Critical Current Operation of the Optimized Self-Magnetic-Pinch Radiographic Diode

The self-magnetic-pinch (SMP) diode is being developed as an intense X-ray source for pulsed power driven radiographic systems. This diode is a critical current limited device described using equations derived from analytic approximations to large aspect ratio (cathode diameter to anode–cathode gap) variant diodes. The radiographic and large-aspect ratio variant of the SMP diode, differ in aspect ratio by around an order of magnitude. Derivation of the critical current limit for the large aspect ratio variant SMP diode requires a number of assumptions; not all of which are valid for the radiographic SMP diode. The applicability of existing critical current approximations to the radiographic SMP diode is discussed. A new critical current description for an optimized radiographic SMP diode configuration is proposed. This new critical current approximation is shown to account well for the radiographic performance (impedance and spot size) of optimized radiographic SMP diodes without the need for an experimentally derived empirical scaling factor.