Methods used at AWE to Retrieve Radiographic Dose and Spot Size From LSP Simulations of Radiographic Diodes

AWE is developing high performance (1000R at 1 m, <2 mm spot size) flash X-ray sources to radiograph explosively driven heavy metal experiments. Intense electron beam diodes are being developed to deliver this capability from pulsed power drivers in a new hydrodynamics research facility known as the CPF [1]. The Large Scale Plasma (LSP) Particle In Cell (PIC) code [2] is being used extensively at AWE in the program to develop improved intense electron beam diodes. LSP does not currently incorporate direct methods to calculate radiographic parameters relevant to AWE such as the dose or spot size associated with a radiographic diode. There is therefore a need for methods that allow retrieval of experimentally measurable radiographic quantities from LSP simulations of radiographic diodes [3]. Two approaches are currently employed at AWE to retrieve such data. Firstly the primary output from LSP may be ported to a suitable Monte Carlo transport code such as MCNP [4]. MCNP can tally the expected Bremsstrahlung radiation from diodes and transport this radiation through simulations of experimental radiographic experiments to infer the spot size and dose from the diode. Secondly the LSP target methods may be used to gain information on the fluence and angular distributions of the electrons at the high atomic number target which may be further processed into source intensity distribution information. These methods are outlined and examples given, the methods have been found to agree with each other and with experiment to around 10%. The target method has been extended to 3D simulations and initial results from these methods are presented.