X-Ray Backlighting of the Initial Stage of Single- and Multiwire $Z$-Pinch

Abstract

The initial stage of single- and multiwire <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> -pinch was investigated by X-ray backlighting using an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -pinch as the soft X-ray source. The experiments were carried out on the pulsed power generator PPG-I (400 kA/500 kV/100 ns), which was designed and constructed by Tsinghua University. The source <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -pinch and object single- or multiwire <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> -pinch are installed in the place of a current-return rod or the center between the anode and the cathode, respectively. The X-ray films with high resolution and high sensitivity were used to record the results. A resistive current probe and a Rogowski coil were used to monitor the current, and a step wedge filter was designed to measure the mass ablation rate of the thin wire. By a large number of imaging experiments, the time sequence of images for the coronal plasma formation, the interwire plasma merging, and the development of plasma instabilities of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> -pinch, as well as some important quantitative parameters such as mass ablation ratio and core expansion ratio, were obtained.