US2820923A - Magnetron - Google Patents

Magnetron Download PDF

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Publication number
US2820923A
US2820923A US300927A US30092752A US2820923A US 2820923 A US2820923 A US 2820923A US 300927 A US300927 A US 300927A US 30092752 A US30092752 A US 30092752A US 2820923 A US2820923 A US 2820923A
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US
United States
Prior art keywords
cathode
anode
space charge
segments
radius
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
US300927A
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English (en)
Inventor
Donald A Wilbur
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co
Original Assignee
General Electric Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to BE521710D priority Critical patent/BE521710A/xx
Priority to NLAANVRAGE8101011,A priority patent/NL180102B/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US300927A priority patent/US2820923A/en
Priority to GB20363/53A priority patent/GB739302A/en
Priority to FR1084418D priority patent/FR1084418A/fr
Priority to DEG12317A priority patent/DE1007441B/de
Application granted granted Critical
Publication of US2820923A publication Critical patent/US2820923A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • 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

Definitions

  • in-phase electrons refers to those electrons having a velocity component in the direction of the alternating field so that they must give up energy to the field.
  • the space charge is thus re-entrant, since the same portion of the space charge, by reason of its rotation about the cathode, may pass under the anode segments more than once until all of the available energy imparted by the direct current source establishing the radial electric field has been eX- tracted.
  • Such re-entrant space charge magnetrons have been able to produce large amounts of power at relatively high efficiencies, and have accordingly found widespread use as high frequency oscillators.
  • the rotating or re-entrant space charge of a magnetron is demodulated at a point or region along its path without materially decreasing the space charge density or energy. This is accomplished by providing a portion of the space charge path with a relatively small ratio of cathode radius to anode radius as compared with the conventionally chosen corresponding ratio of the portion of the space charge path including the output anode segments. After each excursion around the cathode in the space charge chamber the effect of the modulation of he space charge by the high frequency fields of the resonant circuits coupled to the anode segments is removed so that the spacing between the last anode segment on one side of the debunching region and the first anode segment on the other side of the debunching region is not critical.
  • the advantages of a re-entrant space charge are obtained without the restrictions imposed when the space charge bunching is also reentrant.
  • the effectiveness of the magnetron as an oscillator is thus enhanced since loss of synchronism of the reentrant space charge cannot adversely aifect the oscillation, and the magnetron is also adapted for amplifier operation since electronic back-coupling from an output anode section to an input anode section is readily avoided by positioning the debunching means between them.
  • Fig. 1 represents a view partly in section of a magnetron discharge device embodying the principles of my invention
  • Fig. 2 represents a side view of the device of Fig. 1;
  • Fig. 3 is a view of a magnetron electrode structure illustrating a modification of my invention.
  • Fig. 4 is a view of a magnetron electrode structure illustrating another modification of my invention.
  • the electron bunches or'spoke's produced by modulation of the space charge by the anode segments along the normal portion of the space charge path are substantially debunched as they pass around the small radius portion of the cathode.
  • Theanode segmentor segments along the debunching region are primarily useful in maintaining the radial electric field and need not be coupled to theoutput circuit. Consequently, when the space charge thus demodulated reenters the active portion of the space charge chamber, there are no resultant bunches or spokes to be maintained in-synchronism with the alternating fields. Accordingly, space charge. synchronism need be maintained only along the anode segments in the output portion of, the magnetron, and the remainder of the path, including thedfcblunching region, is not critical in length.
  • a' plurality of active anode segments 5 of uniform width togetherw'i'th an additional neutral anode member or segment 16 of .greater width.
  • Each of the segments' is conductively supported from a difierent point on the inner periphery of the spiral .coil' as by welding'thereto.
  • the six anode electrodes or segments '5 are positioned in a generally semi-cylindrical .configuration by virtue of their attachment to the spiral and the wide electrode 6 cornpletes -the side wall of the space charge chamber.
  • the segments are conventionally spaced to provide small interaction gaps between them.
  • a cathode assembly Disposed within the space charge chamber defined between the anode segments is a cathode assembly which is arranged in two parts in "the embodiment shown to simplify heating of the emitting surface.
  • the emitting section of the cathode is shown as comprising a close wound'spiraltungs ten coil 7 which may be coated with a suitable thermionic emissive material of the type well-known in the art, and spaced from it is a cathode member 8 which may be suitably formed from a solid conductor Whose axis is parallel 'to that of the cathode helix and the space charge chamber.
  • the portion of the cathode block facing the anode segments -5 preferably has a constant radius of curvature on the same center as-the radius of curvature of the facing surfaces of the anode segment array.
  • the cathode emitting helix '7 has a -relatively small radius compared to the radius of the cathode member 8 and is positioned adjacent the cathode member 8 between it-and the neutral anode seg ment- 6, the radius ofcurvature of the facing portions of the anode segment 6 being centered on the cathode helix' axis.
  • the portions of the neutral segment dnear the array of active anode segments .5 arepreferablyshaped to provide a gradual transition in radius to that of :the
  • the ratio of the'radiuslof thezhelix 7 to that of the facing portions of the neutral .anode segment 6 is much smaller than the ratio of the .radius of the cathode member '8 to .that of the facing active anode segments 5.
  • the latter'ratio-is-chosenfor a :rela tively high upper-current outed-point for efi'ective operation of the conventional portion of the :rnagne'tron Whereas the former ratio'is chosen to providea low upper+current cutoff.
  • the cutofi point may be considered as changing with the cathode radius of curvature where all anode portions surrounding the cathode assembly have the same or nearly the same spacing from thefacing cathode portions,
  • Conductive connections are made'to the spiral coil through the envelope 1 by means of any suitable glass-tometal hermetic seals, such as the-seals 10. and 11 surrounding the lines 2 and 3 and permitting them to pass through the envelope wall.
  • conductive connections may be made to the cathode helix by the leads 12 and 13 which pass through the envelope Wall at similar glas's-to-rnetal seals L4 and 15.
  • the cathode coil may be rigidly attached to lead '12 at one end and at the other end to a spring tension member 16, rigidly secured to the lead- 13; It will be understood that the spring member '16 holds the cathode helix 7 taut and fixed" in its position relative to the spiral land-anode segments 6.
  • the neutral anodesegrnent-Q also called aneutrode, is advantageously employed in order to further simplify-con struction of .the magnetron by permitting the omission of anumber of active 'anode'segments, which-in this case is six.
  • the segment 6 - is accordingly connectedto themidpoint of the coil 4, which :is the lower-'loop'as oriented-in the drawing, and hence is at a high frequency neutral point.
  • This neutral electrode has-no induced nor imposed high frequency potential variations since it is connected to a point on the transmission line which has a zero high frequency voltage during oscillation.
  • the spokes In order to maintain excitation of the oscillatory circuit the spokes must remain substantially in synchronism with the alternating fields as they advance under successive gaps. This normally calls for utmost precision in the fabrication and assembly of the electrodes, especially since the array is not linear but must provide for reentrant space charge spokes. While a number of active segments 5 are replaced by the neutrode 6, thus simplifying the magnetron construction, there is some tendency for the space charge spokes to exceed the synchronous velocity as they pass under the long neutral segment. Such space charge spokes reentering the active section of the magnetron out of synchronism limit the power output and may even prevent operation altogether.
  • the space charge spokes which represent the regions of bunched in-phase electrons of the rotating space charge are dispersed when these portions of the space charge pass around the relatively small radius portion of the cathode assembly under the neutrode segment 6. Since this electrode is longer than any one of the several active anode segments it replaces, it facilitates arrangement of a relatively long space charge path or large angle of rotation about the small radius cathode helix for increasing the effectiveness of the debunching function. As shown in the illustrated embodiment there is approximately 180 of space charge rotation about the cathode helix. The absence of the alternating fields in the neutrode region tends to make the debunching effect more pronounced.
  • the electron stream is substantially demodulated after passing through the portion having the small cathode radius to anode radius ratio.
  • the space charge is again readily modulated by the fringing electric fields, and the newly formed spokes or bunches of in-phase, electrons are maintained in synchronism until the space charge again enters the debunching region.
  • the fabrication of the magnetron is greatly simplified.
  • the length of the space charge path between the last segment encountered by the rotating space charge and the first segment where it re-enters the active region is not critical. Only the array of active anode segments 5 must be designed and spaced to meet the critical requirements of high frequency magnetron operation. This also permits further structural simplification through the use of longer neutrodes, i. e., neutrodes subtending a greater angle with respect to the cathode so that they may replace a greater number of active anode segments.
  • the neutrode type of construction lends itself readily to such a debunching arrangement since the neutrode is not part of the active anode segment array in which the bunching must be maintained to utilize the anode segments for output purposes.
  • the separation of the emitting portion 7 and the non-emitting portion 8 of the cathode assembly is not necessary to provide the debunching action described. However, it does simplify construction in so far as it permits use of more or less standard emitting helixes or sleeves without the increase in heating current which would be necessary to heat the entire cathode assembly.
  • the cathode emitting portion 7 is substantially isolated from the active anode segments 5, it is not subject to back heating by electrons accelerated by the anode segments. The cathode operating temperature can thus be readily controlled for conservation of the emitting surface.
  • Fig. 3 an electrode assembly is illustrated in which the cathode is shown as a single member rather than as an assembly of cathode emitting and non-emitting members as is Figs. 1 and 2.
  • the tuned circuit conductors 2 and 3 are terminated by a loop 4 as previously described and having an array of anode segments 5 properly connected to maintain the usual 1r mode excitation of the output circuit.
  • a neutrode 6 defines a substantial portion of the space charge chamber, the electrons passing under the neutrode for approximately half the angular rotation about the cathode.
  • the cathode 24 is a single member having one portion with a large radius of curvature together with a smaller portion having a small radius of curvature, the centers of the two portions being displaced from each other in order that the small radius of curvature portion may extend beyond the larger radius.
  • the radii of curvature of the anode portions are centered on the centers of the curvature of the facing cathode portions and do not vary substantially.
  • Such a unitary cathode assembly can range in shape according to the separation of the centers of the two portions from a generally eggshaped or oval cross section to a configuration in which a small cylinder is tangent to a larger one.
  • the small radius of curvature portion of the cathode bulges out from the larger cylinder, the small radius being maintained for approximately in order that a substantial portion of the electron angular rotation may be about this small portion.
  • a heater 25 extending through the cathode permits heating of the entire cathode surface and the cathode coating for the desired thermionic electron emiss sion is applied over the entire outer surface of the cathode to provide a high density space charge.
  • only portions of the cathode need be provided with an emitting coating, as, for example, in the cathode asaaaae;
  • cenr sn nding inihli z asez o. over 60 attir -sp ce char travel about the cathode, having a relativelylage-radius from e cathode axis... itc erd a y, t emat c of the radii; oftthe emb ds-$6;- smt-he adius ithe sutrodesurfiaee.2, ;is 1 small: a cemparedzto the-eQrresP nding -rati ini he euta tzpcrt pn nithemagn tronideuicegthatamu h lowe uppi et z heanaee n rseepnlses travelia 'u d he'neu mde surfiacei i b ainedd th a emaan r as plF- w
  • a traveling wave m gnetron ischarge d vice having a ing at 1pr eand a d esgment surfaces defining econ tinuous sgace charge patharound a cathodqand' means fordeb nching the space charge comprisingza portionof said fa ng-surfacesdefining apartial lengthof the space
  • tune of the ranodesurfaces is relatively low as com: pared to the corresponding :ratioior. other; portions 7 of :said chamber.
  • magnetron discharge ,device cornprisingiau aa todeiasseniblyr having ,a plurality of QSPaeed angdesegngrents drefinkug ar ntrant space char 6 Ch ber hetiveerithei in gflr'gsurfacas and an elongate extending along an axis through said chamber, and means] for: dehunehir glthe space ch rge eQmnriS uaapm im of said space charge chamber extending for a substantial angle about said cathode wherein the ratio of the radius from the axis of the cathode cross section to the distance from the axis to the corresponding facing portion of said anode assembly is small compared to the ratio of the radius from the axis of another portion of the cathode cross section to the distance from the axi
  • a discharge device of a traveling wave magnetron type comprising an elongated cathode surrounded by an anode assembly to provide a re-entrant space charge region, said anode assembly including a group of spaced adjacent anode output segments and a neutral segment, means for providing a static magnetic field in the space between said cathode and said anode assembly along said cathode axis, means for providing an electric field between said cathode and said anode assembly whereby electrons emitted by said cathode are provided with an average velocity about said cathode in a given direction, and means for debunching the space charge in the region between said cathode and said neutral segment wherein the ratio of the radius of a portion of said cathode facing said neutral segment to the neutral segment radius is substantially smaller than the ratio of the radius of another portion of the cathode facing said group of output segments to the output segment radius.

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  • Control Of High-Frequency Heating Circuits (AREA)
US300927A 1952-07-25 1952-07-25 Magnetron Expired - Lifetime US2820923A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
BE521710D BE521710A (is") 1952-07-25
NLAANVRAGE8101011,A NL180102B (nl) 1952-07-25 Werkwijze voor de bereiding van een 3,7-dimethyl-6-octeennitrilverbinding.
US300927A US2820923A (en) 1952-07-25 1952-07-25 Magnetron
GB20363/53A GB739302A (en) 1952-07-25 1953-07-22 Improvements in and relating to magnetrons
FR1084418D FR1084418A (fr) 1952-07-25 1953-07-24 Magnétron
DEG12317A DE1007441B (de) 1952-07-25 1953-07-25 Magnetron mit einem der Entbuendelung der Raumladungspakete dienenden Teil der Elektronenbahn

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US300927A US2820923A (en) 1952-07-25 1952-07-25 Magnetron

Publications (1)

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US2820923A true US2820923A (en) 1958-01-21

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Application Number Title Priority Date Filing Date
US300927A Expired - Lifetime US2820923A (en) 1952-07-25 1952-07-25 Magnetron

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US (1) US2820923A (is")
BE (1) BE521710A (is")
DE (1) DE1007441B (is")
FR (1) FR1084418A (is")
GB (1) GB739302A (is")
NL (1) NL180102B (is")

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3015750A (en) * 1959-10-01 1962-01-02 Raytheon Co Traveling wave electron discharge devices
US3134047A (en) * 1960-11-17 1964-05-19 Gen Electric Neutrode crossed field voltage tuned oscillator
US3491291A (en) * 1966-06-27 1970-01-20 Beloit Iron Works Resonant loop single conductor surface wave device

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1565416A (en) * 1921-02-14 1925-12-15 Westinghouse Electric & Mfg Co Electron-tube oscillator
US1889595A (en) * 1929-10-08 1932-11-29 Gen Electric Electron discharge apparatus
US2162807A (en) * 1936-08-17 1939-06-20 Telefunken Gmbh Magnetron
US2198334A (en) * 1937-06-09 1940-04-23 Telefunken Gmbh Electron discharge device
US2217745A (en) * 1934-03-20 1940-10-15 Rca Corp Ultra high frequency oscillation circuits
US2227078A (en) * 1937-11-11 1940-12-31 Telefunken Gmbh Heterodyne receiver for ultrashort waves
US2511407A (en) * 1947-01-09 1950-06-13 Csf Amplifying valve of the progressive wave type
US2582185A (en) * 1946-05-17 1952-01-08 M O Valve Co Ltd Cavity resonator magnetron
US2597506A (en) * 1944-11-17 1952-05-20 Patelhold Patentverwertung Ultra-short wave electron tube
US2607904A (en) * 1948-10-18 1952-08-19 Csf Electron optical system for cathodes of electron beam tubes
US2617968A (en) * 1946-09-28 1952-11-11 Csf Magnetron tube

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB582489A (en) * 1941-12-31 1946-11-19 Cossor Ltd A C Improvements relating to magnetron electric discharge devices
FR999345A (is") * 1946-11-20 1952-01-29

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1565416A (en) * 1921-02-14 1925-12-15 Westinghouse Electric & Mfg Co Electron-tube oscillator
US1889595A (en) * 1929-10-08 1932-11-29 Gen Electric Electron discharge apparatus
US2217745A (en) * 1934-03-20 1940-10-15 Rca Corp Ultra high frequency oscillation circuits
US2162807A (en) * 1936-08-17 1939-06-20 Telefunken Gmbh Magnetron
US2198334A (en) * 1937-06-09 1940-04-23 Telefunken Gmbh Electron discharge device
US2227078A (en) * 1937-11-11 1940-12-31 Telefunken Gmbh Heterodyne receiver for ultrashort waves
US2597506A (en) * 1944-11-17 1952-05-20 Patelhold Patentverwertung Ultra-short wave electron tube
US2582185A (en) * 1946-05-17 1952-01-08 M O Valve Co Ltd Cavity resonator magnetron
US2617968A (en) * 1946-09-28 1952-11-11 Csf Magnetron tube
US2511407A (en) * 1947-01-09 1950-06-13 Csf Amplifying valve of the progressive wave type
US2607904A (en) * 1948-10-18 1952-08-19 Csf Electron optical system for cathodes of electron beam tubes

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3015750A (en) * 1959-10-01 1962-01-02 Raytheon Co Traveling wave electron discharge devices
US3134047A (en) * 1960-11-17 1964-05-19 Gen Electric Neutrode crossed field voltage tuned oscillator
US3491291A (en) * 1966-06-27 1970-01-20 Beloit Iron Works Resonant loop single conductor surface wave device

Also Published As

Publication number Publication date
NL180102B (nl)
GB739302A (en) 1955-10-26
FR1084418A (fr) 1955-01-19
BE521710A (is")
DE1007441B (de) 1957-05-02

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