Intense nanosecond duration source of 10–250 keV x rays suitable for imaging projectile-induced cavitation in human cadaver tissue

The design, fabrication, and performance of a repetitive nanosecond x-ray source having a pumped field-emission x-ray tube are described. A compact Marx generator, 61 cm in length and storing 12 J energy, directly drives the field-emission tube with voltage pulses >380kV and with <4ns rise time from an equivalent generator impedance of 52Ω. The x-ray dose is 520 μSv at a distance of 30.5 cm. A numerical simulation model is used in which the x-ray tube’s cathode width and anode-cathode gap spacing are permitted to change with time, while electron flow between the cathode and anode is space charge limited and nonrelativistic. The x-ray tube model is coupled to an equivalent circuit representation of the Marx generator that includes the capacitance variation with charging voltage of the BaTiO3 capacitors. The capabilities of the x-ray source for flash radiography have been demonstrated by the study of the evolution of cavitation in human cadaver legs induced by high-velocity projectiles.