Positive Polarity Effects on 16-Wire Cylindrical Z-Pinches

Summary form only given. The Cornell University COBRA pulser is a nominal 1 MA, 1 MV machine, capable of driving up to 16 wire cylindrical Z-pinches. COBRA operates normally in negative polarity, with the driving capacitors charged negative with respect to machine ground. This in turn normally establishes the polarity of the array to be negative with respect to the grounded return conductors that are symmetrically located outside of the array radius. A bolt-on convolute can be arranged to preserve the negative array potential described above. This will be referred to as the "negative polarity" configuration, and in this case the electric field lines terminate on the wires of the array, a condition favorable for generating electron field emission. If a section of the convolute is rotated, then, without changing the polarity of the charge on the driving capacitors, the polarity of the wires in the array can be reversed. The electric field lines in this configuration originate on the wires of the array and this is referred to as "positive polarity" configuration. The electric field magnitude around the wires can be controlled by the proximity of the return current posts, which can be adjusted on the hardware for each shot. Data were collected on 16-wire 12.5 mum aluminum Z-pinches in both polarities, with varying electric field strengths. Time dependent X-ray signals were measured using diodes and diamond detectors. A 150 ps pulsed laser was used as a backlighter to obtain three shadowgraph images that were time-stepped through the evolution of the pinch. Data were also collected from a self-emission XUV quadrant camera and an optical streak camera. The combined effect of electric field strength and polarity was examined.