The study of ablation and implosion dynamics in closely coupled nested cylindrical and star wire array Z pinches

Summary form only given. Plasma dynamics in cylindrical closely coupled and star wire arrays at ablation and implosion stages were studied. Formation of the Z-pinch and its radiative properties were studied in the non-precursor regime and compared with regular ablation regime with a precursor. It is possible to invert the direction of the jxB force in star arrays and in nested cylindrical arrays with closely located wires. In these loads plasma from the inner wires ablates outward, not to the center, and the array implodes in the non precursor regime. In some star array configurations with large number of wires, the inner wires ablate not to the center but within the rays, and do not form a precursor on the axis. This mode of implosion was observed in star and planar wire arrays. In closely coupled nested cylindrical arrays, the inner and outer cylindrical arrays are of equal wire numbers, with 0.5 lmm radial separation between the inner and outer wires. Calculations using the inductance method show outward j xB forces acting on the inner array, which also prohibits early plasma accumulation on the axis. This may also suggest that pairs of wires merging before imploding to the center. In contrast to this, ablation starts at the outer wires, and the plasma of these wires implode into the inner wires before the latter changes position. This behavior is similar to the cascading mode in star arrays. Ablation to the center is partly suppressed, and the ablated plasma forms a weak and late precursor. Shadowgraphy, both at 532nm and 266nm wavelengths, shows cascading features. The better plasma penetration of the UV light permits the resolution finer details, showing the cascading features, while the same region at 532nm probing appears as a mass of non-penetrable plasma. A two-frame 266nm UV-probing allows investigation of the dynamics of ablation implosion in areas opaque for regular probing at 532nm.