Multi-shot performance of a 1-MV, 15-kA rod-pinch-like diode for radiography

A rod-pinch diode, modified to operate in a non-pinching mode, is tested for multi-shot operation at 1 MV and 15 kA. Three different geometry diodes are used. A 3.2-mm or 4.7-mm diameter tungsten-rod anode, tapered on the end, is used to minimize anode damage and to maintain a small source size. The diode parameters are chosen to avoid beam pinching. The diode operates successfully for at least 5 to 9 shots depending on the geometry. The first shot operates at higher impedance due to late-time anode ion turn-on. Multi-shot operation is limited by anode rod damage. The dose on-axis at 1 meter from the source is 0.7 to 0.9 rad(Si) and varies by /spl plusmn/20% from shot to shot. The source diameter is 2 to 4 mm and decreases from the first to the last shot even though the dose is not degraded.