the inner wires. The Al K-shell yield was highest for low wire-number nested arrays, which also imploded earlier. The presence of precursor in star wire arrays was determined by the direction of the jxB forces. Star wire array pairs were designed such that precursor and non-precursor arrays would have minimal differences. The presence of precursor decreased the x-ray yield parameters by 3-15%. Plasma flow control was achieved in these loads by varying the array configuration.;Radiative properties of multicomponent Z-pinches and laser produced plasmas were studied. When high-Z element (W, Au) was mixed with Al plasma in a wire array, a decrease of the electron temperature was observed. The cooling effect was not present in laser-produced Al-Au plasmas, which may be explained by different heating mechanisms.