GB901468A - Improvements in or relating to evaporating ion pumps - Google Patents

Abstract

901,468. Discharge apparatus. HERAEUS G.m.b.H., W. C. April 3, 1959 [May 30, 1958], No. 11421/59. Class 39 (1). A focused electron beam is used to evaporate the end of a wire of gettering material in an ion-getter pump. The pump shown comprises an electron-emitting filament 6 and a cylindrical wire-mesh electrode 5 which is maintained at a positive potential to drive gas ions into a layer of getter material which is deposited on the wall of the casing 3. An electron beam 10 from a filament 8 is focused at a point 11 by a solenoid 9. A wire 12, which may be a composite wire consisting of a wire or wires of one or more gettering materials such as titanium interwound with a support wire of tantalum, is fed through a tube 13 from a reel 16 by a feed device 14 operated by a driving device 15 which may be inside or, as shown, outside the casing 3. The getter wire enters the electron beam 10 at or near the point 11 on the side remote from the electrode system 5, 6 and at an angle α which is preferably less than 30 degrees so that the beam engages a significant length of the wire. Evaporation may be continuous or intermittent. In the latter case, during the intervals, the filament 8 is switched off or the heating reduced, and the getter wire is advanced to maintain the end near the point 11. The voltage applied to the electrode 5 may be switched off during evaporation periods to prevent a gas discharge between the electrode 5 and the casing 3 or filament 6.