Abstract: A color cathode ray tube having a screen with concentric phosphor ring patterns and an electron multiplying channel plate between the screen and the electron gun, the channel plate including a focusing control electrode having a constant focusing action.

Abstract: A channel plate electron multiplier having channels which rapidly decrease in cross-section away from the input aperture and a conductive structure extending across the input aperture to flatten any fringing electrostatic field, resulting in an electrostatic field configuration which causes secondary emitted electrons to collide with the same side of the channel.

Abstract: A flat large-area photocathode intended for use in an intensifier tube is constructed so that a pre-determined potential gradient can be maintained across its surface in operation in order to simplify the electron-optical system of the intensifier. This is done by providing photoemissive material on an electrically resistive layer or sheet on a major surface of which is provided a series of spaced rings of electrically conductive material one inside the other. The spacings and widths of the rings are chosen so that, when a potential difference is applied between the center and the edge of the sheet or layer, the desired potential gradient is set up across the surface of the photocathode. The intensifier tube may be an x-ray image intensifier.