A digital electron deflection system

A novel split plate deflection system for stepped deflection of a 20 KV electron beam to discrete positions of an 8 × 8 square array will be described. The split plate configuration eliminates many of the problems of circuit dissipation and time response of alternate approaches using solid state drivers and conventional digital-analog converters. Overall requirements include high positional accuracy and stability, linear deflection superposition, and mechanical registration; the composite of which positions the beam at each array point to within 3% of maximum deflection. The plates are driven with equal voltages and are weighted in length to provide deflection fields which sum in binary fashion to drive the beam to any of eight positions per axis. The deflection drive is about 85 volts and is switched at 10 mc. Overall delay is on the order of 30 nsec. The drivers are driven by a parallel-fed, low-level, six bit, binary register. The present application involves addressing the electron beam to a specially designed header containing a matrix of silicon diodes. Details of design and construction together with experimental results will be presented.