The optimum design of electrostatically deflected cathode-ray tubes

The optimum design is defined as the one which, for a given spot size and beam current, has minimum defocusing and maximum deflection sensitivity. The following parameters are supposed to be fixed: (1) over-all tube length; (2) screen diameter; (3) maximum accelerating potential; (4) cathode loading. By making use of the equations of motion in a parallel plate deflector system and an expression for limiting current density due to Langmuir, a solution is reached as follows: (a) make the electron gun as short as possible so that the deflectors can be mounted as far as possible from the screen; (b) make the deflectors as large and as sensitive as possible.