Axial x-ray backlighting of wire-array Z-pinches using X pinches

Abstract

For the first time, a geometry has been developed to allow for an axial imaging system for wire-array Z-pinch experiments that produce high-resolution x-ray images. The new geometry required a significant redesign of the electrode hardware. Calibrated areal density measurements of the Z-pinch plasma including wire cores, coronal plasma, streaming plasma, and the precursor were obtained. The system used eight-wire molybdenum (Mo) X pinches in series with and directly below the Z-pinch axis to provide micron-scale x-rays sources for point-projection radiography. The images formed on the x-ray sensitive film had a 15 mm diameter field of view at the center height of the array and a magnification of about 7.5:1. Titanium (Ti) filters in front of the film transmitted radiation in the spectral range of 3-5 keV. For calibration, a separate film with the same thickness Ti filter was placed the same distance from the X pinch. This film had an unobstructed path that bypasses the Z-pinch but included step wedges for calibration of the Z-pinch plasma. The step wedges had thicknesses of tungsten (W) ranging from 0.015 to 1.1 microm to obtain areal density measurements of the W plasma from the wire-array. Images had subnanosecond temporal resolution and about 10 microm spatial resolution.