Experimental development of rod pinch diode radiographic source using modified Kali 1000 pulsed power system

Abstract

This paper highlights the development of Rod Pinch (RP) diode for flash X-ray generation as intense radiographic source at BARC, Vizag. The typical RP diode employed used a small diameter (1–2 mm) anode rod extended through a cathode circular aperture (5–6 mm inner diameter). The diode chamber is maintained at 10−5 Torr vacuum by a rotary backed diffusion pump. Experiments performed on a modified Kali 1000 Pulsed Power System (300 kV, 30 kA, 100 ns) were aimed at optimizing the source by maximizing the figure of merit (dose @ 1m in rad/ spot diameter2 in mm2) with minimizing of the diode impedance. The typical electron beam parameters used in the experiments are 240–270 kV, 20–25 kA, 100 ns, with a few hundreds of kA/cm2 current density. The optimization resulted in a configuration with tungsten anode rod having dimensions of a 1.6 mm diameter, tapering extension length 5–25 mm beyond the graphite cathode aperture (Cathode disk ID = 5 mm, thickness = 3mm) to produce a radiation dose of 150–200 milli rad at 1 m distance having an estimated spot-size of 1–2 mm. The radiation emitted from a rod-pinch diode is measured using Thermoluminscence dosimeters (TLDs) at an angular interval of 15° on either side of the rod in horizontal and vertical plane.