GB505663A - Improvements in or relating to electron discharge apparatus of the electron multiplier type - Google Patents

Abstract

505,663. Electron multipliers. ELECTRICAL RESEARCH PRODUCTS, Inc. Nov. 19, 1937, No. 31885. Convention date, Nov. 20, 1936. [Class 39 (i)] Coaxial, annular, secondary-electron emitting cathodes are arranged in alignment along their common axis between the primary cathode and the anode or collector electrode and are mounted on supports of insulating material carried by or rising from the stem of the envelope, the cathodes having individual leads and means being provided for producing a magnetic field along said axis. The secondary electrodes may be in the form of cylindrical metal bands, preferably coated on their inner surfaces with emitting material and equally spaced along the discharge tube axis, and are at uniformly increasing potentials from primary cathode to collector electrode. The tube is surrounded by a cylindrical magnet or coil producing an axial field of intensity which is greatest in the region of the primary cathode and decreases uniformly towards the collector electrode to compensate for the corresponding variations in the electrostatic field between the secondary electrodes and an auxiliary' electrode in the form of wire arranged along the axis of the discharge tube. The collector electrode is energized from a separate source, the other electrodes being connected to tappings on a potentiometer. In the modification shown in Fig. 4, the primary cathode and secondary electrodes are conical frustums partially nested together and provided with flanges 238 which are clamped to uprights 241, through which pass the potential supply leads 243. The collector electrode 244 is of similar shape. Disposed between the lowermost secondary cathode 237<5> and the electrode 244 is a screen electrode 249 in the form of a number of parallel wires, which serves to prevent reaction upon the secondary cathode of the potential variations upon the electrode 244. The linear rod 222 mounted axially of the system serves as the accelerating electrode, and may comprise several wires through which a current is passed to produce a magnetic field, or the rod may be a permanent magnet. In a further form, the cathodes 265, Fig. 6, are frusto-conical and are supported on insulating uprights 262 having fingers 264 to which are locked flanges on the cathodes; the uprights are carried by a threearmed spider 261 supported by rods from collars 259 clamped round the stem. The leads 275 to the electrodes are passed radially through a flange 258 on the press of the tube and are bent at right-angles so as to lie parallel to the tube axis. A hollow pillar 275 of mica carries inner frusto-conical electrodes 276<1>, one for each of the cathodes and of the same length, which serve as accelerating electrodes for the tube. Either the inner or the outer set of electrodes or both sets may be rendered secondary-emitting and operate as cathodes, and the primary electrode may be photo-electric or thermionic.