Compact pulse transformer for 85 kV, 3.5 μs electron gun anode of compact X-ray Cargo scanner

Design of Compact and reliable 85 kV HV Pulse Transformer for Electron gun Anode pulsing is a major concern, when size and space are constraints. This paper describes design procedures and optimization of various parameters like HV insulation, step up ratio, rise time and flat top of Pulse transformer, operating with input from a 10 stage PFN of 50 ohm impedance and charged at 14 kV. The transformer should deliver rated output voltage of negative polarity 85 kV, 3 to 4 μs pulse width, less than 2 μs rise time and flat top within 10% across an electron gun load, equivalent to a parallel combination of 10 kQ and 200 pF load at a PRF of 250 Hz. Since the Cargo Scanner has to operate on movable carrier, this transformer is designed to operate even in the inclined positions. This transformer has given voltage step up, rise time and flat top of 13.75, 1.5 μs and 4.5% respectively for a 10 kQ and 200 pF load at 250 Hz PRF and also demonstrated operation in 900 tilted transformer positions. An effort has been put to achieve maintenance free Pulse transformer by providing effective sealing in the transformer tank to stop breathing action. Also, special flexing walls of transformer tank accommodate for small changes in volume of oil due to temperature variations.