GB835129A - Magnetic electron multiplier - Google Patents

Abstract

835,129. Electron multipliers; electrode materials. BENDIX AVIATION CORPORATION. Oct. 16, 1956 [Oct. 21, 1955], No. 31487/56. Class 39(1). A magnetic electron multiplier, particularly for use with a mass spectrometer 10 emitting ions on to a secondarily-emitting plate 12, comprises two, preferably parallel conducting surfaces 20, 22 of high resistance on insulating plates 16, 18 of glass or "Bakelite" (Registered Trade Mark), along each of which surfaces a voltage drop is established to create an electric field component normal to the surfaces, and at least one, and preferably both, of the surfaces being secondarily-emissive, so that under the combined influence of the electric field and a magnetic field normal to it the secondary electrons, are accelerated along the emissive surface, and one or more conductive elements such as strips 26, 28, 30, 32 and 38, 40 arranged at one or more pre-determined positions along the length of at least one secondarily-emissive surface intermediate its ends and having a pre-determined voltage or voltages applied thereto from a D.C. source 48. The surfaces 20, 22 can be of tin oxide or a carbon compound. The conductive strips can be straight or curvilinear and can be of silver formed by spraying or of wires and are parallel or transverse to the magnetic field provided by the poles 56. The strips can be in registering positions on the two surfaces 20, 22. End strips 24, 34 are provided on the surface 20 and end strips 36, 42 on the surface 22. One or more strips 32, 34 are connected to the D.C. source 48 through a resistance 50 and also to a pulse source 54 through a capacitance 54 by which electrons emitted from the surface 22 are prevented, when pulses are applied, from passing through the region between the strips 32 and 34 to the deflecting anode 44 and are deflected towards the surface 20. The paths of the electrons can be common, curtate or prolate cycloids.