US3866085A

US3866085A - Collector pole piece for a microwave linear beam tube

Info

Publication number: US3866085A
Application number: US421196A
Authority: US
Inventors: Bertram G James
Original assignee: Varian Associates Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1973-12-03
Filing date: 1973-12-03
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11

Abstract

The collector pole piece for a solenoid focused microwave linear beam tube contains a chamber therein. The output waveguide extends into and through the chamber in the collector pole piece to provide a wave communication passageway between the microwave interaction circuit of the tube and its surrounds. Fluid coolant passageways communicate with the pole piece chamber for directing a flow of coolant through the pole piece structure.

Description

United States Patent 1 1 1111 3,866,085

James Feb. 11, 1975 1 1 COLLECTOR POLE PIECE FOR A 3,322,997 5/1967 Caryotakis 315/535 MICROWAVE LINEAR BEAM TUBE 3,344,306 9/1967 Levin 3,679,929 7/1972 Holm et a], 315/538 Bertram G. James, Redwood City, Calif.

Assignee: Varian Associates, Palo Alto, Calif. Filed: Dec. 3, 1973 Appl. No.: 421,196

Inventor:

U.S. Cl 315/35, 313/22, 313/25, 313/30, 315/535, 315/538 Int. Cl. HOlj 25/34 Field of Search 315/35, 5.35, 5.38; 313/22, 25, 30

References Cited UNITED STATES PATENTS Primary Examiner-James W. Lawrence Assistant Examiner-Saxfield Chatmon, Jr. Attorney, Agent, or Finn-Stanley Z. Cole; D. R. Pressman; Robert K. Stoddard [57] ABSTRACT 6 Claims, 4 Drawing Figures PATEHIED FEB I 1 I975 SHEET 10F 3 PATENTED FEB! 1 I975 SHEET 2 OF 3 PATENTEDFEBWQYB 3.866.085

SHEET 30F 3 v COLLECTOR POLE PIECE FOR A MICROWAVE LINEAR BEAM TUBE GOVERNMENT CONTRACT The invention herein described was made in the course of or under a contract or subcontract thereunder, (or grant) with the Department of the US. Navy.

RELATED CASES The block body construction of the tube of the present invention, as strengthened by a surrounding tubular member, forms the subject matter of and is claimed in copending US. application Ser. No. 421,174 filed Dec. 3, 1973 and assigned to the same assignee as the present invention.

BACKGROUND OF THE INVENTION The present invention relates in general to microwave linear beam tubes and more particularly to animproved collector pole piece for such tubes.

DESCRIPTION OF THE PRIOR ART Heretofore, collector pole piece structures for microwave linear beam tubes have been notched or apertured to permit passage of the output and sometimes the input waveguides therethrough such that the waveguide structures may traverse the region between the microwave circuit and the surrounds of the tube without unduly interrupting or disturbing the beam focus solenoid and/or the beam focus magnetic field produced by the solenoid. Collector pole pieces of this prior construction are disclosed in US. Pat. No. 3,336,491, issued Aug. 15, 1967 and assigned to the same assignee as the present invention.

While such prior art collector pole pieces have been satisfactory for the prior art microwave tubes, it is desirable to provide an improved collector pole piece structure adapted to be detachably secured to a solenoid collector pole piece and to provide fluid coolant passageways therein providing for a flow of coolant between the main body and the beam collector of the tube.

SUMMARY OF THE PRESENT INVENTION The principal object of the present invention is the provision of an improved collector pole piece structure for a solenoid focused microwave linear beam tube.

In one feature of the present invention, the collector pole piece structure includes a chamber therein with the output waveguide structure passing through said chamber of the pole piece.

In another feature of the present invention, the collector pole piece structure includes a chamber having an input and an output waveguide passing therethrough, such waveguide structures being disposed on opposite sides of the beam path and each having an H- plane 90 bend portion disposed within the chamber such that both waveguides pass out of the collector pole piece structure in substantial parallelism on the same side of the beam path, whereby the overall transverse dimensions of the tube are reduced.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal sectional view, longitudinally foreshortened and partly in block diagram form, of a microwave linear beam tube incorporating features of the present invention,

FIG. 2 is an enlarged view of a portion of the structure of FIG. 1 delineated by line 2-2,

FIG. 3 is an enlarged section view of a portion of the structure of FIG. 1 taken along line 3-3 in the direction of the arrow, and

FIG. 4 is a sectional view of the structure of FIG. 1 taken along line 44 in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown an X-band linear beam microwave amplifier tube 11 incorporating features of the present invention. More specifically, the tube 11 includes an electron gun assembly 12 disposed at one end for forming and projecting a beam of electrons over an elongated beam path 13 to a beam collector structure 14 disposed at the terminal end of the beam path for collecting and dissipating the energy of the beam. A main body portion 15 of the tube is disposed intermediate the electron gun 12 and the beam collector 14.

The main body portion 15 includes a microwave circuit 10 disposed along the beam path 13 in electromagnetic wave energy exchanging relation with the beam to produce output microwave energy which is coupled from the tube 11 via an output waveguide 16 for propagation to a suitable utilization device or load, not shown. In the instant case, the microwave tube 11 is an amplifier tube and amplifies input microwave energy in the X-band frequency range coupled to the input end of the microwave circuit 10 via input waveguide 17. The input waveguide 17 passes axially the tube 11 to the input or gun end thereof for coupling microwave energy onto the microwave circuit 10.

An electrically energized solenoid 18 is disposed coaxially surrounding the main body portion 15 for generating an axial magnetic field within the beam path 13 for focusing the electron beam 13 through the microwave interaction circuit.

A fluid coolant chamber or reservoir 19 is disposed surrounding the electron gun 12. The coolant is electrically insulative and heat absorptive. A suitable coolant is a liquid fluorocarbon such as Coolanol 25 commercially available from Monsanto Chemical Company. Such liquid fluorocarbons are conventionally used as hydraulic oil in hydraulic systems. Coolant from the reservoir 19 passes through an inner and an outer circular array of

apertures

20 and 21, respectively, in the cathode pole piece 54 into the interior of the solenoid 18 wherein the flow of fluid coolant is divided into two streams one of which passes into the main body portion 15 of the tube via a circular array of circumferentially spaced apertures 22 in the main body 15 and thence along the length of the main body 15 via a plurality of passageways 23 to a collector pole piece structure 24, as of cold rolled steel.

The collector pole piece structure 24 contains a hollow chamber and the hollow chamber is placed in fluid communication with the longitudinal fluid coolant passageways 23 in the main body portion 15. A circular array of apertures 25 in the collector pole piece 24 provide fluid communication between the collector pole piece chamber and an annular fluid chamber 26 surrounding the beam collector electrode or bucket 27. The fluid coolant is directed through a multitude of perforated cooling fins coupled to the exterior of the beam collector electrode 27 for cooling same. The fluid coolant is collected in a manifold structure 28 connected via tubulation to the input of a heat exchanger and pump 29 for removing the heat picked up by the coolant. The cooled coolant is then returned to the cathode reservoir 19 for recirculation through the tube.

In addition to the longitudinal fluid passageways 23 through the main body portion 15, the solenoid 18 includes a plurality of coils 31 which are axially spaced apart and varied in inside and outside diameter such as to define an annular serpentine shaped fluid coolant passageway 32 in between and around the electrical coils 31 for cooling the solenoid in use. In a typical'example, the fluid coolant flow rate through the entire tube is 3.3 gallons per minute, whereas the fluid coolant flow rate through the main body portion 15 is 1 gallon per minute leaving 2.3 gallons per minute flow through the solenoid 18.

Referring now to FIGS. 2 and 3, there is shown the main body portion 15 of the tube in greater detail. More particularly, the electron gun 12 includes an anode portion 33 which is sealed in a gas tight manner to the exterior envelope of the electron gun assembly 12. Similarly, the main body portion 15 of the tube 11 is sealed in a gas tight manner to, and forms a part of, the anode 33.

The main body portion 15 of the tube includes a cylindrical tubular strengthening member 34, as of 0.020 inch wall thickness non-magnetic stainless steel, sealed, as by brazing, to the anode 33 and extending longitudinally of the tube 11 to the collector pole piece structure 24 to which it is sealed in a gas tight manner as by brazing. The main body 15 includes a block body portion 35, as of copper, in which the microwave interaction circuit is formed. More particularly, the block body portion 35 includes a series of rectangular cavity resonators 36 formed therein preferably in the manner as disclosed and claimed in US. Pat. No. 3,711,943, issued Jan. 23, 1973 and assigned to the same assignee as the present invention. The common walls 37 between adjacent resonators 36 are each centrally apertured to define a beam passageway through successive resonators 36. Adjacent resonators are coupled together via inductive coupling holes 38 in the common wall 37 therebetween. The inductive coupling holes 38 alternate from one side of the beam path to the opposite side of the beam path to provide a serpentine shaped path of wave propagation for wave energy traveling on the interaction circuit 10. This type of microwave interaction circuit has a backward wave fundamental space harmonic mode of operation and is operated on the first space harmonic having between w and 2 1r radians of phase shift per cavity of the circuit 10.

The interaction circuit 10 is divided into a plurality of severed microwave circuit portions. More particularly, there is an input circuit portion 39, an output circuit portion 41, and an intermediate circuit portion 42. The input circuit portion has wave energy to be amplifled applied to the upstream cavity 36' thereof via the input waveguide 17 communicating with the upstream cavity resonator 36 via an input coupling iris 43. The input waveguide 17 extends longitudinally of the block thereto. The downstream end of the input circuit portion 39 is terminated in a lossy circuit sever 44 forming the subject matter of and being claimed in copending US. Pat. application Ser. No. 421,174 filed Dec. 3, 1973 and assigned to the same assignee as the present invention.

Briefly the circuit sever 44 includes a section of rectangular waveguide 45 recessed into a milled out portion of the block body portion 35 and brazed thereto. The circuit sever waveguide 45 is coupled to the last resonator 36 via a E-plane bend section 46 and coupling iris 47. An E-plane tapered wave energy absorptive member 40 is disposed within the terminal end of the circuit sever 44 in heat exchanging relation with the walls of the circuit sever waveguide 45 and the fluid coolant within fluid coolant passageway 23.

The input and output ends of the intermediate circuit portion 42 include circuit severs 44 of the type described with regard to the input section 39 of the microwave circuit. These severs 44 are located in recessed portions of the block body 35 on opposite sides from each other and on the sides of the rectangular cross section block portion 35 displaced 90 circumferentially from the input waveguide 17, as shown in FIG. 3.

Likewise, the output section 41 of the microwave circuit 10 includes a circuit sever 44 coupled to the upstream end thereof and the output waveguide 16 is coupled to the downstream resonator 36' via output iris 51.

The block body portion 35 of the tube is supported from and strengthened by means of an interference fit between the four corners 52 of the block body 35 and the interior bore of the stainless steel strengthening tube 34. As previously described, the block body 35 is of generally rectangular cross section to provide a substantially out-of-round surface spaced from the interior bore of the strengthening tube 34 for defining the four longitudinally directed coolant passageways 23 in the region between the out-of-round block body portion 35 and the inside wall of the strenthening tube 34.

The collector end of the block body portion 35 is brazed to the inner end of an inwardly directed reentrant portion of the collector pole piece 24.

The collector pole piece structure 24 is hollow and is joined in a fluid tight manner as by brazing to the collector end of the tubular strengthening member 34. Rectangular apertures in the pole piece 24 are provided on opposite sides of the beam path 13 to permit the input and output waveguides l7 and 16, respectively to pass from the main body portion 15 into the hollow pole piece structure 24. The apertures which permit the input and

output waveguides

17 and 16 to pass into the hollow pole piece 24 are slightly larger than the outside dimensions of the

waveguides

16 and 17 to provide a fluid communication passageway interconnecting the longitudinal body fluid coolant passageways 23 with the hollow chamber of the collector pole piece 24. In addition, at the output end of the block body portion 35, the corners are removed to permit fluid communication between the side passageways 23, 90 rotationally displaced from the input waveguide 17, and the input and output waveguide passageways 23.

The solenoid 18 includes an annular plate 54, as of cold rolled steel, forming the electron gun pole piece of the solenoid l8, and a similar annular plate 55, as of cold rolled steel, forms the collector pole piece of the solenoid 18. The two pole pieces are joined together by means of an inside tubular jacket 56, as of nonmagnetic stainless steel and an outside tubular magnetic yoke 50, as of cold rolled steel. The jacket and yoke are sealed at their ends in a fluid tight manner as by brazing to each of the annular pole pieces 54 and 55, respectively. The inside ring of perforations in the cathode pole piece 54 provide fluid communication between the cathode reservoir 19 and the body coolant passageways 23 via the ring of apertures 22 in the strengthening cylinder 34 and a similar matching ring of apertures 57 in the inside jacket 56. An annular septum 58 is provided in the solenoid between the inner ring of apertures 20 and the outer ring of apertures 21 in the cathode pole piece 54 for separating the flow of coolant to the solenoid 18 from that flow of coolant to the body 35 of the tube 11. At the collector end of the solenoid a ring of apertures 59 is provided in the collector pole piece 55 of the solenoid 18 and in the collector pole piece 24 of the tube 11 to allow the coolant to flow from the solenoid 18 into the hollow collector pole piece 24 of the tube 11.

The solenoid 18 is sealed in a fluid tight manner to the reservoir 19 via the intermediary of an annular mounting flange 61 and bellows 62. The bellows 62 is sealed between a cover 63 of the reservoir 19 and the mounting flange 61. The mounting flange 61 is secured to the cathode end of the solenoid 18 via a plurality of cap screws 64. An 0 ring 65 is provided between the mounting flange 61 and the cathode pole piece 55 for providing a fluid tight seal therebetween.

Similarly, at the collector end of the solenoid 18, the collector pole piece structure 24 0f the tube 11 is joined in a fluid tight manner to the collector pole piece 55 of the solenoid 18 via a plurality of cap screws 66. An 0 ring 67 is provided between the mating pole pieces 24 and 55 to provide a fluid tight seal therebetween. The cap screws 66 also serve to secure a cylindrical collector housing 68, as of aluminum, to the tube pole piece 24. An 0 ring 69 provides a fluid tight seal between the tube collector pole piece 24 and the housing 68.

The beam collector electrode 27 is secured to the collector pole piece structure 24 via the intermediary of an annular electrical insulator assembly 71 to permit the collector electrode 27 (beam collector bucket) to be operated at a depressed collector potential relative to the potential applied to the block body portion 35 of the tube 11. An 0" ring electrical insulator and seal 72 is disposed encircling the collector fin assembly in between the tins and the inside wall of the collector housing 68. The 0" ring 72 serves to support the collector bucket 27 via the fins and to seal the annular space between the outside of the fins, which are closed off by a cylindrical baffle 70, and the housing 68 such that the fluid coolant is forced to percolate through the perforated fins to the collector manifold 28 at the end of the tube 11.

Electrical potential is applied to the collector bucket 27 via an electrical feedthrough assembly 73 interconnecting the collector bucket 27 and the center conductor of the feedthrough via a flexible wire 74. The end of the collector bucket 27 is insulatively supported from an end wall 76 of the housing 68 via a cylindrical insulator 75' made of a high temperature resistant plastic, such as polyamide having a circular array of radially directed perforations therein permitting the coolant to flow radially into the center of the cylindrical insulator and thence into the manifold 28.

The tube 11 is readily removed and replaced within the solenoid 18 by loosening the collector cap screws 68 such that the tube is disconnected from the solenoid. The tube is then pulled out of the solenoid from the collector end. Since the cathode l2 and the main body portion 15 of the tube have generally the same outside transverse dimensions, the tube 11 is readily removed from the solenoid. The coolant tank 19 and solenoid are carried from a support structure via a mounting bracket assembly, not shown.

In a typical example, the tube 11 is utilized as an X- band power amplifier providing l0 KW of power output at X-band, with 50 db gain and 8 percent instantaneous electronic bandwidth (between 1 db points). The solenoid 18 provides an axial magnetic field within the beam of 2,500 gauss for focussing the beam 13. The beam has a current of 2.5 amps and a beam voltage of 19 14V at a microperveance of 1.0. The tube together with its mounting bracket, waveguides, coolant, connectors, solenoid, and hoses weighs approximately 55 poinds, and is approximately 18 inches long.

Referring now to FIG. 4 the collector pole piece structure 24 is shown in greater detail. More particularly, the pole piece includes an annular chamber 82 which surrounds an axially reentrant centrally apertured cylindrical core portion 83. The core portion 83 is notched at 84 on opposite sides of the beam path with rectangular notches to allow passage of the input and

output waveguides

17 and 16, respectively. The notches 84 have a radial depth greater than the outside height of the waveguides l6 and 17 such as to provide a fluid communication passageway communicating through the oversize notch between the fluid passageways 23 in the main body portion 15 and the chamber 82 of the collector pole piece structure 24.

The annular array of perforations 59, in the wall of the collector pole piece facing the solenoid 18, is axially aligned with similar perforations 59 in the solenoid pole piece 55. The inside wall of chamber 82 which faces the solenoid 18 is provided with an annular recess 85 at a radius corresponding to the radius of the circular array of perforations 59 so as to facilitate flow of coolant through those perforations 59 underlying the

waveguides

16 and 17.

The waveguides l6 and 17 each include an E-bend portion 86 extending radially outwardly of the beam path 13 on opposite sides thereof. The E-bend portions each connect to H-bend elbows 87 for bending the

waveguides

16 and 17 into parallel paths within the chamber 82. The H-bend sections 87 connect to straight sections of rectangular waveguide of lesser dimensions than standard waveguide which pass through the outer wall portion 88 of the pole piece 24 via milled recesses therein at 89. The waveguides l6 and 17 are brazed to the walls of the hollow collector pole piece structure 24 to provide thermally conductive fluid tight seals therebetween.

In a preferred embodiment (See FIGS. 2 and 4), the hollow collector pole piece structure 24 is fabricated by machining a first half 91 of the pole piece structure which faces the beam collector and a matching plate 92 which is brazed to the first half 91 to define the hollow collector pole piece structure 24. The stainless steel tubular main body strengthening member 34 is brazed at 94 to the inner end of the reentrant central core portion 83 of the collector half 91 of the pole piece structure 24.

The core portion 83 of the pole piece structure 24 includes a central bore 95 into which is pressed an electrically and thermally conductive non-magnetic insert 96, as of copper. The insert 96 is centrally counterbored to define the beam passageway therethrough. The insert 96 is brazed within the interior bore 95 of the pole piece core 83. The reentrant end of the core 83 is brazed to the end wall of the block body portion 35 at 97.

What is claimed is:

1. in a microwave linear beam tube:

electron gun means for forming and projecting a beam of electrons over an elongated linear beam path;

beam collector means at the terminal end of said beam path for collecting and dissipating the energy of the electron beam;

microwave interaction circuit means disposed along said beam path intermediate said electron gun means and said beam collector means for electromagnetic wave interaction with the beam to produce output microwave energy;

electrical solenoid means disposed surrounding said microwave interaction circuit means for generating an axial magnetic field in the beam path for focusing the electron beam through said microwave interaction circuit means;

a collector pole piece structure disposed at the beam collector end of said solenoid for shaping the beam focus magnetic field in the region of said beam collector means, said collector pole piece structure being made ofa ferromagnetic material and including a chamber therin; at least four passageways from said chamber through said pole piece structure:

an output waveguide structure for coupling the output microwave energy from said microwave circuit to a utilization device; a portion of said chamber containing a length of said waveguide structure, and said waveguide structure passing into and out of said chamber through two of said passageways; another portion of said chamber formed to contain a fluid coolant, and at least two of said passageways disposed for conduction of said fluid coolant into and out of said chamber.

2. The apparatus of claim 1 wherein said collector pole piece structure includes, a first ferromagnetic portion affixed to and carried from said solenoid means and a second ferromagnetic portion which includes said chamber and which is affixed to and carried from said microwave circuit means and said beam collector means, and means for detachably securing together said first and second portions of said collector pole piece structure.

3. The apparatus of claim 1 including an input waveguide structure for supplying microwave energy to said microwave circuit, said input waveguide structure passing through a portion of said chamber of said ferromagnetic collector pole piece structure.

4. The apparatus of claim 3 wherein said'input and output waveguide structures include, oppositely outwardly directed portion on opposite sides of the beam path, and each of said input and output waveguides having a H-plane bend portion within said collector pole piece structure for causing said input and output waveguide structures to pass through the wall of said collector pole piece structure in general parallelism to each other on the same side of the beam path.

5. The apparatus of claim 1 including body fluid coolant passageway means disposed in heat exchanging relation with said microwave circuit means for directing a flow of fluid coolant therethrough for cooling of said microwave circuit means, collector fluid coolant passageway means disposed in heat exchanging relation with said beam collector means for directing a flow of fluid coolant therethrough for cooling said beam col lector means, and wherein said collector pole piece fluid coolant passageway means is disposed in fluid communication with said body fluid coolant passageway means and with said beam collector fluid passageway means for flow of fluid coolant between said body fluid coolant passageway means and said beam collector fluid coolant passageway means through said collector pole piece fluid coolant passageway means.

6. The apparatus of claim 5 including, solenoid fluid coolant passageway means disposed in heat exchange relation with said solenoid means for directing a flow of fluid coolant therethrough for cooling of said solenoid means, and wherein said collector pole piece fluid coolant passageway means is disposed in fluid communication with said solenoid fluid coolant passageway means.

Claims

1. In a microwave linear beam tube: electron gun means for forming and projecting a beam of electrons over an elongated linear beam path; beam collector means at the terminal end of said beam path for collecting and dissipating the energy of the electron beam; microwave interaction circuit means disposed along said beam path intermediate said electron gun means and said beam collector means for electromagnetic wave interaction with the beam to produce output microwave energy; electrical solenoid means disposed surrounding said microwave interaction circuit means for generating an axial magnetic field in the beam path for focusing the electron beam through said microwave interaction circuit means; a collector pole piece structure disposed at the beam collector end of said solenoid for shaping the beam focus magnetic field in the region of said beam collector means, said collector pole piece structure being made of a ferromagnetic material and including a chamber therin; at least four passageways from said chamber through said pole piece structure: an output waveguide structure for coupling the output microwave energy from said microwave circuit to a utilization device; a portion of said chamber containing a length of said waveguide structure, and said waveguide structure passing into and out of said chamber through two of said passageways; another portion of said chamber formed to contain a fluid coolant, and at least two of said passageways disposed for conduction of said fluid coolant into and out of said chamber.

4. The apparatus of claim 3 wherein said input and output waveguide structures include, oppositely outwardly directed portion on opposite sides of the beam path, and each of said input and output waveguides having a 90* H-plane bend portion within said collector pole piece structure for causing said input and output waveguide structures to pass through the wall of said collector pole piece structure in general parallelism to each other on the same side of the beam path.

5. The apparatus of claim 1 including body fluid coolant passageway means disposed in heat exchanging relation with said microwave circuit means for directing a flow of fluid coolant therethrough for cooling of said microwave circuit means, collector fluid coolant passageway means disposed in heat exchanging relation with said beam collector means for directing a flow of fluid coolant therethrough for cooling said beam collector means, and wherein said collector pole piece fluid coolant passageway means is disposed in fluid communication with said body fluid coolant passageway means and with said beam collector fluid passageway means for flow of fluid coolant between said body fluid coolant passageway means and said beam collector fluid coolant passageway means through said collector pole piece fluid coolant passageway means.