Cathode with optimised thermal efficiency

A cathode structure for an electron gun of a cathode-ray tube having a reduced size and providing a fast cathode start-up time and excellent thermal efficiency. The cathode comprises a closed chamber consisting of a cap supporting an emitting part of the cathode and a dish-shaped skirt having an internal surface which is concave so as to reflect, by radiation, the thermal energy stored in the skirt walls, towards that region of the cap supporting the emitting part. The cathode structure also comprises filament supply leads which pass through the side walls of the skirt and connect to the filament heater contained in the closed chamber.