High-power Linear Diode Bremsstrahlung Source Developments

Bremsstrahlung radiation simulation tests on large area (approximately 1 m/sup 2/) systems will require an array of relativistic electron beam diodes to achieve good dose uniformity. A parallel array of long, linear diodes offers electrical and mechanical advantages over a nested ring diode array. However, beam-generated magnetic pressures could pinch the beam along the long dimension of the diode, thereby reducing die effective source height and degrading the uniformity of emitted radiation. Experiments to determine the performance characteristics of a linear diode have been conducted on the DNA/PITHON pulse generator. A self-magnetically insulated transmission line (MITL) was designed for a 76 cm high by 2.5 cm wide blade cathode at the diode. The MITL and diode designs are presented along with experimental results. A uniform diode (accelerating) gap resulted in a near field X-ray dose distribution peaked near the blade mid-height, with /spl plusmn/20% dose uniformity along less than /spl plusmn/60% of the blade height. Diode gap profiling, which affects the diode current density distribution, enabled the achievement of /spl plusmn/20% near-field X-ray dose uniformity along nearly 90% of the blade height.