GB1052902A - - Google Patents

Abstract

1,052,902. Ion sources. ATLAS MESS-UND ANALYSENTECHNIK G.m.b.H. Feb. 19, 1964 [Feb. 19, 1963], No. 6980/64. Heading H1D. In a field-ionization source, e.g. for a mass spectrometer, the emitter has an emission zone of a very small radius of curvature, e.g. between 0À1 and 10 Á, and preferably 2À5 Á or less, and a length, e.g. 3-8 mm., which is many times longer than its radius of curvature. The emitter may take the form of one or more wires or one or more knife-edged blades. A number of parallel wires may be mounted on a common insulating body or separately mounted on U-shaped brackets. Wires greater than 8 mm. in length may be supported at intermediate points. The emitter may comprise a built-up sandwich of metal and insulating foils. Use may be made of Wollaston wire having a platinum core of 2À5 Á diameter and a silver coating and prepared by etching by electrolysis in a potassium cyanide solution. Remaining micropoints are etched away by a very brief alternating current electrolysis in aqua regia. Suitable wires may comprise quartz threads coated by vaporization, spraying or chemical deposition with metal or semiconductive material. The long dimension of the emitter may be slightly curved. The source shown comprises emitter 9, accelerating electrode 11 and lens and deflector electrodes 13 to 16. Gas or vapour is supplied through pipe 8 and the source is pumped via duct 5. Specific gases and vapours mentioned in association with the source are H 2 , O 2 , CO and CH 4 at a pressure of 10<SP>-4</SP> mm. Hg.