Patent GB-790405-A (GB)
Title: Velocity-modulated electron tube apparatus
IPC: H01J25/12
Filed: 1954-08-09
Abstract: 790,405. Velocity modulated tubes. EITEL-McCULLOUGH, Inc. Aug. 9, 1954 [Dec. 14, 1953], No. 23086/54. Class 39(1). A magnetic lens is provided adjacent the electron gun of a velocitymodulated tube to control the diameter of the electron beam and to guide the beam axially into the field of the main magnetic circuit. The tube shown in Fig. 1 is a threecavity klystron power amplifier comprising an electron gun 2, drift tube sections 4, 6, 7 and 8 resonators 13, 14 and 16, and a collector assembly 3. The electron gun 2 comprises a cathode 17 and focusing electrode 21 mounted on a stem 22 which is brazed to a cupshaped anode 18 of non-magnetic material, preferably copper. The drift tube sections 4, 6, 7 and 8 are preferably made of copper and form side walls of the tube envelope, the gaps between the sections being bridged by the cavity resonators 13, 14 and 16, each comprising a cylinder 38 of insulating material, preferably ceramic, sealed to flanges 39 on copper end walls 36 which are brazed to the drift tube sections. Drift tube section 4 is brazed around an aperture in the anode 18 and provides an elongated neck between the gun 2 and the resonator 13. Water jackets 42, 43, 44 and 46 are provided, or may be omitted for lower power tubes. An end disc 47 for the jacket 46 also serves as a mounting flange for the tube. The collector assembly 3 comprises a cup-shaped electrode 24, preferably of copper, connected to drift'tube section 8 by a glass wall 26 seated between flanges 27, and surrounded by a water jacket 28 having inlet and outlet connections 29 and 31. A tubular projection 32 directs the water along the surface of the collector electrode 24, which carries a metal exhaust tubulation 33. Fig. 2 shows the tube mounted in conjunction with the main magnetic circuit, the magnetic lens, and external resonator extensions. The main magnetic circuit comprises a frame of magnetic material such as iron having upper and lower squareshaped end plates 51 and 52 with cut-off corners which are connected by four side members 53. Two coils 48 are supported by brackets 56 connected to the side members 53 by screws 57 sliding in slots 58 for adjustment purposes. A third coil 49 surrounds a collar 54 projecting from the lower end plate 52. The tube is inserted through an aperture in the upper end plate'51 so that the mounting flange 47 seats on the collar 54 and the aperture is then closed by a split ring 24 so that the end plate 51 shields the electron gun from the main magnetic circuit. A magnetic lens 59, provided about the elongated neck of the tube, guides the electron beam axially into the main magnetic field and also serves to focus the beam. The lens 59 comprises a coil 61 housed in a split disc and cup 62 and 63 of magnetic material, such as iron supported by flanged posts 64 and screws 66 passing through oversize holes 67 in the end plate 51 to permit transverse adjustment. The external resonator extensions 68 are rectangular box-like metal structures comprising two halves locked together by hasps 71. Resilient contact strips 69 engage the tube resonator walls 36. A rectangular tuning plunger 72 operated by a rod 73 is positioned in each half of the external resonator, and coupling to the input and output resonators may be made in any conventional manner through the side walls of the external resonator structures. Permanent magnets may be used in place of the coils 48 and 49. Specification 790,406 is referred to.