Patent GB-961961-A (GB)
Title: High frequency tube apparatus
IPC: H01J23/033
Filed: 1960-08-08
Abstract: 961,961. Velocity-modulated beam tubes. VARIAN ASSOCIATES. Aug. 8, 1960 [Aug. 6, 1959], No. 27487/60. Heading H1D. [Also in Division H5] High-frequency tube appartus includes means for producing and directing a beam of charged particles over a predetermined path longitudinally of the tube, means for collecting the beam at the terminating end of the beam path, means disposed along the beam path for producing successive electromagnetic interaction with the beam and for extracting high-frequency energy from the beam and a vacuum tight envelope enclosing the beam path, wherein the envelope is made up of a plurality of tubular metallic segments having outwardly directed mating flanges, the mating flanges on adjacent tubular segments being sealed together at their periphery to form a rigid elongated tubular metallic vacuum envelope. One embodiment, Fig. 1, comprises a U.H.F. seven cavity stagger-tuned klystron amplifier. Gun structure.-The electron gun structure, Fig. 4, comprises a concave emitter button 61 heated by a radiant heater including an incandescent double spiral wound helical element 62 carried from a conical refractory metallic base member 63, e.g. of molybdenum, via the intermediary of radially disposed refractory insulator assemblies 64. The insulator assembly 64 includes a lower support member 60, e.g. of alumina ceramic, notched to receive therewithin the seating element 62, thus preventing sagging of the element. Envelope and resonator construction.-The tubular envelope 1 is made up of a plurality of tubular portions 15, Fig. 7, each comprising a hollow cylindrical member 16, e.g. of stainless steel serving both as the outer vacuum envelope and the side wall of the cavity resonator 4. Outwardly directed flange members 17 are provided at the ends of the cylindrical members 16 for mating with similar flanges 17 on adjacent cylindrical members and are sealed thereto by welding. A tubular drift tube section 19 is carried by a transversely disposed annular cavity header 18, and when the portions are assembled the drift tube segments P9 are in axial alignment, the spaces between successive cavity headers 18 define the cavity resonators, and the spaces between the drift tube portions defines the interaction gap. Each module carries a capacitive tuner assembly 21 extending into each of the cavity resonators 4, the position of which may be adjusted by rotation of a tuner stem 24. Surrounding the tubular envelope is a cylindrical X-ray shield 53, e.g. of lead # inch thick, on the outside of which is disposed a cylindrical beam focusing solenoid 5. Both the X-ray shield and solenoid are provided with holes 32 for the insertion of a tuning tool, and both structures may be removed from the tube envelope with the aid of wheels 48 disposed around the outer surface of the envelope. Electron collector.-The electron collector structure 3, Fig. 1, comprises a thin walled hollow cylindrical bucket 91, Fig. 9, e.g. of copper, closed at one end by a thin transverse wall 92, and is adapted to receive the beam over its interior side walls. The exterior of the collector bucket is provided with a plurality of relatively shallow channels 93, e.g. 0.1 inch deep milled therein, and the outer periphery of the bucket is surrounded by a tightly fitting collector sleeve 94 (Fig. 8, not shown). The configuration of the channels is such that there are a number of longitudinal passes N l  and a number transverse passes N t  all lying on parallel chords of the circular end wall 92, the pattern being defined by the relationship N l  = 2N t  + 2. Output Coupler.-The output coupler takes the form of a broad band low capacitive iris 10, Fig. 13, formed in the transverse wall of the output resonator, and takes the form of a slot 127 of part annular shape which subtends approximately 180 degrees of circumferential arc about the longitudinal axis of the tube. The slot 127 is symmetrical with respect to a radius subtending 30 degrees to the vertical to offset the R.F. coupling effect of the tuner assembly 21. The central portion of the slot 127 is enlarged radially outward at 128 to minimize the capacitive reactance of the iris. A wrappedaround output waveguide 9, Fig. 1, provides means for extracting the very high R.F. power for the output cavity, without the necessity for a break in the solenoid 5, and the power is led via a coaxial line 11 through an output window 13 to the output guide 14. Reflectionless matching over a 12% tuning range is obtained by use of two broad band waveguide transitions; from waveguide 9 to coaxial line 11 by use of a saddle 131, and from coaxial line 11 to output guide 14 by a door-knob transition 12. Specifications 961,962, 961,963 and 961,964 are referred to.