US3538366A

US3538366A - Fluid cooled electromagnetic structure for traveling wave tubes

Info

Publication number: US3538366A
Application number: US777288A
Authority: US
Inventors: Hans Glien; Paul Meyerer; Franz Weinzierl; Herbert Sarnezki
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1967-11-28
Filing date: 1968-11-20
Publication date: 1970-11-03
Anticipated expiration: 1987-11-03
Also published as: GB1207035A; FR1592814A

Description

INVENTORS 6749/7, fiw/ My ref flev'e/"fa/waz/ ATTYS.

I, T X Q y, fl I! I i F; 7 ///A H. GLIEN ETAL Filed NOV. 20, .1968

FOR TRAVELING WAVE TUBES FLUID COOLED ELECTROMAGNETIC STRUCTURE Nov. 3, 1970 2 a M l R H N m QN I l. I 1 6| L 1// l m 1 H M 7/ m 7 PM a w? 1 T wm mwwmmezs Q 5;;

United States Patent Oifice 3,538,366 Patented Nov. 3, 1970 US. Cl. 313-24 6 Claims ABSTRACT OF THE DISCLOSURE An arrangement for the bundled guidance of an electron beam in a traveling wave tube having at least one fluid cooled magnetic coil, in which the latter is divided into a plurality of individual coil sections disposed on a tubularly shaped double-Walled carrier body, on Which are also disposed cooling fins which are interposed between respective pairs of adjacent coil sections, with inlet and outlet connections being provided for effecting the passage of coolant between the double-wall of the carrier body.

BACKGROUND OF THE INVENTION The invention relates to an arrangement for the bundled guidance ofthe electron beam of a traveling wave tube utilizing at least one fluid cooled electromagnetic coil and radially extending heat conducting plates or the like.

Magnet arrangements of this general type are known in the prior art (see for example The Bell System Technical Journal, 42 July 1963, No. 4, part 3, page 1832). However, the magnetic field values attainable with permanent magnet systems are no longer suflicient for the bundling of electron beams of high perveance, and in their place electromagnetic coil arrangements must be utilized, which because of their relatively high power loss of several kw. are generally cooled by means of a suitable liquid. As a consequence, various proposals have heretofore been made for the design of such type of fluidcooled electromagnetic coils. Thus, for example, in one embodiment, proposed in the above cited article, water conducting cooling coils are disposed adjacent the radial sides or ends of the control coil. However, in many cases such cooling is inadequate and ultimately leads to a considerable localization of heat within the coil.

It has been attempted to eliminate these difficulties by forming the electromagnetic arrangement into a plurality of individual coils which were separated by water cooled plates (see Journal of Electronics and Control, 1. Ser. vol. 14, No. 1, January 1966, page 41).

However, in this type of magnetic arrangement, the division of the coil structure into individual coil sections cannot be carried sufficiently far to solve the cooling problems of the individual coil sections arranged between the water cooled plates, because the necessary thickness of the latter to provide adequate stability produces detrimental effects with respect to the magnetic field produced by the coil structure. Furthermore, this type of construction results in an enlargement of the outer diameter of the coil structure without a corresponding magnetic gain, due to the disposition of the cooling fluid feed connections at the outer circumference, which in turn, in most cases, further complicates the installation of traveling wave tubes with such focusing coils into the load circuit. The technical cooling problems concerning electromagnetic coil focusing arrangements know in the prior art can be brought within reasonable limits by designing the coils with very large dimensions, i.e. having a relatively large outer diameter for a predetermined inner diameter of a size to receive the traveling wave tube, as in such case the power loss to be dissipated is smaller than in a comparable coil with a smaller outer diameter. However, this results in the handling of the coils and retaining frames therefor of suflicient stability being more cumbersome because of the additional relatively great Weight involved.

.BRIEF SUMMARY OF THE INVENTION The invention is directed to the problem of avoiding the disadvantages of the magnetic arrangements known in the prior art and to produce an arrangement which, even with increased power losses resulting from a reduction in the outer diameter of the coil, still assures adequate cooling of all portions of the coil.

In the proposed solution, according to the invention, of this problem, the electromagnetic arrangement comprises a fluid cooled magnetic coil divided into a plurality of individual coil sections which are placed on a common tubular carrier body of double-walled construction, which is provided with inlet and outlet connections for the cooling fluid, on which carrier body radially extending cooling ribs or fins are disposed. The respective cooling fins may be of annular disc-like formation, extending perpendicularly to the longitudinal axis of the carrier body and respectively disposed between the individual coil sections of the electromagnetic coil. The interior of the double wall of the carrier body may be provided with partitioning means, preferably in the form of a double pitch helix, whereby the inlet and outlet connections for the cooling fluid, for example water, are disposed at the same end of the electromagnetic coil.

Such inlet and outlet connections for the cooling fluid of the electromagnetic arrangement are preferably disposed at the end thereof adjacent the catcher of an inserted tube, enabling the use of an additional, externally disposed coil at the opposite end of the arrangement, which coil may be specially designed to provided desired field strength characteristics adjacent the beam entrance into the area of uniform field strength within the electromagnetic arrangement, thereby increasing the stability of the electron beam between the electron gun and the adjacent end of the magnetic arrangement.

Eflicient removal of heat by means of the fluid cooled carrier body makes further possible the use of a plurality of relatively thin cooling fins or ribs which are sufficiently thin that they do not disturb the course of the magnetic field, and as a result thereof coil sections of narrow axial width may be employed, which when disposed between two consecutive fins substantially completely eliminates the existence of any localization of heat within the coil sections. Furthermore, by employing individual coil sections with different winding arrangements, a desired predetermined course of the magnetic field can be achieved.

Furthermore, by utilization of an arrangement in which the fluid cooling is disposed within the coils, enabling the simultaneous use of the cooling structure as a carrier body for the respective windings, exceptionally good thermal contact can be provided between the carrier body and the cooling fins for example by means of a soldered connection, which type of structure is practically unattainable where an externally arranged cooling structure of tubular shape is employed which, for example, must be pushed or suitably shrunk on, over the cooling fins of the completed coil assembly.

Any possible localized residual heat still remaining, primarily between the insulated layers of the wire, can be eliminated by effecting the winding operation by means of a so-called wet winding operation with epoxy resin and a subsequent hardening thereof, to provide a more efficient heat conduction through the coil structure and at the same time improving the mechanical strength of the coil.

BRIEF DESCRIPTION OF THE DRAWING The figure of the drawing represents a longitudinal sectional view through an electromagnetic structure, constructed in accordance with the present invention, for a traveling wave tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment of the invention illustrated, the electromagnetic coil is divided into a plurality of individual, annular shaped coil sections 1 to 14 which are supported on an elongated tubular shaped carrier body of double-walled construction, comprising a pair of concentric tubular walls 31, the space therebetween being closed at the respective ends of the body structure, with the latter thus extending through the central opening in each of the coil sections. Secured, in good heat conducting relation, to the exterior wall 31 of the carrier body are a plurality of cooling ribs or fins, made for example of brass and soldered to the adjacent wall 31, with the respective cooling fins being disposed between adjacent coil sections. A suitable hollow conductor 18 is connected at the catcher end of the structure by means of which the high frequency energy of the tube may be conducted therefrom, and disposed at the ends of the electromagnetic arrangement are

respective pole plates

16 and 17 of iron or the like, whereby the magnetic field produced at the ends exhibits a high flank steepness with almost a vertical rise to the saturation value. Disposed adjacent the pole plate 17 and separated therefrom by a spacer ring 19, for example of brass, is an external coil which produces a magnetic field adjacent the entrance into the electromagnetic arrangement whereby the electron beam initially enters a field exhibiting a small maximum following which a minimum is traversed prior to entry into the uniform field, which construction promotes a particularly efiicient guidance of the electron beam entering from the left, as viewed in the figure, along the axis 34 of the following magnetic arrangement, only a portion of the adjacent structure at the entrance end of the electromagnetic arrangement being illustrative.

In addition, a tubular metal cylinder, not shown, can be inserted in the carrier body, such cylinder or tube being provided at its opposite end adjacent the catcher with an edge of irregular shape, such that it compensates for irregularities in the field of the coil.

The coil section 1 adjacent the catcher end of the electromagnetic arrangement is provided with a larger internal diameter than the remaining coil sections to provide space for the accommodation of inlet and outlet connections 22, 23, disposed one behind the other as viewed in the figure, the inner ends of which connections communicate with the interior between the walls 31 of the carrier body whereby fluid can circulate therebetween. To effect a distribution of cooling fluid over the entire area of the carrier body suitable partition means is disposed between the respective walls 31 of the carrier body, such partition walls being arranged to provide a circuitous fluid flow between the inlet and outlet connections. In the embodiment illustrated such partition means is in the form of a double pitched helix, formed by wire 33 of suitable gauge, disposed in fixed relation between the wall 31 with the pitch being so selected that the cross-sectional area of the respective passageways formed thereby is equal to the cross-sectional area of the respective inlet and outlet connections. If it is desired to increase the travel, this may be readily accomplished by utilizing a suitable multiple pitch greater than 2.

Good heat conduction between the respective coil sections and the carrier body and cooling fins carried thereby may be achieved by embedding the respective coil sections in epoxy resins, of the type commonly employed in connection with potted structures, whereby exceptionally good heat-conducting contact will be effected between adjacent surfaces of the respective coil sections and cooperable cooling fins and external wall 31 of the carrier body. Preferably the winding of the respective coils is effected by means of a so-called wet winding operation employing an epoxy resin paste which is subsequently permitted to harden, whereby the resulting coil section is in the form of a solid block, having increased mechanical strength and providing efiicient heat conduction from the coil interior outwardly to eliminate any possible remaining residual heat concentration within the coil section which primarily occur between the insulated layers of the wire forming the coil.

Having thus described our invention it will be apparent that various immaterial modifications may be made in the same without departing from the spirit of our invention, hence we do not wish to be understood as limiting ourselves to the exact form, construction, arrangement and combination of parts herein shown or described.

What we claim is:

1. An arrangement for the bundled guidance of an electron beam in traveling wave tubes having at least one fiuid cooled magnetic coil provided with cooperable heat dissipating members thereof, characterised by the fact that each fluid cooled magnetic coil is divided into a plurality of individual annular shaped coil sections, a tubular shaped double-walled carrier body on which said coil sections are disposed, radially extending cooling fins disposed on said carrier body and connected thereto in good heat conducting relation therewith, said cooling fins each being disposed between a respective pair of adjacent coil sections, in good heat conducting relation therewith, and fluid inlet and outlet connections secured to said carrier body for operatively supplying a fluid coolant to the interior of said carrier body.

'2. An arrangement according to claim 1, comprising in further combination, partition means disposed in said carrier body between the double-wall thereof, for distributing fluid flow across substantially the entire effective cooling area of said body.

3. An arrangement according to claim 2, wherein said partition means is of helix configuration and is at least of double-pitch.

4. An arrangement according to claim 1, wherein each coil section is embedded in epoxy resin.

5. An arrangement according to claim 1, wherein said inlet and outlet connections are disposed at the end of the carrier body which is to be adjacent the catcher end of a cooperable traveling wave tube when the latter is disposed in operating position in said body.

6. An arrangement according to claim 5, wherein each winding turn of a coil section is embedded in epoxy resin to provide improved heat conduction from the interior of such coil section outwardly.

No references cited.

JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner US. Cl. X.R.