Measurements of the structural evolution of X pinches and the formation of radiating hot spots

Abstract

In previous work on the X pinch (XP) facility (470 kA, 100 ns), we found that an on-axis z pinch forms in the cross point region during the final few ns prior to the radiation bursts. The rapid collapse of the z pinch results in a gap in the observable mass distribution, which we refer to as a minidiode. Improved measurements of the collapse of this z pinch have been made, allowing more reliable estimates of the pinch velocities prior to the radiation burst, and the expansion velocities after the radiation burst. We have also observed self-similar structure in different stages of the z pinch collapse. In addition, the source of the radiation bursts was localized to within 10 microns within the observed z pinch structure using a technique reported during ICOPS 1999. Using three X pinches to backlight one another, two images of each X pinch can be obtained. Thus, the hot spot of one of the X pinches and the z-pinch structure both prior to and after its radiation burst can be determined. These results should enable us to better understand the role of the X-ray source in the dynamics of the X pinch.