Radiation from wire arrays imploding on an axial target

Adding thin wires on the axis of cylindrical and conical wire arrays significantly affected the x-ray emission of the conical wire arrays, while having practically no effect on that of the cylindrical ones. The experimental study was performed using Al wire arrays with central Al and Cu wires on the 1 MA Zebra Z-pinch generator at the Nevada Terawatt Facility. Adding wires on the axis of cylindrical wire arrays led to a decrease in plasma temperature and produced practically no change in the total radiation yield. In contrast, for conical wire arrays, both the plasma temperature and the total radiation yield increased approximately proportional with the central wire thickness. Both effects were stronger for Cu center wires than for Al center wires. When using Cu, radiative cooling played a substantial role in the implosion dynamics, leading to a more compact pinch than for Al wires. Adding Al wires on the axis of conical arrays produced a cocoon-shaped emissivity distribution, with a minimum on axis. For the case of Cu wires, a short-lived, straight, and narrow filament emitting photons with energy greater than 2.5 keV formed on the axis of the cocoon. This hot filament is produced by a transient heating mechanism intense enough to fully ionize Al, and the cocoon represents plasma heated by a conical shock formed in the conical array.