Advances in pulsed-power-driven radiography system design

Flash X-RAY radiography has undergone a transformation in recent years with the resurgence of interest in compact, high intensity pulsed-power-driven electron beam sources. The radiographic requirements determine the X-ray source requirements, which can be met by demonstrated Induction Voltage Adder (IVA) accelerators driving a variety of focused electron beam diode loads. Each diode option provides capabilities for a specific regime of voltage and brightness, but requires significantly different accelerator drive characteristics. For example, the rod-pinch diode is a 45 Ohm load while the paraxial diode operates at 200 Ohms. A flexible IVA that can efficiently drive either low or high impedance diode loads is potentially both cost effective and programmatically attractive. This paper summarizes recent research on high intensity electron beam diode loads for radiography, on both high and low impedance IV As. The paper also discusses an approach which links the different diode operating points through a non-linear retrapping phenomenon (converting cathode sheath electrons into usable bound current) in the magnetically insulated vacuum transmission line which connects the IVA accelerator to the diode load.