US3412284A - Microwave tube apparatus having an improved slot mode absorber - Google Patents

Microwave tube apparatus having an improved slot mode absorber Download PDF

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Publication number
US3412284A
US3412284A US497791A US49779165A US3412284A US 3412284 A US3412284 A US 3412284A US 497791 A US497791 A US 497791A US 49779165 A US49779165 A US 49779165A US 3412284 A US3412284 A US 3412284A
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United States
Prior art keywords
absorber
mode
anode
slot
slot mode
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Expired - Lifetime
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US497791A
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English (en)
Inventor
George E Glenfield
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SFD LAB Inc
S-F-D LABORATORIES Inc
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SFD LAB Inc
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Priority to US497791A priority Critical patent/US3412284A/en
Priority to GB42194/66A priority patent/GB1142037A/en
Priority to DE19661541062 priority patent/DE1541062C/de
Priority to JP41067245A priority patent/JPS5248456B1/ja
Priority to FR80287A priority patent/FR1500494A/fr
Application granted granted Critical
Publication of US3412284A publication Critical patent/US3412284A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
    • H01J23/18—Resonators
    • H01J23/20—Cavity resonators; Adjustment or tuning thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/50—Magnetrons, i.e. tubes with a magnet system producing an H-field crossing the E-field
    • H01J25/52—Magnetrons, i.e. tubes with a magnet system producing an H-field crossing the E-field with an electron space having a shape that does not prevent any electron from moving completely around the cathode or guide electrode
    • H01J25/54—Magnetrons, i.e. tubes with a magnet system producing an H-field crossing the E-field with an electron space having a shape that does not prevent any electron from moving completely around the cathode or guide electrode having only one cavity or other resonator, e.g. neutrode tubes
    • H01J25/55—Coaxial cavity magnetrons
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/16—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion
    • H01P1/162—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion absorbing spurious or unwanted modes of propagation

Definitions

  • a coaxial magnetron tube includes a cathode electrode concentrically disposed of an anode electrode structure.
  • the anode electrode structure includes a circular array of anode resonators facing the cathode electrode and defining a magnetron interaction region in the space therebetween.
  • the anode structure includes a circular electric mode cavity resonator coaxially disposed of the array of anode resonators and communicating with the anode resonators via an array of axially directed coupling slots communicating through the anode structure between alternate ones of the anode resonators and the circular electric mode cavity resonator.
  • the array of coupling slots serves to lock the 11' mode of the array of anode resonators to the circular electric mode of the cavity resonator.
  • a slot mode absorbing member is disposed adjacent the ends of the slots for selectively damping unwanted oscillations associated with radio frequency energy storage in the slots.
  • the slot mode absorbing member comprises a porous ceramic member impregnated with carbon.
  • a metallic support member is bonded to the lossy ceramic member over a substantial surface area thereof which is on the opposite side of the lossy member from the slots, whereby thermal energy is uniformly distributed over the slot mode absorbing member to prevent fracture 1n use.
  • slot mode absorbers for absorbin the energy of the unwanted slot mode of resonance.
  • the slot mode absorber has taken the form of a lossy ring-shaped member usually made of carbon impregnated alumina which is disposed adjacent a circular array of axially directed resonant slots which communicate through the back wall of an array of vane resonators into a relatively large coaxial circular electric mode cavity for locking the 1r mode of the vane resonators to the circular electric mode of the coaxial cavity.
  • This circular array of coupling slots forms a resonant system and may store energy at one of its resonant frequencies.
  • the slot resonators like the coaxial cavity, are coupled to the magnetron interaction region via the intermediary of the vane resonators, it is' possible for the slot resonators, if they can store sufficient energy, to lock the vane resonators to the slot mode of resonance rather than to the desired circular electric mode of resonance of the coaxial resonator.
  • the purpose of the slot mode absorber is to absorb the energy of the slot resonant mode thereby preventing it from storing sufiicient energy to lock the vane resonator to its resonant frequency In microware tubes operating at high power levels, i.e., 350 kilowatts peak and 120 watts average at 3 gigacycles, the energy absorbed by the slot mode absorber becomes very high.
  • the slot mode absorber is provided with an axially coextensive metallic sleeve, as of copper, bonded or otherwise intimately joined in a thermally conductive manner to the mode absorber whereby heat is more evenly distributed over the mode absorber and conduction of heat therefrom to a suitable heat sink is facilitated.
  • This improved mode absorber support structure is that the peak and average power output of the microwave tube employing same is greatly increased, when compared to prior tubes, without producing failure or excessive outgassin of the mode absorber.
  • the principal object of the present invention is to -pr0- vide an improved crossed field microwave tube.
  • One feature of the present invention is the provision of an improved slot mode absorber having an axially coextensive thermally conductive sleevse, as of copper, bonded or otherwise intimately joined to the absorber via the intermediary of a thermally conductive joint whereby transfer of heat from the absorber to a suitable heat sink is facilitated to prevent failure or excessive outgassing of the mode absorber in use.
  • thermally conductive joint is formed by brazing the conductive sleeve to the mode absorber.
  • Another feature of the present invention is the same as any one or more of the preceding features wherein the mode absorber is directly brazed to a pole piece of the magnetic circuit of the tube structure whereby the pole piece serves the dual function of conductive sleeve and heat sink.
  • mode absorber is made of carbon impregnated ceramic.
  • FIG. 1 is a perspective view of a reverse magnetron tube, according to the invention.
  • FIG. 2 is a fragmentary cross section view, taken along the line 22 of FIG. 1;
  • FIG. 3 is a fragmentary enlarged cross section view of the structure of FIG. 2 delineated by line 33;
  • FIG. 4 is an enlarged fragmentary view of a portion of a structure of FIG. 3 delineated by line 44;
  • FIG. 5 is a fragmentary cross section view of an alternative tube structure characteristic of a normal coaxial magnetron and embodying the mode absorber of the present invention
  • FIG. 6 is an alternative structure to that of FIG. 5;
  • FIG. 7 is an alternative structure to that of FIG. 5.
  • a reverse magnetron comprises a hollow tubular supporting body 10, which may be made of copper, to which is brazed a tubular output waveguide assembly 12 and a tuner assembly 14, all in axial alignment.
  • a cathode lead-in insulator structure 16 extends from the main body 10 in quadrature with the axially aligned output waveguide and tuner assembly, respectively.
  • FIG. 2 a section of the magnetron is depicted wherein a circular electric mode cavity 18 is disposed centrally of the supporting anode body 10 along the axis of the tube.
  • a circumferential array of outwardly directed vanes 20 surround the circular electric mode cavity 18 and form an arrangement of anode resonators by the spaces between adjacent vanes.
  • Alternate anode resonators are 3 electromagnetically coupled to the circular electric mode cavity 18 by means of axially directed slots 22 communicating through the common wall between the anode resonators and the circular electric mode cavity.
  • a magnetron interaction region 24 surrounds the outer tips of the vanes and is defined by the space between the vanes and a surrounding cathode emitter ring 26.
  • a strong axial magnetic field of 12,000 to 15,000 gauss for the magnetron interaction region 24 is provided by a magnet structure 28 (only partially shown in FIG. 2) enveloping the anode body 10.
  • the magnet 28 has a re-entrant internal magnetic gap extending in the axial direction through the magnetron interaction region 24 between magnetic pole pieces 29 disposed on oppposite sides of the anode vanes 20.
  • the disk 30 may be driven axially by means of a captured nut and bellows assembly 34, partially shown.
  • a slot mode absorber 36 (shown in enlarged form in FIG. 3) is mounted adjacent the cylindrical anode wall 38.
  • the annular slot mode absorber 36 is positioned adjacent the ends of the slots 22 and suppresses the undesired slot mode.
  • the slot mode absorber 36 is formed from an alumina ceramic or beryllium oxide material that is about 30% porous and is impregnated with sucrose C H O Before impregnation, the surface of the absorber which is rernote from the slotted wall 38 is metalized with molybdenum manganese to within 0.010" from the tapered tip 39 of the absorber. Prior to assembly in the tube, the impregnated body is fired at about 910 centigrade in a hydrogen atmosphere to reduce the sucrose to carbon, thereby providing a lossy black surface.
  • the slot mode absorber 36 is jacketed with an axially coextensive high thermal conducting thin sleeve 40, made for example of 0.007 thick cop per sheet.
  • the copper jacket 40 is joined to the absorber and the pole piece 29 by brazing, for example.
  • the jacket 40 is substantially coextensive with the surface of absorber 36 which is remote from the slots and follows a gradual taper 42, about 30, at one end of the absorber.
  • the tip of the absorber 36 has a larger cross-sectional area than a configuration with a sharp taper in order to facilitate transfer of heat from the thin tip of the absorber 39 to the remainder of the absorber and to the jacket 40.
  • the taper '42 affords convenient assembly when inserting the absorber into position during manufacture.
  • the other end of the heat conductive sleeve or jacket 40 is bonded to the pole piece 29 whereby heat may be readily transferred to and dissipated in the more massive body of the metallic pole piece thereby forming a heat sink.
  • the mode suppressor is placed in thermal communication with a heat sink providing a good heat conduction path and prohibiting it from experiencing localized elevated temperatures.
  • Brazing of the metallic jacket 40 to the ceramic body 36 may be achieved by metalizing the ceramic structure prior to carbonization.
  • a metallic layer 44 (shown in FIG. 4) formed from a mixture of maganese, titanium, molybdenum or tungsten, by way of example, is applied to the ceramic. After impregnation of the ceramic, the brazing process is accomplished by means of the metalizing layer 44. Details of the formation of such assemblies are described in detail in US. Patent 3,197,290.
  • the copper jacket 40 provides a means of uniform thermal distribution over the mode absorber 36 thereby precluding localized heating. By providing uniform heat distribution over the absorber structure, fracture of the absorber is avoided, .and by-drawing heat from the absorber undesirable formation of gas is minimized. Therefore, the operating power level over a wide range of frequencies is substantially increased.
  • a tunable reverse magnetron of the type shown in FIGS. 1-3 wasoperated at 340 kilowatts power, watts .average at 3 gigacycles without evidence of mode absorber heating problems. Not only is a stable mode suppressor realized, but higher power levels are achieved.
  • FIG. 5 there is shown an alternative embodiment of the present invention for use in normal coaxial magnetron tubes of the type wherein a circular electric mode resonant cavity 51 surrounds a circular array of vane resonators 52 and is coupled thereto via the intermediary of an array of axially directed slots 53 communicating through a common wall 54 therebetween.
  • a circular electric mode resonant cavity 51 surrounds a circular array of vane resonators 52 and is coupled thereto via the intermediary of an array of axially directed slots 53 communicating through a common wall 54 therebetween.
  • Such a tube structure is shown and described in-U.S. Patent 3,169,211, issued Feb. 9, 1965.
  • the same slot mode control problem exists in this type of magnetron tube .as exists in the reverse coaxial magnetron previously described and depicted in FIGS. 13.
  • a ringlike lossy slot mode absorber 55 is disposed adjacent the ends of the slots 53 for absorbing the energy of the unwanted slot resonant mode.
  • the mode absorber as of carbon impregnated alumina ceramic, previously described, is brazed to a thermally conductive metallic sleeve 56, as of copper, which in turn is brazed to a massive iron pole piece 57 of the tubes magnetic circuit.
  • the massive iron pole piece thereby forms .a heat sink for the mode absorber.
  • the magnetic circuit which includes the pole piece 57, provides a strong axial magnetic field in the annular magnetron interaction region 58 between the array of anode vanes 52 and a cathode emitter 59.
  • the copper sleeve 56 which forms a bonded interface between the mode absorber 55 and the pole piece, allows good heat transfer from the absorber to-the heat sink and yields a uniform heat distribution over the mode absorber 55 to prevent thermally produced shock and fracture.
  • FIG. 6 there is shown an alternative embodiment to the structure of FIG. 5, wherein a thermally conductive metallic cylindrical sleeve 61, as of copper, is brazed substantially over its length to the mode absorbing ring 55 but is only brazed at its constricted end portion 62 to the pole piece 57.
  • This configuration permits strains produced by diiferences in thermal expansion between the pole piece 57 and the mode absorber 55 to be taken up by fiexure of the thin flexible sleeve 61 while providing a good thermal path along the length of the mode absorber 55 to the heat sinking pole piece 57.
  • FIG. 7 there is shown another alternative embodiment of the structure of FIG. 5 wherein the metalized mode absorber ring 55 is brazed directly to the pole piece 57 over substantially its entire axial and circumferential length whereby a low resistance heat path to the heat sinking pole piece 57 is obtained to provide the aforementioned advantages.
  • a cathode electrode an anode electrode structure coaxially disposed of said cathode and having a circular array of anode resonators facing said cathode electrode, said anode and cathode being spaced apart to define a circular crossed field interaction region therebetween, said anode structure having a circular electric mode cavity resonator formed therein coaxially with said cathode and said array of anode resonators, means forming an array of axially directed coupling slots formed in said anode structure and communicating through said anode structure between alternate ones of said anode resonators and said circular electric mode cavity resonator for locking the 1r mode of said array of anode resonators to the circular electric mode of said cavity resonator, means for extracting radio frequency output wave energy from said circular electric mode resonator for use, slot mode absorbing means disposed adjacent the ends of said slots for selectively damping unwanted radio frequency oscillations which cause radio frequency energy storage in said
  • said metallic support member is a metallic sleeve which is in turn bonded via a thermally conductive joint to a more massive heat sinking means whereby heat is readily transferred from said mode absorbing member to said heat sinking member.
  • said support member is a cylindrical pole piece member of a magnetic circuit of the tube apparatus disposed inside of and bonded to the inside surface of said lossy ring-shaped mode absorber member, whereby said pole piece serves as a heat sink for said mode absorber member.
  • HERMAN KARL SAALBACH Primary Examiner. S. CHATMON, JR., Assistant Examiner.

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  • Microwave Tubes (AREA)
  • Non-Reversible Transmitting Devices (AREA)
  • Constitution Of High-Frequency Heating (AREA)
US497791A 1965-10-19 1965-10-19 Microwave tube apparatus having an improved slot mode absorber Expired - Lifetime US3412284A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US497791A US3412284A (en) 1965-10-19 1965-10-19 Microwave tube apparatus having an improved slot mode absorber
GB42194/66A GB1142037A (en) 1965-10-19 1966-09-21 Microwave tube apparatus having an improved slot mode absorber
DE19661541062 DE1541062C (de) 1965-10-19 1966-09-29 Mikrowellenröhre mit Modusunterdrücker
JP41067245A JPS5248456B1 (enrdf_load_stackoverflow) 1965-10-19 1966-10-14
FR80287A FR1500494A (fr) 1965-10-19 1966-10-17 Absorbeur de modes indésirables dus aux fentes, pour magnétron

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Application Number Priority Date Filing Date Title
US497791A US3412284A (en) 1965-10-19 1965-10-19 Microwave tube apparatus having an improved slot mode absorber

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US3412284A true US3412284A (en) 1968-11-19

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US (1) US3412284A (enrdf_load_stackoverflow)
JP (1) JPS5248456B1 (enrdf_load_stackoverflow)
FR (1) FR1500494A (enrdf_load_stackoverflow)
GB (1) GB1142037A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3479556A (en) * 1967-09-27 1969-11-18 Sfd Lab Inc Reverse magnetron having an output circuit employing mode absorbers in the internal cavity
US4053850A (en) * 1976-09-23 1977-10-11 Varian Associates, Inc. Magnetron slot mode absorber
KR100487329B1 (ko) * 2002-10-10 2005-05-03 엘지전자 주식회사 응축식 의류건조기 및 그 제어방법

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2821659A (en) * 1954-11-18 1958-01-28 Bell Telephone Labor Inc Magnetron
US3169211A (en) * 1961-04-26 1965-02-09 Sfd Lab Inc Magnetron
US3231781A (en) * 1962-08-10 1966-01-25 Sfd Lab Inc Reverse magnetron with slot mode absorber

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2821659A (en) * 1954-11-18 1958-01-28 Bell Telephone Labor Inc Magnetron
US3169211A (en) * 1961-04-26 1965-02-09 Sfd Lab Inc Magnetron
US3231781A (en) * 1962-08-10 1966-01-25 Sfd Lab Inc Reverse magnetron with slot mode absorber

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3479556A (en) * 1967-09-27 1969-11-18 Sfd Lab Inc Reverse magnetron having an output circuit employing mode absorbers in the internal cavity
US4053850A (en) * 1976-09-23 1977-10-11 Varian Associates, Inc. Magnetron slot mode absorber
KR100487329B1 (ko) * 2002-10-10 2005-05-03 엘지전자 주식회사 응축식 의류건조기 및 그 제어방법

Also Published As

Publication number Publication date
DE1541062B2 (de) 1972-08-03
JPS5248456B1 (enrdf_load_stackoverflow) 1977-12-09
GB1142037A (en) 1969-02-05
FR1500494A (fr) 1967-11-03
DE1541062A1 (de) 1969-07-24

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