A Multi-Axis, Information Theory Based Figure of Merit for Flash Radiographc Sources

The Atomic Weapons Establishment (AWE) has a requirement to develop intense (1000 R at lm), fast duration (50 ns) Bremsstrahlung x-ray sources from small areas (<2mm diameter uniformly filled disc equivalent) at high peak energies (>10 MeV). These sources are required to provide high quality, transmission radiographic images through thick (hundreds of grams/cm² of lead equivalent density times thickness), high atomic number, explosively driven metal systems in a proposed new hydrodynamics research facility [1]. This new hydrodynamics facility is being designed with multiple radiographic axes capable of being used simultaneously or in a time sequence to interrogate temporal or three-dimensional aspects of hydrodynamic phenomena. A method by which the total information content generated by a number of intense Bremsstrahlung sources can be quantified is described. This information content is represented within a radiographic figure of merit that can be used to examine trade off in number of radiographic views and the quality of each radiographic view. The technique builds upon information theory based figures of merit developed by Fellget and Linfoot [2]. Application of the figure of merit in the determination of specifications for pulsed power driven x-radiographic sources, and advanced detector systems to be used in hydrodynamic experimental facilities is described. The impact on these specifications of whether multiple radiographic views are being used to determine temporal or three-dimensional information of hydrodynamic phenomena is noted. The use of the figure of merit to optimise the pace of delivery of enhancements to radiographic systems is in the context of hydrodynamic facility development at AWE is also discussed.