Comparisons of the self pinch diode and the paraxial diode electron distributions at the conversion target using LSP

Simulations of radiographic diodes are routinely used at AWE to investigate the operation of X-ray sources used to radiograph hydrodynamic experiments. The X-ray generation is heavily dependant on the distribution of the electrons striking the bremsstrahlung conversion target and being able to accurately describe this distribution is key to any given simulation being useful. The time resolved distributions of electrons striking the bremsstrahlung conversion target for both the self magnetic pinch diode and paraxial diodes are described and compared to both each other and the common fist approximations of a shell of electrons and fully filled cone respectively. It is found that electron distributions in both diodes are not described well by such simple approximations, with the large scale plasma code (LSP) simulations predicting a double peaked distribution going out to around 25 degrees for the paraxial diode and a distributed distribution extending all the way to 90 degrees for the pinch diode.