EP0221920B1 - Elektromagnet mit hoher homogenität des magnetfeldes - Google Patents

Elektromagnet mit hoher homogenität des magnetfeldes Download PDF

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Publication number
EP0221920B1
EP0221920B1 EP86902431A EP86902431A EP0221920B1 EP 0221920 B1 EP0221920 B1 EP 0221920B1 EP 86902431 A EP86902431 A EP 86902431A EP 86902431 A EP86902431 A EP 86902431A EP 0221920 B1 EP0221920 B1 EP 0221920B1
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EP
European Patent Office
Prior art keywords
coils
conductors
coil
magnet
current
Prior art date
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Expired - Lifetime
Application number
EP86902431A
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English (en)
French (fr)
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EP0221920A1 (de
Inventor
Guy Aubert
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General Electric CGR SA
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General Electric CGR SA
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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 due to the collaboration of the National Service of the Intensive Fields of the CNRS (Director M. AUBERT) relates to a solenoid 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, that is to say from 1 to 10 ppm, comprising several coils having the same inside and outside diameters, arranged along a longitudinal axis. common, and spaced from each other symmetrically with respect to a median transverse plane of an area of interest or must reign the magnetic field, said coils being electrically interconnected in series, characterized in that said coils are interconnected in series, for current flow in a first forward direction, by first conductors disposed parallel to said axis and extending respect i vely in the spaces between said coils, in that the second conductors, used in part to the current flow in a second return direction, are arranged longitudinally in the vicinity of said first conductor, also in the spaces e ntre said coils, and in that these second conductors are connected by distribution rings to third conductors shaped and / or arranged at the location of each coil, all around each coil, substantially parallel to said axis, to distribute the current current
  • the coils constituting the magnet described above are preferably Bitter coils.
  • Bitter coils are well known for the production of strong magnetic fields.
  • the structure proposed by Bitter is a winding made up of metallic annular discs (generally copper or aluminum), split to form as many turns and connected to define a substantially hecoidal 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.
  • 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 aforementioned tie rods can be used to make the aforementioned third conductors, distributing the return current over a surface substantially cylindrical and coaxial with the coils, in the sections of the magnet occupied by the latter.
  • the ends of the tie rods can be electrically connected by placing at each axial end of each coil, an open crown, that is to say having a radial slot through which the connection point between said first corresponding conductor and said coil.
  • the crown is of course isolated from the coil and a pair of aforementioned second conductors is arranged on either side of said first conductor, each second conductor being connected to one end of said crown.
  • a part of a solenoid magnet 11 with annular Bitter discs consisting of several coils aligned along the same main axis of symmetry z'z. More specifically, the two coils 14 and 15 are shown closest to an axial end of the magnet opposite to that where the means for connection to a DC power source are arranged, not shown.
  • NMR imaging it is possible to obtain a magnetic field of required homogeneity in a sphere of interest of sufficient volume whose center is coincident with that of the magnet, from a set of seven coils for example, by choosing the lengths of these coils and the spacings between these coils.
  • a possible method of calculating the characteristics of the coils of the magnet and the spacings between these coils is indicated in another French patent application FR-A-2,574,980 filed by the Applicant and this method of calculation is not part of the present invention 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 18 regularly distributed over a cylindrical surface of axis z'z. All the coils are connected in series.
  • the tie rods 18 are specific to each coil; they do not extend into the spaces defined between them, they are of course electrically isolated from the Bitter discs that they maintain.
  • the tie rods or some of them are also used to bring the current back to the current source, that is to say towards the axial end of the magnet which is not shown.
  • a current distribution plate 19 (not split) is located at the outer end of the coil 15 and welded to the last turn thereof to ensure a substantially uniform distribution of the flow of return current between the tie rods, which are in electrical contact with said distribution plate.
  • the tie rods of each coil are connected to each other at the two ends of this coil so as to define a sort of squirrel cage. The interconnection of the tie rods will be described later.
  • the tie rods are traversed by substantially equal fractions of the return current. They thus compensate for the small axial component of current due to the helical pitch of the winding defined by the Bitter discs, in the corresponding coil.
  • 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 flowing in this coil.
  • the coils are connected in series by first conductors such as 20 extending respectively in the spaces between neighboring coils while second conductors 21, participating in the return of the current, are arranged longitudinally in the vicinity of said first conductors, to surround them at least partially.
  • first conductors such as 20 extending respectively in the spaces between neighboring coils while second conductors 21, participating in the return of the current, are arranged longitudinally in the vicinity of said first conductors, to surround them at least partially.
  • each conductor 20, 21 has a rectangular section and two conductors 21, isolated from the conductor 20, are joined along two parallel faces of the latter. All of the current passing through the coils therefore flows in each conductor 20 while the reverse current flowing in the opposite direction is shared more or less equally in the two conductors 21.
  • the connection structure between two coils which has just been described does not create stray field in the space between the two coils considered.
  • the continuity of the current return circuit is ensured by third conductors interconnected between the second conductors, these third conductors being nothing other than, in the example described, the groups of tie rods 18 associated with the different coils or at least some of these tie rods regularly spaced from each other.
  • the second conductors 21 and the tie rods 18 are connected in series as a whole with the coils themselves in series, via the distribution plate 19.
  • the connections between said second conductors and the groups of tie rods are ensured by crowns open 22 disposed at the axial ends of the coils and with which the tie rods 18 on the one hand and the ends of the conductors 21 on the other hand are interconnected.
  • each ring isolated from the coil at the end of which it is fixed using tie rods, comprises a slot 23 in which is located the connection point between the first conductor 20 and the end of the coil corresponding while the ends 24 of the crown materialized by the slot 23, are connected to the ends of the two corresponding conductors 21.
  • the tie rods of each coil pass through the corresponding crowns 22 (a crown and the plate 19 with regard to the coil 15) and are tightened by means of nuts between said crowns, which ensures correct electrical contact between these crowns. and these tie rods.
  • each coil has an odd number of half-turns so that, on either side of the same coil, the arrangements of conductors 20, 21 are opposite with respect to the axis z'z.
  • the tie rods 18 are more or less “distant” from the connection points of the conductors 21 to the ring 22 and this distance depends on the position of the tie rod considered relative to the slot 23. This could result in differences in intensity between the currents flowing in the tie rods, due to the more or less long portion of crown 22 placed in series with each of them.

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

Claims (5)

1. Elektromagnet mit hoher Homogenität des Magnetfeldes, das heißt von 1 bis 10 ppm, mit mehreren Spulen (14, 15), die jeweils denselben Innen- und Außendurchmesser aufweisen und längs einer gemeinsamen Längsachse (z, z') angeordnet und voneinander symmetrisch im Verhältnis zu einer mittleren Querebene einer Interessenzone auseinanderliegen, in der das Magnetfeld herrschen soll, wobei diese Spulen elektrisch seriengeschaltet sind, dadurch gekennzeichnet, daß diese Spulen für den Stromdurchgang in einer ersten Zuflußrichtung durch erste Leiter (20) seriengeschaltet sind, die parallel zu dieser Achse (z, z') angeordnet sind und sich jeweils in den Leerräumen zwischen diesen Spulen erstrecken, dadurch, daß zweite Leiter (21), die teilweise für den Stromdurchgang in einer zweiten Rückflußrichtung verwendet werden, in der Nachbarschaft dieser ersten Leiter (20) ebenfalls in den Leerräumen zwischen diesen Spulen längs angeordnet sind, und dadurch, daß diese zweiten Leiter (21) durch Verteilungskränze (22) an dritte Leiter (18) angeschlossen sind, die an jeder Spulenstelle ganz um jede Spule herum und etwa -parallel zu dieser Achse gebildet und/oder angeordnet sind, um den Rückstrom zu verteilen und darauf hinzuzielen, daß die Dichte dieses Rückstroms etwa gleichmäßig auf einer zu dieser Achse koaxialen zylindrischen Fläche ist, wobei einige dieser um eine Endspule des Magnets herum gelegenen dritten Leiter (18) mit dieser Endspule durch ein Verteilungsplateau (19) seriengeschaltet sind, um die Stromrückkehr zum anderen axialen Ende dieses Magnets hin zu sichern.
2. Elektromagnet nach Anspruch 1 des Typs, in dem die vorgenannten Spulen mit Scheiben versehene Bitter-Spulen sind, dadurch gekennzeichnet, daß diese Scheiben jeder Spule auf an sich bekannte Weise durch von dieser isolierte und regelmäßig über eine koaxiale zylindrische Fläche verteilte Zuganker (18) aufrechterhalten werden, und die dritten vorgenannten Leiter (18) von zumindest einigen dieser regelmäßig voneinander abstehenden Zuganker gebildet werden.
3. Elektromagnet nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß er in jedem Leerraum zwischen zwei benachbarten Spulen einen ersten vorgenannten Leiter (20) und zwei vorgenannte zweite Leiter (21) umfaßt, die aneinanderliegend symmetrisch entlang diesem ersten Leiter verlaufen.
4. Magnet nach der Gesamtheit der Ansprüche 2 und 3, dadurch gekennzeichnet, daß in der Nachbarschaft jeder Spule diese zweiten Leiter (21) mit den äußeren Enden eines offenen Kranzes (22) verbunden sind, und darin, daß der Anschlußpunkt zwischen diesem ersten Leiter (20) und der entsprechenden Spule in der Öffnung dieses Kranzes liegt und darin, daß jeder Kranz von der Spule, an deren Ende sie montiert ist, isoliert und mit den Zugankern (18) verbunden ist, welche die dritten vorgenannten Leiter bilden.
5. Elektromagnet nach einem der vorausgehenden Ansprüche, dadurch gekennzeichnet, daß jede Spule eine ungerade Anzahl von halben Windungen trägt.
EP86902431A 1985-05-10 1986-04-22 Elektromagnet mit hoher homogenität des magnetfeldes Expired - Lifetime EP0221920B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8507151 1985-05-10
FR8507151A FR2581760B1 (fr) 1985-05-10 1985-05-10 Aimant solenoidal a haute homogeneite de champ magnetique

Publications (2)

Publication Number Publication Date
EP0221920A1 EP0221920A1 (de) 1987-05-20
EP0221920B1 true EP0221920B1 (de) 1990-02-07

Family

ID=9319175

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86902431A Expired - Lifetime EP0221920B1 (de) 1985-05-10 1986-04-22 Elektromagnet mit hoher homogenität des magnetfeldes

Country Status (5)

Country Link
US (1) US4743879A (de)
EP (1) EP0221920B1 (de)
DE (1) DE3669009D1 (de)
FR (1) FR2581760B1 (de)
WO (1) WO1986006869A1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2621731B1 (fr) * 1987-10-09 1990-02-09 Thomson Cgr Bobine, aimant comprenant une telle bobine, dispositif d'imagerie par rmn comportant un tel aimant et procede de realisation d'un tel aimant
US6876288B2 (en) * 2002-03-29 2005-04-05 Andrey V. Gavrilin Transverse field bitter-type magnet
US20060127247A1 (en) * 2004-12-10 2006-06-15 Hamilton Sundstrand Corporation Magnetic pulse pump/compressor system

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3281737A (en) * 1963-09-26 1966-10-25 Gen Electric Superconductive solenoid
FR1491786A (fr) * 1966-09-05 1967-08-11 Advanced Kinetics Transformateurs d'impulsions permettant d'obtenir des impulsions de très forte intensité
JPS5844546B2 (ja) * 1981-03-10 1983-10-04 東京パ−ツ株式会社 ブラシ付蓋を有する粘性液用容器
JPS59232831A (ja) * 1983-06-16 1984-12-27 Idemitsu Petrochem Co Ltd 熱可塑性樹脂発泡体の製造方法

Also Published As

Publication number Publication date
EP0221920A1 (de) 1987-05-20
WO1986006869A1 (fr) 1986-11-20
DE3669009D1 (de) 1990-03-15
FR2581760B1 (fr) 1987-06-12
US4743879A (en) 1988-05-10
FR2581760A1 (fr) 1986-11-14

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