GB1148974A - Improvements in or relating to electric discharge tubes - Google Patents

Abstract

1,148,974. Discharge tubes. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 28 March, 1967 [30 March, 1966], No. 13974/67. Heading H1D. In an electric discharge tube comprising an oxide cathode and a non-evaporated getter of zirconium or titanium, wherein, during operation of the tube, the temperature of the getter is less than 75‹ C., there is incorporated within the tube a separate quantity of a titaniumhydrogen and/or a zirconium-hydrogen system which in operation of the tube is maintained at such a temperature as to enable a hydrogen pressure of substantially 10<SP>-7</SP> Torr to be maintained. As shown, a Ti ring 8 is saturated with H 2 according to the formula TiH 0 . 3 so that sufficient H 2 is present to provide a hydrogen pressure of 10<SP>-5</SP> Torr during the ageing process and of 10<SP>-7</SP> Torr during normal operation. Ti ring 8 is preferably so positioned close to cathode 1 and within grid 3 that it is heated by conduction or radiation from the cathode. In an alternative embodiment, Fig. 2 (not shown), a part (9) of the grid is formed of hydrogensaturated titanium, or a molybdenum plate (3), Fig. 3 (not shown), surrounding the cathode may be covered by a layer of titanium hydride of 150-200 Ám. granular size. The getter (not shown) also accommodated in the discharge tube may comprise a mixture of 500 mg. of Zr and W powder in equal parts by weight, and of 5 and 2 Ám. granular size respectively.