GB1386251A - Source of sublimable material - Google Patents

Abstract

1386251 Ion pumps; gettering discharge apparatus BRITISH OXYGEN CO Ltd [trading as EDWARDS HIGH VACUUM INTERNATIONAL] 21 March 1972 [24 March 1971] 7745/71 Heading H1D A source of sublimable material suitable for sublimation pumps (e.g. REF pumps), includes a longitudinal sublimable body 20 (e.g. Ti or Ti alloy) spaced axially and radially from a non- sublimable housing 22 (e.g. of Ta or Ta alloy, Mo or other refractory metal), and means for heating the housing, the housing having perforations 26 distributed angularly and longitudinally through which sublimed material passes. Heating of body 20 by radiation reduces hydrocarbon formation. Housing 22 may be electron heated (in REF pumps) or Joule heated. In the latter case, body 20 support is insulated from the housing. Rod 2 may be of alumina, and shield 22 electroresistive, perforations 26 preferably being transaxial slots overlapping longitudinally, the metal being of serpentine form. The perforations may be replaced by a helical slot and may be formed by the spaced apart edges of a strip of helically wound electroresistive material. The housing may alternatively be frusto-conical or other contoured shape. Preferably end caps 24 are also non-sublimable material. Perforations may cover 10-20% of the area for example, and may be shaped as in a grater, preferably in opposite directions on each side of a central plane to ensure deposition over a larger area and also more uniformly. Patterning of the perforations 26 may also affect operation. Fig. 1 (not shown) is an REF pump with anode (2), a water cooled housing acting as earthed cathode (4), reflector (12), filaments (16), one or both being heated, and supports (14) preventing electrons falling on anode (2). Electron orbits may be circular or elliptical crosssection.