Patent GB-853668-A (GB)
Title: Electron tube apparatus
IPC: H01J25/12
Filed: 1956-12-31
Abstract: 853,668. Tuning cavity resonators. EITELMcCULLOUGH Inc. Dec. 31, 1956 [March 6, 1956], No. 39628/56. Class 40(8). [Also in Group XL(a)] The magnetic focusing circuit for an electron beam tube, preferably a klystron, has at least one coil 103,Fig. 5, or permanent magnet associated with longitudinally extending side members 108 of magnetic material (four in Fig. 5) end plates 106, 107 of magnetic material secured to the side members to form pole-pieces, the end plate at the gun end of the tube having an outer portion 131 and an inner portion 133 which is adjustable axially with respect to the outer portion. The klystron preferably comprises four resonators with intervening drift tube sections, each resonator having identical capacitive tuning means comprising a dielectric plunger 71, Fig. 3. The plunger 71 has a reduced diameter and fitting in member 76 which has a threaded socket for tuning screw 78. Plug 87 is a tight fit in plug 84 so as to form a bearing surface for the screw head and houses an actuating shaft for the tuning screw, a spring 83 tending to urge the shaft 76 and consequently the plunger 71 downwards. The vacuum is maintained by a collar 79 sealed in an aperture in 72 and bellows 81 sealed at one end to collar 71 and at the other end to 76. The resonators are formed of rectangular plates 64, 68, 69, 70, 67 and four side wall members 66. In assembly of the tuning structure members 82, 78, 84, 87 are inserted over 76, 81 so that screw 91 engages the underside of a reference surface 92 on collar 79. Cooling means is provided by a fan 102, Fig. 5, which draws air over cooling fins 48, Fig. 3, on the cup shaped collector, the latter also carrying exhaust tube 49. Magnetic focusing coils 103, 104, Fig. 5, at the gun and collector ends respectively are mounted from an iron frame comprising side members 108 by magnetic discs 106, 107, 152 and screws 117, 121, the discs having segments cut off where they are attached to the side members 108, the frame supporting the tube as well as completing the magnetic circuit. Cylinder 109 engages the collector and two jaws attached to 108 by screws engage the output wave-guide. The blocks 116 also house adjusting screws 156 for adjusting coil 103 transversely. The iron plate 106 also serves as a magnetic shield for the gun, the effective position of the shield with respect to the beam throat being adjustable by means of an axially movable part 132, 133, which threadedly engages plate 106 and is rotated by handle 138. Part 132 is in two radially split parts for assembly around the tube neck and is held in member 133 by a snap in ring 134. The screws 117, 121 are disposed in grooves in side members 108 to allow longitudinal adjustment of coil 103, but this is a coarse adjustment and is not intended to give for example the fine adjustment of magnetic plate 106 with respect to the beam throat. To insert the klystron, coil 103 and plate 106 are removed and the klystron pushed into the aperture of coil 104 until the collector is engaged by the fingers of collar 109, after which 103, 106 are refixed in position. The coils 103, 104 may if desired be replaced by permanent magnets. Output is taken via iris opening 62 and ceramic window 63 to wave-guide 61, the window increasing the capacitive coupling from resonator to wave-guide. The Pierce type gun has a glass seal between the focusing electrode 32 and a kovar extension of anode 52. The collector is sealed to the magnetic end plate 67 by alternately disposed members 42, 43, 44, 46, 47 of glass and kovar, the metal to metal joints being made by brazing. The device described is a power amplifier producing an output of more than 50 watts continuous wave.