Pre-pulse minimisation on Blumlein-based X-ray machines by optimisation of balance circuit parameters

At AWE, pulsed-power machines are routinely used to drive electron-beam diodes for flash X-ray radiographic applications in the 1–10 MV range. Some diode types are sensitive to relatively low levels of pre-pulse voltage, during the pulse-forming line (PFL) charging phase, due to small anode-cathode gaps and geometries that enhance electric fields. This results in electron emission prior to the main pulse, which alters conditions in the anode-cathode gap preventing proper diode operation. Limiting the pre-pulse voltage at the diode to below the emission level is therefore crucial.