GB844621A - Velocity-modulated electron discharge tube apparatus - Google Patents

Abstract

844,621. Tuning cavity resonators. VARIAN ASSOCIATES. Oct. 5, 1956 [Nov. 14, 1955], No. 30467/56. Class 40(8). [Also in Group XL(a)] In a velocity modulation electron discharge tube having at least one cavity resonator and a tuning plunger for tuning the resonator, movement of the plunger varying the inductance of the resonator, there is provided a shield associated with the plunger and adapted to prevent the capacitance of the resonator from being substantially affected by movement of the plunger whereby the linearity of the resonance frequency versus plunger displacement characteristic of the cavity is improved. The tube shown comprises a cathode assembly 1 and a collector assembly 2 between which are arranged an input buncher resonator 7, two further buncher resonators 8 and 9 and an output resonator 11 separated by drift tube sections 12. Resonator 7 is tuned by a copper plunger 28 (Fig. 5) surrounded by a shield 29 provided with a slot 32 to permit magnetic coupling to the space inside the shield. The tuner actuating mechanism comprises a bearing 35 of oil impregnated brass which slides on a guide rod 34, a vacuum-sealed bellows 37 of non-magnetic stainless steel, an arm 36, a hollow rod 38 containing a septum 41 to allow cooling fluid to be circulated, and a windlass operated by a worm gear 56. The windlass has four semi-cylindrical drums 45 each provided with a straddling channel member 46 having a projection engaging an adapter 47 holding one end of a metal tuning band 49 which passes over a roller to a further adapter 52 secured to a threaded plug 53 screwed into a tuner rod extension 42. Resonators 8 and 9 are provided with similar tuning arrangements, but to reduce the overall length of the tube the output resonator 11 and its plunger are upside down compared with the other resonators so that this tuning plunger moves in the opposite direction to the other plungers thus necessitating a modified tuning arrangement (Figs. 8 and 9 not shown) for this plunger to allow simultaneous gang tuning of all the resonators. A screw 48 threaded through each channel member 46 allows individual adjustment of the tuning plungers. An assembly of three frusto-conical members 23, 26 and 27 provides for axial and transverse alignment of the cathode assembly 1 and enables the cathode to be renewed by breaking and remaking a single welded joint between members 26 and 27. The output waveguide structure 16, the cavity resonator interaction gaps and the window 18 in the output waveguide are described in Specifications 844,622, 844,623 [Group XL(a)] and 844,624 respectively.