US3421036A - Varying inner diameter collector electrode for an electron beam tube,particularly high powered travelling-wave tubes - Google Patents

Varying inner diameter collector electrode for an electron beam tube,particularly high powered travelling-wave tubes Download PDF

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Publication number
US3421036A
US3421036A US581097A US3421036DA US3421036A US 3421036 A US3421036 A US 3421036A US 581097 A US581097 A US 581097A US 3421036D A US3421036D A US 3421036DA US 3421036 A US3421036 A US 3421036A
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United States
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collector electrode
electron beam
collector
wall
tube
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Expired - Lifetime
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US581097A
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English (en)
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Roland Wolfram
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Siemens AG
Siemens Corp
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Siemens 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
    • H01J23/027—Collectors

Definitions

  • the invention relates to an electron beam tube, in particular to a travelling-wave tube of high power, with a cup-shaped collector electrode which receives the electron beam, such collector electrode being arranged coaxially with respect to the beam axis and presents a rotationally symmetrical inner space which has a varying internal diameter and in which the electron beam diverges concentrically to the beam axis.
  • velocity modulated tubes for example, such as klystron amplifier tubes or travellingwave tubes
  • collector electrodes are in the form of a cup-shaped metal part which is arranged coaxially with respect to the electron beam axis and consists of a material with good heat-conducting capacity, for example of copper.
  • the electron beam tends to generally uniformly diverge within the cup-shaped metal part so that the majority of the electrons strike upon the lateral wall-plane of the collector electrode.
  • the heat occurring through the impact of the beam electrons upon the collector wall may not exceed a certain value if impermissible high temperature peaks are to be avoided.
  • the local heating of the collector is dependent on the power-density of the electrons applied to the inner wall of the collector electrode. If the rotationally symmetrical collector has, corresponding to the customary constructions, an inner wall extending parallel to the tube axis, the power density is the greatest, assuming that the electron beam continues to spread out, on the collector wall at the point of impact of the electron beam edge or periphery and then decreases towards the collector bottom, while it can again assume larger values on the actual bottom of the collector. Consequently, the power density of the electron bundle is, in this case, distributed irregularly over the length of the collector electrode. As a result, in order to avoid local over-heating the collector must be larger than otherwise required for the reception of the total power of the electron beam.
  • Electron beam tubes with rotationally symmetrical collector electrodes are also known, in which the inner diameter thereof becomes steadily or gradually smaller toward the electron entrance. It is possible that such a collector electrode is loaded more uniformly as to the beam power towards the collector bottom than a collector with a cylindrical inner space, assuming a steadily diverging electron beam. However, an uneven distribution of the power density still remains which may "become impermissibly high, especially in the front portion of the collector electrode.
  • N is the direct-current power contained in the electron beam during its entrance into the collector electrode
  • n is the permissible power density during electron bombardment on the inner wall of the collector electrode
  • z is a coordinate in longitudinal direction of the collector electrode
  • r designates the respective inner radius of the collector electrode
  • a designates the respective angle between the inner wall of the collector electrode and the beam axis
  • r as function of z represents the respective beam radius, considered as if the edge of the electron beam would spread out without hindrance after impact upon the collector electrode
  • (,o designates the appropriate angle between beam edge and beam axis.
  • N as the direct-current power of the electron beam upon its entrance into the collector
  • m as the maximum permissible power density on the collector wall
  • the functions r (z) and %(Z) which characterize the electron beam course may be determined for each tube installation by experiments or by calculations.
  • the desired contour line for the inner space of a collector electrode, the inner diameter of which changes in dependence on the z-axis, may be determined by a graphical approximation solution or by means of an analog computer.
  • the configuration of the collector electrode obtained in this manner assures that the power contained in the electron beam is distributed practically completely uniformly over the inner wall of the collector. This eliminates local power peaks on the collector wall during electron reception so that the collector electrode may be of smaller construction than the known pot-shaped elec tron beam collectors.
  • the collector electrode of an electron beam tube When constructing the collector electrode of an electron beam tube according to the invention, it is preferable to proceed from the feature that in the center range of the inner collector space at the location of a small, axisparallel wall zone ((1:0), a maximum inner radius exists.
  • the selection of this maximum inner radius depends upon the structure of the collector electrode and upon the total power contained in the electron beam, the radius fulfilling the function ao gab zvo (20)
  • the respective inner radius of the collector electrode is selected somewhat larger than the calculated beam radius ahead of the point at which the beam edge impacts.
  • the advantage of this measure consists of the feature that a sufficiently open space exists for possible deviations of the beam course from its supposed value which may be, for example, based upon variations when the electrons are shot in.
  • FIGURE 1 illustrates the principle of construction of the collector electrode of a velocity modulated tube in accordance with the invention
  • FIGURE 2 is a chart illustrating operating characteristics of a tube employing the invention.
  • FIGURE 3 is a schematic figure, similar to FIGURE 1, illustrating a collector having an internal contour in accordance with the invention.
  • the reference numeral 1 designates a cup-shaped collector electrode which has an inner contour with a rotationally symmetrical configuration of varying diameter.
  • An electron beam 2 which endeavors to continuously spread out within the collector electrode according to the beam edge curve 3, enters such collector electrode which may, for example, consist of copper and is to be constructed as a part of the discharge vessel of an electron beam tube.
  • the electron beam 2 is not further braked within the collector electrode 1, that the power density in the beam cross section is essentially constant, and that the individual electron paths resemble each other, the following formula is applicable for the power density of the collector electrode:
  • N is the direct-current power of the electron beam in the collector electrode, while all other values are functions of the coordinate z in longitudinal direction of the collector electrode, and that is to say, n(z) represents the power density on the collector wall; r (z) represents the calculated value of the beam radius following impact of the beam edge upon the collector wall; (z) represents the angle which is enclosed by the beam edge with respect to the beam axis; r represents the inner radius of the collector and a the angle which is enclosed by the inner wall of the collector with respect to the abscissa z.
  • r designates a maximum collector radius, the selection of which depends upon the power N and upon the entire construction (collector material, cooling, etc.).
  • the near or inner part of the collector may be divided into equal sections Z0, Z1, 2 etc. Proceeding from 2 a starting tangent with the angle e 0 is drawn to Z1.
  • the value a may then be computed according to the formula min
  • This principle may be continued according to the known tangent lay-out method.
  • ⁇ Vith regard to the ascertainment of the collector contour ahead of the point Z it should be observed that generally the inner radius of the collector electrode 1 will not coincide with the beam radius r at the abscissa z but aready lies within the beam-edge. Consequently, with regard to values z z there would be the danger that the permissible power density is exceeded at the beam edge. Consequently when the differential equation proposed according to the invention is solved graphically, it is recommended to begin with a chord extending towards the collector mouth and to then continue to calculate according to the chord lay-out method.
  • a practical constructional example for the collector electrode of a travelling-wave tube according to the invention is hereinafter described.
  • This example is based upon a direct-current power loss N of 4.1 kw., while the construction of the tube provides a maximum inner radius r :l.7 cm.
  • N direct-current power loss
  • the beam course r (z) and p (Z) was computed by means of an analog computer in the manner illustrated in FIGURE 2. In this figure, the path distance 2.
  • the collector contour, as actually constructed, which is also represented for the values z z as dash-line 6, is somewhat simplified.
  • the circular enlargement at the collector bottom accommodates itself to the fact that an ideal peak is not possible and that the heat occurring at the collector bottom because of this is advantageously uniformly conducted off towards several sides.
  • the reference numeral 8 designates a soft-magnetic shielding cover which is provided to magnetically shield the inner space of the collector with respect to a magnetic guidance-field which is customarily required, at least partially, for the bundled guidance of the electron beam of a travelling-wave tube so that a spreading out of the beam within the collector electrode on the strength of the space-charging forces is possible.
  • An electron beam tube such as a travelling-wave tube of high power, with a cup-shaped collector electrode for receiving the electron beam, which collector electrode is arranged coaxially with the beam axis and pos sesses a rotationally symmetrical inner space which has a varying inner diameter, and in which the electron beam steadily diverges concentrically to the beam axis, characterized in that the contour lines of the inner space of the collector electrode follow approximately the dilferential equation in which equation N is the direct-current power contained in the electron beam at its entrance into the collector electrode, n is the permissible power density during electron impact on the inner wall of the collector electrode, 1 is a coordinate in longitudinal direction of the collector electrode, r represents the respective inner radius of the collector electrode, on represents the respective angle between the inner wall of the collector electrode and the beam axis, r represents, as function of z, the respective beam radius, considered as if the edge of the electron beam would diverge, without hindrance after impacting the collector electrode, and represents the appropriate angle between the beam edge and beam

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US581097A 1965-09-21 1966-09-21 Varying inner diameter collector electrode for an electron beam tube,particularly high powered travelling-wave tubes Expired - Lifetime US3421036A (en)

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DES0099535 1965-09-21

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US (1) US3421036A (cs)
DE (1) DE1491465A1 (cs)
FR (1) FR1498681A (cs)
GB (1) GB1149010A (cs)
NL (1) NL6610246A (cs)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3585429A (en) * 1968-02-16 1971-06-15 English Electric Valve Co Ltd An electron beam discharge tube having a shaped collector with a plurality of cooling stages
US3806755A (en) * 1972-05-31 1974-04-23 Varian Associates Electron collector having means for reducing secondary electron interference in a linear beam microwave tube

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2894169A (en) * 1953-03-24 1959-07-07 Emi Ltd Electron discharge devices

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2894169A (en) * 1953-03-24 1959-07-07 Emi Ltd Electron discharge devices

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3585429A (en) * 1968-02-16 1971-06-15 English Electric Valve Co Ltd An electron beam discharge tube having a shaped collector with a plurality of cooling stages
US3806755A (en) * 1972-05-31 1974-04-23 Varian Associates Electron collector having means for reducing secondary electron interference in a linear beam microwave tube

Also Published As

Publication number Publication date
DE1491465A1 (de) 1969-05-22
GB1149010A (en) 1969-04-16
FR1498681A (fr) 1967-10-20
NL6610246A (cs) 1967-03-22

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