US2876373A - Magnet system for the focusing of electron beams - Google Patents

Magnet system for the focusing of electron beams Download PDF

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Publication number
US2876373A
US2876373A US630781A US63078156A US2876373A US 2876373 A US2876373 A US 2876373A US 630781 A US630781 A US 630781A US 63078156 A US63078156 A US 63078156A US 2876373 A US2876373 A US 2876373A
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United States
Prior art keywords
magnets
electron beam
poles
field
focusing
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Expired - Lifetime
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US630781A
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English (en)
Inventor
Veith Werner Adam
Meyerer Paul
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Siemens and Halske AG
Siemens AG
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Siemens AG
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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
    • H01J23/08—Focusing arrangements, e.g. for concentrating stream of electrons, for preventing spreading of stream
    • H01J23/087—Magnetic focusing arrangements
    • H01J23/0873—Magnetic focusing arrangements with at least one axial-field reversal along the interaction space, e.g. P.P.M. focusing

Definitions

  • the present invention relates to a system of magnets for focusing at least one electron beam, particularly for traveling wave tubes, in which the polarity of the mag- 1 netic poles or pole shoes of the focusing magnet, which poles or shoes are arranged one behind the other in the direction of the electro-n beam, is periodically alternated so as to produce an alternating magnetic eld having a distribution of the magnetic field intensity which extends sinusoidally in the direction of the electron beam.
  • the difficulty occurs, as is known, of conducting the electron beam elo-se by the delay line in order to obtain a good coupling of the electromagnetic wave with .the electrons kand nevertheless prevent an electron impingement on the delay line.
  • the electron beam be conducted in focused form along its direction of discharge.
  • the wavelength of the electromagnetic wave which is to be amplified or produced has a lower limit in the case of traveling wave tubes or similar veryhigh frequency tubes while there is an upper limit for the amplification o-r the output power, as will be presently explained more in detail.
  • the essential feature of the invention is that the direc,- tions of magnetizationin the magnet ends of the focusing magnets extend substantially at 'right angles through the electron beam or perpendicularly to the direction of the electron beam.
  • the invention makes it possible, in a particularly advantageous manner, to select the focusing magnets as long as desired in their magnetizing direction by arranging bar magnets in a plurality of planes at right angle to the axis of the discharge system and outside the discharge vessel in such a manner that two magnets are opposite each other in a plane symmetric to the electron beam.
  • the poles of the magnets are so connectedwith the pole sho-es that those poles of the magnets which are adjacent to the electron beam are provided with pole shoes shaped in such -a manner that in planes at right angles to the axis of the discharge system similar poles which are adjacent to the electron beam are connected and that the pole shoes have a polarity which alternates along the direction of discharge.
  • a further feature of the invention is that a plurality of focusingv magnets, ⁇ the magnetizing directions of which extend in the magnet poles at right angles to the electron beam 'are so developed and arranged that the lmagnet poles extend parallel 'to each other and parallel to the electron beam.
  • the magnets are in such arrangement of very large width as compared with the yknown bar magnets, this width extending over the entire discharge path, and the height and thickness of the magnets are 'dimensioned so as to obtain the magnetic llux and required field intensity for'the sinusoidal eld necessary in the direction of discharge. If the field intensity requirement of such an arrangement is veryhigh, as is true in particular at Very high frequencies, itis advantageous -to arrange two toroid-like magnets symmetrically to the electron beam in such a manner that two similar magnet poles arealways opposite each other.
  • the invention provides an arrangement wherein every two 'magnets are similarly spaced from the electron beam and so located ina plane formed by the longitudinal axis land by any arbitrary straight line perpeudicularto the longitudinal axis that their magnet poles adjacent the electron 'beam have the same polarity.
  • the arrangement of the magnets parallel to the electron beam makes it in a simple manner possible to connect the south poles adjacent to the electron beam magnetically with each other and the north poles adjacent to the electron beam magnetically with cach other by a plurality of pole shoes, such that a pole shoe which connects the south poles is followed alternately in the direction of discharge by a pole shoe which connects the north poles.
  • the poles of the magnets which are located remote from the electron beam are suitably magnetically connected with thick soft iron plates so that the magnetic impedance in these plates is negligibly small.
  • a further feature of the invention is that the focusing magnets form an even-numbered polygon around the electron beam in a plane perpendicular thereto and that similar poles adjoin each other at the corners.
  • the magnets form a square polygon extending in' a plane perpendicular to the electron beam, the center of which forms the axis of the electron beam.
  • the similar poles at the corners are connected by pole shoes, the longitudinal axis of the pole shoes extending at right angles through the electron beam.
  • pole shoes of soft iron with a larger cross-section in the vicinity of the magnets than in the vicinity of the electron beam so that the flux requirement necessary for the production of the sinusoidal field distribution can be obtained from the magnets.
  • the pole shoes serving for the magnetic coupling of similar poles are each provided with a bore to receive the discharge vessel, for instance an elongated discharge vessel, in the case of traveling Wave tubes.
  • the magnets having the first and last pole shoes respectively are disposed at right angles to the longitudinal axis of the discharge vessel and to provide bar magnets also located at right angles to the longitudinal axis of the discharge vessel at a distance away from the ends of the magnet necessary for the coupling and decoupling respectively.
  • the bar magnets may for this purpose be provided near the wall of the vessel with an annular pole shoe for connecting similar poles.
  • the bar magnets are suitably of such dimensions and so connected with soft iron plates with their poles located away from the electron beam that a magnetic steady field is formed between the annular pole shoe and the first and last pole shoes, respectively, of the magneticvsystem in the direction of the longitudinal axis of the discharge system.
  • Figs. 1a and lb show the construction and distribution of the field intensity of the known arrangement
  • Figs. 2 to 9 show in greatly simplified and in part schematic presentation various embodiments in the parts thereof which are essential for the invention.
  • Fig. la there is shown a part of the known, previously mentioned magnetic focusing device for traveling wave tubes in which the intensity of the field strength in zdirection alternates and is approximately sinusoidal.
  • annular permananent magnets 1 are serially so arranged that similar poles are adjacent to each other.
  • annular pole shoes 2 having cylindrical rings 3 near the discharge vessel 4.
  • a helix 5 through which the electron beam is projected.
  • Magnetic lines of flux 6 extend from the cylindrical parts 3 of the pole shoes. The direction of the magnetic lines of flux 6 depends on the polarity of the pole shoes and is shown by arrows.
  • Fig. 1b the field intensity H which occurs along the z-axis of the discharge system of Fig. la is plotted in the direction of the z-axis.
  • the solid sinusoidal curve 7 represents the theoretical field distribution which is necessaryv for the dependable focusing of the electron beam.
  • the dotted line 8 shows approximately the actual field distribution of the arrangement of Fig. 1a produced by the fact that the annular magnets 1 cannot be made magnetically so identical that the amplitudes of the sinusoidal curve of the field intensity are equal.
  • the field strength of a magnet depends on its length, it is not possible in accordance with Fig. 1a to increase the fieldA intensity if it is desired to go over to a higher frequency. Furthermore, with a higher frequency of the wave conducted over the helix, the plasma wavelength becomes smaller.
  • the length L of the sinusoidal wave of the field intensity is in such relationship to the plasma Wavelength that with a decrease in the plasmal wavelength, the length L of the sinusoidal wave of the field intensity must also become smaller.
  • l is the distance between the pole shoes 2 which is. determinative for the stray-field shunt outside the discharge vessel; d determines the loss produced by the strong field between the cylindrical rings 3; and R is the radius of the cylindrical ring 3 on which the size of the field-strength distribution on the z-axis depends.
  • Fig. 2 shows schematically an arrangement of bar magnets which makes it possible to produce the sinusoidal kfield along the z-axis of the electron beam, in which connection the length L of one cycle of the sinusoidal magnetic field can be dimensioned in accordance with the above conditions corresponding to the maximum frequencies occurring in traveling wave tubes.
  • the magnets 9 and 10 are arranged horizontal and symmetric to the electron beam, the north poles adjoining the pole shoe 11.
  • the pole shoe 11 is provided with a borehole 12 to receive the discharge vessel such as 4 in Fig. 1a.
  • the magnets 13 and 14 are arranged vertically and also symmetrically opposite each other with respect to the axis z of the electron beam.
  • the south poles are connected Yby the pole shoe 1S so that a magnetic field is produced between the poles shoes 11 and 15.
  • the pole shoe 15 also has a bore-hole .12 to receive the discharge vessel such as the vessel 4 in Fig. la. In the direction of the axis z of the electron beam, there then again follows a magnet arrangement with north poles adjoining the pole shoes.
  • the system of magnets shown in Fig. 2 in contradistinction to that shown in Fig. l, has a greater degree of freedom with respect to the dimensioning of the magnets.
  • the length of the magnets which is determinative with respect to the field strength, can be selected as large as desired.
  • the arrangement of the magnets at right angles has the advantage that the. magnetic stray fields outside the field of action of the pole shoes are very small.
  • Fig. 3 shows the construction of the system of magnets indicated in Fig. 2.
  • the vertical magnets 13, 14 are followed by the horizontal magnets 9, 10. They are then followed by a pair of vertical magnets and then again by a pair of horizontal ones, and so forth, until the entire system of magnets extends over the discharge path of the electron beam.
  • the outside poles of the bar magnets are connected withsoft iron plates 16 and 17.
  • the soft iron plates 16 connect all similar poles to each other, while the soft iron plates 17 serve to connect the dissimilar poles.
  • the soft iron plates are suitably of such size that the magnetic resistance is negligibly small.
  • the magnets 18 and 19 have a direction of magnetization which is perpendicular to the z-axis. The height of these magnets is small as compared with their width.
  • the south poles of magnets 18 and 19 are connected by trapezoidal pole shoes 20 and 21 with the rectangular pole shoe 22.
  • the pole shoes 20, 21 and 22 are advantageously made of soft iron so that as high a density of the magnetic lines of force emerging from the pole shoes 22 as desired is possible.
  • the cross-section 23 in the vicinity of the south pole of magnet 1S is selected larger than the cross-section 24 so that the flux requirement determined by the cross-section can be obtained as large as possible from the magnet.
  • the pole shoes 22 are also provided with boreholes 25 to receive the discharge vessel such as 4 shown in Fig. la.
  • Fig. is a front View of the arrangement of the magnetic system shown in part in Fig. 4 and Fig. 6 is a perspective view, partially in section of the arrangement shown in Fig. 5.
  • the vertical magnets 18, 19, as already shown in Fig. 4 are connected with pole shoes 20, 21 and 22 which are arranged one behind the other in the z-direction. Perpendicular to this pair of magnets 18 and 19 there are arranged parallel to each other two magnets 26 and 27 which are likewise connected with pole shoes 28, 29 and 30.
  • the polarity of the' vertical pole shoe 22 must be opposed to the polarity of the horizontal pole shoe 30.
  • the pole shoes 22 and 30 alternate in z-direction so that an alternating magnetic field is produced.
  • the thickness of the pole shoes 22 and 30 and the distance from pole shoe 22 to pole shoe 30 must be in a given relationship to each other. The most favorable relationship can easily be found by experiment.
  • the elongated magnets 18, 19, 26, 27 and the alternation in zdirection of pole shoes 22 and 30 it has become possible to shape the distribution of the field strength on the z-axis sinusoi-dally in the manner shown by curve 7 in Fig. lb. Any possible places of interference in magnets 18, 19,26 and 27 are counteracted by the elongated form.
  • the outside poles of the elongated magnets 18, 19, 26 and 27 are magnetically short-circuited by means of the soft iron plates 31 to 38.
  • Fig. 7 there is shown a variation of the arrangement of the magnets shown in Fig. 6.
  • This arrangement is particularly advantageous for very high frequency tubes, due to the fact that the field intensity can be greatly increased by means of the toroid-like magnets 39 and 40.
  • the field intensity of a magnet depends on its length. Due to the toroidal shape, a possibility is afforded of increasing the field strength as much as desired so that this magnetic system can be used for extremely high frequencies.
  • the arrangement of the pole shoes is the same as already described in connection with Fig. 6.
  • FIG. 8 A'possibility of simultaneously varying the field intensity and the iiux requirement and therefore, for all practical purposes, the energy content of the magnets within wide limits, is shown in Fig. 8.
  • the magnets 45, 46, 47 and 48 are so arranged symmetrical to the z-axis of the electron beam that they form the sides of a square around the electron beam with similar poles always abutting against each other at the corners of the square. The result is that the opposite corners of the square have similar polarity.
  • the corners of similar polarity are connected horizontally with the pole shoes 43 and 44 by way of the central pole shoe 30. In vertical direction, the pole shoes 41 and 42 are connected by way of the central pole shoe 22.
  • the arrangement of the focusing magnets according to Fig. 8 represents a particularly favorable embodiment with respect to the manner lof manufacture and the dimensioning of the field intensity distribution obtained on the z-axis.
  • Experimental results have given for this embodiment extremely good approximations to the theoretical sinusoidal curve of the field strength distribution on the z-axis.
  • Fig. 9a shows an example of how, in the case of the arrangement shown in Fig. 6, a steady field is produced at the beginning of the magnet system.
  • the two bar magnets 49 and 50 are arranged at right angles ⁇ to the electron beam.
  • the direction of magnetization of the bar magnets 49 and 50 is advantageously selected to be the same as the directions of magnetization of the magnets 18 and 19, since the length of the steady field is relatively large and the field intensity must be increased.
  • At a distance from the end of the magnet system required for the coupling or uncoupling bar magnets 51 and 52 are also arranged at a right angle to the electron beam, these magnets being 'magnetically so oriented that the field intensity of the steady field is further jincreased.
  • the bar magnets S0 and 52 are com nected with a soft iron yoke 54.
  • the bar magnets 49 and 51 are magnetically coupled in exactly the same manner with a soft iron yoke 53.
  • the bar magnets 5l and 52 advantageously have an annular soft iron pole shoe 56 which together with the pole shoe 22 produces a homogeneous steady tield.
  • Fig. 9b the eld intensity is plotted over the z-axis of the electron beam.
  • the sinusoidal curve 57 represents the magnetic field strength in the magnet system 18, 19.
  • Curve 57 shows the magnetic field intensities of the steady eld in the coupling space.
  • This field intensity of the coupling space is suitably selected in the order of magnitude of the effective value of the sinusoidal wave of the field intensity of the magnet system in order to reduce the initial ripple of the electron beam.
  • the present invention is not only applicable to traveling-wave tubes or the like, but can also be employed advantageously whenever it is desired to conduct electron beams in focused form over a relatively long path, and the term travelling wave tube as used in the claims therefore is to be interpreted with sensible latitude as including dilerent structures to which the invention may be applied.
  • the invention may also be applied to three, four or six-wing magnet systems.
  • a magnet system for focusing at least one electron beam in connection with a travelling wave tube and the like comprising a plurality of focusing magnets disposed serially in a direction paralleling the direction of propagation of the electron beam and surrounding the electron beam for the extent of the focusing path, the directions of the lines of force extending in said magnets perpendicular to the direction of propagation of said electron beam, pole pieces respectively cooperating with said magnets being similarly serially disposed and alternately magnetically interconnected with identical poles thereof, whereby an alternating magnetic field is produced creating along the beam axis a substantially sinusoidal distribution of the magnetic eld intensity, said focusing magnets torming along planes extending perpendicular to the electron beam structures exhibiting substantially rectangular con; iguration surrounding the electron beam, identical poles of said magnets being interconnected by the respective pole pieces cooperating therewith.
  • a magnet system according to claim l wherein the respective magnet poles extend parallel to one another and parallel to the electron beam.
  • a magnet system according to claim l wherein said magnets form a structure exhibiting a square configuration in a plane extending perpendicular to the electron beam, said beam passing centrally through said magnets.
  • a magnet system according to claim 2 wherein said magnets form a structure exhibiting a square configuration in a plane extending perpendicular to the electron beam, said beam passing centrally through said magnets.
  • a magnet system according to claim 2 wherein the longitudinal axes of said pole pieces extend in directions perpendicular to the direction of the electron beam.
  • pole pieces are made of soft iron exhibiting a cross-section adjacent the corresponding magnet poles which exceeds the cross-section thereof in the neighborhood of the electron beam.

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US630781A 1956-03-01 1956-12-27 Magnet system for the focusing of electron beams Expired - Lifetime US2876373A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DES47742A DE1076280B (de) 1956-03-01 1956-03-01 Permanentmagnetsystem zur gebuendelten Fuehrung mindestens eines Elektronenstrahls ueber eine groessere Wegstrecke, insbesondere fuer Wanderfeldroehren

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US630781A Expired - Lifetime US2876373A (en) 1956-03-01 1956-12-27 Magnet system for the focusing of electron beams

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US (1) US2876373A (fr)
CH (1) CH355530A (fr)
DE (1) DE1076280B (fr)
FR (1) FR1164780A (fr)
GB (1) GB853061A (fr)
NL (2) NL214979A (fr)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2956193A (en) * 1957-07-11 1960-10-11 Philips Corp Magnet system for travelling wave tubes
US2965782A (en) * 1958-03-12 1960-12-20 English Electric Valve Co Ltd Magnetic focusing systems for travelling wave tubes
US2988659A (en) * 1958-06-27 1961-06-13 Philips Corp Electron beam focusing magnet system for traveling wave tubes
US3106659A (en) * 1959-03-24 1963-10-08 Kearfott Company Inc Microwave tube construction
US3164742A (en) * 1960-12-27 1965-01-05 Gen Electric High frequency energy interchange device
US3183398A (en) * 1960-08-04 1965-05-11 Raytheon Co Beam focusing magnet
US3188533A (en) * 1962-02-23 1965-06-08 Telefunken Patent Focussing system for an electron beam incorporating axially magnetized annular magnets
US3237059A (en) * 1962-10-04 1966-02-22 Siemens Ag Permanent magnet system for producing a magnetic field for the focused passage of a beam of electrons
US3254273A (en) * 1963-10-31 1966-05-31 Radio Frequency Lab Inc Standard magnet
US3265978A (en) * 1959-08-17 1966-08-09 Westinghouse Electric Corp D. c. pumped quadrupole parametric amplifier
DE1298197B (de) * 1961-05-02 1969-06-26 Siemens Ag Permanentmagnetsystem zur gebuendelten Fuehrung des Elektronenstrahls einer Lauffeldroehre
DE4411405A1 (de) * 1993-04-02 1994-10-06 Litton Systems Inc Fokussiersystem mit periodischen Permanentmagneten für Elektronenstrahl
US20120153129A1 (en) * 2009-07-15 2012-06-21 Pioneer Corporation Imaging apparatus
CN108776129A (zh) * 2018-07-06 2018-11-09 中国科学院西安光学精密机械研究所 多功能环形磁铁阵列激光等离子体约束装置及其应用系统

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1226217B (de) * 1961-04-19 1966-10-06 Telefunken Patent Dauermagnetanordnung zur periodischen Fokussierung eines innerhalb einer Vakuumhuelle verlaufenden Elektronenstrahles

Citations (7)

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US2102045A (en) * 1936-05-13 1937-12-14 Albert G Thomas Electron discharge tube
US2157182A (en) * 1935-12-31 1939-05-09 Rca Corp Cathode ray deflecting device
US2730678A (en) * 1951-12-29 1956-01-10 Csf Improvements in interdigital delay lines
US2801361A (en) * 1948-12-10 1957-07-30 Bell Telephone Labor Inc High frequency amplifier
US2804548A (en) * 1948-10-01 1957-08-27 Siemens Ag Device for adjusting the refractive power of electron lenses operating with permanent magnet excitation
US2812470A (en) * 1954-10-22 1957-11-05 Bell Telephone Labor Inc Periodic focusing in traveling wave tubes
US2847607A (en) * 1953-04-29 1958-08-12 Bell Telephone Labor Inc Magnetic focusing system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1071237B (fr) * 1953-04-29

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2157182A (en) * 1935-12-31 1939-05-09 Rca Corp Cathode ray deflecting device
US2102045A (en) * 1936-05-13 1937-12-14 Albert G Thomas Electron discharge tube
US2804548A (en) * 1948-10-01 1957-08-27 Siemens Ag Device for adjusting the refractive power of electron lenses operating with permanent magnet excitation
US2801361A (en) * 1948-12-10 1957-07-30 Bell Telephone Labor Inc High frequency amplifier
US2730678A (en) * 1951-12-29 1956-01-10 Csf Improvements in interdigital delay lines
US2847607A (en) * 1953-04-29 1958-08-12 Bell Telephone Labor Inc Magnetic focusing system
US2812470A (en) * 1954-10-22 1957-11-05 Bell Telephone Labor Inc Periodic focusing in traveling wave tubes

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2956193A (en) * 1957-07-11 1960-10-11 Philips Corp Magnet system for travelling wave tubes
US2965782A (en) * 1958-03-12 1960-12-20 English Electric Valve Co Ltd Magnetic focusing systems for travelling wave tubes
US2988659A (en) * 1958-06-27 1961-06-13 Philips Corp Electron beam focusing magnet system for traveling wave tubes
US3106659A (en) * 1959-03-24 1963-10-08 Kearfott Company Inc Microwave tube construction
US3265978A (en) * 1959-08-17 1966-08-09 Westinghouse Electric Corp D. c. pumped quadrupole parametric amplifier
US3183398A (en) * 1960-08-04 1965-05-11 Raytheon Co Beam focusing magnet
US3164742A (en) * 1960-12-27 1965-01-05 Gen Electric High frequency energy interchange device
DE1298197B (de) * 1961-05-02 1969-06-26 Siemens Ag Permanentmagnetsystem zur gebuendelten Fuehrung des Elektronenstrahls einer Lauffeldroehre
US3188533A (en) * 1962-02-23 1965-06-08 Telefunken Patent Focussing system for an electron beam incorporating axially magnetized annular magnets
US3237059A (en) * 1962-10-04 1966-02-22 Siemens Ag Permanent magnet system for producing a magnetic field for the focused passage of a beam of electrons
US3254273A (en) * 1963-10-31 1966-05-31 Radio Frequency Lab Inc Standard magnet
DE4411405A1 (de) * 1993-04-02 1994-10-06 Litton Systems Inc Fokussiersystem mit periodischen Permanentmagneten für Elektronenstrahl
US5744910A (en) * 1993-04-02 1998-04-28 Litton Systems, Inc. Periodic permanent magnet focusing system for electron beam
US20120153129A1 (en) * 2009-07-15 2012-06-21 Pioneer Corporation Imaging apparatus
CN108776129A (zh) * 2018-07-06 2018-11-09 中国科学院西安光学精密机械研究所 多功能环形磁铁阵列激光等离子体约束装置及其应用系统
CN108776129B (zh) * 2018-07-06 2023-12-08 中国科学院西安光学精密机械研究所 多功能环形磁铁阵列激光等离子体约束装置及其应用系统

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NL99653C (fr)
FR1164780A (fr) 1958-10-14
NL214979A (fr)
CH355530A (de) 1961-07-15
DE1076280B (de) 1960-02-25
GB853061A (en) 1960-11-02

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