Further work on the implementation of rod pinch diodes on negative polarity pulse power drivers

Recent work by the AWE Pulsed Power Group has been to implement a rod pinch diode on some of the UK lower voltage (800kV to 4MV) negative polarity pulse power drivers. The rod pinch diode is normally fielded on positive polarity drivers which eliminates stray emission from the cathode emitter to the surrounding support structure. All the UK radiographic machines operate in negative polarity and cannot readily be switched to positive. This has consequences for electron trajectories, potential loss current paths and x-ray photon attenuation in the anode support structure. Although successful in its implementation, the diode performance is partly limited by the x-ray photon attenuation in the anode support structure. This poster reports on the further work undertaken in implementing the existing diode design on higher voltage drivers as well as experiments with an alternative diode designed to overcome attenuation from the anode structure.