US3241089A

US3241089A - Liquid-cooled waveguide load

Info

Publication number: US3241089A
Application number: US254358A
Authority: US
Inventors: Treen Kenneth Frederick
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1962-02-16
Filing date: 1963-01-28
Publication date: 1966-03-15
Anticipated expiration: 1983-03-15
Also published as: NL289114A; BE628391A; GB934616A

Description

2 Sheets-Sheet 1 Filed Jan. 28, 1963 lnvem'or Kf/VIVET/r' A TREf/V 2 Sheets-Sheet 2 Filed Jan. 28, 1963 Inventor KENNETH F. TREEN y ;7

Allorney United States Patent 3,241,089 LIQUID-COOLED WAVEGUIDE LOAD Kenneth Frederick Treen, London, England, assignor to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Filed Jan. 28, 1963, Ser. No. 254,358 Claims priority, application Great Britain, Feb. 16, 1962,

35/62 3 Claims. (Cl. 333-22) This invention relates to loads for the non-reflective dissipation of radio frequency (RF) power in waveguides, and has particular, though not exclusive, application when the power to be dissipated is of the order of kilowatts.

A load constructed according to the principles of the invention is of tapered form to give a good match to incident RF power over a broad band in a waveguide, and is arranged to have liquid circulating through it as the actual power absorber. The interior of the load is arranged to minimize in use the formation of pockets of stagnant liquid at the power-source end of it, since such stagnant pockets might overheat enough to boil and rupture the walls. It is at the power source end of the load that such stagnancy might occur, as the liquid is introduced and exhausted at the other end.

According to the invention, therefore, there is provided a waveguide load including a vessel smoothly tapered from a large end to an apex and having inlet and outlet conduits near the large end for a continuous flow of liquid through the vessel, static means within the vessel to distribute the flow, and means in the said distributing means resistant to the liquid flow to cause turbulence in the liquid in the vicinity of the said small end.

Since overheating may also occur due to power absorption within the walls of the load, they should be as thin as is consistent with structural rigidity, and of a material which is transparent to RF power.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a partially sectionalized plan view of a waveguide equipped with an RF load;

FIG. 2 is a side view of part of the waveguide shown in FIG. 1; and

FIG. 3 shows an end view and a side view of a detail of the arrangement shown in FIG. 2.

Referring to FIG. 1, there is shown a tapered insulating vessel 1 which constitutes the outer jacket of a load located within, and bolted to a waveguide termination section 2. The vessel 1 is smoothly tapered down from a large end 3, where it has approximately the internal dimensions of the waveguide, to an apex end 3a, where it has an indentation 4 for the location and attachment by a suitable adhesive of a centrally disposed tube 5. The tube 5 extends within the vessel 2 from adjacent the large end 3, to the indented region of attachment 4 at the apex end 3a. Adjacent the large end 3, the tube 5 is attached to an inlet water conduit 6, and at the indentation 4, the tube is castellated at 7, (see also FIG. 3). Exit conduits 8 provide an exit for water entering inlet conduit 6. The end of the waveguide 1 is closed, to prevent RF leakage, by a copper gasket 9 clamped by a rigid plate 10, through which pass the conduits 6 and 8. An inductive iris 11 and adjustable capacitive screws 12 at the other end of the waveguide 1 constitute matching for the slight geometrical discontinuity presented by the load to the power source.

The vessel 1 and the tube 5 are made of fiber glass, which material has a low coefiicient of absorption for power at frequencies of hundreds of megacycles.

In operation, water is fed to the inlet conduit 6, whence it flows down the tube 5, through the apertures formed 3,241,089 Patented Mar. 15, 1966 by the vessel 1 and the castellations 7, and thence via the outer jacket of the load to the exit conduits 8. A sufiicient head of water is fed to the load for the resistance of the apertures to cause, at least locally, a turbulent flow. This turbulence tends to prevent the formation of pockets of stagnant water at the apex end, and so should be present to ensure safe operation.

With reference to the load shown in FIG. 1 it is necessary to take into account the total flow of water required to dissipate the maximum expected RF power without overall overheating, the dimensions of the inner tube and its castellations needed to pass the said total flow with the required degree of turbulence and the head of water available.

Referring to FIG. 2 which shows a side View of the waveguide equipped with the load seen in FIG. 1, there are seen two inspection tubes 13, 13. The presence of these tubes enables inspection of the apex end of the load during operation, reduces the electric field in the region of this end, and permits the insertion of probes to sample the RF field. Also the inspection tubes 13, 13 can serve as a safety release for water in the event of the load rupturing or leaking. To cooperate in such a release action, an RF window may be provided in the source end 14 of the waveguide section 2. The diameters of the inspection tubes 13, 13 are chosen so that their cut-off frequency is above the operating frequency of the waveguide 2, so that RF loss through them is negligible.

FIG. 3 shows an end view and a side view of the tube 5 before the attachment of its castellated end to the apex end of the vessel 1 and of its other end to the inlet conduit 6 (FIG. 1).

Fiber glass is chosen as the material for the vessel 1 and the tube 5 not only for its low RF absorption coefticient, but also because of its rigidity, and facility of moulding. Of course other nonconductive materials may be used, but it should be borne in mind that a high RF absorption will tend to nullify the advantages given by the turbulent flow according to the invention in minimizing local overheating.

The provision of thermometers in inlet and exit conduits 6 and 8, and of means for measuring the water flow will enable the measurement of RF power dissipation in the water.

With tap-water circulating through the load, and copper foil screening at the large end of it, RF power losses as low as 50 db below the incident power level have been measured at 2000 mc./s. This figure ShOWS the efficacy of a load according to the invention in the almost complete dissipation of the incident power.

Variations from the above-described embodiment without departure from the principles of the invention will readily occur to those skilled in the art.

For instance, the tapering of the vessel 1 may be in one dimension only, the water may be circulated in the reverse direction through the load, liquids, or solutions instead of water may be used in the load, the vessel 1 may be conical for insertion in circular waveguide, or there may be apertures near the end of the tube 4 instead of the castellations 7.

While I have described the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the ac companying claims.

What is claimed is:

1. A waveguide load utilizing a flow of liquid coolant comprising:

a vessel smoothly tapered from a large end to a small end and having at least one inlet conduit and at 3 4 leastone outlet conduit connected to said large end, normal to said waveguide adjacent to said small end of wherebygacontinuous flowv of liquid may be forced said tube. t a r through said vessel along the axis thereof; means for mounting said vessel in the waveguide; References Cited by the Examiner a tube, centrally disposed in said vessel, having one 5 end connected to said inlet conduit and its other end UNITED STATES PATENTS connected to said small end of said vessel, said other 3,040,252 6/1962 NOYak 33322 end having a serrated edge adjacent the inside sur- 3,044,027 6/1962 Chm et a1 333*22 face of said small end of said vessel; and said vessel having a protuberance axially disposed at 10 FOREIGN PATENTS .said small end, which cooperates With said serrated l 576040 5/1959 Canada- :igie to cause turbulence of the liquid in said small OTHER REFERENCES I 2.A Waveguide load, according to claim 1, wherein: Freedman! Radio E ic Engineering, May 1954, i i said serrated edge surrounds said protuberance. 15 Pages 35 rehcd upon} 3. A waveguide load according to claim 1 further comprising other tubes attached to said waveguide, each said ELI LIEBERMAN, Primary Examinerother tube having a cut-off frequency exceeding the operating frequency of said waveguide, and being disposed HERMAN KARL SAALBACH Examiner

Claims

1. A WAVEGUIDE LOAD UTILIZING A FLOW OF LIQUID COOLANT COMPRISING: A VESSEL SMOOTHLY TAPERED FROM A LARGE END TO A SMALL END AND HAVING AT LEAST ONE INLET CONDUIT AND AT LEAST ONE OUTLET CONDUIT CONNECTED TO SAID LARGE END, WHEREBY A CONTINUOUS FLOW OF LIQUID MAY BE FORCED THROUGH SAID VESSEL ALONG THE AXIS THEREOF; MEANS FOR MOUNTING SAID VESSEL IN THE WAVEGUIDE; A TUBE, CENTRALLY DISPOSED IN SAID VESSEL, HAVING ONE END CONNECTED TO SAID INLET CONDUIT AND ITS OTHER END CONNECTED TO SAID SMALL END OF SAID VESSEL, SAID OTHER END HAVING A SERRATED EDGE ADJACENT THE INSIDE SURFACE OF SAID SMALL END OF SAID VESSEL; AND SAID VESSEL HAVING A PROTUBERANCE AXIALLY DISPOSED AT SAID SMALL END, WHICH COOPERATES WITH SAID SERRATED EDGE TO CAUSE TURBULENCE OF THE LIQUID IN SAID SMALL END.