GB910607A - - Google Patents

Abstract

910,607. Discharge apparatus. VARIAN ASSOCIATES. July 23, 1959 [Aug. 1, 1958], No. 25376/59. Class 39 (1). A getter pump has a central chamber and a plurality of outer chambers extending radially from and communicating with the central chamber, each outer chamber having anode and cathode electrodes, a glow discharge being produced between the anodes and cathodes. There may be four outer rectangular chambers and one central rectangular chamber, or, as shown in the modified embodiment of Fig. 8, a circular inner chamber and a large number of rectangular outer chambers. Each outer chamber contains two plate cathodes 14, Fig. 7, and a cellular Ti Sheet anode 17, the cathodes 14 being insulated from the anode 17 by four conical ceramic insulators 21. The cathode plates are Ti or Tr or of Mo, W, Ta, Nb, Fe, Cr, Ni, Ba, Al, Tb, Mg, Ca, Sr and other transition elements of the IV, V and VI groups of the Periodic Table and also the rare earths. Each pair of cathode plates 14 and anode 17 forms a sub-assembly termed a pumping canister which is removable and replaceable as a unit. The unit also comprises rectangular end blocks 13 of stainless steel, the cathode plates 14 having longitudinal slots at their upper ends which slidably receive pins 16 carried from end block 13 to allow for thermal expansion. The envelope, is of steel plate with end walls of stainless steel. Two spacers 24 of Ti interconnect the two cathode plates 14. Rectangular stainless steel guide tabs 25 are attached to guide retainers (not shown) to hold the canisters within the outer lesser chambers. The anode copper lead strips are brought out through hollow cylindrical insulators and the anode 17 has a rectangular frame 18 of stainless steel straps. The cathode plates 14 are grounded to the envelope through the end blocks 13 and guide tabs 28. Magnetic fields perpendicular to the cathode plates are produced by stacks of rectangular permanent magnets 35, F104, of Ni-Al steel secured to iron polepieces 37 (plates) and a square-sectioned iron rod 38 by bolts 36. In a modification, Fig. 3A (not shown), the permanent magnets are longer and disposed at the outer extremities of the polepieces. In both embodiments the magnetic circuit is carried by rectangular end spacer plates, Fig. 1 (not shown), of stainless steel having stainless steel retainer plates also rectangular. In the modified embodiment of Fig. 8, sector-shaped permanent magnets 43 interleaved between the outer chambers have clamping studs 44 with nuts. The getter pump produces a high vacuum in vacuum tubes, linear accelerators and electron microscopes. Prior art constructions having a plurality of cellular anode members interleaved with cathode plates and a solenoid or permanent magnet or one cellular anode between two cathode plates are referred to. Specification 910,608 is referred to.