Patent GB-578271-A (GB)
Title: Improvements in electron discharge devices employing secondary emission
IPC: H01J25/10
Filed: 1942-04-30
Abstract: 578,271. Velocity modulated electron multipliers. STANDARD TELEPHONES & CABLES, Ltd. (Western Electric Co., Inc.). April 30, 1942, No. 5820. [Classes 39 (i) and 40 (v)] In a velocity modulated electron discharge tube, the velocity modulated beam impinges on the initial or only electrode of an electron multiplier. A small beam from a cathode 2, Fig. 2, is accelerated by the flanges 6, 7 of a resonator to impinge on a secondary emitter 4 maintained at a potential slightly positive to the cathode to reduce the velocity of impact; the beam is velocity modulated as it passes the flanges 6, 7 from the cathode to the electrode 4 and the emitted secondaries move past the gap to give an amplified output. The flanges 6, 7 may be the control electrodes of a resonator with a loop output or form part of a concentric conductor 14, 15 which is at the end of a wave guide of the kind described in Specification 468,548, the closure 16 being telescopic. The electrode 4 is nearer the flange 7 than the distance between the cathode and flange 6. The slow electrons may not impact the electrode 4. In a further form, using two resonators 24, 32, Fig. 5, a diaphragm 29 at cathode potential is interposed between them and allows only those electrons whose velocity has been raised at the gap 28 to flow to the secondary emitter 34 ; the two chambers 24, 32 are at the same potential and the emitter is slightly positive. Both the primary electron beam and the secondary stream yield energy to the output resonator 32. In an oscillation generator, the secondary emitter 43, Fig. 6, is placed between the two resonators 41, 45, which have a common wall 47 with a back coupling loop 48. A collector 46 withdraws the electrons which have passed through the second resonator 45. In other forms where the secondary emitter or multiplier is between two resonator chambers, this emitter may be (i) a thin plate, Fig. 7 (not shown), which when struck on one side by the primary beam emits secondary electrons on the other ; (ii) a per forated plate, Figs. 8-10 (not shown), with secondary emissive material carried in the perforations; (iii) a multi-stage multiplier, Fig. 11 (not shown) ; (iv) a single or multi-stage multiplier, Figs. 12 and 13 (not shown), with the secondary electrodes parallel to the axis of the tubes and working with crossed electrostatic and electro-magnetic fields. In a further form, electrons after velocity modulations at the gap 96, Fig. 14, pass through a drift space 101 and retarding electrode 113 so that the density modulated stream impinges on the first electrode 102 of the multiplier at a suitable speed. A cross-electromagnetic field is set up by a coil or permanent magnet 117 to direct the secondary streams on the electrodes 103, 104, 105, whence the amplified stream is directed by the accelerating and focusing electrodes 120, 121 to the gap in the output resonator 109. The primary beam may be circular or in the form of a line or pencil, the resonators and electrodes being suitably shaped according to the beam form. The focusing system may be designed by the method set out in Specification 545,835.