GB1146490A - Improvements in or relating to getter pump assemblies - Google Patents

Abstract

1,146,490. Ionization pumps. SIEMENS A.G. 29 June, 1966 [30 June, 1966], No. 29158/66. Heading HID. A discharge tube-e.g. a travelling wave tubehaving a main cathode includes also a getter pump assembly having an indirectly heated auxiliary cathode mounted adajcent at least one target electrode coated with or formed of a getter substance, such that the auxiliary cathode both heats the target electrode by electron bombardment and also ionizes the gas. A metal capillary dispenser auxiliary cathode (Fig. 1, not shown) may be mounted in front of a zirconium or titanium coated molybdenum disc target electrode, the region directly opposite the cathode being left uncoated. The normal radial decrease in temperature of the disc may be modified to provide optimum temperatures for the gettering of a plurality of gases by a variation of the disc thickness with radius, and by adjustment of the voltage applied across the electrodes. In an alternative arrangement, as shown, two getter-coated target electrodes 2 and 3, the latter being apertured, are employed, the temperatures being determined by the relative potentials and spacing. In a further embodiment (Fig. 3, not shown) a cylindrical dispenser cathode having an emitting surface at each end is disposed between two gettercoated electrodes. The ionizing effect of the electron beam may be increased by using a convex or concave cathode surface, and a gettercoated electrode in the form of a hollow cylinder, with an open end facing the cathode and getter material at the bottom of the cylinder, is referred to. The heating element of the auxiliary cathode may be connected in series or parallel with that of the main cathode of the discharge tube; in a further arrangement, the tube incorporates a two-faced cathode, one emissive surface acting as the main cathode of the tube, and the other as the auxiliary cathode.