AN ELECTRON-OPTICAL THEORY OF BEAM BLANKING

Trajectory equations are derived in closed form for electrons in time- dependent electric fields produced by beam blankers. Simple parallel p late and double-deflection blankers with transmission delay lines are evaluated. Lens imaging of the apparent beam motion is analyzed by dev eloping the virtual electron trajectories obtained from linear extrapo lation back into the blanker region. Lens excitation effects and conju gate blanking optics can then be described. The blanker voltage is rep resented by a damped exponential cosine term, which satisfies a typica l circuit equation for the driver-amplifier. The form of the trajector y equation is written as a 3 X 3 matrix, which comprises a set of cond itional solutions that are determined by blanker geometry. The optimum delay line length of any double-deflection blanker can then be determ ined. The blanker-induced beam jitter is shown to be significantly red uced by using this configuration. The effect of the blanker beam stop on the motion at the target plane is given by combining results on the real and apparent beam trajectories.