US2438194A - Magnetron - Google Patents

Magnetron Download PDF

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Publication number
US2438194A
US2438194A US677463A US67746346A US2438194A US 2438194 A US2438194 A US 2438194A US 677463 A US677463 A US 677463A US 67746346 A US67746346 A US 67746346A US 2438194 A US2438194 A US 2438194A
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US
United States
Prior art keywords
cathode
anode
magnetron
pipe
cavity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US677463A
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English (en)
Inventor
Jr Howard L Steele
John W Mcnall
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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Filing date
Publication date
Priority to BE473942D priority Critical patent/BE473942A/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US677463A priority patent/US2438194A/en
Priority to FR950897D priority patent/FR950897A/fr
Application granted granted Critical
Publication of US2438194A publication Critical patent/US2438194A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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
    • H01J25/58—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 a number of resonators; having a composite resonator, e.g. a helix
    • H01J25/587—Multi-cavity magnetrons

Definitions

  • This invention relates to ⁇ magnetrons, and more particularly to the cathode structure thereof.
  • Electron discharge devices of the magnetron type are employed in the art for generating or sustaining electricaloscillations of very high frequency. Such devices usually contain lan anode of generally cylindrical shape with an elongated electro-n emitting cathode axially sustained therein with both elements functioning in a Vacuum.
  • the gravity of the heat exchange for eiiiciency is rendered more evident by the fact that, when the device is in normal operation, the developed heat is so intense that the external cathode heater vpower may be reduced sometimes even to zero and the device 'continues to operate as well as while the power was being applied. If, however, the anode voltage is interrupted for suilicient length of time, the bombardment of the cathode and emission stop and then to re-start the operation the cathode heater lament has to be used to again operate the cathode at the proper emissive temperature.
  • Bombardment results in the loss and destruction of the thermionically active material on the surface of the cathode. Also'the higher temperature than normal for the cathode results in serious But with more y evaporation of the active material, and in either event the active material lost from the cathode is in greater part found to be deposited on the inner concave face of the anode. 'I'his deposit on the anode interferes somewhat with the operating characteristics of the magnetron.
  • the invention has an objective of eliminating the defects referred to above and thereby increase the operating life and efIicency of the magnetron.
  • Another object is to provide an improved magnetron assembly and combination of parts.
  • an object of the invention is to provide improved means for limiting and regulating the eiective temperature of the cathode derived from electron bombardment.
  • a further object of the invention is to utilize the main cathode exclusively as a secondary emitter of electrons.
  • the invention contemplates oscillation initiation from a source other than the main cathode.
  • the present concept includes provision of an auxiliary cathode as a primary emitter.
  • Important amongst the objects of the invention is inclusion of a primary emitter protected from runaway eiect that would cause it to draw larger currents due to temperature increase.
  • Figure 2 is a cross-sectional view on line II-II of Fig. 1;
  • Figure 3 is a sectional view of the cathode similar to the showingsthereof in Fig. 1, but onalarger scale;
  • Figure 4 is a cross section on line IV-IV of Figure 3.
  • the reference numeral I0 designates a cylindrical magnetron body having end plates or covers I I sealed thereto whereby the interior may be evacuated.
  • the interior of said body is formed to comprise an anode I2 of generally cylindrical shape, shorter than the outside portion of the body which has ⁇ end flanges I3 for spacing the covers II from' vthe anode so as to open into both end spaces 14, Y,
  • the said radiating cavities constitute cavity resonators and electrical coupling thereof is obtained by straps i8 here the ends of the anode and each of which connects different alternate walls l'l thereof.
  • ⁇ vl5 Coaxially within the aforementioned cathode cavity.
  • ⁇ vl5 is a cylindrical. secondary emission cathode I9.
  • this cathode it is preferable that this cathode have its upper end lower than the plane of the upper end of the anode.
  • Heating of this cathode which for brevity willbe distinguished as the main cathode, is derived from electron bombardment, and means are provided for limiting and regulating temperature of said cathode of optimum intensity for maximum efciency as a secondary emitter but of insumcient intensity to cause any substantial primary emission.
  • This heat control is shown accomplished by provision of a hollow within the cathode to and from which a fluid cooling medium is circulated by means exterior to the magnetron.
  • Air, aswell as water, oil and other liquids, are examples of cooling mediums which may be used. Circulation is obtained by provisionof an entry or in-iiow pipe coaxially within an out-flow or discharge pipe 21.' The discharge pipe extends Well Vwithin the cathode coaxially thereof whereas the in-iiow pipe 20fis shorter so as to accommodate fluid passage Vfrom the end thereof into the vregion exterior to the in-flow pipe but interior of the out-flow pipe.
  • the pipes are preferably assembled in proper terminal relation and the end of the outer pipe is then lled with a plug 22A after which the body material for the cathode is cast directly around the pipe.
  • the secondary emitter or main cathode I9 maybe shown as rin-gs at j and has been an undesired source of electronY is exemplified by the structure at the upper end of theranode in upper end space I4.
  • an auxiliary cathode 24 is provided oppo- ⁇ site the upper end of the main cathode I9V in coaxial alinement therewith but spacedk therefrom.
  • the two cathodes are of approximately the same diameter, but it is desirable to have thel auxiliary cathode of slightly smaller diameter than the main cathode in order to avoid evaporation diiculties.
  • the auxiliary cathode is of a character which is copiously emissive of thermionic electrons.
  • the auxiliary cathode 24 is a coil of wire which is emissive material throughout or some metal coated with emissive material such as strontium or barium oxide, vor ⁇ which is otherwise rendered copiously emissive.
  • the coil constitutes a thermionic cathode and accordingly is constructed with appropriate electrical resistance so it can be heated by flow of current therethrough, for which purpose it is in electrical lcontinuity with lead-in wires 25 whichare introduced from the exterior radially through the end anges i3 of the magnetron body into the end space lll.
  • Appropriate seal and insulation for these lead-in wires 25 is provided, one form ofV which may be. seen in Fig. 2 as comprising a hollow nipple 2B sealed to the magnetron body and having a sleeve 21 sealed at its outer end and which in turn is sealed to a glass cap 28 through which the wire passes in sealed contact.
  • Said end wall of hat 29 has holes therein for passage of the ends of the auxiliary cathode therethrough, insulators 30 of suitable material for thepurpose, of which Y silver-magnesium is preferred; beryllium-copper alloy is .another suitable material;y and otheriexamples may be given of copper ⁇ bases onwhich a coating is applied, for instance a coating of sprayed aluminum.
  • the coaxial pipes 20, 2l project from what will be termed the lower end of the main cathode and into the end space It thereat, and that the said lower end of the cathode is substantially in a common plane with the lower end of the anode.
  • Said Yhat is of greater diameter than the main cathode and preferably at least equal to the diameter of the cathode cavity of the anode. The function of the hat in the prior art has been to conne the electrons from escape at the end of the cathode cavity.
  • the hat has suffered .from electron bomdepends from the end wall .of the hat toward the being provided in the holes for electrically isolating the said ends from the hat.
  • This hat 29, by virtue of its cup shape, is furthermore provided ⁇ with a peripheral wall or skirt 3l which anode and girdles the auxiliary cathode, said skirt preferably being as deep as the auxiliary cathode so the latter is contained entirely within the recess of the hat.
  • the end'of the hat 29 toward the ymain cathode and anode preferably has an outer diameter substantially as great as the diameter of the cathode cavity l5 and thus,
  • Vauxiliary cathode 2li functions to deter escape of electrons into the end space Hl.
  • Saidhat V29 is preferably non-magnetic and a good heat conductor of high melting point, such'as molybdenum.
  • VA further feature of the present invention is provisionof means for cooling the auxiliary cathode hat or gun This is accomplished by means quite similar to that described above for cooling the main cathode.
  • said means comprises inner and outer coaxial pipes 32, 33 which are respectively employed as inlet and outlet for a cooling medium or fluid such as air, water or oil.
  • the outer or outlet pipe 33 has its inner end secured in a radially disposed hole in said cap 29 preferably in the region of the end wall of said cap. Since the cap is preferably molybdenum, a copper solder or braze may be employed to secure the pipe tightly in the cap.
  • the said outlet pipe 33 projects radially through the ilange I3 of the magnetron body and through a nipple 34 sealed to said flange but with the pipe out of contact from either the flange or nipple.
  • a sleeve 35 sealed thereto and of metal capable of sealing to one end of a glass collar 36 the other end of which is sealed to a similar sleeve 31 which in turn is sealed to a metallic head 38.
  • Pipe 33 extends from the cap 29 through the nipple 34, sleeves 35, 31 and collar 36 to said head 38 and opens at its end into a lateral passage 39 from which a discharge pipe lll projects for carrying off fluid from the outlet pipe 33.
  • a suitable choke el is-provided on outlet pipe 33 to prevent ow of radio frequency current from the magnetron by that path.
  • Inner or inlet pipe 32 has its inner end or end toward the cap 29 inset from the end of the outer pipe 33 thereby permitting fiuid'flow from the end of the inner pipe into the end region of the outlet pipe and then back to the discharge outlet through the space between the outer surface of the inner pipe and the inner surface of the outer pipe.
  • the other or outer end of the inner pipe 32 passes through the aforementioned lateral passage 39 beyond the end of the outer pipe and is sealed in said head and in communication with a supply pipe 42.
  • the electrical connection for applying the direct current potential may be made to head 33 by virtue of metallic pipe connection 33 from the head to the hat which will act as an electrical conductor and support insulated from the magnetron body.
  • Use of a more positive potential on the hat will increase primary emission from auxiliary cathode 24 and permit utilization of a lower emitter temperature and heating power.
  • the potential on the hat is kept as least positive as possible, or even negative.
  • for the main cathode is like that for the gun and that the outlet pipe for the cathode constitutes an electrical connection for application of desired potential to the said cathode.
  • a magnetron comprising an evacuated enclosing housing having an anode therein, said anode providing a cathode cavity longitudinally central thereof, a cathode coaxial of and within said cavity and emission from which is substantially secondary electrons only, and means at one end of said cathode for conducting a cooling medium both to and from said cathode.
  • a magnetron comprising an evacuated enclosing housing having an anode therein, said anode providing a cathode cavity longitudinally central thereof, a main cathode coaxial of and within said cavity and emission from which is substantially secondary electrons only, means at one end of said cathode for conducting a cooling medium both to and from said cathode, and an auxiliary cathode at the opposite end of said main cathode from said means.
  • a magnetron comprising an evacuated enclosing housing having an anode therein, a main cathode in said anode, an auxiliary cathode emissive of primary electrons opposite an end of said main cathode, means around said auxiliary cathode for confining the region perlpherally around said auxiliary cathode, and means connected with and for conducting a cooling medium both to and from said conlining means.
  • a magnetron comprising an evacuated enclosing housing having an anode therein, said anode providing a cathode cavity longitudinally central thereof, a main cathode coaxial of and within said cavity emission from which is substantially secondary electrons only, an auxiliary cathode at an end of said main cathode, said auxiliary cathode being emissive of primary electrons,
  • a magnetron comprising an evacuatedV en V closing housing having ananode'thereimsaid Vanode providing a cathode cavity'longitudinally means around saidv auxiliary cathoderforconfin-v ing the region peripherally around said auxiliary cathode, and means connected with and for conducting cooling medium both to and from' said confining means and to and from the main cathode.
  • a magnetron comprising an evacuated enclosing housing having an* anode'the'rein, said anode providing a Vcathode cavity longitudinally central thereof, a cathode coaxial of andwithin said cavity emissionv from which is substantially secondary electrons only, and means proximate to and for conducting acooiing means to and from said cathode, said conducting means comprising pipes one within another of which the inner pipe opens at its end within the outer pipe and of which the outer diameter of the inner pipe is less 'than the inner diameter ofthe outer pipe for eiecting ow passage from one pipe to the other and between said pipes.
  • a magnetron comprising an evacuated enclosing housing having an anode therein, a main cathode in said anode, an. auxiliary cathode emissive 'of primary electrons opposite an end of said main cathode, means around ysaid auxiliary cathode for confining the regiony ⁇ peripheralli around said auxiliary cathode, and means proximate to and for conducting a cooling mediuml both to and from said coniining means, said econducting means comprising'pipes one within another of Which'the inner pipe opens vat its end next said confining means Within the outer'pipe and of which the outer diameter of theinner pipe is less than the inner diameter of the outer pipe for eiecting iiow passage from one pipe to the other and between said pipes.
  • a magnetron comprising an evacuated enclosing housing having an anode therein, said anode providing a cathode cavity longitudinally central of the anode opening at opposite ends thereof, a cathode in said cathode cavity, hats opposite and in proximity to the open ends of said cathode cavity, and means connected with and forY conducting cooling fluid to and effective upon each of said hats for cooling the same.
  • a magnetron comprising an evacuated enclosing housing having an anode therein, said anode providing a cathode cavity longitudinally central of the anode opening at oppositcends thereof, 'a main cathode in said'cathode cavity, hats opposite andinproximity to the open vends of said cathode cavity, one of said hats having a recess directed toward and on a commonaxis Iwith the cathode cavity, ⁇ and an'auxiliarycath'- ode in said recess, said cathodes both' being cylindrical on a common axis and substantially equal in diameter.
  • a magnetron comprising an evacuatedfen.- closing housing having an'anode therein, said anode providing a cathode cavity longitudinally central of the anode opening at oppositeends thereof, a main cathode in rsaid cathode cavity, hats opposite 'and in proximity to the operi ends of said cathode cavity, one ofY said hats having aY recess directed toward and on a common axis Y withthe cathode cavity, an auxiliary cathode in said recess, Vand means connected with and for conducting cooling fiuid to said recessed hat.
  • a magnetron comprising an evacuated enclosingr housing having an anode therein, said anode providing a cathode Vcavity Alongitudinally central ofr the ⁇ anode opening at yopposite ends thereof, a main cathode in saidcathode cavity, hats opposite'and in proximity to the ends oi said cathode cavity, one ofrsaid hats having a recess directed toward and on a common axis with the cathode cavity, an auxiliary cathodev in said recess, means* connected with andfcr conductingy cooling fluid to said recessed hat, and means connected with and for conducting cooling fluid intosaid main cathode at the end thereof remotev from said recessed hat andvr through the other of said hats.

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US677463A 1946-06-18 1946-06-18 Magnetron Expired - Lifetime US2438194A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE473942D BE473942A (enrdf_load_stackoverflow) 1946-06-18
US677463A US2438194A (en) 1946-06-18 1946-06-18 Magnetron
FR950897D FR950897A (fr) 1946-06-18 1947-06-18 Magnetron

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Application Number Priority Date Filing Date Title
US677463A US2438194A (en) 1946-06-18 1946-06-18 Magnetron

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BE (1) BE473942A (enrdf_load_stackoverflow)
FR (1) FR950897A (enrdf_load_stackoverflow)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2475526A (en) * 1947-09-26 1949-07-05 Raytheon Mfg Co Electron-discharge device of the magnetron type
US2508473A (en) * 1947-05-10 1950-05-23 Westinghouse Electric Corp Electron discharge device
US2530172A (en) * 1945-02-17 1950-11-14 Westinghouse Electric Corp Ultra high frequency generator
US2530948A (en) * 1948-10-21 1950-11-21 Bell Telephone Labor Inc Electron injection space discharge device
US2556181A (en) * 1946-12-28 1951-06-12 Sperry Corp High-frequency electron discharge device
US2567624A (en) * 1946-09-03 1951-09-11 Thomson Amherst Felix Home Cathode arrangement for electron discharge devices
US2591322A (en) * 1946-08-30 1952-04-01 Csf Generator of ultra-short electromagnetic waves
US2633556A (en) * 1951-08-02 1953-03-31 Beverly D Kumpfer Millimeter wave generator
US2782342A (en) * 1947-07-01 1957-02-19 Rca Corp Magnetron
US3096457A (en) * 1959-03-31 1963-07-02 Raytheon Co Traveling wave tube utilizing a secondary emissive cathode
US3227915A (en) * 1960-10-17 1966-01-04 Eitel Mccullough Inc Fluid cooling of hollow tuner and radio frequency probe in klystron
US4028583A (en) * 1975-08-07 1977-06-07 Atomic Energy Of Canada Limited High power-double strapped vane type magnetron

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2163157A (en) * 1937-07-22 1939-06-20 Bell Telephone Labor Inc Electron discharge apparatus
US2409038A (en) * 1942-12-31 1946-10-08 Rca Corp Magnetron and circuit therefor
US2410396A (en) * 1943-01-25 1946-10-29 Raytheon Mfg Co High efficiency magnetron
US2411601A (en) * 1941-09-30 1946-11-26 Raytheon Mfg Co Electronic discharge device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2163157A (en) * 1937-07-22 1939-06-20 Bell Telephone Labor Inc Electron discharge apparatus
US2411601A (en) * 1941-09-30 1946-11-26 Raytheon Mfg Co Electronic discharge device
US2409038A (en) * 1942-12-31 1946-10-08 Rca Corp Magnetron and circuit therefor
US2410396A (en) * 1943-01-25 1946-10-29 Raytheon Mfg Co High efficiency magnetron

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2530172A (en) * 1945-02-17 1950-11-14 Westinghouse Electric Corp Ultra high frequency generator
US2591322A (en) * 1946-08-30 1952-04-01 Csf Generator of ultra-short electromagnetic waves
US2567624A (en) * 1946-09-03 1951-09-11 Thomson Amherst Felix Home Cathode arrangement for electron discharge devices
US2556181A (en) * 1946-12-28 1951-06-12 Sperry Corp High-frequency electron discharge device
US2508473A (en) * 1947-05-10 1950-05-23 Westinghouse Electric Corp Electron discharge device
US2782342A (en) * 1947-07-01 1957-02-19 Rca Corp Magnetron
US2475526A (en) * 1947-09-26 1949-07-05 Raytheon Mfg Co Electron-discharge device of the magnetron type
US2530948A (en) * 1948-10-21 1950-11-21 Bell Telephone Labor Inc Electron injection space discharge device
US2633556A (en) * 1951-08-02 1953-03-31 Beverly D Kumpfer Millimeter wave generator
US3096457A (en) * 1959-03-31 1963-07-02 Raytheon Co Traveling wave tube utilizing a secondary emissive cathode
US3227915A (en) * 1960-10-17 1966-01-04 Eitel Mccullough Inc Fluid cooling of hollow tuner and radio frequency probe in klystron
US4028583A (en) * 1975-08-07 1977-06-07 Atomic Energy Of Canada Limited High power-double strapped vane type magnetron

Also Published As

Publication number Publication date
FR950897A (fr) 1949-10-10
BE473942A (enrdf_load_stackoverflow)

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