Positive polarity effect on 8-wire cylindrical Z-pinches

Summary form only given. The Cornell University COBRA pulser is a nominal 1 MA, 1 MV machine, capable of driving upto 8 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 establish 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 one end of the array is attached to machine ground, and one end of each of the return conductors, still outside the radius of the array, is connected to the negative machine potential. The electric field lines in this configuration originate on the wires of the array, and this is referred to as the "positive polarity" configuration. Data were collected on 8-wire 12.5 in aluminum Z-pinches in both polarities. Time dependent X-ray signals were measured using diodes and diamond detectors. A 6 ns pulsed laser was used as a back lighter to obtain images that were time-stepped through the evolution of the pinch. Pinches in positive polarity showed an increase in the power and total energy of the soft X-rays, and a decrease in the power and total energy of the emitted hard X-rays as compared to negative polarity pinches. Initial observations indicated that the pinch column in positive polarity began to form earlier than in negative polarity, and the structure of the imploding material was shown to be drastically different for the two polarity configurations