US3241007A

US3241007A - Permanent magnet system for focusing an electron beam

Info

Publication number: US3241007A
Application number: US331011A
Authority: US
Inventors: Eder Felix
Original assignee: Siemens AG
Current assignee: Siemens and Halske AG; Siemens AG
Priority date: 1962-12-21
Filing date: 1963-12-16
Publication date: 1966-03-15
Anticipated expiration: 1983-03-15
Also published as: NL300134A; GB989775A; DE1233070B

Description

F. EDER 3,241,007

PERMANENT MAGNET SYSTEM FOR FOCUSING AN ELECTRON BEAM March 15, 1966 Filed Dec. 16, 1963 United States Patent 3,241,007 PERMANENT MAGNET SYSTEM FOR FOCUSING AN ELEQTRON BEAM Felix Eder, Munich, Germany, assignor t0 Siemens &

Halske Aktiengesellschaft, Berlin and Munich, Germany, a corporation of Germany Filed Dec. 16, 1963, Ser. No. 331,011 Claims priority, application Germany, Dec. 21, 1962, S 83,006 5 Claims. (Cl. 317200) The invention disclosed herein is concerned with a permanent magnet system for the focused guiding of an electron beam, especially for traveling wave tubes, comprising permanent magnets arranged axially symmetrically with respect to the electron beam and having pole pieces of soft iron which are successively disposed in the direction of the electron beam and magnetically interconnect poles of the permanent magnets of identical polarity lying mutually oppositely in planes extending perpendicularly to the electron beam direction, the respective pole pieces having bores formed therein centrally thereof, for receiving the discharge vessel and being, in longitudinal section through the magnet system, of a width which is in the region of the respective bores less than at regions thereof which are disposed adjacent the magnets.

Permanent magnet systems of this general type, for producing a periodic directionally alternating magnetic field, are known. The pole pieces are made narrower in the region of the bore for receiving the discharge vessel than in the vicinity of the magnets so as to obtain from the magnets a magnetic flux as great as possible, such flux being determined by the cross section of the portions of the pole pieces which are arranged adjacent the magnets. These known pole pieces are produced by milling a forced blank and subsequently grinding it to its final shape. Such production entails great expenditure due to the required milling and grinding operations. Difficult and elaborate milling and grinding operations are particularly required in cases in which the pole pieces are to receive a discharge vessel having a diameter which exceeds the transverse dimension of the pole pieces in the vicinity of the magnets. In such a case, the forged blank must be machined so that the pole pieces are, as seen in the electron beam direction, centrally wider than in the vicinity of the magnets so as to enable provision, centrally of the pole pieces, of a correspondingly large bore for receiving the discharge vessel.

The present invention proposes to avoid the above indicated difiiculties occuring in connection with a permanent magnet system of the initially described type, by the provision of pole pieces made respectively from a flat cross-sectional rectangular strip of soft iron, such strip being twisted with respect to its central portion by 90 about its longitudinal axis, such that the central portion thereof, in which is formed the bore, is displaced by 90 with respect to the longitudinal plane of the untw-isted portions of the strip.

The advantage of the permanent magnet system according to the invention resides in that the pole pieces can be produced without resorting to milling and grinding operations. All that is necessary is to provide crosssectionally rectangular metal strips with a bore formed therein centrally thereof and to twist such a prefabricated strip twice. The twisting is effected by a simple forging operation.

The various details and features of the invention will appear from the appended claims and from the description of an embodiment thereof which is rendered below with reference to the accompanying drawing.

3,241,007 Patented Mar. 15, 1966 FIG. 1 shows a side View of a pole piece of the permanent magnet system according to the invention;

FIG. 2 represents the pole piece as seen from the front, that is, in the electron beam direction;

FIG. 3 illustrates the front view of a permanent magnet system according to the invention, for producing a periodic directionally alternating magnetic field; and

FIG. 4 shows the system in section taken along the lines A-B of FIG. 3.

Referring now to FIGS. 1 and 2, the pole piece 1 consists of a cr-oss-sect-ionally rectangular metallic strip of uniform thickness having a bore 2 formed therein centrally thereof, for receiving a discharge vessel, and being by a forging operation twisted about its longitudinal axis by with respect to its central portion. The width of the pole piece, along a longitudinal section through the magnet system, is by this construction narrower in the region of the bore 2 than in the outer portions thereof (FIG. 1) while having, as seen in the electron beam direction (FIG. 2), a central portion which is wider than the outer portions thereof. The outer portions 4 and 4' of the pole piece are in the illustrated example twisted in the same sense with respect to the central portion in which is formed the bore 2. However, the twisting may also be effected in opposite sense.

As seen from FIGS. 3 and 4, the magnets 5, 6, 7, 8 are arranged symmetrically to the axis of the electron beam, thus forming the sides of a square. Identical poles of the magnets, which are magnetized in circumferential direction of the square, coincide at the corners of the square. Accordingly, oppoistely disposed corners of the square have the same polarity. These corners are interconnected alternately in vertical and horizontal direction by pole pieces 1 and 1 made as shown in FIGS. 1 and 2. The pole pieces 1 and 1, respectively, which are successively in alignment, border directly one on the other adjacent the magnets. A soft iron ring 9 is provided in the respective bores 2 of the pole pieces 1 and 1, such ring serving for compensating disturbances in the rotation symmetry of the periodic magnetic field, which may be caused in the event that the twisted planes of the pole pieces 1 and 1' do not extend exactly perpendicularly with respect to an another.

The invention is not inherently limited to a permanent magnet system according to FIGS. 3 and 4. It is, for example, possible to use a pole piece such as shown in FIGS. 1 and 2 in connection with a permanent magnet system in which the magnetic field does not change its direction periodically.

Changes may be made Within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

I claim:

1. A permanent magnet system for the focused guiding of an electron beam, especially for travelling Wave tubes, comprising permanent magnets arranged axially symmetrically along the path of such an electron beam and having pole pieces of soft iron which are successively disposed in the direction of the electron beam path and magnetically interconnect magnetic faces of identical polarity disposed in planes extending in the direction of the electron beam path, the respective pole pieces having bores formed therein centrally thereof for receiving a discharge vessel and being, in longitudinal section through the magnet system, of a width which is in the region of the respective bores less than at regions thereof which are disposed adjacent the magnets, thereby characterized that each respective pole piece is formed of a fiat cross-sectional rectangular strip of soft iron having a bore formed in the central portion thereof, the outer portions of said strip which extend from said central portion being twisted by 90 with respect thereto so that the central portion in which is formed said bore is displaced by 90 with respect to the longitudinal planes of the respective outer portions.

2. A permanent magnet system according to claim 1, wherein the outer portions of said strip are twisted in identical sense with respect to said central portion.

3. A permanent magnet system according to claim 2, comprising a ring of soft iron which is inserted in said bore.

4. A permanent magnet system according to claim 3, wherein said permanent magnets are arranged so as to form in planes extending perpendicularly to the electron beam a quadratic square wherein poles of identical polarity are in circumferential direction mutually adjacently disposed, said pole pieces interconnecting alternately oppositely positioned corners of the square so References Cited by the Examiner UNITED STATES PATENTS 3,061,754 10/1962 Kajihara.

FOREIGN PATENTS 601,511 8/1934 Germany.

BERNARD A. GILHEANY, Primary Examiner.

LARAMIE E, ASKIN, Examiner.

Claims

1. A PERMANENT MAGNET SYSTEM FOR THE FOCUSED GUIDING OF AN ELECTRON BEAM, ESPECIALLY FOR TRAVELLING WAVE TUBES, COMPRISING PERMANENT MAGNETS ARRANGED AXIALLY SYMMETRICALLY ALONG THE PATH OF SUCH AN ELECTRON BEAM AND HAVING POLE PIECES OF SOFT IRON WHICH ARE SUCCESSIVELY DISPOSED IN THE DIRECTION OF THE ELECTRON BEAM PATH AND MAGNETICALLY INTERCONNECT MAGNETIC FACES OF IDENTICAL POLARITY DISPOSED IN PLANES EXTENDING IN THE DIRECTION OF THE ELECTRON BEAM PATH, THE RESPECTIVE POLE PIECES HAVING BORES FORMED THEREIN CENTRALLY THEREOF FOR RECEIVING A DISCHARGE VESSEL AND BEING, IN LONGITUDINAL SECTION THROUGH THE MAGNET SYSTEM, OF A WIDTH WHICH IS IN THE REGION OF THE RESPECTIVE BORES LESS THAN AT REGIONS THEREOF WHICH ARE DISPOSED ADJACENT THE MAGNETS, THEREBY CHARACTERIZED THAT EACH RESPECTIVE POLE PIECE IS FORMED OF A FLAT CROSS-SECTIONAL RECTANGULAR STRIP OF SOFT IRON HAVING A BORE FORMED IN THE CENTRAL PORTION THEREOF, THE OUTER PORTIONS OF SAID STRIP WHICH EXTEND FROM SAID CENTRAL PORTION BEING TWISTED BY 90* WITH RESPECT THERETO SO THAT THE CENTRAL PORTION IN WHICH IS FORMED SAID BORE IS DISPLACED BY 90* WITH RESPECT TO THE LONGITUDINAL PLANES OF THE RESPECTIVE OUTER PORTIONS.