GB883214A - Electrical vacuum pump apparatus - Google Patents

Abstract

883,214. Discharge apparatus. VARIAN ASSOCIATES. May 4, 1959 [June 16, 1958], No. 15199/59. Class 39(1) An ion sputter vacuum pump comprises a plurality of anodes and cathodes interleaved or assembled in separate stacks, at least one of and preferably all the anodes being cellular, a longitudinal magnetic field and a glow discharge being set up between the anodes and cathodes whereby cathode material by positive ion bombardment is atomised and deposits on the anodes and other parts of the apparatus so as to act as a getter for residual gas in the apparatus (a mechanical pump giving a rough vacuum). The cathode plates are of Mo, W, Ta, Ni, Fe, Tr, Ni, Ba, Al, Th, Mg, Sr and elements of atomic numbers 22-24, 40-42 and 72-74 and the rare earths. The cathodes and anodes have spacers 3, 9 respectively Fig. 3, of stainless steel threaded over pairs of rods 2, 11 respectively held by stainless steel crosspieces at the ends, 4, 12 are gas circulation holes. The cellular anodes are of titanium carried by brackets 8 of the same material spot welded to 7, 9, and anode support rods 11 are also of stainless steel. The anode support rods 11 have conical insulators 13 attached to the crosspieces by screws; 15 are shields. The anode-cathode assembly is carried by two brackets secured to the crosspieces by screws 23 and envelope 21 is of stainless steel. The anode lead 17 also of stainless steel is taken out through a " Kovar" " (Registered Trade Mark) ceramic-kovar seal which has a shield for atomised cathode material. A solenoid 28 has a helical coolant tube each being in two concentric layers and is associated with an iron yoke 31 and circular polepieces 32, 33. The seal 21-29, 31-36 has a copper gasket, 34, 35 being of stainless steel. The cathode plates 1 are earthed via the envelope 21. The anodes can be removed and replaced or sand blasted or chemically treated to remove atomised cathode material. The cathode plates may be multiapertured the apertures being aligned with the intersections of the anode cells, Fig. 4 (not shown). In another embodiment, Figs. 5, 6 (not shown) magnetic focusing is by six C shaped permanent magnets with common hexagonal iron polepieces. The anode insulators (as 13) are secured to recesses in an internal polepiece portion. Further sets of anodes, cathodes and C magnets can be arranged along an envelope of extended length. The devices are used in linear accelerators and electron microscopes.