EP0276933A1 - Strahlungskollektor mit geringen elektrischen Verlusten - Google Patents

Strahlungskollektor mit geringen elektrischen Verlusten Download PDF

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Publication number
EP0276933A1
EP0276933A1 EP19880300336 EP88300336A EP0276933A1 EP 0276933 A1 EP0276933 A1 EP 0276933A1 EP 19880300336 EP19880300336 EP 19880300336 EP 88300336 A EP88300336 A EP 88300336A EP 0276933 A1 EP0276933 A1 EP 0276933A1
Authority
EP
European Patent Office
Prior art keywords
collector
collector means
casing
bands
band
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.)
Ceased
Application number
EP19880300336
Other languages
English (en)
French (fr)
Inventor
James G. Bertram
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.)
Varian Medical Systems Inc
Original Assignee
Varian Associates Inc
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
Application filed by Varian Associates Inc filed Critical Varian Associates Inc
Publication of EP0276933A1 publication Critical patent/EP0276933A1/de
Ceased legal-status Critical Current

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Classifications

    • 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
    • H01J23/027—Collectors

Definitions

  • the invention pertains to electron beam tubes such as traveling-wave tubes (TWT's) and klystrons which conventionally have a discrete electrode to collect the beam after it has traversed the inter­action circuit which is usually at ground potential.
  • Conversion efficiency of these tubes, particularly TWT's is often improved by biasing negative to ground (“depressed collector") so that the electrons give up kinetic energy before dissipating the remainder on the collector surface. Depression is particularly helpful in millimeter-wave tubes where the inherent interaction efficiency is low due to the high-­impedance beams necessary for beam focusing through the tiny circuit, the resultant poor coupling between beam and circuit and the relatively high circuit losses.
  • FIGS. 1 and 2 A self-contained depressed-collector design of the prior art is shown in FIGS. 1 and 2.
  • the TWT is enclosed in a metallic vacuum envelope 10 as of copper.
  • An electron beam 12 from a gun traverses an interaction circuit, as a helix of tungsten wire 14 supported by a number of dielectric rods 16 as of sapphire inside a copper casing 32 which is part of envelope 10.
  • the terminal end of helix 14 extends out conductor 18 through envelope 10 via an insulating vacuum seal 20.
  • Beam 12 after passage through circuit 14 wherein it is confined to a small cylinder by an axial magnetic field (not shown), expands into hollow collector electrode 22, as of copper.
  • collector electrode 22 and envelope 10 are shrink-fitted a plurality of dielectric rods 24 as a beryllium oxide ceramic which provide mechanical support, electrical insulation and thermal conductivity to envelope 10 which is cooled by a grounded heat sink (not shown) such as air fins, liquid channels or a conductive path.
  • a grounded heat sink such as air fins, liquid channels or a conductive path.
  • Current is supplied to collector 22 by a lead 26 through an insulating vacuum seal 28.
  • the prior-art collector of FIGS. 1, 2 has some inherent problems. Since the insulating structure is in a high vacuum, thermal conductivity is poor through the small-area contacts to the rods 24. (In vacuum, only radiative transfer is possible except for the tiny areas of atomic-scale physical contact.)
  • the invention provides a collector assembly for an electron beam tube as set out in Claim 1.
  • FIG. 3 a schematic section of a collector embodying the invention.
  • Electron beam 12 ⁇ after passing through the interaction structure (not shown) of a TWT encased in a vacuum envelope 10 ⁇ , enters a hollow beam collector electrode 22 ⁇ , where it expands and is intercepted on the inner wall.
  • Collector 22 ⁇ is preferably formed with inner and outer surfaces shaped as right circular cylinders, for ease of manufacture and easy cooling.
  • Collector 22 ⁇ is mounted and sealed off as part of the tube's vacuum envelope 10 ⁇ by an insulating, hollow, dielectric cylinder 30 as of high-alumina ceramic.
  • the heat generated in collector 22 ⁇ is carried radially outward to a surrounding casing 32 ⁇ as of copper.
  • Casing 32 ⁇ is eventually sealed off by welding lip 34 of an end closure 38 to lip 36 of casing 32 ⁇ .
  • the space 44 between collector 22 ⁇ and enclosure 32 ⁇ is largely filled by two concentric bands of solid dielectric material 24 ⁇ ,40 such as beryllia ceramic which has high thermal conductivity.
  • the inner band is a layer of closely-packed dielectic rods 24 ⁇
  • the outer band is a hollow dielectric cylinder 40. Dielectrics 24 ⁇ ,40 fit tightly to optimize thermal conduction.
  • collector 22 ⁇ Electrical connection to collector 22 ⁇ is brought out by a wire 26 ⁇ passing through casing 32 ⁇ via an insulating seal 28 ⁇ .
  • Insulating bands 24 ⁇ ,40 are preferably inserted after the vacuum processing of the tube to avoid contamination during bakeout by volatile materials. Casing 32 ⁇ is then sealed shut by installing end closure 38. In a succeeding manufacturing step the space 44 between collector 22 ⁇ and casing 40 is filled via a tubulation 46 with a dielectric fluid such as nitrous oxide which has good thermal con­ductivity and voltage breakdown, or a halogenated organic gas which has excellent voltage-breakdown characteristics. In applications where breakdown is not a limiting factor, improved thermal transfer may be obtained with a gas of low molecular weight such as hydrogen or helium. Alternatively, a liquid dielectric may be used, but this would be more critical of filling and would present thermal expansion problems. For applications having lower breakdown requirements an air filling may suffice.
  • a dielectric fluid such as nitrous oxide which has good thermal con­ductivity and voltage breakdown, or a halogenated organic gas which has excellent voltage-breakdown characteristics.
  • a gas of low molecular weight such as hydrogen or helium.
  • the dielectric fluid improves heat trans­fer by adding convection between the close-fitting parts.
  • heat transfer occurred only by radiation across the vacuum except through the small areas of actual molecular contact. After filling, space 44 is sealed off by closing tubulation 46.
  • an insulating band 24 can become electrically leaking by being coated with metal from its contact with a metal part 22.
  • rods such as 24 can become free and rotate during the thermal expansion cycles, making the entire surface somewhat conducting.
  • such rods do not contact a second metallic electrode on the side opposite the first, but a second insulator.
  • the formation of a leakage path across the electrically series bridge is inhibited.
  • the second dielectric band is formed, as by the described cylinder 40, so that if any radial gap surfaces exist, as by accidental thermal cracking of the cylinder, there is only a very small probability that they align with the leakage paths of the first band 24 ⁇ .
  • FIG. 5 is a schematic axial section of an alternative embodiment in which the outer dielectric band is cut into segments 42 to alleviate cracking by thermal stresses.
  • the segments are shaped so as not to rotate during cycling, so radial paths can not be coated by contact and there is small chance of the radial cracks aligning with gaps between inner band cylinders 24 ⁇ .
  • FIG. 6 is a schematic axial section of another embodiment.
  • the second band may be composed of a second layer of cylindrical rods 44. As described above, these rods are cheap and readily obtainable. The outward leakage paths are broken by the discontinuities between rods, and their gaps are generally not aligned.
  • dielectric elements can be quite diverse.
  • the cylindrical rods 24 ⁇ are cheap and easily obtainable.
  • For the second band 40 a vast number of shapes may be used. It is only desirable that these elements not be rotatable. It is not completely essential that the insulating space be filled by a dielectric fluid, although this is desirable.

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  • Microwave Tubes (AREA)
EP19880300336 1987-01-27 1988-01-15 Strahlungskollektor mit geringen elektrischen Verlusten Ceased EP0276933A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US723287A 1987-01-27 1987-01-27
US7232 2001-11-05

Publications (1)

Publication Number Publication Date
EP0276933A1 true EP0276933A1 (de) 1988-08-03

Family

ID=21724976

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19880300336 Ceased EP0276933A1 (de) 1987-01-27 1988-01-15 Strahlungskollektor mit geringen elektrischen Verlusten

Country Status (2)

Country Link
EP (1) EP0276933A1 (de)
JP (1) JPS63284736A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2273199A (en) * 1992-12-03 1994-06-08 Litton Systems Inc Electron beam collector
WO2000024026A1 (en) * 1998-10-22 2000-04-27 Litton Systems, Inc. Ceramic electron collector assembly having metal sleeve for high temperature operation
US6653787B2 (en) 2002-03-05 2003-11-25 L-3 Communications Corporation High power density multistage depressed collector

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1238822A (de) * 1969-03-28 1971-07-14
US3749962A (en) * 1972-03-24 1973-07-31 Us Navy Traveling wave tube with heat pipe cooling
DE2906657A1 (de) * 1979-02-21 1980-08-28 Licentia Gmbh Lauffeldroehre

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1238822A (de) * 1969-03-28 1971-07-14
US3749962A (en) * 1972-03-24 1973-07-31 Us Navy Traveling wave tube with heat pipe cooling
DE2906657A1 (de) * 1979-02-21 1980-08-28 Licentia Gmbh Lauffeldroehre

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2273199A (en) * 1992-12-03 1994-06-08 Litton Systems Inc Electron beam collector
US5436525A (en) * 1992-12-03 1995-07-25 Litton Systems, Inc. Highly depressed, high thermal capacity, conduction cooled collector
GB2273199B (en) * 1992-12-03 1996-08-07 Litton Systems Inc Electron beam collector
WO2000024026A1 (en) * 1998-10-22 2000-04-27 Litton Systems, Inc. Ceramic electron collector assembly having metal sleeve for high temperature operation
US6320315B1 (en) 1998-10-22 2001-11-20 Litton Systems, Inc. Ceramic electron collector assembly having metal sleeve for high temperature operation
US6653787B2 (en) 2002-03-05 2003-11-25 L-3 Communications Corporation High power density multistage depressed collector

Also Published As

Publication number Publication date
JPS63284736A (ja) 1988-11-22

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