US2939991A - Electron velocity modulation tubes - Google Patents

Electron velocity modulation tubes Download PDF

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Publication number
US2939991A
US2939991A US745688A US74568858A US2939991A US 2939991 A US2939991 A US 2939991A US 745688 A US745688 A US 745688A US 74568858 A US74568858 A US 74568858A US 2939991 A US2939991 A US 2939991A
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United States
Prior art keywords
electron
tube
resonator
velocity modulation
collector
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Expired - Lifetime
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US745688A
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English (en)
Inventor
Beck Arnold Hugh William
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International Standard Electric Corp
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International Standard Electric Corp
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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
    • H01J25/02—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators
    • H01J25/10—Klystrons, i.e. tubes having two or more resonators, without reflection of the electron stream, and in which the stream is modulated mainly by velocity in the zone of the input resonator
    • H01J25/12—Klystrons, i.e. tubes having two or more resonators, without reflection of the electron stream, and in which the stream is modulated mainly by velocity in the zone of the input resonator with pencil-like electron stream in the axis of the resonators
    • 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 present invention relates to high power electron velocity modulation tubes and is particularly concerned with electron collector arrangements therefor.
  • the drop in efiiciency follows because the electron beam at exit from the output resonator is very strongly velocity modulated and, when confronted with a low D.C. collector voltage, many of the electrons have insutficient energy to overcome the retarding field of the collector region.
  • Fig. 3 is a fragmentary drawing of the output end of a klystron tube according to the invention.
  • an electron gun cathode from which the electron beam emanates, is indicated by the rectangle 1 and the electron collector electrode is shown at 2.
  • the path of the electron beam is indicated by the dotted lines 3.
  • the beam passes through a region of its path in which it is coupled, by electrode means not shown, to electromagnetic fields with which it interchanges energy. This region is indicated by the chain-lined rectangle 4.
  • the region 4 comprises two or more resonant cavities separated by drift tubes, while in the case of a travelling wave tube the region comprises a helix or other form of slow wave structure linked with the electron beam path together with input and output waveguide or coaxial line feeders and the necessary impedance matching arrangements well known in the art.
  • the waveguides and, usually, the coaxial line feeders just mentioned, are not part of the tube itself, but are coupled to the slow. wave structure within the tube envelope by the said matching arrangements, part of which will, normally, be within the envelope enclosure.
  • the electron beam within the interaction region, at least at the output cavity or the end of the slow wave structure will be subject to high D.C.
  • the invention is based upon the realisation that if the according to the invention, by effectively suppressing the electron velocity modulation of the beam at the collector electrode; it may be carried out either by subjecting the beam to strong V.P. energy absorbtion after leaving the output resonator or slow wave structure by the expedient of passing the beam through a separate resonant elec- .1 trode means which may comprise a highly damped additional resonator,or the placing of 'an electron collector "at the end of a drift tube maintained at high D.C. po-
  • the electron collector electrode in this second case surrounds, as in conventional practice, a hollow space, but the entrance to this hollow space is gridded so as to provide a flat collecting field and help in the suppression of secondary emission.
  • Fig. 1 shows, purely diagrammatically, a velocity modulation tube having an extra beam-demodulating cavity resonator according to the invention
  • the beam passes along a further length of drift tube 5 and through a cavity resonator 6 all at high D.C. potential.
  • the resonator 6 is caused to be very heavily loaded. If the parallel load resistance of the resonator 6 is made much lower than the load for optimum power extraction, the ratio frequency voltage developed is very low and the beam at ,exit is of practically uniform velocity. At the same time the Q of the resonator is very low while the energy absorbing gap in the resonator can be made long and the capacity across the lips of the gaps correspondingly low, giving flat tuning; thus the resonator. does not .have. to be tunable.
  • resonator ,6 canbe .dissipitated either in a built-in load .ormay be added to the useful output from the outputresonator proper. Afterpassing the resonator 6, the electrons are collected by electrode 2 which may be of conventional type and be located at any convenient distance beyond the output gap, but may now beoperated at or but little above the cathode potential.” It follows-.from what has been saidabove about the characteristics of the resonator 6 that-the drift tubes may he made any con venient length.
  • drift tube is used to. reduce the velocity modulation of the electrons.
  • the collector electrode 2 is joined to resonator 9 through insulators 11,.and the drift tube 7 is fixed in This. arrangement is based on' the space charge wave.
  • the output gap could extract all the power from the beam, the A.C..current of the plasma waves would be reduced to zero. and the beam would be left with no velocity modulation at all; the electron collector electrode could then be placed at any subsequent position and'be maintained at cathode potential without repelling any electrons.
  • the output gap not only does not demodulate the beam completely, but the high R.F. voltage developed across the lips of the gap re-' modulates the electron beam, and, from the point of of velocity modulation for the beam.
  • An analogous argument can be developed for other typesof tubesuch as thetravelling Wave tube or backward wave tube.
  • the end of the slow wave structure is to be regarded as the wall of resonator 9.
  • the mouth of the collector electrode is closed by an electron permeable grid 13,
  • the length of the drift tube 7 should be made greater than x 4 for the best compromise of velocitymodulation suppression at the collector electrode; the collector electrode would also. have to be somewhat above cathode potential. From this theory it would ap pear that the best position forthe electron collector electrode is where theAC. velocities. corresponding to the first and secondorder modesare-equal and opposite.
  • this drifttuhe 7 7 should be made of length K /,4 long, where-A is the: elc
  • Fig. 2 where a D.C. source 8 is represented as connected between the cathode and drifttube '7 and collector 2 is connected near the cathode'end of source 8.
  • the gap between collector 2 and'drift tube 7 may be. made asshort as allowed by A practical example of the invention of Fig. 2 as applied'to a klystron is shown in Fig. 3, which illustrates the basic construction of the output end of the tube.
  • the 'outputresonator is indicated'at 9, the maindrift-tube at 10, and the additional drifttube and the collector elec-' 't-rode are identified by the same reference numerals as 7 example and notfas' a limitation o'nthe scope of the in- 7 '60 gt e n in d t c w en t em.
  • the collector as in conventional practice, isrnade hollow, but its mouth is V a practical construction the exact collector position for maximum collection efiiciency can be determined empirically.
  • I c j An electron velocity modulationtube comprising electrode meausforprojeotingkan electron beam from a cathode along a given pathin'energy interactingrelationship with electromagnetic waves "in a given region of the path, means providing a high'direct potential operating a on said beam at the end of the said given region a' drif-t tube maintained at the-said high potential following ihe beam exit fromthe said region and of length exceeding one quarter electron plasma wavelength of the fi'rst'rriode of plasma waves by an'amourrt such'that'the: alternating current velocities of the first and seco'nd' modes of plasma waves on thesaid beam'are equaland opposite, an electron collector electrode at a potential near that ofthe said cathode, located'at the exit from the said drift tube, the said collector electrode providing a'liollow spaceior the collection of theelectrons and an electron permeable grid covering the end of the said hollow space to provide a substantially flat
  • An'electron velocity modulation tube comprising electrode means for projecting an electron beam. from a cathode along a given path. energy interacting'relaiiom.

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  • Microwave Tubes (AREA)
US745688A 1957-08-22 1958-06-30 Electron velocity modulation tubes Expired - Lifetime US2939991A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB361618X 1957-08-22

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US2939991A true US2939991A (en) 1960-06-07

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US745688A Expired - Lifetime US2939991A (en) 1957-08-22 1958-06-30 Electron velocity modulation tubes

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US (1) US2939991A (en(2012))
BE (1) BE570553A (en(2012))
CH (1) CH361618A (en(2012))
FR (1) FR1213512A (en(2012))

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3312857A (en) * 1963-04-19 1967-04-04 Itt Microwave amplifier utilizing multipaction to produce periodically bunched electrons

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2240183A (en) * 1937-07-14 1941-04-29 Gen Electric Electric discharge device
US2312723A (en) * 1939-08-16 1943-03-02 Bell Telephone Labor Inc Electron discharge device
US2681951A (en) * 1948-09-01 1954-06-22 Csf Low background noise amplifying system for ultra-short waves

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2240183A (en) * 1937-07-14 1941-04-29 Gen Electric Electric discharge device
US2312723A (en) * 1939-08-16 1943-03-02 Bell Telephone Labor Inc Electron discharge device
US2681951A (en) * 1948-09-01 1954-06-22 Csf Low background noise amplifying system for ultra-short waves

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3312857A (en) * 1963-04-19 1967-04-04 Itt Microwave amplifier utilizing multipaction to produce periodically bunched electrons

Also Published As

Publication number Publication date
FR1213512A (fr) 1960-04-01
CH361618A (de) 1962-04-30
BE570553A (en(2012))

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