EP0215832B1 - Elektromagnet mit grosser magnetfeldhomogenität - Google Patents

Elektromagnet mit grosser magnetfeldhomogenität Download PDF

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Publication number
EP0215832B1
EP0215832B1 EP86901415A EP86901415A EP0215832B1 EP 0215832 B1 EP0215832 B1 EP 0215832B1 EP 86901415 A EP86901415 A EP 86901415A EP 86901415 A EP86901415 A EP 86901415A EP 0215832 B1 EP0215832 B1 EP 0215832B1
Authority
EP
European Patent Office
Prior art keywords
coils
rods
current
coil
magnet coil
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP86901415A
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English (en)
French (fr)
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EP0215832A1 (de
Inventor
Guy Aubert
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General Electric CGR SA
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General Electric CGR SA
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Publication date
Application filed by General Electric CGR SA filed Critical General Electric CGR SA
Publication of EP0215832A1 publication Critical patent/EP0215832A1/de
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Publication of EP0215832B1 publication Critical patent/EP0215832B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/06—Electromagnets; Actuators including electromagnets
    • H01F7/20—Electromagnets; Actuators including electromagnets without armatures
    • H01F7/202—Electromagnets for high magnetic field strength

Definitions

  • the invention generally relates to a solenoidal magnet with high homogeneity of magnetic field, consisting of several coils spaced from each other; more particularly, it relates to a connection structure between the coils, making it possible to avoid the creation of components of stray fields.
  • NMR imaging installations require a large magnet capable of generating a uniform magnetic field in a determined region of space. Typically, it is necessary to generate a magnetic field of 0.15 to 0.5 teslas with a homogeneity of 1 to 10 parts per million (ppm) in a sphere of at least 40 cm in diameter.
  • the invention relates to a solenoid magnet with high homogeneity of magnetic field, consisting of a set of coils of the same inside and outside diameter of a coil with respect to the others, spaced apart from each other by distances chosen along of a common axis, said coils being connected in series, characterized in that each coil is connected to the neighboring coil by two groups of conductors symmetrical with respect to a plane passing through said axis and by the connection points of said neighboring coils, so that the current components in said groups of conductors, create ampere-turns in opposition, at any point in the space between said coils, such that the magnetic field components generated by these components and current cancel each other out.
  • each of the two aforementioned groups of conductors is embodied by one or more circular conductive rings, each group thus comprising the parts of rings situated on either side of the aforementioned plane.
  • This or (preferably) these rings are arranged substantially transversely to said axis while being slightly deformed to define, each, two substantially helical and opposite half-turns.
  • this or these rings are connected to the connection points of said coils on the one hand and / or between them on the other hand, by successively diametrically opposite junctions. In other words, if a single ring is used (case of a relatively small spacing between two adjacent coils), this is connected to the two connection points of the two adjacent coils at diametrically opposite points.
  • the first ring is connected to a coil end at a first connection point and to an adjacent ring at a second diametrically connection point opposite and so on until the connection of the last ring with the end of the other coil.
  • Bitter coils are well known for the production of strong magnetic fields.
  • the structure proposed by Bitter is a coil made up of metallic annular discs (generally made of copper or aluminum), split to form as many turns and connected to define a substantially helical winding with flat turns.
  • the stack of discs is maintained by a plurality of tie rods.
  • This structure is advantageous because it allows efficient cooling of the magnet, by making holes in the discs (and in the insulators separating these discs), these holes being arranged in the same configuration from one disc to another to materialize.
  • a set of channels parallel to the axis of the coil in which circulates a cooling fluid, for example deionized water, kerosene or oil.
  • the invention preferably applies to a magnet constructed from such Bitter coils insofar as, in particular, at least some of the above-mentioned tie rods can be used to produce the current return conductors, distributing this current over a surface substantially cylindrical and coaxial with the coils, as indicated above.
  • a solenoid magnet 11 with annular discs of Bitter known per se, consisting of seven coils 13a, 14a, 15a, 16, 13b, 14b, 15b aligned along the same main axis of symmetry z'z.
  • NMR imaging it is possible to obtain a magnetic field of required homogeneity in a sphere of interest of sufficient volume whose center 0 is coincident with that of the magnet, by choosing the lengths of the coils and the spacings between these coils.
  • the magnet is symmetrical with respect to a transverse plane passing through O.
  • a possible method of calculating the characteristics of the coils of the magnet and the spacings between these coils is indicated in document WO 86/03882 published on 03.07. 86, filed by the Applicant, and is not part of the invention presently described.
  • the term “Bitter coil” is understood to mean any coil meeting the definition recalled above.
  • the radially split discs constituting the turns are connected, for example welded, end to end and held in a tight stack by means of a plurality of tie rods 18a or 18b regularly distributed over a cylindrical surface of axis z ' z. All the coils are connected in series.
  • the current source not shown, is for example connected to the external end of the coil 13a.
  • the tie rods 18a are in several sections specific to each coil; they do not extend into the spaces defined between them.
  • the tie rods 18b extend over the entire length of the magnet and are therefore common to all the coils.
  • This plate is also in electrical contact with the tie rods 18b so that this arrangement defines a sort of squirrel cage connected in series as a whole with the coils of the magnet, the tie rods 18b being traversed by substantially equal fractions of the current. total crossing the coils.
  • the tie rods of the Bitter coils it is not essential to use the tie rods of the Bitter coils to compensate for the axial component of the current. If this compensation is sought, a simple cylindrical tubular casing external to the coils and coaxial can be used to ensure the return of current.
  • One can also use a "squirrel cage" defined from other conductive rods than the tie rods.
  • each group of conductors mentioned above consists of the halves of two circular conductive rings 28, 29 situated respectively by the same side of the plane P.
  • each ring 28 or 29 consists of several (for example two) concentric circular conductors 30 and 31 fixed by any suitable means to connecting pieces 35, 36, 37.
  • the ring 28 is fixed at the end 25 of the coil 15b by a metallic connecting piece 35.
  • the ring 29 is fixed to the end 26 of the coil 14b by a similar metallic connecting piece 36.
  • the rings 28 and 29 are connected to each other by a metallic connecting piece 37 diametrically opposite to the pieces 35 and 36.
  • Two tie rods 18a located in the plane P and belonging respectively to the two coils to be connected are used to fix the connecting pieces 35 and 36 at the ends of these coils (mounting holes 40).
  • one of the tie rods 18b provided with its spacer crosses the connecting piece 37 (hole 41).
  • the other tie rods 18b pass between the two concentric conductors 30 and 31 of each ring. These are of rectangular section and are fixed by screws and / or welded to the various connection pieces (see Figures 2 and 3).
  • the conductive rings 28 and 29 are arranged substantially transversely to the axis while being slightly deformed longitudinally to each define two approximately helical half-turns and opposite, symmetrical with respect to the plane P. Consequently, at the output of the coil 15b considered, the current is also shared in the two half-turns and the current components flowing in the two half-turns of the same ring create amperes- towers in opposition, this at any point in the space between coils. Substantially no axial magnetic field is therefore generated by the connection system between the coils. Furthermore, as mentioned previously, the axial current component, however small it may be, can be fairly precisely compensated by the current return tie rods.
  • the magnet coils are actually Bitter coils
  • the number of rings used in a given space between two coils will depend on the length of this space.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Claims (8)

1. Solenoidförmiger Magnet mit großer Magnetfeldhomogenität, der aus einem Satz von Spulen (13a, 13b, 14a, 14b, 15a, 15b, 16) gebildet ist, wobei jede Spule in bezug auf die anderen den gleichen Innen- und Außendurchmesser aufweist, wobei sich die Spulen entlang einer gemeinsamen Achse (z, z') voneinander in ausgewählten Abständen befinden und wobei die Spulen in Reihe geschaltet sind, dadurch gekennzeichnet, daß jede Spule mit der benachbarten Spule durch zwei Gruppen (gi, g2) von Leitern verbunden ist, die in bezug auf eine durch die Achse (z, z') und durch die Verbindungspunkte der benachbarten Spulen verlaufende Ebene (P) symmetrisch sind, derart, daß die Stromkomponenten in den Gruppen (gi, g2) von Leitern in jedem Raumpukt zwischen diesen Spulen entgegengesetzte Amperewindungen erzeugen, so daß sich die durch diese Stromkomponenten erzeugten Magnetfeldkomponenten gegenseitig aufheben.
2. Solenoidförmiger Magnet gemäß Anspruch 1, dadurch gekennzeichnet, daß jede der zwei oben erwähnten Gruppen (g1' g2) von Leitern von einem oder mehreren kreisförmigen Leiterringen (28, 29) gebildet wird, die genau transversal zur Achse (z, z') angeordnet sind und dabei leicht verformt sind, um dadurch jeweils zwei entgegengesetzte und genau spiralförmige Halbwindungen zu definieren, und daß diese Ringe einerseits mit den Verbindungspunkten der Spulen und/ oder andererseits miteinander durch nacheinander diametral entgegengesetzte Verbindungsstellen (35, 36, 37) verbunden sind, wobei jede Gruppe (g1' g2) auf diese Weise diejenigen Teile des Rings enthält, die auf derselben Seite der Ebene (P) angeordnet sind.
3. Solenoidförmiger Magnet gemäß Anspruch 1 oder 2, gekennzeichnet durch wenigstens einen Rückstromleiter, der so gestaltet und/oder angeordnet ist, daß er den abfließenden Rückstrom wenigstens in jedem Raum zwischen zwei Spulen völlig regelmäßig auf einer zylindrischen, zur Achse (z, z') koaxialen Oberfläche verteilt.
4. Solenoidförmiger Magnet gemäß Anspruch 3, dadurch gekennzeichnet, daß er eine Mehrzahl von longitudinalen Stiften (18b) umfaßt, die auf der zylindrischen Oberfläche regelmäßig verteilt sind, und daß die Stifte (18b) untereinander derart verbunden sind, daß sie eine Art Käfigwicklung definieren, wobei dieser Käfig in seiner Gesamtheit mit den Spulen in Reihe geschaltet ist, derart, daß die Stifte (18b) über genau gleiche Anteile den die Spulen durchfließenden Gesamtstrom führen.
5. Solenoidförmiger Magnet gemäß Anspruch 4, dadurch gekennzeichnet, daß die Spulen Bitter-Spulen sind, die durch Schichtungen von ringförmigen, leitenden Scheiben, zwischen die ein Isolator eingebracht ist, gebildet werden, wobei jede Scheibe einen eine Spiralenwindung ausbildenden Schlitz und außerdem Stäbe (18a) aufweist, die die Schichtungen der Scheiben zusammenhalten, und daß die Stifte (18b) von allen Spulen gemeinsamen Stäben gebildet werden.
6. Solenoidförmiger Magnet gemäß Anspruch 5, dadurch gekennzeichnet, daß die die Stifte bildenden Stäbe (18b) in den oben erwähnten Räumen zwischen benachbarten Spulen von Abstandstücke bildenden starren, isolierten Röhren (20) umgeben sind, wobei die Längen dieser Abstandsstücke die gewünschten Zwischenräume zwischen den Spulen bestimmen.
7. Solenoidförmiger Magnet gemäß einem der Ansprüche 2 bis 6, dadurch gekennzeichnet, daß jeder der oben erwähnten Ringleiter (28, 29) aus einer Mehrzahl von kreisföromigen, konzentrischen Leitern (30, 31) zusammengesetzt ist.
8. Solenoidförmiger Magnet gemäß den Ansprüchen 5 und 7, dadurch gekennzeichnet, daß die oben erwähnten, zwei benachbarte Spulen verbindenden Leiterringe von ringförmigen Bitter-Scheiben gebildet werden, die nicht wie die Scheiben der Spulen geschlitzt sind.
EP86901415A 1985-03-19 1986-02-21 Elektromagnet mit grosser magnetfeldhomogenität Expired - Lifetime EP0215832B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8504050A FR2579362B1 (fr) 1985-03-19 1985-03-19 Aimant solenoidal a haute homogeneite de champ magnetique
FR8504050 1985-03-19

Publications (2)

Publication Number Publication Date
EP0215832A1 EP0215832A1 (de) 1987-04-01
EP0215832B1 true EP0215832B1 (de) 1990-10-17

Family

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Family Applications (1)

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EP86901415A Expired - Lifetime EP0215832B1 (de) 1985-03-19 1986-02-21 Elektromagnet mit grosser magnetfeldhomogenität

Country Status (5)

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US (1) US4774487A (de)
EP (1) EP0215832B1 (de)
DE (1) DE3674973D1 (de)
FR (1) FR2579362B1 (de)
WO (1) WO1986005624A1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0245902A (ja) * 1988-08-08 1990-02-15 Kanazawa Univ 交流強磁場用成層渦電流型コイル
US6876288B2 (en) * 2002-03-29 2005-04-05 Andrey V. Gavrilin Transverse field bitter-type magnet
US7609139B2 (en) * 2006-03-10 2009-10-27 Florida State University Research Foundation Split Florida-helix magnet
FI126486B (fi) * 2010-09-23 2017-01-13 Valmet Automation Oy Sähkömagneetti matalakenttäisiin ydinmagneettiresonanssimittauksiin ja menetelmä sen valmistamiseksi
EP2742860B1 (de) * 2011-08-09 2016-05-25 Hitachi Metals, Ltd. Spulenvorrichtung und gerät für die magnetresonanzbildgebung

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986003882A1 (fr) * 1984-12-14 1986-07-03 Thomson-Cgr Aimant solenoidal a champ magnetique homogene

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3227930A (en) * 1963-02-25 1966-01-04 Nat Res Corp Superconducting magnet with planar windings oriented transversely to the magnetic field
DE1290248B (de) * 1964-05-15 1969-03-06 Licentia Gmbh Aus zwei in konzentrischen Lagen uebereinandergewickelten und parallelgeschalteten Spulen aus Flachdraht bestehende Roehrenwicklung fuer Transformatoren und Drosselspulen

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986003882A1 (fr) * 1984-12-14 1986-07-03 Thomson-Cgr Aimant solenoidal a champ magnetique homogene

Also Published As

Publication number Publication date
FR2579362B1 (fr) 1987-05-15
DE3674973D1 (de) 1990-11-22
US4774487A (en) 1988-09-27
EP0215832A1 (de) 1987-04-01
FR2579362A1 (fr) 1986-09-26
WO1986005624A1 (fr) 1986-09-25

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