JP6628407B2 - Low leakage shaking type open magnetic shield structure - Google Patents

Description

  The present invention relates to a low-leakage shaking type open magnetic shield structure, and more particularly to an open type magnetic shield structure that suppresses leakage of shaking noise while improving shielding performance by using magnetic shaking.

  Electron microscopes, EB exposure apparatuses, and EB steppers used in semiconductor manufacturing facilities, etc., apply electron beam application equipment such as an electron beam trajectory to change the trajectory of the electron beam even with a slight magnetic fluctuation. It is required to be installed in a magnetically shielded room (magnetically shielded space) controlled to 1 mG) or less. The conventional general magnetic shield space is made of a magnetic material with high magnetic permeability such as PC permalloy and has a structure that covers the entire floor, wall, and ceiling without any gap (closed magnetic shield structure). The number of parts has increased, and performance degradation due to the intrusion of a disturbance magnetic field from the joint has been a problem. On the other hand, as shown in FIG. 14, a magnetic shield structure (open magnetic shield structure) 5 using a band-shaped magnetic plate (strip-shaped magnetic plate) arranged in a cord or louver shape has been developed (Patent Document 1). 1).

  The open magnetic shield structure 5 is formed by stacking a plurality of band-shaped magnetic plates 2 having a width of, for example, about 50 mm at a required interval d in the thickness direction such that the central axes C in the longitudinal direction are arranged in parallel on the same plane F. 3 (see FIG. 14 (A)), and a plurality of shield magnetic members 3a, 3b, 3c, 3d are magnetically joined to each other by overlapping the corresponding joining portions 9 at the edges to form an annularly closed band-like magnetic plate ( A ring-shaped magnetic plate 10 is formed, and a space to be magnetically shielded is surrounded by a plurality of ring-shaped magnetic plates 10 (see FIG. 14B). By designing an appropriate distance d between the ring-shaped magnetic plates 10, a magnetic flux is applied to the ring-shaped magnetic plates 10 (magnetic circuit) while providing openness (transparency, light-transmitting properties, heat-radiating properties) to the space to be magnetically shielded. And the intrusion and leakage of magnetic flux from the distance d (deterioration in performance) can be reduced. In addition, since magnetic continuity is easily ensured at the joint portion 9, the structure has a structure in which performance deterioration is small and the desired performance is easily exhibited. Furthermore, the safety factor can be kept low, and the number of materials used can be reduced as compared with the conventional closed magnetic shield structure.

  In the open type magnetic shield structure 5, when the frequency of the disturbance magnetic field is increased, the magnetic shield performance may be deteriorated due to the eddy current flowing through the cross section of the annular magnetic plate 10, but the annular magnetic plate 10 (magnetic circuit) may have a copper plate or the like. By adding a ring-shaped conductor (conductor circuit) such as an aluminum plate and superimposing the conductor shielding effect, it is possible to exhibit a shielding performance equal to or higher than a DC magnetic field even in a disturbance magnetic field (AC magnetic field) up to about 200 Hz. (See Patent Document 2). That is, if a magnetic shield space is constructed by the open magnetic shield structure 5 composed of a ring-shaped magnetic plate or the open magnetic shield structure 5 to which a conductor circuit is added as required, environmental magnetic noise (disturbance magnetic field fluctuation) can be obtained. Can be efficiently shut down to 100 nT or less, and a magnetic environment (magnetic shield space) suitable for installing an electron beam application device or the like can be provided.

  On the other hand, the SQUID (Superconducting Quantum Interference Device) applied equipment used in medical facilities and research facilities requires an installation space of 1 nT or less to measure ultra-small magnetic fields such as magnetoencephalograms and magnetocardiograms generated by the activities of the brain and heart. It is required to control the magnetic environment. Magnetic shaking has been proposed as a means for obtaining such an ultra-high magnetic environment (see Patent Documents 3, 4 and Non-Patent Document 1). The magnetic shaking is a method of applying a periodically changing magnetic field (shaking magnetic field) to a magnetic body to fluctuate a magnetic flux inside the magnetic body to improve the magnetic properties (effective magnetic permeability) of the magnetic body. For example, Patent Document 3 discloses that a hermetically sealed magnetic shield structure is formed of a film (or ribbon) -like amorphous magnetic ribbon material having a thickness of 20 μm or more and 500 μm or less which can be manufactured at a relatively low cost, and has a performance similar to that of Permalloy by magnetic shaking. We report that we got.

  In magnetic shaking, in order to oscillate (shake) a magnetic flux inside a magnetic material, a shaking coil is wound almost perpendicularly around an axis in the direction of easy magnetization of the magnetic material, and a frequency f higher than a frequency component fn of environmental magnetic noise to be shielded is set. (Shaking current) is applied to generate a shaking magnetic field. For example, as shown in FIG. 15, a magnetic shield member 40 for a sealed magnetic shield disclosed in Patent Document 4 has eight ribbon-shaped amorphous magnetic ribbons 42a formed on a surface of a base material 41 in a longitudinal direction. Are arranged at predetermined intervals so that they are parallel to each other, and eight ribbon-like amorphous magnetic ribbons 42b are arranged at predetermined intervals on the surface so that their longitudinal directions are parallel in the horizontal direction. A shaking coil 43 is wound around a predetermined gap between the bands 42a and 42b so as to sew the front and back. In the illustrated example, the shaking coil 43 divides the space between the input terminal 44 and the output terminal 45 into 16 portions, and allows the odd-numbered portions to pass through the front surface and the even-numbered portions to pass through the back surface as shown in FIG. As a result, the magnetic ribbons 42a and 42b are wound substantially perpendicularly to any longitudinal direction.

International Publication No. 2004/084603 pamphlet JP 2014-086647 A JP-A-3-066839 JP 2013-197290 A JP 2006-135116 A

Small and Medium Enterprise Agency, “2012 Strategic Fundamental Technology Advancement Support Project“ Development of Heat Treatment Technology for Magnetic Materials for High-Performance Magnetic Shielding Equipment ”Research and Development Results Report,” March 2013, Internet <http: // www. chusho. meti. go. jp / keyie / sapoin / portal / seika / 2010/22131316088. pdf>

  However, the conventional magnetic shaking has a problem that an applied magnetic field (shaking magnetic field) for shaking the inside of the magnetic material leaks to the magnetic shield space. For example, in the magnetic shield member 40 shown in FIG. 15, the magnetic field outside the coil is canceled out in a portion where the shaking coil 43 is adjacent and parallel to both sides of the front and back surfaces, so that leakage to the magnetic shield space can be suppressed to some extent. In the peripheral portion where is located only on one side of the front or back surface, the magnetic field (shaking noise) outside the coil leaks into the magnetic shield space. Further, although it is desirable to uniformly shake the inside of the magnetic material in order to enhance the shaking effect, in the magnetic shield member 40 shown in FIG. 15, the magnetic thin strips 42a and 42b are respectively provided with the shaking magnetic field in the longitudinal direction and the other. Since the shaking magnetic field in a direction intersecting the longitudinal direction of the magnetic ribbons 42a and 42b is simultaneously applied, there is also a problem that the insides of the magnetic ribbons 42a and 42b are not evenly shaken.

  In order to prevent leakage of shaking noise, for example, Non-Patent Document 1 discloses a three-layer structure in which the inside of an amorphous layer around which a shaking coil is wound is covered with an aluminum layer, and the inside of the aluminum layer is further covered with an amorphous layer without magnetic shaking. Have proposed. However, shaking noise exceeding 10 nT has been measured in the vicinity of the inner wall of the magnetically shielded space even with such a three-layer structure. In addition, there is a problem that a noise countermeasure such as a three-layer structure leads to a rise in construction cost of a magnetic shield. In order to realize a magnetic shield space of 1 nT or less by magnetic shaking, it is necessary to uniformly shake the inside of the magnetic material and to reduce shaking noise.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a low leakage shaking type open magnetic shield structure capable of suppressing the leakage of shaking noise.

Referring to the embodiment of FIGS . 1 and 11 , a low-leakage shaking type open magnetic shield structure according to the present invention includes a plurality of parallel parallel shafts intersecting a first direction axis Az penetrating a magnetic shield target space 1 at a predetermined interval dz. An annular magnetic plate 10 (see FIGS. 1 (A) and 1 (B)) and an annular magnetic plate 10 provided on the respective flat surfaces Pz1, Pz2,. The wire coil unit 20 (see FIG. 1 (C) and FIG. 1 (C)) which is wound around a plurality of portions distributed in the direction of the annular axis of each of the stages and attached and wound in a direction substantially perpendicular to the annular axis and both ends 22a, 22b thereof are drawn out in parallel. (D) refer), binding wire 26 to a plurality of conductors coil units 20 in each stage connected sequentially in series in the annular axial ring band magnetic plate 10, flow reverse current in adjacent parallel placement to its binding wire 26 -Loop wire 27, and bond wires 26 and the coil driving device each conductor coil unit 20 via the loop conductor 27 applies a shaking current I1 having a predetermined frequency to the lead portions 22a, 22b connected in series and each coil of wire units 20 with 30, is made of a leakage magnetic field coupling conductor 26 and the loop conductor 27 out consumption and the reverse current with the ring band-like magnetic plate 10 by the generated magnetic field of each coil of wire units 20 to magnetic shaking.

  In a preferred embodiment, as shown in FIG. 1E, both ends 22a and 22b of each wire coil unit 20 are pulled out while twisting each other. In a more preferred embodiment, as shown in FIG. 10 (A), each conductive coil unit 20 is wound around each step of the ring-shaped magnetic plate 10 so as to form the same right-handed or left-handed winding. Shaking currents I1 and I2 in opposite directions are applied to adjacent stages of the strip-shaped magnetic plate 10. Alternatively, as shown in FIG. 10 (B), each conductive coil unit 20 is wound in a reverse right-handed or left-handed manner for each adjacent step of the ring-shaped magnetic plate 10, and the ring-shaped magnetic plate is The shaking current I1 in the same direction may be applied to each of the ten stages.

  In a preferred embodiment, the mutual interval T between the winding portions of the conductive coil unit 20 at each stage of the annular magnetic plate 10 is set such that the shaking magnetic field induced inside the annular magnetic plate 10 is uniform. it can.

The low-leakage shaking type open magnetic shield structure according to the present invention comprises a magnetic shield on a plurality of parallel planes Pz1, Pz2,... Which intersect with a first direction axis Az penetrating the magnetic shield target space 1 at a predetermined interval dz. A ring-shaped magnetic plate 10 is provided so as to surround the target space 1 with a predetermined band width W, and a plurality of portions of the ring-shaped magnetic plate 10 which are distributed in the direction of the circular axis at respective stages are substantially perpendicular to the circular axis. 20 is wound and attached, and both ends 22a and 22b thereof are pulled out in parallel and adjacent to each other. A plurality of wire coil units 20 of each stage of the annular magnetic plate 10 are connected in series in the direction of the annular axis by a connecting wire 26 in order. bond wires 26 and is adjacent arranged parallel loop conductor 27 to flow a reverse current, the lead portion of each lead coil unit 20 by the coil driver 30 2a, since canceling the reverse current leakage magnetic field coupling conductor 26 and the loop conductor 27 with the ring band-like magnetic plate 10 by the magnetic field generated by applying a shaking current I1 having a predetermined frequency to 22b magnetically shaking, the following Has an advantageous effect.

(A) A wire coil unit 20 is wound around each step of the annular magnetic plate 10 in a direction substantially perpendicular to the annular axis, and currents of the same magnitude and substantially opposite directions are annularly symmetric about the annular axis of the annular magnetic plate 10. , A uniform shaking magnetic field is generated along the axial direction inside the ring-shaped magnetic plate 10, and a leakage magnetic field (shaking noise) from the conductive coil unit 20 is generated due to the countercurrent effect of the reverse current flowing in a point-symmetric manner. Can be reduced.
(B) By generating a uniform shaking magnetic field along the ring axis inside the ring-shaped magnetic plate 10, the magnetic flux inside the magnetic body can be fluctuated evenly and the magnetic characteristics can be improved efficiently.
(C) In addition, by pulling out both ends 22a, 22b of the wire coil unit 20 wound around the ring-shaped magnetic plate 10 in parallel and adjacent to each other, the effect of canceling the reverse current flowing through the lead-out portions 22a, 22b causes the portions other than the wound portion. Leakage magnetic field (shaking noise) can be reduced.

(D) Further, by pulling out both ends 22a, 22b of the lead coil unit 20 while twisting each other, the effect of canceling the reverse current flowing through the lead portions 22a, 22b is enhanced, and the leakage magnetic field from the lead coil unit 20 is extremely small. Can be suppressed.
(E) In addition, the direction of the shaking current is reversed for each adjacent step of the annular magnetic plate 10 or the winding direction of the wire coil unit 20 is reversed, and the reverse direction leaks from the wire coil unit 20 of the adjacent step. By mutually canceling out the magnetic fields, the leakage magnetic field (shaking noise) can be further reduced.
(F) Evenly oscillating the magnetic flux inside the ring-shaped magnetic plate 10 to improve the magnetic properties efficiently and suppressing the magnetic field (shaking noise) leaking into the magnetic shield space to reduce the open magnetic shield structure. It can be expected that the shielding performance is surely and significantly improved, and the disturbance magnetic field fluctuation is controlled to 1 nT or less.

Hereinafter, embodiments and examples for carrying out the present invention will be described with reference to the accompanying drawings.
Explanatory drawing of an embodiment of a shaking type open magnetic shield structure according to the present invention in which a conductive coil unit 20 is wound around a plurality of portions of an annular belt-shaped magnetic plate 10 in each direction of an annular axis at respective stages in a direction substantially perpendicular to the annular axis. It is. FIG. 3 is an explanatory view of a shaking type open magnetic shield structure in which conductive coils 25 are attached to each stage of the ring-shaped magnetic plate 10 at predetermined pitches T independently of each other. FIG. 5 is an explanatory view of an embodiment of a shaking type open magnetic shield structure in which a conductive coil 25 is continuously wound at a predetermined pitch T on each stage of the annular magnetic plate 10. 4 is an experimental result showing a leakage magnetic field distribution in an evaluation target area R by a shaking current of the magnetic shield structure of FIG. 2. 4 is an experimental result showing a leakage magnetic field distribution in an evaluation target area R by a shaking current of the magnetic shield structure of FIG. 3. FIG. 4 is an explanatory view of a shaking type open magnetic shield structure in which conductive coils 25 are attached independently at a predetermined pitch T interval over a plurality of stages of the annular magnetic plate 10. 7 is an experimental result showing a leakage magnetic field distribution in an evaluation target area R by a shaking current of the magnetic shield structure of FIG. 6. It is explanatory drawing of the shaking type | formula open type magnetic shield structure which wound the conductive wire coil 25 continuously by the predetermined pitch T over the several steps of the ring-shaped magnetic plate 10. 9 is an experimental result showing a leakage magnetic field distribution in an evaluation target area R by a shaking current of the magnetic shield structure of FIG. FIG. 3 is an explanatory view of an embodiment of a shaking type open magnetic shield structure according to the present invention in which the direction of the shaking current is reversed for each adjacent stage of the ring-shaped magnetic plate 10 or the winding direction of the conductor coil unit 20 is reversed. . FIG. 3 is an explanatory view of an embodiment of a shaking type open magnetic shield structure according to the present invention in which conductive coil units 20 wound around a plurality of portions of each ring-shaped magnetic plate 10 are sequentially connected (connected) in series. It is explanatory drawing of the shaking type | formula open type magnetic shield structure 5x, 5y, 5z arrange | positioned in a nest shape. FIG. 13 is an explanatory diagram of a method of applying a shaking current to the shaking open magnetic shield structure 5z of FIG. It is explanatory drawing of the conventional open type magnetic shield structure. It is explanatory drawing of the magnetic shield member using the conventional shaking.

  FIG. 1 shows an embodiment of a shaking type open magnetic shield structure according to the present invention which is arranged around a magnetic shield target space 1 (for example, a magnetic shield room). The open magnetic shield structure 5z shown in FIG. 1A is arranged on a plurality of parallel planes Pz1, Pz2,... Which intersect at a predetermined interval dz with a first direction axis Az passing through the center point O of the space 1 to be magnetically shielded. A ring-shaped magnetic plate 10 surrounding each space with a predetermined band width W (for example, 50 mm) is arranged, and a plurality of ring-shaped magnetic plates 10 surround the magnetic shield target space 1 as in FIG. 14B. FIG. 1B shows an XY plan view including the annular magnetic plate 10 at any stage of the open type magnetic shield structure 5z. FIG. 1C shows an enlarged plan view and an enlarged side view of an elliptic C portion. (D) is shown. In the illustrated example, the first direction axis Az, which is the central axis of each ring-shaped magnetic plate 10, is a vertical axis (Z axis), but the direction axis Az can be appropriately selected according to the arrival direction of the external magnetic field. As shown in FIGS. 12B and 12C, the horizontal X-axis or the Y-axis passing through the target space 1 can be used. In the illustrated example, each plane Pz on which the ring-shaped magnetic plate 10 is provided is orthogonal to the first direction axis Az, but the intersection angle may be other than orthogonal.

  As shown in FIG. 14A, for example, the ring-shaped magnetic plate 10 has a band width W and an appropriate length along an intersecting line between a plane Pz intersecting the first direction axis Az and the inner surface of the target space. It is created by joining a plurality of strip-shaped conductor plates 2 into a flat polygonal shape (for example, a cross-girder shape) by overlapping edges. The ring-shaped magnetic plate 10 can be made of a magnetic material whose magnetic properties can be expected to be improved by magnetic shaking. For example, a cobalt-based or iron-based amorphous, permalloy, electromagnetic steel plate, or the like is used. Is desirably a cobalt-based amorphous material having a significantly higher magnetic permeability than others. In general, cobalt-based amorphous is provided as a thin strip magnetic plate having a width of about 50 mm at the maximum, and no wider material is provided. Therefore, in the closed magnetic shield structure, as shown in FIG. It takes time to form the magnetic shield surface by arranging the magnetic shield surface in the open magnetic shield structure. However, in the open magnetic shield structure, the annular magnetic plate 10 can be formed by using the thin magnetic plate as it is. be able to.

  As shown in FIGS. 1A and 1B, the magnetic shield structure of the illustrated example includes a conductive coil unit 20 wound around a plurality of portions of the annular magnetic plate 10 at each stage of the open magnetic shield structure 5z. It has a coil driving device 30 for applying a shaking current of a predetermined frequency to the conductor coil unit 20. The lead coil unit 20 is not continuously wound around the entire annular magnetic plate 10, but is dispersed and wound around a plurality of portions of the annular magnetic plate 10 separated in the annular axis direction. In order to improve the magnetic properties of the annular magnetic plate 10, it is effective to excite a uniform shaking magnetic field inside the annular magnetic plate 10, and it is necessary to continuously wind a conductor coil around the entire annular magnetic plate 10. Can generate a uniform shaking magnetic field, but it is difficult to keep the leakage magnetic field (shaking noise) outside the coil low (see Experimental Example 3 described later). By using the conductive coil units 20 dispersed in the annular axis direction of the ring-shaped magnetic plate 10, the leakage magnetic field (shaking noise) can be relatively easily reduced while generating a uniform shaking magnetic field inside the ring-shaped magnetic plate 10. can do.

  As shown in the enlarged plan view and the enlarged side view of FIGS. 1 (C) and 1 (D), the conductive coil unit 20 of the illustrated example has an intermediate portion thereof attached to the annular magnetic plate 10 in a direction substantially perpendicular to its annular axis. The coil is wound, and both ends 22a and 22b are pulled out in parallel and adjacent to each other and connected to the coil driving device 30. For example, by winding the intermediate portion of the wire coil unit 20 around the ring-shaped magnetic plate 10 having a band width of 50 mm at a pitch of about 1 to 2 mm, the angle formed by the wire coil unit 20 (current direction) with respect to the annular axis of the ring-shaped magnetic plate 10 is adjusted. It is about 89 °. As shown in FIG. 1 (D), the conductive coil unit 20 wound substantially perpendicular to the annular axis is shaken at a point symmetrical position with respect to the center of gravity of a cross section (cross section of the magnetic circuit) intersecting the annular axis. By applying a current, a uniform shaking magnetic field is generated inside the ring-shaped magnetic plate 10 along the axial direction, and the magnetic flux inside the ring-shaped magnetic plate 10 is evenly fluctuated to exert a magnetic shaking effect. .

  In addition, the conductive coil unit 20 wound substantially perpendicular to the annular axis has a leakage magnetic field to the outside of the annular magnetic plate 10 due to the countercurrent effect of the reverse current flowing point-symmetrically with respect to the center of gravity of the cross section of the magnetic circuit. (Shaking noise) can be kept low. Furthermore, by drawing out the lead portions 22a and 22b of the lead coil unit 20 in parallel and adjacent, the leakage magnetic field (shaking noise) from portions other than the winding portion is also reduced due to the effect of canceling the reverse current flowing through the lead portions 22a and 22b. it can. As shown in FIG. 1 (E), by mutually twisting the lead portions 22a and 22b of the conductor coil unit 20, it is expected that the effect of canceling the reverse current is enhanced and the leakage magnetic field is further suppressed. As described above, in the conductor coil unit 20 shown in the drawing, the open magnetic shield structure is easier than the closed magnetic shield structure because it is easy to uniformly shake the inside of the magnetic body and to reduce the shaking noise outside the magnetic body. As a result, a significant improvement in shielding performance by magnetic shaking can be expected.

  The coil driving device 30 shown in FIG. 1 applies a shaking current I1 having a predetermined frequency in parallel to the lead portions 22a and 22b of each conductive wire coil unit 20. That is, the wire coil unit 20 is wound around each step of the ring-shaped magnetic plate 10 so as to form the same clockwise or counterclockwise winding, and the input / output loop conductive wires 23a and 23b having substantially the same diameter as the ring-shaped magnetic plate 10 are arranged adjacent to each other. Arranged in parallel, one lead 22a of each conductor coil unit 20 is connected to an input loop conductor (or output loop conductor) 23a, and the other lead 22b is connected to an output loop conductor (or input loop conductor) 23b. By doing so, each conductor coil unit 20 is connected in parallel with the coil driving device 30 via the loop conductors 23a and 23b.

  In the embodiment of FIG. 1, magnetic field leakage from the input / output loop conductors 23a and 23b connecting the respective conductor coil units 20 may be a problem, but as shown in the illustrated example, the input / output loop conductors 23a and 23b are adjacent to and parallel to each other. By arranging, the generated magnetic field is canceled by the input / output current in the opposite direction, and the leakage magnetic field from the input / output loop conductors 23a and 23b can be suppressed to a small value. If necessary, the canceling effect can be enhanced by twisting the input / output loop conductors 23a and 23b. It is not necessary to provide a plurality of input / output loop conductors 23a and 23b corresponding to each stage of the ring-shaped magnetic plate 10, and as shown in FIG. Shaking current I1 can be applied in parallel to a plurality of conductor coil units 20.

  Further, the connection between the coil driving device 30 and each of the conductor coil units 20 is not limited to the parallel connection as shown in FIG. 1. For example, as shown in FIG. The sections 22a and 22b can be sequentially connected (connected) in series, and the shaking current I1 can be applied in series to the lead sections 22a and 22b of each conductive coil unit 20 by the coil driving device 30. In the embodiment shown in FIG. 11A, the wire coil unit 20 is wound around a plurality of portions of each step of the ring-shaped magnetic plate 10 in a direction substantially perpendicular to the annular axis, and the lead portions 22a at both ends of each wire coil unit 20 are provided. , 22b are pulled out in parallel and adjacent, and the lead-out portions 22a, 22b of the respective lead wire coil units 20 adjacent in the annular axis direction are connected in series by a connecting wire 26. FIG. 11B shows an XY plan view of the ring-shaped magnetic plate 10, and FIGS. 11C and 11D show an enlarged plan view and an enlarged side view of the elliptic C portion.

  In the embodiment shown in FIG. 11, magnetic field leakage from the coupling conductor 26 connecting the respective conductor coil units 20 in series may be a problem. However, as shown in FIG. 26, a loop conductor 27 through which a current flows in the opposite direction is arranged in parallel, and each conductor coil unit 20 is connected in series to the coil driving device 30 via the coupling conductor 26 and the loop conductor 27, whereby the coupling conductor 26 And the leakage magnetic field can be suppressed small. If necessary, the canceling effect can be enhanced by twisting the coupling conductor 26 and the loop conductor 27.

  For example, as shown in FIG. 11, a plurality of conductor coil units 20 of the ring-shaped magnetic plate 10 are connected in series in the annular axial direction from the starting end portion to the terminal end portion by the coupling conductive wire 26, and are connected in the annular axial direction from the terminal end portion to the starting end portion. Is used as a loop conductor 27, and a shaking current I1 from the coil driving device 30 is sequentially applied to each conductor coil unit 20 from the start end portion to the end portion via the coupling conductor 26, and the loop end 27 is terminated. The part is returned to the coil driving device 30 via the loop conductor 27 and the start end part. In the illustrated example, one conductor is continuously wound around the plurality of annular magnetic plates 10. However, the conductor coil units 20 in different stages do not necessarily need to be connected to each other. It is sufficient that the coil units 20 are connected in series. For example, a coil driving device 30 may be provided for each stage, and a shaking current may be individually applied to the conductive coil unit 20 directly connected to each stage.

[Experimental example 1]
Before confirming that the leakage magnetic field (shaking noise) can be reduced by the shaking type open magnetic shield structure of FIG. 1, first, the conductive wire coil 25 was wound around the annular magnetic plate 10 of each stage of the open type magnetic shield structure 5z. In order to confirm the leakage magnetic field in the case, a model experiment as shown in FIG. 2 was performed. In this experiment, as shown in FIG. 2 (A), four strip-shaped magnetic plates having a width of 50 mm, a length of 1000 mm, and a thickness of 5 mm were joined in a grid pattern to form a ring-shaped magnetic plate 10 (magnetic circuit) having an outer shape of 950 mm. The ring-shaped magnetic plates 10 are arranged in five stages at a predetermined interval dz = 200 mm to form an open magnetic shield structure 5z. Was wound at a predetermined pitch T, and a shaking current (frequency: 200 Hz) was applied. The size of the outer shape of the annular magnetic plate 10 indicates the length of the central axis of the annular magnetic circuit.

  FIG. 2B is a plan view of the open magnetic shield structure 5z parallel to the XY plane, and FIG. 2C is a cross-sectional view of the open magnetic shield structure 5z parallel to the YZ plane. 2D is a schematic plan view of the coil current obtained by enlarging an elliptical D portion in FIG. 2B, and FIG. 2E is a schematic side view of the coil current viewed from the annular axis direction of the annular magnetic plate 10. The figure is shown. As shown in FIGS. 2B and 2D, the conductive coil 25 in this case is assumed to be a closed circuit that is not continuous with each other and independent of each other at each winding position at a predetermined pitch T interval. Each coil (hereinafter sometimes referred to as a single-stage coil) 20 shown in FIGS. 2C and 2E is point-symmetric with respect to the center of gravity of the cross section of the magnetic circuit in consideration of the canceling effect of the generated magnetic field. And the size of the cross section is 50 mm × 5 mm.

  For comparison, as shown in FIG. 6, the conductive coil 25 is wound at a predetermined pitch T together on a five-stage ring-shaped magnetic plate 10 (magnetic circuit) of an open type magnetic shield structure 5z to form a shaking current (frequency 200 Hz). ) Was applied. Each coil (hereinafter, also referred to as a five-stage coil) 20 shown in FIG. 6 is not continuous with each other, and assumes a closed circuit independent of each other at each winding position at a predetermined pitch T interval. Is 50 mm × 805 mm. Shaking currents were respectively applied to the first-stage coil of FIG. 2 and the five-stage coil of FIG. 6, and the generated magnetic field inside the coil and the leakage magnetic field outside the coil were obtained by numerical simulation (three-dimensional nonlinear magnetic field analysis).

  In this experiment, in order to equalize the shaking strength of the magnetic circuit between the one-stage coil of FIG. 2 and the five-stage coil of FIG. 6, the one-stage coil was adjusted so that the magnetic flux density induced inside the ring-shaped magnetic plate 10 matched. Shaking currents of the coil and the five-stage coil were set. That is, when a 1A shaking current is applied to the one-stage coil of FIG. 2, the magnetic flux density at the center of each side of the magnetic circuit of each stage is 19.6 mT, whereas the five-stage coil of FIG. When a current is applied, the magnetic flux density at the center of the side of the magnetic circuit in each stage is 38.7 mT in the first and fifth stages, and 57.8 mT in the second to fourth stages. Became bigger. This is because the five-stage coil extends between the magnetic circuits of each stage, and the current path is long. Therefore, the current value of the shaking current applied to the five-stage coil was set to 0.339 A so that the magnetic flux densities of the second to fourth stages matched 19.6 mT of the first-stage coil.

  4 (A) and 4 (B) show the leakage magnetic field outside the one-stage coil of FIG. 2 and the contour of the magnetic field distribution of the evaluation area R inside the open magnetic shield structure shown in FIGS. 2 (B) and 2 (C). This is represented as a diagram / vector diagram. 7A and 7B show the leakage magnetic field outside the five-stage coil in FIG. 6 as a contour diagram / vector diagram of the magnetic field distribution in the evaluation target area R. FIGS. 4 and 7 show the leakage magnetic field when only the coil having no magnetic circuit is arranged. When the magnetic circuit is present, the magnetic field generated from the magnetic material magnetized by the shaking current is shown. Are superimposed, the magnetic field distribution in the evaluation target area R becomes large. However, the value to be superimposed varies depending on the type, thickness (number of layers), size, etc. of the magnetic material. Therefore, in order to evaluate only the magnetic field generated from the shaking coil, only the coil without the magnetic material circuit needs to be evaluated. It is effective to consider the leakage magnetic field.

  Comparing the magnetic field distribution of FIG. 4 formed by the one-stage coil with the magnetic field distribution of FIG. 7 formed by the five-stage coil, it can be seen that the one-stage coil is smaller by about 1/13. In each case, the leakage magnetic field has only a horizontal component, and the magnetic field in the vertical direction hardly leaks. The reason for this is that, as can be seen from the schematic diagrams of the coil currents shown in FIGS. 2D and 2E, the currents Ia, Ib, Ic and Id flowing through the coils are point-symmetric with respect to the center of gravity of the cross section of the magnetic circuit. The magnetic field (vertical component) generated from the currents Ia and Ic cancels out to zero, and is generated from the currents Ib and Id because they are at the same position (a point symmetrical position when viewed from the annular axis direction) and have the same magnitude but different directions. This is because only the generated magnetic field (horizontal component) leaks to the evaluation target area R. The five-stage coil has a large leakage magnetic field because the vertical current path for inducing the horizontal component of the magnetic field is long despite the small current value. Although the leakage magnetic field in the vertical direction is relatively large in the vicinity of the coil (periphery of the evaluation target area R), the effect of canceling out increases as the distance from the coil increases, and the central part of the evaluation target area R (the central part of the magnetic shield target space). ) Is suddenly smaller.

  From the comparison of the magnetic field distributions of FIGS. 4 and 7, as shown in FIG. 2, a conducting coil 25 is wound around the annular magnetic plate 10 of each stage of the open magnetic shield structure 5z along the annular axis to apply a shaking current. This indicates that the magnetic field (shaking noise) leaking to the outside of the conductive coil 25 can be sufficiently reduced. When the closed magnetic shield structure is to be shaken, a coil similar to the five-stage coil shown in FIG. 6 is required. Therefore, the open magnetic shield structure can reduce the leakage magnetic field of the magnetic shaking as compared with the closed magnetic shield structure. It can be said that there are advantages. Further, as shown in FIG. 2E, the single-stage coil wound at a point-symmetric position when viewed from the axial direction of the magnetic circuit generates only a shaking magnetic field along the axial direction inside the magnetic circuit. Therefore, it can be seen that the magnetic flux inside the annular magnetic plate is fluctuated evenly.

[Experimental example 2]
In the model experiment of FIG. 2, an independent closed circuit coil is wound at each winding position of the annular magnetic plate 10 at a predetermined pitch T, but the actual annular magnetic plate 10 having the open magnetic shield structure 5z is closed. It is difficult to shake. Then, next, in order to confirm the leakage magnetic field (shaking noise) when continuously winding the conductive wire coil 25 at a predetermined pitch T along the annular axis of the annular magnetic plate 10 of each stage as shown in FIG. An open type magnetic shield structure in which five annular belt-shaped magnetic plates 10 (magnetic circuit) having an outer shape (length of the central axis of the annular magnetic circuit) of 950 mm are arranged at predetermined intervals dz = 200 mm in the same manner as in Experimental Example 1 described above. 5z, and as shown in FIGS. 3B and 3C, a predetermined pitch T (one turn with a width of 100 mm, each side of the ring-shaped magnetic plate 10 in the direction of the ring axis of the five-stage ring-shaped magnetic plate 10). The winding coil 25 is continuously wound for 9 turns at 900 mm), a shaking current (frequency 200 Hz) is applied, and the generated magnetic field inside the coil and the leakage magnetic field outside the coil are obtained by numerical simulation. Experiments were carried out. FIG. 3B is a plan view of the open magnetic shield structure 5z parallel to the XY plane, and FIG. 3C is a cross-sectional view of the open magnetic shield structure 5z parallel to the YZ plane. 3D is a schematic plan view of the coil current obtained by enlarging the portion of the ellipse D in FIG. 3B, and FIG. 3E is a schematic side view of the coil current as viewed from the direction of the annular axis of the annular magnetic plate 10. The figure is shown.

  For comparison, as shown in FIG. 8, the conductive coil 25 is integrated on a five-stage ring-shaped magnetic plate 10 (magnetic circuit) of an open type magnetic shield structure 5z and a lead coil 25 is arranged at a predetermined pitch T (one turn at a width of 100 mm, ring). An experiment was conducted in which the winding was continuously wound around each side (900 mm) of the strip-shaped magnetic plate (9 turns), a shaking current was applied, and a generated magnetic field inside the coil and a leakage magnetic field outside the coil were obtained by numerical simulation. In order to make the magnetic flux density induced inside the ring-shaped magnetic plate 10 equal to that of Experimental Example 1 (in the case of the single-stage coil of FIG. 2), the value of the shaking current applied to the single-stage coil of FIG. The shaking current applied to the five-stage coil shown in FIG. 8 was set to 0.339 A.

  FIGS. 5A and 5B show the leakage magnetic field outside the one-stage coil in FIG. 3 as a contour diagram / vector diagram of the magnetic field distribution in the evaluation target area R inside the open magnetic shield structure. 9A and 9B show the leakage magnetic field outside the five-stage coil in FIG. 8 as a contour diagram / vector diagram of the magnetic field distribution in the evaluation target area R. 5 and 9, similarly to FIGS. 4 and 7 of Experimental Example 1, in order to avoid the superposition of the magnetic field generated from the magnetic material, the leakage magnetic field in the case where only the coil having no magnetic circuit is arranged is reduced. Is shown.

  When comparing the magnetic field distribution of FIG. 5 formed by the single-stage coil with the magnetic field distribution of FIG. 9 formed by the five-stage coil, the vertical component of the leakage magnetic field is dominant, and the leakage current of the single-stage coil is about 30 times larger. You can see that. This is because, as can be seen from the schematic diagrams of the coil currents shown in FIGS. 3D and 3E, the currents Ia and Ic flowing through the coils have the same magnitude but different directions on the XY plane. This is because the effect of canceling the vertical component of the generated magnetic field becomes insufficient. In the five-stage coil shown in FIG. 9, the currents Ia and Ic are far apart, so that a certain degree of canceling effect can be seen. However, in the one-stage coil shown in FIG. 5, the vertical component of the leakage magnetic field is large. Although the currents Ib and Id flowing through the coils are also displaced in the Y-axis direction, the influence on the leakage magnetic field (horizontal component) is relatively small.

  From the comparison of the magnetic field distributions shown in FIGS. 5 and 9, when the shaking current is applied by continuously winding the conductive wire coil 25 at a predetermined pitch T (one turn with a width of 100 mm) around the magnetic circuit having the open magnetic shield structure, It can be seen that the leakage magnetic field of the one-stage coil of FIG. 3 is larger than the leakage magnetic field of the five-stage coil of FIG. That is, as shown in FIG. 3, the single-stage coil that applies a shaking current to a point-symmetrical position when viewed from the direction of the annular axis of the annular magnetic plate 10 makes the magnetic flux inside the annular magnetic plate 10 fluctuate evenly, and the magnetic shaking effect is obtained. However, there is a concern that the magnetic environment is degraded by the leakage magnetic field (shaking noise) accompanying the shaking current.

  In the open magnetic shield structure 5z shown in FIG. 3, the conductive coil 25 is continuously wound around the ring-shaped magnetic plates 10 arranged in five stages, and one end and the other end of the coil 20 are connected to the input / output lines 20a and 20b. In addition, a shaking current is applied to the input / output lines 20a and 20b from the coil driving device 30, which is an AC power supply. In this case, the leakage of the magnetic field from the input / output lines 20a and 20b together with the coil 20 wound around the magnetic circuit of each stage may be a problem. However, as shown in the illustrated example, the input / output lines 20a and 20b are arranged adjacent to and parallel to each other. By arranging, the magnetic field generated in the input / output lines 20a and 20b can be canceled by the input / output current in the opposite direction, so that the leakage magnetic field can be suppressed to be small. It is also effective to twist the output lines 20a and 20b as necessary to enhance the canceling effect. However, the conducting wire coil 25 does not need to be continuously wound around the ring-shaped magnetic plate 10 in a plurality of stages as in the illustrated example, and it is sufficient that the conductor coil 25 is continuous in at least one stage. In that case, a coil driving device 30 is provided for each stage, and a shaking current is individually applied to the conductive wire coil 25 for each stage.

[Experimental example 3]
As shown in FIG. 3, in the open type magnetic shield structure 5z in which each side of the ring-shaped magnetic plate 10 of each stage is continuously wound around the conductive wire coil 25 at a predetermined pitch T, a predetermined shape shown in FIGS. If the coil currents Ia and Ic of the conductor coil 25 having the pitch T are brought closer on the XY plane like the coil currents Ia and Ic of the conductor coil 25 shown in FIGS. 2D and 2E, one step in FIG. It can be expected that the magnetic field distribution of FIG. 5 formed by the coil 20 is made closer to the magnetic field distribution of FIG. Therefore, the predetermined pitch T of the conductive wire coil 25 continuously wound around each side (900 mm) of the ring-shaped magnetic plate 10 in FIG. 3 is set to (a) 100 mm (9 turns at 900 mm width) and (b) 50 mm (900 mm width at 900 mm width). Experiments were repeated in which the leakage magnetic field in the evaluation target region R was sequentially obtained by numerical simulation while changing the values to 18 turns), (c) 20 mm (45 turns for a 900 mm width), and (d) 10 mm (90 turns for a 900 mm width).

  Regardless of the predetermined pitch T of the conductor coil 25, if the magnetic flux density induced inside the annular magnetic plate 10 is made equal to that of the first experimental example (in the case of the single-stage coil in FIG. 2), (a) the predetermined pitch T = 100 mm In this case, the current value of the shaking current is 1.414 A, (b) 50 mm, 1.118 A, (c) 20 mm, 1.020 A, and (d) 10 mm, 1.005 A. Further, when the predetermined pitch T is reduced, the number of turns (the number of turns) increases, so that the leakage of shaking noise can be expected to be further reduced by reducing the value of the shaking current in accordance with the increase in the number of turns.

  In general, a shaking current (excitation current) necessary for shaking the inside of the ring-shaped magnetic plate 10 can be expressed by a current value (A) of the wound conductive wire coil 25 × the number of turns (T) = ampere turn (AT). it can. Therefore, in this experiment, irrespective of the predetermined pitch T of the conductor coil 25, (a) such that the ampere turn (AT) matches the experimental example 1 (in the case of the single-stage coil in FIG. 2) in consideration of the number of turns. The current value of the shaking current is 1.414 A when the predetermined pitch T = 100 mm, 0.559 A when (b) 50 mm, 0.204 A when (c) 20 mm, and 0.100 A when (d) 10 mm. Set to. Table 1 shows the results of this experiment.

  The column of the five-stage coil (continuous) in Table 1 shows the leakage magnetic field in the evaluation target area R of the conductor coil 25 continuously wound at a predetermined pitch of 100 mm around the five-stage ring-shaped magnetic plate 10 as shown in FIG. The average value field of the leakage magnetic field of the single-stage coil (continuous) in Table 1 indicates the leakage of the evaluation target area R when the predetermined pitch T of the single-stage conductive coil 25 in FIG. 3 is switched to 100 mm, 50 mm, 20 mm, and 10 mm. The average value of the magnetic field in the horizontal plane and the change of the average value in the vertical plane are shown. As can be seen from the column of the ratio with the five-stage coil (continuous) in Table 1, both the horizontal and vertical leakage magnetic fields created by the one-stage coil of FIG. Although it is larger than the magnetic field, if the predetermined pitch T of the single-stage coil is reduced (the number of turns is increased), the coil currents Ia and Ic approach in the XY plane (see FIGS. 3D and 3E). By increasing the cancellation ratio, it is possible to reduce both the leakage magnetic fields on the horizontal plane and the vertical plane.

  From Table 1, it can be seen that the conductor coil (first-stage coil) 20 is wound at a predetermined pitch T along each axis of the annular magnetic plate 10 surrounding the magnetic shield space 1 in the axial direction so that the leakage magnetic field outside the conductor coil 25 is canceled. By setting a predetermined winding pitch T of the wire coil 25 to uniformly fluctuate the magnetic flux inside the ring-shaped magnetic plate 10 to improve the magnetic characteristics efficiently, at the same time, the leakage magnetic field to the magnetic shield space 1 (shaking) It can be seen that noise) can be reduced. However, even if the predetermined pitch T of the one-stage coil is reduced to 10 mm, the leakage magnetic field does not become smaller than that of the five-stage coil having the predetermined pitch of 100 mm. Is required.

  However, Table 1 shows the simulation results of the stray magnetic field by the model experiment of FIG. 3, and the stray magnetic field differs with different models. In the model experiment shown in FIG. 3, the leakage magnetic field is large due to its relatively small size. However, if the size of the magnetic shield space 1 changes, the leakage magnetic field decreases due to the distance attenuation effect, and the magnetic field of a normal medical facility or research facility is reduced. It is considered that the leakage magnetic field is greatly reduced when the size of the shield room is increased. That is, if the predetermined pitch T of the conductive coil 25 is appropriately set according to the design conditions and the required performance, the conductive coil 25 is continuously wound at a predetermined pitch T on each stage of the annular magnetic plate 10 as shown in FIG. The shaking-type open magnetic shield structure is sufficiently practical.

[Experimental example 4]
As confirmed in Experimental Example 3, the open-type magnetic shield structure 5z in which the conductor coil 25 is continuously wound around each step of the annular magnetic plate 10 surrounding the magnetic shield space 1 generates relatively large shaking noise (vertical component). Because of the leakage, as shown in FIG. 1 (A), in the open-type magnetic shield structure 5z in which five annular belt-shaped magnetic plates 10 (magnetic circuits) each having an outer shape (length of the central axis) of 950 mm are arranged. The conductive coil unit 20 is attached to a plurality of predetermined portions (three portions on each side) dispersed in the annular axis direction of the belt-shaped magnetic plate 10 by winding the same right-handed or left-handed three turns substantially perpendicular to the annular axis. The coil drive device 30 applies a shaking current I1 (frequency 200 Hz) in the same direction by pulling out the two ends 22a and 22b of the wrapped portion in parallel and adjacent. Leakage magnetic field when (shaking noise) Experiments were conducted to determine the numerical simulation. The lead portions 22a and 22b of each lead coil unit 20 were drawn as stranded wires as shown in FIG. 1 (E) and connected to the coil driving device 30 in parallel.

  Also in this experiment, the shaking current (excitation current) was set so that the ampere-turn (AT) matched Experimental Example 1 (in the case of the single-stage coil in FIG. 2) and Experimental Example 3 (in the case of the single-stage coil in FIG. 3). Was set. That is, in FIG. 1A, since there are 9 turns per each side (900 mm) of the annular magnetic plate 10, the shaking current (excitation current) becomes 9AT as in the first and third examples. The value of the current flowing through each conductor coil unit 20 was set to 1A. When the magnitude of the shaking current is changed, the shaking current can be adjusted by the value of the current flowing through each conductor coil unit 20, but can also be adjusted by the number of turns (the number of turns) of the conductor coil unit 20 at each predetermined portion. It can be adjusted by increasing or decreasing the mounting position of the conductive coil unit 20 on the annular magnetic plate 10. The results of this experiment are shown in Table 1 together with the results of Experimental Example 3 described above.

  The average value column of the stray magnetic field in the coil distribution (upper column of the upper and lower two columns) in Table 1 is a conductor coil distributed and mounted in the annular axis direction of each annular magnetic plate 10 as shown in FIG. The average value in the horizontal plane and the change in the average value in the vertical plane of the leakage magnetic field in the evaluation target area R when the shaking current I1 in the same direction is applied to the unit 20 are shown. As can be seen from the column of the ratio with the five-stage coil (continuous) in Table 1, the leakage magnetic field produced by the conductor coil unit 20 dispersed in the annular magnetic plate 10 as shown in FIG. It is 0.02 or less (less than 1/50) of the leakage magnetic field produced by the five-stage coil shown in FIG. 8, and is smaller than the leakage magnetic field produced by the conductor coil 25 continuously wound around the ring-shaped magnetic plate 10 as shown in FIG. It is possible to make it small enough.

  In this experiment, the shaking of the ring-shaped magnetic plate 10 was performed by winding the conductive coil unit 20 around a plurality of portions dispersed in the direction of the ring axis of the ring-shaped magnetic plate 10 in a direction substantially perpendicular to the ring axis and passing the shaking current I1. It has been confirmed that the leakage magnetic field (shaking noise) accompanying the above can be greatly reduced. The wire coil unit 20 wound substantially perpendicular to the annular axis of the magnetic circuit effectively eliminates shaking noise from the winding portion by a reverse current flowing point-symmetrically with respect to the center of gravity of the cross section of the magnetic circuit. This is considered to be due to the fact that the shaking noise from portions other than the winding portion could be efficiently canceled by the reverse currents flowing through the lead portions 22a and 22b drawn out in parallel and adjacent to each other.

  From these experimental results, the shaking type open magnetic shield structure of FIG. 1 shows that the magnetic flux inside the magnetic material is evenly fluctuated and the magnetic properties are efficiently improved, while the leakage magnetic field into the magnetic shield room is sufficiently small. The shielding performance can be reliably and significantly improved. Further, if the size of the magnetic shield space 1 changes, the leakage magnetic field decreases due to the distance attenuation effect, so it is considered that the leakage magnetic field when applied to a magnetic shield room of a normal medical facility or research facility becomes extremely small. By appropriately setting the winding part (mounting pitch), the number of turns (turn number), and the value and direction of the shaking current to be applied to the conductive coil unit 20 according to design conditions and required performance, the disturbance magnetic field fluctuation is 1 nT or less. A magnetically shielded room can be realized.

[Experimental example 5]
As described above, by shaping the conductive coil unit 20 around each step of the annular magnetic plate 10 in a direction substantially perpendicular to the annular axis as shown in FIG. 1 and flowing the shaking current I1, shaking noise can be sufficiently suppressed. However, if the shaking noise that leaks from each adjacent step of the annular magnetic plate 10 is reversed, the leakage of the shaking noise to the magnetic shield space 1 can be further reduced by canceling out the leakage magnetic fields of each adjacent step. Can be expected. To confirm this, as shown in FIG. 10 (A), the wire coil unit 20 is wound around each step of the ring-shaped magnetic plate 10 in the same right-handed or left-handed manner. An experiment was performed in which opposite shaking currents I1 and I2 (frequency 200 Hz) were applied to adjacent stages of the ring-shaped magnetic plate 10 by 30b, and the leakage magnetic field of the magnetic shield space 1 was obtained by numerical simulation. The results of this experiment are shown in Table 1 together with the results of Experimental Example 4 described above.

  The average value column of the stray magnetic field of the coil distribution (lower column of the upper and lower two columns) in Table 1 shows the shaking currents I1, I2 in the opposite directions for each adjacent stage of the ring-shaped magnetic plate 10 as shown in FIG. The average value in the horizontal plane and the change in the average value in the vertical plane of the leakage magnetic field in the evaluation target area R when I2 is applied are shown. As can be seen from the column of the ratio with the five-stage coil (continuous) in Table 1, the leakage magnetic field in FIG. 10A is 0.05 or less (1) of the leakage magnetic field created by the five-stage coil in FIG. / 200 or less), and the leakage magnetic field (shaking noise) is reduced to about 1/4 as compared with the case where the shaking current I1 in the same direction is applied to each step of the annular magnetic plate 10 as shown in FIG. This shows that it can be made smaller.

  Also, as shown in FIG. 10B, the coil unit 20 is wound in the opposite right-handed or left-handed winding direction for each adjacent step of the ring-shaped magnetic plate 10, and then the ring-shaped magnetic plate 10 is wound by the coil driving device 30. An experiment was performed in which a shaking current in the same direction was applied to each stage of the magnetic plate 10 and the leakage magnetic field of the magnetic shield space 1 was obtained by numerical simulation. The results of this experiment were the same as the coil dispersion (lower column of the upper and lower two columns) in Table 1 described above. From these experimental results, the direction of the shaking current I1 applied to each step of the ring-shaped magnetic plate 10 surrounding the magnetic shield space 1 or the direction of winding of the conductive coil unit 20 wound around each step of the ring-shaped magnetic plate 10 is reversed. Thus, it was confirmed that the leakage of the shaking noise to the magnetic shield space 1 can be reduced by canceling out the leakage magnetic fields of the adjacent stages.

  Thus, it is possible to achieve the object of the present invention to provide a "low-leakage shaking-type open magnetic shield structure that can suppress the leakage of shaking noise".

  Although the open type magnetic shield structure 5z of FIG. 1 is mainly intended to shield a disturbance magnetic field in one or two directions in the XY plane, a disturbance magnetic field in three directions is provided in the magnetic shield target space 1 in which the direction of the disturbance magnetic field is not determined. In the case where is to be shielded, the structure shown in FIG. 1 can be used as a basic unit to form an open magnetic shield structure in which a plurality of units are combined as shown in FIGS. FIG. 12 shows an example of a cubic open magnetic shield room having a basic size of 2550 mm on each side, which is installed in a medical facility or a research facility.

  FIG. 12A shows a case where the target space 1 is surrounded by a predetermined band width W on a plurality of parallel planes Pz which intersect at a predetermined interval dz with a first direction axis Az (Z axis) penetrating the magnetic shield target space 1. An open magnetic shield structure 5z similar to FIG. 1 provided with the annular magnetic plate 10 as described above is shown. FIG. 12B shows the target space 1 with a predetermined band width W on a plurality of parallel planes Px intersecting at a predetermined interval dx with a second direction axis Ax (X axis) penetrating the magnetic shield target space 1. FIG. 12C shows an open type magnetic shield structure 5x in which an annular magnetic plate 10 is provided so as to surround the same, and FIG. 12C shows a plurality of axes which intersect with a third direction axis Ay (Y axis) passing through the magnetic shield target space 1 at a predetermined interval dy. The open type magnetic shield structure 5y in which the annular magnetic plate 10 is provided so as to surround the target space 1 with a predetermined band width W on a plane Py parallel to the steps is shown. Three open magnetic shield structures 5z, 5x, 5y are nested around the magnetic shield target space 1, or any two of the open magnetic shield structures 5z, 5x, 5y are selected and nested. By arranging and integrating them, a magnetically shielded room that shields a disturbance magnetic field in three directions can be provided.

  Each of the ring-shaped magnetic plates 10 shown in FIGS. 12A to 12C is formed by assembling strips of cobalt-based amorphous (thickness of 23 μm × 20 sheets, width of 50 mm) in a grid pattern. The open magnetic shield structures 5z, 5x, and 5y can be arranged in 12 stages at 200 mm. The open magnetic shield structures 5z and 5x are provided with openings surrounded by door frames 14a, 14b, 14c and 14d made of the same band-like magnetic plate (cobalt-based amorphous) 10, and the PC permalloy plate ( A door 12 having a two-layer (inside and outside) structure with a thickness of 1 mm × two layers is attached.

  The annular magnetic plate 10 of each stage of the open type magnetic shield structure 5z, 5x, 5y has substantially the same shape as that of FIGS. The wire coil unit 20 is wound in a direction perpendicular to the upper direction, and both ends 22a and 22b are pulled out in parallel and connected to the coil driving device 30, and a shaking current of a predetermined frequency is applied to each wire coil unit 20 by the coil driving device 30. Then, the magnetic shield structures 5z, 5x, 5y are magnetically shaken. The winding part (mounting pitch), number of turns (turn number), and the value and direction of the shaking current applied to the conductive coil unit 20 are appropriately determined according to design conditions and required performance (magnetic field environment required). Can be determined.

[Experimental example 6]
FIG. 13A shows an example of a method of attaching the conductive coil units 20 to the annular magnetic plate (magnetic circuit) 10 of each stage of the open magnetic shield structure 5y having no opening at a predetermined mutual interval (attachment pitch) T. Show. In FIG. 13A, in order to confirm the change in the magnetic flux density induced inside the annular magnetic plate 10 by the mutual interval T between the winding portions of the conductive coil unit 20, the mutual interval T between the winding portions of the conductive coil unit 20 is checked. (A) 150 mm (15 wrapping parts on one side), (b) 300 mm (8 wrapping parts on one side), (c) 525 mm (5 wrapping parts on one side), (d) 1050 mm (3 wrapping parts on one side) An experiment was performed in which the distribution of the magnetic flux density induced inside the ring-shaped magnetic plate 10 was determined by numerical simulation while switching to the position (a).

  In this experiment, irrespective of the interval T, the conductor coil unit 20 was wound around each winding portion in a direction substantially perpendicular to the annular axis for eight turns (number of windings = 8T), as shown in FIGS. 1 (C) and (D). Eight closed circuits each having a width of 52 mm and a height of 5 mm were formed at a pitch of 2 mm at each winding site. Further, since the magnetic flux density induced inside the annular magnetic plate 10 is uniform regardless of the mutual interval T, the shaking current (exciting current) per side of the annular magnetic plate (magnetic circuit) 10 is 12AT. Thus, (a) the current value of the shaking current I1 is 0.1 A when the mutual interval T is 150 mm, (b) 0.1875 A when the distance is 300 mm, (C) 0.3 A when the distance is 525 mm, and (d). At 1050 mm, it was set to 0.5A. Table 2 shows the results of this experiment.

  The column of the magnetic flux density in Table 2 excludes the corners when the shaking current is applied to the conductive coil unit 20 while switching the mutual interval T in the annular magnetic plate (magnetic circuit) 10 of FIG. It shows the maximum value, the minimum value, and the minimum value of the magnetic flux density induced inside the magnetic material. As can be seen from Table 2, the variation in the induced magnetic flux density (the ratio of (maximum value-minimum value) to the average value) increases as the mutual interval T between the winding portions of the wire coil unit 20 increases. Is 525 mm or less, the variation in the magnetic flux density is about 6% or less, and it can be said that there is no problem from the viewpoint of uniformly shaking the inside of the annular magnetic plate 10 to obtain the magnetic shaking effect. On the other hand, when the interval T is 1050 mm, the variation of the magnetic flux density exceeds 30%, and it is difficult to evenly swing the inside of the annular magnetic plate 10.

  According to this experiment, the mutual interval T between the winding portions of the conductive coil unit 20 at each stage of the annular magnetic plate 10 is within the range where the shaking magnetic field induced inside the annular magnetic plate 10 is uniform, for example, the variation of the magnetic flux density. Was desirably set to be 6% or less. Therefore, as shown in FIG. 13 (A), for example, a plurality of ring-shaped magnetic plates 10 around which the conductor coil units 20 are wound with a mutual interval T of 525 mm intersect with the third direction axis Ay (Y axis) at a predetermined interval dy. By arranging them on the parallel planes Py of the steps, an open magnetic shield structure 5y having no opening can be constructed. The ring-shaped magnetic plates 10 of the open type magnetic shield structures 5z and 5x having openings can be similarly configured.

  FIG. 13B shows an example of a method of mounting the conductive coil units 20 at a predetermined mutual interval (mounting pitch) T on the annular magnetic plate 10 of the open magnetic shield structure 5z having an opening. In the illustrated example, the conductor coil unit 20 is attached only to the side of the ring-shaped magnetic plate 10 where the door 12 is located, but the conductor coil unit 20 is attached to the other three sides at a predetermined mutual interval T in the same manner. Can be The ring-shaped magnetic plate 10 having an open magnetic shield structure 5x having an opening can be similarly configured.

  Both ends 22a and 22b of each wire coil unit 20 attached to the annular magnetic plate 10 of FIGS. 13A and 13B are drawn out in parallel and adjacent to each other, for example, as shown in FIGS. 1A, 10A, or As shown in FIG. 10B, the coil driving device 30 is connected, and the shaking current I1 is applied to the lead portions 22a and 22b of each conductive coil unit 20 in parallel by the coil driving device 30. Alternatively, as shown in FIG. 11 (A), the lead portions 22a and 22b of the respective conductor coil units 20 are connected in series by the coupling conductor 26, the shaking current I1 is applied in series by the coil driving device 30, and the coupling conductor 26 is connected to the coupling conductor 26. A current (−I1) in the opposite direction is caused to flow through the adjacent loop conductor 27 that is arranged in parallel.

DESCRIPTION OF SYMBOLS 1 ... Magnetic shield target space 2 ... Strip-shaped magnetic plate 3 ... Shield screen 5 ... Open magnetic shield structure 8 ... Magnetic sensor 9 ... Edge (overlapping part)
DESCRIPTION OF SYMBOLS 10 ... Ring-shaped magnetic plate 12 ... Door 14 ... Door frame 20 ... Conductor coil unit 21 ... Winding part 22a, 22b ... Leader 23a, 23b ... Input / output loop conductor 24a, 24b ... Input / output line 25 ... Conductor coil 26 ... Coupling Conducting wire 27 ... Loop conducting wire 30 ... Coil driving device 40 ... Magnetic shield member 41 ... Base materials 42a, 42b ... Magnetic ribbon 43 ... Conducting wire coil (shaking coil)
44 ... input terminal 45 ... output terminal Ax, Ay, Az ... axis d ... interval I ... current L ... current carrier (coil)
M: Disturbance magnetic field O: Center point Px, Py, Pz: Plane R: Evaluation area T: Pitch W: Band width of annular magnetic plate

Claims (7)

A ring-shaped magnetic plate provided on a plurality of parallel planes intersecting at a predetermined interval with a first direction axis passing through a space to be magnetically shielded so as to surround the space with a predetermined band width, and each step of the ring-shaped magnetic plate; A coil unit wound around a plurality of portions dispersed in the direction of the annular axis, each of which is wound substantially perpendicular to the annular axis, and whose two ends are drawn in parallel and adjacent to each other; A coupling conductor for sequentially connecting the coil units in series in the annular axial direction, a loop conductor for passing an opposite current in an adjacent parallel arrangement to the coupling conductor, and each conductor coil unit connected in series via the coupling conductor and the loop conductor. and a coil driving device for applying a shaking current of a predetermined frequency to the lead portion of each lead coil units, annulus by the generated magnetic field of each coil of wire units Low leakage shaking type open magnetic shield structure comprising a leakage magnetic field coupling conductor and the loop conductor and out consumption and the reverse current while magnetic shaking the magnetic plate. 2. The low-leakage shaking type open magnetic shield structure according to claim 1, wherein the lead portions of the respective wire coil units are pulled out while twisting each other. 3. The structure according to claim 1, wherein each of the conductive wire coil units is wound around each step of the ring-shaped magnetic plate so as to have the same right-handed or left-handed winding, and the coil driving device reverses each adjacent step of the ring-shaped magnetic plate. A low-leakage shaking open magnetic shield structure that applies a shaking current in the desired direction. 3. The structure according to claim 1, wherein each of the conductive wire coil units is wound so as to be reversed right-handed or left-handed in each adjacent step of the ring-shaped magnetic plate, and is wound around each step of the ring-shaped magnetic plate by the coil driving device. Low leakage shaking type open magnetic shield structure by applying shaking current in the same direction. 5. The structure according to claim 1 , wherein the distance between the winding portions of the conductive coil unit at each stage of the annular magnetic plate is set such that a shaking magnetic field induced inside the annular magnetic plate is uniform. Low leakage shaking type open magnetic shield structure set. The structure according to any one of claims 1 to 5 , wherein the space is provided on a plurality of parallel planes intersecting at a predetermined interval with a second direction axis passing through the space to be magnetically shielded so as to surround the space with a predetermined band width. The second annular magnetic plate group, and a plurality of portions of each of the second annular magnetic plates, which are dispersed in the direction of the annular axis, are respectively wound around the annular axis in a direction substantially perpendicular to the annular axis, and both ends thereof are adjacent in parallel. A second conductive coil unit is provided and pulled out, and a ring-shaped magnetic plate group and a second ring-shaped magnetic plate group are nested around the target space. A low-leakage shaking open magnetic shield structure in which each annular magnetic plate group is magnetically shaken by applying a shaking current of a frequency. 7. The third ring-shaped magnetic member according to claim 6 , wherein a plurality of parallel planes intersecting at a predetermined interval with a third direction axis passing through the space to be magnetically shielded are provided so as to surround the space with a predetermined band width. The third annular band-shaped magnetic plate is wound around a plurality of portions of each of the third annular magnetic plates, which are distributed in the direction of the annular axis in a direction substantially perpendicular to the annular axis, and is pulled out with both ends parallel to each other. A three-wire coil unit is provided, and a ring-shaped magnetic plate group, a second ring-shaped magnetic plate group, and a third ring-shaped magnetic plate group are nested around the target space. A low-leakage shaking type open magnetic shield structure in which a shaking current of a predetermined frequency is applied to the unit to magnetically shake each ring-shaped magnetic plate group.