US2871397A

US2871397A - Electron tube of the klystron type

Info

Publication number: US2871397A
Application number: US495151A
Authority: US
Inventors: Donald H Preist; Clayton E Murdock
Original assignee: Eitel Mccullough Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1955-03-18
Filing date: 1955-03-18
Publication date: 1959-01-27
Anticipated expiration: 1976-01-27
Also published as: CH336510A; FR1131772A; NL201813A; GB803893A

Description

Jan. 27, 1959 D. H. PRElsT ET AL ELEcTRoN TUBE: ,0T THE KLYsTRoN TYPE Filed March 18, 1955 wm MN m. m. ww 9T N IN VEN TORS Dana/d H. Pre/5f' BY C/ayon E. Murdock J' f? ATTORNEY ELECTRON TUBE OF THE KLYSTRN TYPE Donald H. Preist, Mill Valley, and Clayton E. Murdock, Millbrae, Calif., assigner-s to Eitel-McCullough, Ine., San Bruno, Calif., a corporation of 'California Application March i8, 1955, Serial -N o. 495,151

Claims. (Cl. S15-5.46)

Our invention relates to beam type electron tubes and more particularly to tubes having cavity resonators along the beam axis, such as klystrons. Our vimprovements are directed to amplifier type klystrons capable of producing large powers in the upper frequency ranges, say of the order of a kilowatt or more average power at frequencies above 1,000 mc. l

It is among the objects of our invention to provide an improved externally tunable klystron capable of tuning over a wide band of frequencies.

Another object is to provide such a klystron in which vacuum retaining walls are arranged in the resonators to permit the tuning mechanism to lie outside the evacuated portion of the tube envelope.

Another object is to provide a klystron of the character described wherein the external portions of the resonators are formed as a structurally integral part of the envelope.

Still another object is to provide a tube structure having a great deal of mechanical rigidity and stability in electrical performance.

A further object is to provide an improved structure which facilitates assembling the klystron.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of our invention. It is to be understood that we do not limit ourselves to this disclosure of species of our invention, as we may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

Figure l is an axial sectional View of a three-cavity klystron embodying our invention; and

Figure 2 is a transverse sectional View taken in a plane indicated by line 2 2 of Figure l.

In its preferred form, our improved klystron comprises an elongated evacuated envelope having an electron gun stem structure ll at one end and collector electrode assembly 2 at the other end. The electron beam traveling from the gun to the collector passes through several drift tube sections 3 of metal with gaps 4 therebetween. The gaps are bridged by three cavity resonators generally designated 6.

Stem l of the gun structure comprises a metal anode 7, say of copper, brazed at 5 to a reduced neck 8 having an axial passage 9 opening into the first drift tube section. The rest of the stem comprises three insulating cylinders itl, li and 12, preferably of ceramic, the larger cylinder 9 being interposed between anode l and a metal terminal ring i3. A terminal ring 14 is also sealed between the cylinders l1 and l2, and a metal end plate 16 provides a further terminal. Suitable sealing flanges 17 between the ceramic cylinders and metal members seal the whole into a vacuum-tight closure.

Cathode l?, of the electron lgun is disk-shaped and is mounted on a tubular support 19 connected to terminal 14. The cathode is surrounded by a cylindrical focusing electrode 2l mounted on terminal ring 13. A suitable Patented Jan. 27, 1959 EC@ j cathode heater coil 22 is connectedv at one end to the cathode and at the other end to terminal 16.

The forward end of neck 8 also has fixed to it at brazo 23 a circular mounting plate 24 which is used to fasten the entire stem structure to the main RF portion of the tube, as later described. Elongated neck 8 of the stem facilitates the application of external magnetic circuitry which is usually associated with klystrons of this kind. The stem structure up to and including the mounting plate 24 is a unitary subassem-bly which may be separately fabricated and then fastened to the main body of the tube.

Collector structure 2 at the opposite end of the envelope is also made up as a separate unit. It comprises a cup-shaped collector electrode 26 having a core 27 and carries a suitable cooler 28 as well as the exhaust tubulation 29. All yof this is supported on and insulated from a reduced neck 31 by a pair of flanges 32 brazed in place at 33 and having an insulating cylinder 34 therebetween. Cylinder 34 is preferably of ceramic and is secured b-y sealing anges 36. Neck 31 has an axial passage 3i) opening from the last drift tube section and also carries a mounting plate 37 `fixed at braze 38, which plate is used to fasten the collector assembly unit to the main portion of the tube in a nranner similar to the 4stem unit rst described.

The main RF portion of the tube which contains the cavity resonators 6 embodies important features of our improved tube construction. End walls of the cavity resonatorscomprise circular metal flanges 39 extending radially from drift tube sections 3. These flanges may be disk-shaped pieces separately fabricated and fastened to tubular drift tube `parts as shown at the two center sections, or the ilanges and drift tube sections may be integrally formed as indicated at the end sections. This choice is largely a matter of convenience in fabrication.

Circular metal extension flanges 42 brazed at 43 to flanges .39 form continuation walls of the cavity resona tors. Extensions 42 may be fabricated separately and brazed in place, as shown, or may be formed integrally with the core flanges 39; in either case it being noted that the entire resonator is a structurally integral part of the vacuum tube. The vacuum portion of the device is divided from the external portions of the resonators by vacuumtight insulating partition walls 44. These are cylinders of insulating material, preferably ceramic, secured to core flanges 39 by sealing anges 46. Metal webs 47 brazed between circular wall flanges 42 make up the side walls of the resonators and provide cavities of generally rectangular shape as shown in Figure 2.

The stem and collector assemblies are joined to the main body of the tube by means of radial sealing flanges 4S on end ianges 39 and the adjacent mounting plates 24 and 37. These circular sealing anges have registering edges welded together at the metallic bond 49. Axial alignment of the parts is achieved by interengaging centering means, as by a plug and socket joint comprising projections on necks 8 and 31 seating into recesses provided in the end flanges 39 as seen in Figure l.

Tuning is accomplished by plungers 51 in the external portions of the resonators, having fingers 52 providing contact with the resonator walls. Movement of the tuning plungers is achieved by means of adjusting screws 53 threaded through cross walls 54 of the resonators. This construction provides resonators which are a structurally integral part of the tube yet permits tuning over a wide band of frequencies and by mechanism which is outside the vacuum.

We have constructed and tested tubes embodying our invention at frequencies around 2000 mc., producing an average power output of about 1 kw., and tunable over a range of approximately 1700 to 2400 rnc. As apparent and very rugged mechanically. This leads to good frequency stability in its electrical performance, which stability is always diicult to achieve in the higher frequency ranges.

We claim:

l. A klystron having metal drift tube sections separated by gaps spaced along the drift tube axis, generally rectangular resonators at the gaps having end walls comprising radial metal llanges on said drift tube sections, cylinders of insulating material sealed between the tlanges providing vacuum-tight partitions in the resonators, a pair of parallel metal webs between the flanges outside the partition cylinders and forming side walls of the resonators, and movable tuning means closing the resonators external to and on opposite sides of the partition cylinders, said drift `tube sections, said end wall flanges and side wall webs being rigidly bonded to each other forming a unit comprising a structurally integral part of the klystron whereby said movable tuning means may be moved immediately adjacent said cylinders.

2. A klystron comprising a body unit having drift tube sections and associated resonators, an end unit adjoining the body unit and having a passage communicating with a drift tube section of the body u nit, interengaging centering means on said end and body units for axially aligning said passage with the adjacent drift tube section, metal sealing ilanges on the end and body units and having registering edges, and a metallic bond uniting said edges, said registering edges being positioned a substantial distance radially outwardly of said centering means.

3. A klystron comprising a body unit having drift tube sections and associated resonators, an end unit adjoining the body unit and having a passage communicating with a drift tube section of the body unit, interengaging centering means on said end and body units for axially aligning said passage with the adjacent drift tube section, metal sealing llanges on the end and body units and having registering edges, said sealing flanges being substantially parallel and extending radially from the axis of the klystron, and a metallic bond uniting said edges, said edges being positioned a substantial distance radially outwardly of said centering means.

4. A klystron comprisingia body unit having drift tube sections and associated resonators, an electron gun, an

f end unit containing the gun adjoining the body unit and having a passage communicating with a drift tube section of the body unit, a collector electrode, a second end unit containing the collector electrode adjoining the body unit and having a passage communicating with another drift tube section of the body unit, interengaging centering means on said end and body units for axially aligning said passages with the adjacent drift tube sections, metal sealing flanges on the end and body units and having registering edges, and a metallic bond uniting said edges, said registering edges being positioned a substantial distance radially outwardly of said centering means.

5. A klystron having metal drift tube sections separated by a gap, a generally rectangular resonator at the gap having end walls comprising radial metal anges on said drift tube sections, a cylinder of insulating material positioned between said anges radially outwardly of said drift tube sections, sealing means joining the ends of said insulating cylinder to said end wall flanges to forin a vacuum-tight partition in the resonator, metal webs brazed between said end wall flanges outside said insulating cylinder and forming side walls of the resonator, said end wall flanges and side wall webs comprising a structurally integral part of the klystron, and tuning plungers within said resonator outwardly of said insulating cylinder and movable radially of the cylinder in sliding contact with the inner surfaces of said end and side walls, the inner surfaces of said end Walls forming at planar surfaces extending outwardly from Said sealing means whereby said tuning plunger is free to move inwardly to said sealing means.

References Cited in the le of this patent UNITED STATES PATENTS 2,446,269 Drieschrnan Aug. 3, 1948 2,457,194 Anderson Dec. 28, 1948 2,492,618 Bowie Dec. 27, 1949 2,619,611 Norton et al c Nov. 25, 1952