Plasma focus as a possible x-ray source for radiography

Abstract

A study of x-ray emission from a low energy (1.8 kJ) plasma focus (PF) device powered by a 9 µF capacitor bank, charged at 20 kV and giving peak discharge current of about 175 kA by using three different anode shapes with a lead insert at the tip is reported. Quantrad Si PIN-diodes with differential filtering are employed as time-resolved x-ray detectors, whereas a multipinhole camera with suitable absorption filters is used for time-integrated analysis. The x-ray flux in different energy windows is measured as a function of the hydrogen filling pressure for each anode. The maximum values of the energy-integrated x-ray flux are found to be 1.36±0.06 J sr−1, 2.70±0.11 J sr−1 and 2.17±0.09 J sr−1 for a cylindrical anode with a 75° cut at the tip, a tapered anode with a 75° cut at the tip and a tapered anode without any cut, respectively. The maximum x-ray emission in 4π-geometry is estimated to be 17.09±0.75 J, 27.91±1.28 J and 27.25±1.13 J with a cylindrical anode with a 75° cut at the tip, a tapered anode with a 75° cut at the tip and a tapered anode without any cut, respectively, and the corresponding wall plug efficiencies for x-ray generation are 0.95%, 1.55% and 1.51%. X-ray emission, presumably due to the electrons' bombardment activity at the anode tip, was dominant, which is confirmed by the pinhole images. To demonstrate the feasibility of the present PF device as a possible x-ray source for good contrast radiography, a set of experimental images is presented.