New possibilities for the design of Plumbicon® tubes

The design to be described is based on an electrostatically focused gun which contains an accelerating lens. The triode part, which contains a limiting aperture, can consequently be biased at a low voltage, thus leading to a reduction in beam-discharge lag. A gun of this kind can be placed in a normal straight camera tube envelope, but it can also be combined with an enlarged head carrying the target, the outer diameter of the head being equal to that of the deflection coils, In this way the useful scan diagonal of the target can be made equal to the inner diameter of the envelope of the gun. A version with an enlarged head of this type has been made in the Philips Research Laboratory, making use of the Plumbicon
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tube. A description of the main parts of the tube such as the triode, the focusing lens, and the landing correction lens is given. Measurements of the beam acceptance, speed of response, and modulation depth are also presented. The Appendix gives calculations of the modulation depth, taking thermal velocities, space charge, and spherical aberration into account.