Parallel X pinches and the Affect of Polarity

Summary form only given. X pinches are often arranged in parallel. Parallel X pinches allow one to get point-projection radiograph images of a single object either at different times, different perspectives, or both. Also, when X pinches are in parallel, each one can make a point-projection radiograph of the other. During the formation of the X pinch neck and hot spots, current is divided between the parallel X pinches according to their relative inductance. The self-adjusting nature of the current distribution usually results in the parallel X pinches producing better sources than single X pinches. Parallel X pinches more often develop only one hot spot and generate electron beams of less intensity than single X pinches. These two characteristics are very important for point-projection radiography. Presented here are the results of experiments to characterize the behavior of parallel X pinches. Experimental parameters included wire material, wire diameter, number of wires, and polarity of the radial electric field. Of particular interest was the current measured individually through each X pinch. By keeping the return current path of each X pinch separate, we were able to monitor any changes in or interactions between the individual currents. The relative time between the occurrences of individual pinches on the same shot was observed using PCDs. Also of interest was the effect of polarity on the time evolution of four-wire X pinches. This information was obtained from a series of point-projection radiographs taken at different times on different shots. It was shown that the diameters of the wire cores at the time of the pinch were significantly larger in positive polarity than compared to negative polarity.