US3558970A - Resonant cavity magnetrons using cathode heater currents to intensify magnetic fields - Google Patents

Resonant cavity magnetrons using cathode heater currents to intensify magnetic fields Download PDF

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Publication number
US3558970A
US3558970A US822680A US3558970DA US3558970A US 3558970 A US3558970 A US 3558970A US 822680 A US822680 A US 822680A US 3558970D A US3558970D A US 3558970DA US 3558970 A US3558970 A US 3558970A
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United States
Prior art keywords
magnetron
magnetic field
cathode
resonant cavity
approximately
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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
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US822680A
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English (en)
Inventor
Johannes Antonius Van De Coor
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US Philips Corp
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US Philips Corp
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Publication date
Application filed by US Philips Corp filed Critical US Philips Corp
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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
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/04—Cathodes
    • H01J23/05—Cathodes having a cylindrical emissive surface, e.g. cathodes for magnetrons
    • 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
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/10—Magnet systems for directing or deflecting the discharge along a desired path, e.g. a spiral path

Definitions

  • the invention relates to a device for producing an unmodulated electric wave by means of a resonant cavity magnetron provided with a single helical directly-heated cathode.
  • Magnetrons of the foregoing type usually operate at a frequency which is low compared with that at which magnetrons for radar installations operate.
  • magnetrons for example, for ovens for preparing food
  • the magnetic field in the reaction space between the anode and the cathode has a strength of from approximately 1,000 to L500 gauss.
  • the magnetic field is usually produced by means of perforated pole shoes in which the parts of the magnetron housing which surround the ends of the cathode are incorporated.
  • the magnetic field in the anode-cathode reaction space is strongly inhomogeneous.
  • the voltage-current characteristic of the magnetron has a less sharp bend than would be the case in a homogeneous magnetic field.
  • the inhomogeneous magnetic field as such is already unfavorable for the efficiency of the magnetron with a readily smoothed supply voltage. With a supply voltage having a strong ripple, which often occurs in devices of the type described, the efficiency is even further reduced.
  • the filament current of the cathode is a direct current of such a direction that the magnetic field produced by the cathode intensifies the magnetic field in the anode-cathode reaction space.
  • the intensification of the magnetic field in the anodecathode space according to the invention results in said field becoming homogeneous which considerably improves the efficiency particularly when a nonor poorly smoothed supply voltage is used.
  • the magnetron operates in a constant magnetic field and not in an alternately intensified and weakened field. This also influences the efficiency favorably.
  • the field produced by the cathode can be taken into account.
  • FIG. 1 shows an elevation of a magnetron for a device according to the invention incorporated in the magnetic system
  • FIG. 2 is a cross-sectional view of the magnetron with the pole shoes connected thereto.
  • FIG. I the elevation is shown in the direction of the output coupling I.
  • the cathode line 2 is shown on the right-hand side.
  • the cooling fins are denoted by 3, the two concave cylindrical pole shoes by 4, the conical edge thereof by 5, the flattened sides by 6.
  • Blocks of permanent magnetic material 7 connected by soft magnetic terminating members 8 adjoin the flattened sides.
  • the material of 7 and 8 may also be interchanged.
  • the pole shoes 4 are secured to the ends of the magnetron by means of bolts 9. I
  • FIG. 2 the flattened sides 6 of the pole shoes 4 extend parallel to the plane of the drawing. In this figure, the cooling fins are not shown.
  • a number of anode vanes 10 are situated, which are alternately connected by straps 11.
  • the cathode line 2 From the cathode line 2, a central conductor 12 and a sleeve 13 situated coaxially around it, lead to the cathode consisting of the helix 15.
  • the helix 15 consists of Sltums of 1 mm. thick tungsten thorium wire having an outside diameter of approximately l3.5 mm.
  • a direct current of 30 a. is conducted through the cathode at a voltage of 5.5 v., which after starting the oscillations of the magnetron, is reduced to 18 to l9 a.
  • the field produced by the pole shoes has a strength of approximately l,l00gauss.
  • the anode voltage is approximately S kv. and the anode current 0.4 a.
  • the produced power at 2,450 me. is l kw.
  • a resonant cavity magnetron comprising a space resonant housing, magnetic means for producing a magnetic field within said housing, a plurality of anode vanes coaxially mounted within said housing for electric field interaction with said magnetic field, a single directly-heated cathode axially positioned within said anode vanes and having a helical configuration to produce a second magnetic field along the axis thereof, and means to supply direct current to said helix to produce therein said second magnetic field in the direction of the magnetic field of said magnetic means.
  • a direct current of 30 a. is conducted through the cathode at a voltage of 5.5 v., which after starting the oscillations of the magnetron, is reduced to 18 to 19 a.
  • the field produced by the pole shoes has a strength of approximately 1,100 gauss.
  • the anode voltage is approximately 5 kv. and the anode current 0.4 a.
  • the produced power at 2,450 me. is l kw.

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  • Microwave Tubes (AREA)
US822680A 1968-05-14 1969-05-07 Resonant cavity magnetrons using cathode heater currents to intensify magnetic fields Expired - Lifetime US3558970A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6806783A NL6806783A (enrdf_load_stackoverflow) 1968-05-14 1968-05-14

Publications (1)

Publication Number Publication Date
US3558970A true US3558970A (en) 1971-01-26

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US822680A Expired - Lifetime US3558970A (en) 1968-05-14 1969-05-07 Resonant cavity magnetrons using cathode heater currents to intensify magnetic fields

Country Status (7)

Country Link
US (1) US3558970A (enrdf_load_stackoverflow)
AT (1) AT291402B (enrdf_load_stackoverflow)
CH (1) CH488331A (enrdf_load_stackoverflow)
DE (1) DE1922243A1 (enrdf_load_stackoverflow)
FR (1) FR2008496A1 (enrdf_load_stackoverflow)
GB (1) GB1197046A (enrdf_load_stackoverflow)
NL (1) NL6806783A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4039892A (en) * 1975-03-13 1977-08-02 U.S. Philips Corporation Resonant cavity magnetron having a magnet system and magnetron destined for such a combination
US4143295A (en) * 1976-08-09 1979-03-06 Hitachi, Ltd. Cathode structure for an electron tube
US4233540A (en) * 1978-01-18 1980-11-11 Tokyo Shibaura Denki Kabushiki Kaisha Magnetron for microwave oven
RU2138878C1 (ru) * 1996-05-13 1999-09-27 Сысоев Анатолий Петрович Магнетрон

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2496887A (en) * 1945-06-23 1950-02-07 Gen Electric High-frequency electrical apparatus
US2579630A (en) * 1947-07-30 1951-12-25 Patelhold Patentverwertung Microwave generator
US3392308A (en) * 1965-05-25 1968-07-09 Varian Associates Crossed field tube having a pair of permanent magnets of different magn etomotive force

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2496887A (en) * 1945-06-23 1950-02-07 Gen Electric High-frequency electrical apparatus
US2579630A (en) * 1947-07-30 1951-12-25 Patelhold Patentverwertung Microwave generator
US3392308A (en) * 1965-05-25 1968-07-09 Varian Associates Crossed field tube having a pair of permanent magnets of different magn etomotive force

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4039892A (en) * 1975-03-13 1977-08-02 U.S. Philips Corporation Resonant cavity magnetron having a magnet system and magnetron destined for such a combination
US4143295A (en) * 1976-08-09 1979-03-06 Hitachi, Ltd. Cathode structure for an electron tube
US4233540A (en) * 1978-01-18 1980-11-11 Tokyo Shibaura Denki Kabushiki Kaisha Magnetron for microwave oven
RU2138878C1 (ru) * 1996-05-13 1999-09-27 Сысоев Анатолий Петрович Магнетрон

Also Published As

Publication number Publication date
FR2008496A1 (enrdf_load_stackoverflow) 1970-01-23
GB1197046A (en) 1970-07-01
AT291402B (de) 1971-07-12
CH488331A (de) 1970-03-31
DE1922243A1 (de) 1969-11-27
NL6806783A (enrdf_load_stackoverflow) 1969-11-18

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