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

A high resolution axial x-ray imaging system for wire-array Z-pinch experiments has been developed. Calibrated areal density measurements of the Z-pinch plasma; including wire cores, coronal plasma, streaming plasma, and precursor can be obtained. The system uses Mo X pinches in series and below the Z-pinch load to provide point sources of x-rays for point-projection radiography. Images have a 15 mm diameter field of view at the center height of the array and a magnification of about 7.5:1. Ti filters in front of the film transmit continuum radiation in the spectral range of 3-5 keV. A separate film of the same thickness Ti and placed the same distance away with an unobstructed path includes step wedges for calibration of the Z-pinch plasma. The step wedges have thicknesses of W ranging from 0.015 to 1.1 $\mu $m to obtain areal density measurements of the W plasma from the wire-array. Images have subnanosecond temporal resolution and about 10 $\mu $m spatial resolution. The diagnostic will also be used in the future for imaging thin foil cylinder Z-pinches. Recent calibrated images as well as a discussion of future foil experiments will be presented.