Cathode screen for gas discharge lamps

A mica apertured plate (10, 20) has been developed for the purpose of manufacturing long-life fluorescent tubes in machines with the tubes lying horizontally, where diffusion pumping cannot be performed by the introduction of mercury droplets into the tube, but where it is necessary to purge the tube with alternating tube evacuating steps. In the case of one embodiment, this plate has a circular shape and is provided with slots (12, 13) which extend from the periphery of the circular plate in towards a central hole (11), such as to form intermediate tongues (14). The apertured plate is supported by support devices (8, 9) at a constant distance from the lamp electrode (3), such as to form between the plate (10) and the lamp tube a gap in which electrons and ions of the emission material released from the electrode (3) recombine. In another embodiment, the apertured plate (20) is oval and is provided with a central hole (21) and with a recess (23) which is located in the edge of the plate and in which support devices can engage.