Protective vessel for a getter material

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a protective vessel for a getter material which comprises a first sheet of thermally stable material which is attached to a layer of adhesive which in turn is attached to a second sheet of thermo-retractable organic plastic material; the first and second sheets enclosing said getter material.
With reference now to FIG.
1 there is shown an exploded view of a protective vessel 100 which comprises a first sheet 102 of thermally stable material 104 in the form of a first circular disc 106.
Thermally stable material 104 can be any material suitable for use in a vacuum environment, with a low outgassing rate, but should preferably also have a low gas permeability.
It may be of organic plastic such as polyethylene or polyvinylchloride (PVC) or polystyrene, or of an easily formed, but rigid material such as metal, for instance, a thin sheet of stainless steel, nickel or aluminium.
The organic plastic may be coated with a thin film of metal (such as aluminium) or with other organic plastic films with reduced permeability to atmospheric gases to improve gas tightness of the package.
Examples of these "barrier" materials are PVDC (vinylidene chloride copolymers) and EVOH (ethylene vinyl alcohol copolymers), which may be applied as a single coating or on top of the organic plastic or by coextrusion.
Within first sheet 102 is press formed a hollow receptacle or depression 108 in the form of a shallow cylinder 110 which has an outer wall 112 and a bottom wall 114 leaving an annular boarder 115 in disc 106.
Shallow cylinder 110 contains getter material 116.
Any getter material that requires protection may be used such as barium or activated non-evaporated getter materials but the reactive non-evaporating barium getter alloys are particularly preferred.
Depression 108 and hence shallow cylinder 110 containing getter material 116, is sealed by means of a second sheet 118 of thermo-retractable organic plastic material 120 in the form of a second circular disc 122