Characterization of the rod-pinch diode x-ray source on Cygnus

The rod-pinch diode is a self-magnetically insulated electron beam diode that is capable of producing a very bright source of hard X-rays. As fielded on the Cygnus accelerator, the diode operates at an impedance of 50 Ohms and produces short pulse ( ~50 ns) bremsstrahlung radiation with a 2 MeV photon endpoint energy and dose of 4 rad measured at one meter, with an X-ray spot size ~ 1 mm. The source can be used to image through ~ 40 g/cm² of material with spatial resolution of order 300 ¿m. Recently, a series of experiments on Cygnus have been conducted to better characterize the diode´s operation and X-ray output. In particular, the x-ray spectral content, source spot-size, and shot-to-shot reproducibility have been diagnosed. The intent of these experiments is to enable improvements that may extend the diode´s radiographic utility. An array of diagnostics have been utilized which include, end-on and side view X-ray pin hole imaging, time resolved and time integrated spot size measurements, step wedges, X-ray p-i-n diodes, and diode/MITL current measurements. High fidelity, PIC/Monte-Carlo simulations have also been conducted to help analyze the data. An overview of these experiments, simulations, and the conclusions from analysis is presented.