US2841739A - Electron beam systems - Google Patents

Electron beam systems Download PDF

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Publication number
US2841739A
US2841739A US351984A US35198453A US2841739A US 2841739 A US2841739 A US 2841739A US 351984 A US351984 A US 351984A US 35198453 A US35198453 A US 35198453A US 2841739 A US2841739 A US 2841739A
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United States
Prior art keywords
electron
path
magnetic field
flow
magnetic
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Expired - Lifetime
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US351984A
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English (en)
Inventor
John R Pierce
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AT&T Corp
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Bell Telephone Laboratories Inc
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Publication date
Priority to NL95352D priority Critical patent/NL95352C/xx
Priority to US25189D priority patent/USRE25189E/en
Priority to DENDAT1071237D priority patent/DE1071237B/de
Priority to BE528454D priority patent/BE528454A/xx
Priority to US351874A priority patent/US2855537A/en
Priority to US351983A priority patent/US2847607A/en
Priority to US351977A priority patent/US2844754A/en
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US351984A priority patent/US2841739A/en
Priority to FR1099234D priority patent/FR1099234A/fr
Priority to DEW25876A priority patent/DE1127498B/de
Priority to GB12311/54A priority patent/GB757369A/en
Priority to CH342662D priority patent/CH342662A/fr
Application granted granted Critical
Publication of US2841739A publication Critical patent/US2841739A/en
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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

  • One common expedient in the traveling wave tube art for keeping the electron flow cylindrical is to immerse the beam path in a magnetic field in which the magnetic lines are parallel to the longitudinal direction of electron flow.
  • a magnetic field in which the magnetic lines are parallel to the longitudinal direction of electron flow.
  • the electron gun is enclosed in a magnetic shield, and the electrons are caused to spiral as they enter the region of longitudinal magnetic field from the shielded region.
  • This inward force is adjusted to counterbalance exactly the sum of outward mutually repulsive forces of the electrons (the so-called space charge forces) and the outward centrifugal force of the spiraling electrons.
  • the principal object of the present invention is to effect economies in the requirements of the magnetic field necessary for good magnetic focusing of a stream of charged particles.
  • the present invention relates to a system of magnetic focusing in which the intensity of the magnetic field varies periodically with distance along the path of flow rather than being constant therealong.
  • Atent Q "ice 2 tudinal magnetic field in the vicinity of the beam has the same magnitude as the uniform axial field characteristic of Brillouin focusing. It is obvious that for a given average field value, a larger R. M. S. field value results if the field is localized in a succession of relatively short regions instead of being uniform over a relatively long region. Accordingly, the necessary value of R, M. S. field necessary for a non-diverging beam can be achieved with a minimum of driving magnetomotive force by con- 5.: centrating the longitudinal magnetic field along a periodic series of short gaps along the path of how.
  • a usual expedient for achieving the desired longitudinal magnetic field is to surround the tube envelope with a solenoid which when energized establishes an axial mag netic field which immerses the path of electron flow.
  • economies in the driving magnetomotive force necessary are achieved by suitably shielding the electron path from the solenoid field along much of its length and localizing the field to a succession of unshielded regions and arranging to have the magnetic field reverse direction at each unshielded region.
  • an annular structure of a material of low reluctance such as soft iron surrounds the electron path, the structure having an outer cylindrical surface which is continuous for forming a low reluctance magnetic path and an inner cylindrical surface which is provided with. a regular succession of apertures surrounding the path of flow.
  • a succession of solenoids is wound in the interior of the annular frame for forming a succession of magnetic fields which leak out at the apertures in the inner cylindrical surface for creating regions of longitudinal magnetic fields along the adjacent portions of the electron path, successive solenoids being oppositely wound whereby the direction of the field reverses with successive regions.
  • Fig. 1 shows an electron beam system which utilizes a timoconstant spatially alternating magnetic field to focus the beam
  • Fig. 2 shows a traveling wave tube which utilizes the electron beam system of Fig. l in accordance with the invention
  • Fig. 3 shows a traveling wave tube which utilizes an electron beam system which provides a unidirectional magnetic field which is varied periodically in intensity
  • Figs. 4A through 4C and 5 through 8 are plots which will be useful in explaining the principles of the invention.
  • evacuated envelope 11 of a suitable non-magnetic terial such as glass houses the electron beam
  • an electron gun 12 serves as the source of a solid beam of electrons.
  • an electron gun customarily includles an electron emissive cathod I beam focusing electrode, and an accelerating electrode system, for purposes of simplicity, the electron gun is shown schematically merely as a cathode.
  • a target electrode 13 serves to collect the spent electrons at the end of their path.
  • an interaction circuit is provided therebetween which is maintained at an appropriate positive D. C. potential with respect to the electron source.
  • an electrode memher is disposed along the path of flow in the form of a resistive coating'iionthe inner surface of the envelope for providing an acceleratingfield.
  • the focusing of the electron beam is achieved by a succession of regions of longitudinal inagneticfield along the path.
  • the solenoids l5 arespaced apart'along and with their'axis coinciding with the path'of; ftoiv.
  • Each solenoid is Surrounded by a' magnetic'shield in which serves as a i'luxguide and isopen only along a short gap 17 adjacent the path'of flow where the n netic field escapes into the path of flow for creating a region of longitudinal magnetic field.
  • the spacing of the gaps is adjusted in'accordance withthe principles set forth in the analysis which follows hereinafter.
  • thearrangement may be viewed as comprising an annular frame member 16 of a material having a high permeability such as soft iron for serving as a low reluctance magnetic path for which the driving rnsgnetomotive force is provided by the plurality of solenoids l5 spaced apart within the annular interior of frame member.
  • the framemember is closed eitsuccessicn of cylindrical gaps 17 along its surface which permit leakage of the'magnetic field jacent regions of the electron path.
  • the successive are separated by a succession of transverse ctic disks it ⁇ which isolate the separate solenoids f ⁇ sible the reversal of the direction of longitudinal magnetic field along successive gaps by a reversal of the direction of current flow through successive solenoids.
  • Equation 3 now becomes,
  • B the peak value of magnetic field at the axis
  • L the magnet period (equal to twice the mean distance between gaps or solenoids)
  • Equation 5 Equation 5 becomes a+ )(i+c s 2T)o-- :0 (c) 2 w 2 or a where T is equal to art and i is equal to For convenience let,
  • Equation 6 This non-linear ditferential'equation can be solved for values of or and [5' of interest to thestudy of practical traveling wave tubes.
  • Figs. 4A through 40 show plots of thebeam radius as a function of the distance along the path of flow z for various values of the parameter a with ,8 held constant.
  • B and c is proportional to thebcam current 1 and therefore varying or is equivalent to vary ing the peak magnetic field B
  • the perturbations of the b 21m radios are seen to be a minimum (Pig. and this is me so called optimum field.
  • E For higher values of peak mag netic field E the average radius of the beam isdecreased (Fig. 4C) and for lower values of B it is increased (Fig. 4A).
  • V is twice the beam voltage
  • B is the peak magnetic field
  • K is the beam perveance
  • Equation 7 it can be seen that the first two terms comprise Mathieus diiferential equation while the last term is due to the space charge forces a of the electrons.
  • Mathieus equation An analysis of Mathieus equation can be found in a book entitled Theory and Applications of Mathieu Functions by H. W. MacLachlan published by the Oxford University Press (1947). If the solution to the homogeneous equation without space charge (Mathieus equation) diverges, then it is reasonable to suppose that the addition of the space charge term will not restore stability. (However, the converse is not necessarily true, i.
  • Equation 7 From Equation 7 the constants a and q of the standard form of Mathieus equation becomes respectively 1 and 1/2 and therefore describe a straight line on the stability chart (Fig. 6). (Also shown is the line corresponding to the case where the solenoids are wound so that the field of each is in the same direction.) This line intersects the boundaries of the stable and unstable regions at points which define the values of leaf 2 w v (the constant at which separate the pass and stop bands of periodic focusing.
  • Equation 8 For a particular experimental focusing structure A was measured to be 1/ 3, so Equation 8'becomes a+.562( f [1.055+.667 cos 27 Ignoring the cos4T term, and rewriting in terms of the previous constants c and ,3, for Aiding Fields, Equation 8 becomes The case of aidingfields is, however, of interest.
  • a simplified analysis-which can be carried out is to assume that along the 'path of flow the regions of longitudinal magnetic field are short compared to the distance separating them, so that the succession of focusing fields may be regarded as a series of thin converging lenses. Then if the beam is started in such a manner that it is cylindrical midway between two adjacent lenses, and if the lenses are chosen of the right strength, the flow will be cylindrical between the next two lenses.
  • the converging etfect of the lenses is on the average just balanced out by the diverging effect of the space charge between the lenses, and the electron beam flow is identical between each successive pair of lenses.
  • an envelope 21 of a non-magnetic material such as glass houses various tube elements. Many of the details whose need will be obvious to a worker in the tube art have not been showni Alternatively, it 'is possible to employ an envelope of a magnetic material such as kovar if the envelope is made so thin as to become magnetically saturated so readily as to' little reduce the magnetic field in the interior. of the envelope.
  • an electron source 22 and a target electrode 23 At the two opposite ends of the envelope are-positioned an electron source 22 and a target electrode 23.
  • the electron source is an electron.
  • Disposed along the path of flow is a helically coiled conductor; aplurality of: operating wavelengths long, which serves both as the interaction circuit for propagating a slow electromagnetic wave in coupling relation with the 'electron beam and also as an electrode for accelerating the-:kelectrombeam;
  • Theahelix 26 is joined at: opposite ends to an input couplingwtrip 27 by an impedance matching section 29 audio an-outputcoupling strip 28 by an impedance-matchingcsection 3 0i -
  • the matching sections 29 and- 30 are simplysextensionsof :the conductor 26 in which the pitch of;thezhelixris-igradually-increased.
  • An input wave is applied:toitheeupstream end of the helix interaction circuit bysway-of inpubwave guide coupling connection 31 and-theioutputiwaveisabstracted at the downstream end by way of output wave guide couplingconnection 32.
  • Each of thezinput and output coupling strips 27 and 28 is sup-.
  • Input waves are applied to the input wave guideacoupling connection 31 to have a mode of propagationrhavingran electric field direction parallel to the cow pling strip 27.
  • an electromagnetic wave is introduced: into the helix interaction circuit for travel therealongin. coupling relation with the electron beam.
  • The:electrongun isaligned to form a solid cylindrical beam for projection coaxially through the helix.
  • the helix is maintained byisuitable-lead-in connections not shown at a potential which is positive with respect to that on the cathode 24 and approximately equal to that on the target 23.
  • the description hitherto has been of a conventional form of traveling wave tube essentially of the kind described in United; States Patent No. 2,575,383 which issued to L. M. Field on November 20, 1951'.
  • each of a succession of solenoids 33 are spaced apart along the ,path of flow.
  • Each solenoid is enclosed within a magnetic shieldor flux guide 34 which is open only along a short gap 35 adjacent the path of electron flow where the magnetic field-v escapes into the path of flow for creating a region of longitudinal magnetic field.
  • the current through the windings oi successive solenoids is adjusted to introduce. a reversal in the direction of longitudinal magnetic field set up across successive gaps 35. It is these successive regions of longitudinal magnetic field that efiect the desired focusing.
  • the aperture side walls 31A, 31B, 32A and 32B of each or" wave guide connections 31 and 32 are made of :1 material of high permeability while the other pairs of side walls together with the end' closures 31C and 32C made of a non-magnetic material such as copper.
  • Magnetic flux producing means are bridged across the two pairs of apertured' side Walls 31A, 31B and 32A, 32B. These magnetic means are illustrated in the embodiment of Fig. 2 as the electromagnets 37 and 38.
  • the sidewalls 31B and 32Bv are provided with projecting sleeves 39 and 40 which closely surround portions of the glass envelope 21' for forming with side walls 31A and 32A gaps 41 and 42, respectively, similar to the air gaps 35 along the magnetic shield 34;
  • the electromagnets 37 and 38 of appropriate strength, theregion of periodically varying longitudinal magnetic field'can be extended along the path of electron flow" past the two wave guide connections.
  • Fig. 3 shows a traveling have tube similar to'that shown in Fig. 2 with which is associated a focusingsystem which provides an array of'unidirectionallongitudinal field regions.
  • the focusing system shown: in Fig. 3 comprises essentially a single solenoid 52' which-provides the magnetomotive drivingforce for the succession of regions of longitudinal'field along the path of'fiow.
  • thedrift regions of low magnetic field which separate the regions of high magnetic field are long so thatit is feasible'to allow those portions of'the electron path corresponding to travel within the input and output wave guides-53-and 54'serve as drift spaces.
  • the wave guides 53 and 54 be entirely of a material of high permeability to provide magnetic shielding of the regions they enclose, and to have the solenoid 52 extend between thewave guides 53 and 54.
  • the periodic-regions of longitudinal magnetic field can be extended along the the path of flow, a succession of cylindrical sleeves 55' of a material of high permeability are disposed around the envelope 21 for serving as flux guides, and there is formed a succession of air gaps 56 along the path of flow across which are set up longitudinal components of magnetic field. It is characteristic of this arrangement that the direction of the longitudinal magnetic field is the same in successive air gaps so that the applicable analysis is that of the fields aiding case. Additionally, a cylindrical jacket 57 of high permeability surrounds the outside of the solenoid for serving as a low reluctance flux guide therealong.
  • an electron source and a target electrode defining therealong a path of electron flow, electrode means disposed along the path of flow for accelerating the electron stream, a plurality of identical solenoids disposed along the path of flow at equal distances, adjacent solenoids being in field opposing relation, and a succession of identical annular permeable members, each forming a low reluctance path around a solenoid which is open at equal distances along an annular region adjacent to and surrounding the path of flow for establishing longitudinal magnetic flux along the corresponding region of the electron path, the successive uniform regions of magnetic flux serving as successive identical converging lenses having a convergence sufiicient for overcoming the space charge divergence between successive sive regions.
  • an electron source and a target defining therealong a path of electron flow, a helical conductor along the path of flow for accelerating the electron stream and for propagating waves for interaction with said flow, a succession of identical solenoids disposed along and surrounding successive regions of the path of electron flow at equal distances, adjacent solenoids being in field opposing relation, and a succession of identical permeable members, each enclosing a solenoid for forming a path of low magnetic reluctance therearound and having an annular aperture in the surface adjacent the path of electron flow for allowing penetration of the path of electron how by the magnetic field.
  • a traveling wave tube means forming a path of electron flow, a wave circuit for propagating a slow wave for interaction with the electron flow, a wave guide connected to the upstream end of the wave circuit having a pair of permeable opposite walls, magnetic means for establishing a magnetic field along the path of flow between the pair of walls, a successsion of identical solenoids disposed along and surrounding successive regions of the path of electron flow at equal distances, adjacent solenoids being in field opposing relation, and a succession of identical permeable members, each enclosing a different solenoid and having an annular aperture adja- 10 cent the path of electron flow for allowing penetration of the path of electron flow by the magnetic field.
  • an electron source and collector electrode defining therebetween a path of electron fiow, an interaction circuit for propagating a slow electromagnetic wave in field coupling relation with said electron flow, a succession of identical solenoids disposed along and surrounding the electron path at equal distances, adjacent solenoids being in field opposing relation, and a succession of annular shielding means enclosing the succession of solenoids, said shielding means comprising annular metallic members having high permeability resulting in low magnetic reluctance paths, each shielding means being apertured through its center and thereby aligned coaxially and positioned uniformly along and adjacent the axis of the tube envelope, the side of said shielding means adjacent the path of electron flow having an opening defining a succession of equal spaced gaps along the axis of electron flow.
  • a traveling wave tube comprising an envelope, an electron source and collector electrode at opposite ends of said envelope and defining therebetween a path of electron flow, on interaction circuit for propagating a slow electromagnetic wave in field coupling relation with said electron flow, a succession of identical solenoids disposed along and surrounding the electron path at equal distances, adjacent solenoids being in field opposing relation, and magnetic shielding means encompassing said solenoids except for a succession of gaps along the path of said electron flow, said gaps being of equal lengths, the distances between adjacent gaps being equal, and one gap being associated with each of said solenoids.
  • a traveling wave tube comprising an evacuated envelope, means for forming a cylindrical beam of electrons for flow axially through said envelope, an interaction circuit for propagating a slow electromagnetic wave in field coupling relation with said beam, and means for maintaining the electron beam cylindrical and of substantially uniform diameter during its progression past said interaction circuit, said means comprising a succession of identical pole pieces spaced equal distances apart along the path of said flow, and a plurality of substantially identical magnet means interposed between adjacent pole pieces, each of said pole pieces being common to like poles of two adjacent magnet means and each adjacent pair of said pole pieces defining a gap of the same length as the other of said gaps, whereby said pole pieces and magnet means provide a longitudinal region of periodic spatially alternating magnetic field along the axis of the electron beam.

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  • Microwave Tubes (AREA)
US351984A 1953-04-29 1953-04-29 Electron beam systems Expired - Lifetime US2841739A (en)

Priority Applications (12)

Application Number Priority Date Filing Date Title
DENDAT1071237D DE1071237B (es) 1953-04-29
BE528454D BE528454A (es) 1953-04-29
NL95352D NL95352C (es) 1953-04-29
US25189D USRE25189E (en) 1953-04-29 cioffi
US351983A US2847607A (en) 1953-04-29 1953-04-29 Magnetic focusing system
US351977A US2844754A (en) 1953-04-29 1953-04-29 Electron beam focusing system
US351874A US2855537A (en) 1953-04-29 1953-04-29 Electron beam focusing
US351984A US2841739A (en) 1953-04-29 1953-04-29 Electron beam systems
FR1099234D FR1099234A (fr) 1953-04-29 1954-03-23 Concentration d'un faisceau d'électrons
DEW25876A DE1127498B (de) 1953-04-29 1954-03-29 Fokussierungseinrichtung zur gebuendelten Fuehrung des Elektronenhohlstrahls einer langgestreckten Laufzeitroehre, insbesondere Wanderfeldroehre
GB12311/54A GB757369A (en) 1953-04-29 1954-04-28 Improvements in or relating to electron beam focusing systems
CH342662D CH342662A (fr) 1953-04-29 1954-04-29 Dispositif de focalisation d'un faisceau d'électrons

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US351984A US2841739A (en) 1953-04-29 1953-04-29 Electron beam systems

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US351984A Expired - Lifetime US2841739A (en) 1953-04-29 1953-04-29 Electron beam systems

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CH (1) CH342662A (es)
DE (2) DE1127498B (es)
FR (1) FR1099234A (es)
GB (1) GB757369A (es)
NL (1) NL95352C (es)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2925508A (en) * 1955-07-28 1960-02-16 Sperry Rand Corp Electron beam focusing structure
US2939995A (en) * 1958-05-19 1960-06-07 Bell Telephone Labor Inc Traveling wave tube
US2945153A (en) * 1956-08-31 1960-07-12 Rca Corp Electron beam tube
US2965782A (en) * 1958-03-12 1960-12-20 English Electric Valve Co Ltd Magnetic focusing systems for travelling wave tubes
US2966609A (en) * 1957-11-22 1960-12-27 Gen Electric Magnetic structures for high frequency energy interchange apparatus
US2991391A (en) * 1957-07-24 1961-07-04 Varian Associates Electron beam discharge apparatus
DE2738644A1 (de) * 1976-08-27 1978-03-02 Thomson Csf Kopplungsvorrichtung fuer eine hoechstfrequenzroehre
EP3163596A4 (en) * 2014-06-30 2018-03-14 Nec Network And Sensor Systems, Ltd. Traveling wave tube and high-frequency circuit system
WO2022104168A3 (en) * 2020-11-15 2022-06-23 Elve Inc. Magneto-electrostatic sensing, focusing, and steering of electron beams in vacuum electron devices

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL99653C (es) * 1956-03-01
DE1276217B (de) * 1958-06-25 1968-08-29 Siemens Ag Elektronenstrahlroehre mit Geschwindigkeitsmodulation, insbesondere Lauffeldroehre
NL277862A (es) * 1961-05-02
US3265925A (en) * 1962-07-03 1966-08-09 Bell Telephone Labor Inc Field perturbing means for preventing beam scalloping in reversed field focusing system
GB2152742B (en) * 1980-04-28 1986-02-19 Emi Varian Ltd Microwave amplifiers and oscillators
GB2152741B (en) * 1980-04-28 1986-02-12 Emi Varian Ltd Producing an electron beam
US5332948A (en) * 1992-05-13 1994-07-26 Litton Systems, Inc. X-z geometry periodic permanent magnet focusing system

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2200039A (en) * 1937-11-01 1940-05-07 Emi Ltd Permanent magnet device for producing axially symmetrical magnetic fields
US2300052A (en) * 1940-05-04 1942-10-27 Rca Corp Electron discharge device system
US2305884A (en) * 1940-07-13 1942-12-22 Int Standard Electric Corp Electron beam concentrating system
US2306875A (en) * 1940-02-06 1942-12-29 Int Standard Electric Corp Electron discharge apparatus
US2741718A (en) * 1953-03-10 1956-04-10 Sperry Rand Corp High frequency apparatus

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR956343A (es) * 1947-10-31 1950-01-31

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2200039A (en) * 1937-11-01 1940-05-07 Emi Ltd Permanent magnet device for producing axially symmetrical magnetic fields
US2306875A (en) * 1940-02-06 1942-12-29 Int Standard Electric Corp Electron discharge apparatus
US2300052A (en) * 1940-05-04 1942-10-27 Rca Corp Electron discharge device system
US2305884A (en) * 1940-07-13 1942-12-22 Int Standard Electric Corp Electron beam concentrating system
US2741718A (en) * 1953-03-10 1956-04-10 Sperry Rand Corp High frequency apparatus

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2925508A (en) * 1955-07-28 1960-02-16 Sperry Rand Corp Electron beam focusing structure
US2945153A (en) * 1956-08-31 1960-07-12 Rca Corp Electron beam tube
US2991391A (en) * 1957-07-24 1961-07-04 Varian Associates Electron beam discharge apparatus
US2966609A (en) * 1957-11-22 1960-12-27 Gen Electric Magnetic structures for high frequency energy interchange apparatus
US2965782A (en) * 1958-03-12 1960-12-20 English Electric Valve Co Ltd Magnetic focusing systems for travelling wave tubes
US2939995A (en) * 1958-05-19 1960-06-07 Bell Telephone Labor Inc Traveling wave tube
DE2738644A1 (de) * 1976-08-27 1978-03-02 Thomson Csf Kopplungsvorrichtung fuer eine hoechstfrequenzroehre
EP3163596A4 (en) * 2014-06-30 2018-03-14 Nec Network And Sensor Systems, Ltd. Traveling wave tube and high-frequency circuit system
US10068738B2 (en) 2014-06-30 2018-09-04 Nec Network And Sensor Systems, Ltd. Traveling wave tube and high-frequency circuit system
WO2022104168A3 (en) * 2020-11-15 2022-06-23 Elve Inc. Magneto-electrostatic sensing, focusing, and steering of electron beams in vacuum electron devices
US11894208B2 (en) 2020-11-15 2024-02-06 Elve Inc. Multi-layer vacuum electron device and method of manufacture
US11961693B2 (en) 2020-11-15 2024-04-16 Elve Inc. Magneto-electrostatic sensing, focusing, and steering of electron beams in vacuum electron devices

Also Published As

Publication number Publication date
FR1099234A (fr) 1955-08-31
USRE25189E (en) 1962-06-19
GB757369A (en) 1956-09-19
DE1071237B (es)
BE528454A (es)
NL95352C (es)
CH342662A (fr) 1959-11-30
DE1127498B (de) 1962-04-12

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