Cathode structure for indirectly heated, narrow, ellongated oxide cathodes

Summary form only given, as follows. In special electronic devices a flat, elongated, cathode is required which may be six to eight inches long and 1/8 inch or more wide. For successful operation this structure must be held firmly in position and maintain its geometry. This objective has been achieved by mounting two telescoping U-channels on a sapphire rod and placing the heater in the interspace. The structure is simplified when one channel is replaced by square-cross-section tubing to which the second channel is spot-welded or brazed. The sapphire or ceramic rod is supported at its ends by suitable brackets which permit free sliding of the rod on heating.