Abstract:
In a photomultiplier tube, antimony layers of a photocathode and a plurality of dynodes are simultaneously sensitized by exposure to the vapors of sodium and potassium at an initial temperature of less than about 120.degree. C. The temperature of exposure is gradually increased at a rate of less than about 10.degree. C. per minute until a final temperature of about 200.degree. C. is reached. Then, the photocathode and dynodes are baked at the final temperature until substantially maximum photosensitivity is achieved. The photocathode and dynodes are thereafter exposed to cesium and may be superficially oxidized until substantially maximum photosensitivity is achieved.
Abstract:
Monoatomic layers to reduce the work function of photocathodes, secondary emission electrodes and field emission electrodes are obtained by surface segregation as a result of a thermal treatment after preceding indiffusion of the activator. Examples are in particular p-semiconductors such as silicon and III-V compounds with alkali metals.
Abstract:
A method for manufacturing secondary emission electrode deposited on a thin supporting film by vacuum evaporation, wherein a rigid body is arranged adjacent to a surface of the thin film opposite to the vaporizing surface. The opposite surfaces of the rigid body and the thin film may be arranged in parallel and at a distance, for example, about 0.05 mm or they may be so arranged to increase the distance at locations radially more distant from the central portion of the thin film. An evaporating material is vapor deposited onto the supporting surface, thus a secondary emission electrode layer having a uniform thickness can be obtained.
Abstract:
An illustrative embodiment of the invention is directed to method and apparatus for manufacturing microchannel devices. Typically, the individual glass tubes in a hexagonal bundle are sealed on one end to individual hangers from which they are suspended vertically in a furnace. A vacuum is drawn within the furnace so that the inner surfaces of the tubes, exposed to atmospheric pressure, will not collapse during heating and drawing. At temperature, the bundle is drawn and elongates under the controlled forces applied through a modified Atwood''s machine to reduce the bundle cross section by a ratio of about 50 to 1. The elongated bundle is cut into lengths as it is drawn, and these individual lengths are stacked together within a tube of glass that has a higher melting point than the glass in the drawn lengths. The channels are once more sealed and the assemblies are subjected to a secondary fusion process prior to slicing into thin discs. The annular glass rings are removed from the discs and the microstructures are placed in a molten wax bath in order to fill the channels with wax before grinding and polishing. After grinding and polishing, the wax is removed.
Abstract:
An electrode includes an electron or irradiation transmissive conducting layer and an electron-emissive layer of insulating material in spongy form. This layer may be of BaF2, LiF2, MgF2, MgO, Al2O2, CsI, KCl or NaCl and preferably has a density of only about 1% of the same material in bulk form, e.g. 0.01 to 0.1 gms. per cc. with a thickness of 10 to 100 m . The layer may be formed by deposition in a gaseous atmosphere, e.g. argon at 1 to 2 mm. of Hg pressure, with a spacing of about 3 inches between the evaporator and the receiver, which may be rotating. Alternatively magnesium may be burnt in air at atmospheric pressure about 14 inches from the receiver. The receiver may be an aluminium film supported by a metal ring and formed by vacuum deposition of aluminium on to a film of thermally removable cellulose nitrate to a thickness of 140 to 1000 . Specifications 792,507, 862,211 and 898,433 are referred to.