Improvements in avalanche-transistor sweep circuitry for electrooptic streak cameras

The performance of the avalanche transistor deflector driver (sweep) circuitry used in the high speed, electrooptic streak camera was improved. In the previous design for the sweep circuit, trigger to output delay time drifted on some cameras. This delay drift is a function of a somewhat randomly unstable breakdown voltage of some avalanche transistors. Both temperature and differences in manufacturing methods for transistors affect this instability. However, a significant improvement in system performance is achieved by long term burn in and by selection of only the most stable transistors for the sweep circuit. The peak to peak sweep voltage was increased about 80% by increasing the number of avalanche transistors in the string and raising the Q of the resonant circuit resulted in an improvement in sweep uniformity. Design equations for selecting components are given. Fast recovery diodes are used to prevent undershoot and to keep the beam out of the intensifier field of view until after the intensifier is gated off. The sweep time range is extended to over 100 ns.