JP2017147412A - Low leakage shaking open type magnetic shield structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low leakage shaking open type magnetic shield structure capable suppressing leakage of shaking noise small.SOLUTION: On multiple stages of parallel planes Pz1, Pz2, ... crossing a first direction axis Az penetrating a magnetic shield object space 1 at predetermined intervals dz, annular band-like magnetic plates 10 are provided in such a manner that the object space 1 is surrounded with a predetermined band width W. In multiple portions that are distributed in an annular axial direction, on each of the stages of the annular band-like magnetic plates 10, a lead wire coil unit 20 is wound and fitted in a direction that is substantially perpendicular to the annular axis, and both ends 22a and 22b of the lead wire coil unit are pulled out adjacently in parallel. The annular band-like magnetic plate 10 is magnetically shaken by a magnetic field that is generated by applying a shaking current I1 in a predetermined frequency in parallel to the pulled-out portions 22a and 22b of each lead wire coil unit 20 by a coil drive device 30. Preferably, both the ends 22a and 22b of each of the lead wire coil units 20 are pulled out while being twisted mutually.SELECTED DRAWING: Figure 1

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 uses magnetic shaking to improve shielding performance and suppresses leakage of shaking noise.

  Electron beam application devices such as electron microscopes, EB exposure devices, and EB steppers used in semiconductor manufacturing facilities, etc., even with weak magnetic fluctuations, change the trajectory of the electron beam and degrade the product quality. It is required to be installed in a magnetic shield room (magnetic shield space) controlled to 1 mG or less. The conventional general magnetic shield space is a structure (sealed magnetic shield structure) that covers the entire floor, wall, and ceiling with a magnetic material with high permeability such as PC permalloy (sealed magnetic shield structure). The number of parts increased, and the performance degradation due to the penetration of the disturbance magnetic field from the joints was a problem. On the other hand, as shown in FIG. 14, a magnetic shield structure (open magnetic shield structure) 5 using strip-shaped magnetic plates (strip-shaped magnetic plates) arranged in a bowl shape or a louver shape has been developed (Patent Literature). 1).

  The open type magnetic shield structure 5 includes a plurality of strip-like magnetic plates 2 having a width of about 50 mm, for example, which are stacked at a required thickness direction interval d so that the longitudinal central axes C are arranged in parallel on the same plane F. 3 (see FIG. 14 (A)), a plurality of shield housings 3a, 3b, 3c, 3d are magnetically joined by overlapping the corresponding joints 9 at the end edges, and a belt-like magnetic plate (annularly closed) (Hereinafter, referred to as an annular belt-shaped magnetic plate) 10 is formed, and a magnetic shield target space is surrounded by a plurality of annular belt-shaped magnetic plates 10 (see FIG. 14B). By designing an appropriate distance d of the ring-shaped magnetic plate 10, magnetic flux is applied to the ring-shaped magnetic plate 10 (magnetic circuit) while providing openness (permeability, translucency, heat dissipation) to the magnetic shield target space. , And the magnetic flux intrusion and leakage (performance degradation) from the interval d can be kept small. In addition, since the magnetic continuity can be easily secured at the joint 9, the performance is less deteriorated and the desired performance can be easily achieved. Furthermore, since the safety factor can be reduced and the amount of material used can be reduced compared to the conventional sealed magnetic shield structure, there is an advantage that leads to cost reduction.

  In the open type magnetic shield structure 5, the magnetic shield performance can be deteriorated by the eddy current flowing in the cross section of the ring-shaped magnetic plate 10 when the frequency of the disturbance magnetic field is increased. By adding a ring-shaped conductor (conductor circuit) such as an aluminum plate and superimposing the conductor shielding effect, even a disturbance magnetic field (AC magnetic field) up to about 200 Hz can exhibit shielding performance equivalent to or better than a DC magnetic field. (See Patent Document 2). That is, if the magnetic shield space is constructed by the open type magnetic shield structure 5 constituted by an annular magnetic plate 5 or the open type magnetic shield structure 5 to which a conductor circuit is added if necessary, environmental magnetic noise (disturbance magnetic field fluctuation) Can be effectively cut down to 100 nT or less, and a magnetic environment (magnetic shield space) suitable for installing an electron beam application apparatus or the like can be provided.

  On the other hand, SQUID (Superconducting Quantum Interference Device) application devices used in medical facilities and research facilities measure the magnetic field such as ultra-weak brain magnetic waves and magneto-magnetic waves generated by the activity of the brain and heart. It is required to control the magnetic environment. Magnetic shaking has been proposed as means for obtaining such an ultra-high magnetic environment (see Patent Documents 3 and 4, Non-Patent Document 1). Magnetic shaking is a technique for improving the magnetic properties (effective permeability) of a magnetic material by applying a periodically varying magnetic field (shaking magnetic field) to the magnetic material to sway the magnetic flux inside the magnetic material. For example, in Patent Document 3, a sealed magnetic shield structure is constituted by an amorphous magnetic ribbon material in the form of a film (or ribbon) having a thickness of 20 μm or more and 500 μm or less which can be manufactured at a relatively low cost. It is reported that I got it.

  In magnetic shaking, since the magnetic flux is swayed (shaked) inside the magnetic body, a shaking coil is wound almost perpendicularly around the axis of the magnetization direction of the magnetic body, and the frequency f higher than the frequency component fn of the environmental magnetic noise to be shielded. Is applied (shaking current) 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-like amorphous magnetic ribbons 42a on the surface of a base material 41 in the longitudinal direction. Are arranged with a predetermined gap so as to be parallel with each other, and eight ribbon-like amorphous magnetic ribbons 42b are arranged with a predetermined gap so that the longitudinal direction thereof is parallel with the lateral direction on the surface thereof. The shaking coil 43 is wound so as to sew the front and back in a predetermined gap between the bands 42a and 42b. In the illustrated example, the shaking coil 43 is divided into 16 parts between the input terminal 44 and the output terminal 45, and the front part passes through the odd part and the rear part passes through the back part as shown in FIG. 15B. By doing so, the magnetic ribbons 42a and 42b are wound in a substantially vertical direction with respect to any longitudinal direction.

International Publication No. 2004/084603 Pamphlet JP 2014-0866647 A Japanese Patent Laid-Open No. 3-066839 JP 2013-197290 A JP 2006-135116 A

SME Agency “2012 Strategic Fundamental Technology Advancement Support Project“ Development of Heat Treatment Technology for Magnetic Materials for High-Performance Magnetic Shielding Devices ”Research and Development Report” March 2013, Internet <http: // www. chusho. meti. go. jp / keiei / sapon / portal / seika / 2010/22113116088. 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 of FIG. 15, the magnetic field outside the coil is canceled at the portion where the shaking coil 43 is adjacent and parallel on 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 only the front surface or the back surface is disposed, the magnetic field (shaking noise) outside the coil leaks into the magnetic shield space. Further, in order to enhance the shaking effect, it is desirable to shake the inside of the magnetic material evenly. However, in the magnetic shield member 40 shown in FIG. Since the shaking magnetic field in the direction intersecting with the longitudinal direction of the magnetic ribbons is simultaneously applied, there is a problem that the insides of the magnetic ribbons 42a and 42b are not shaken evenly.

  In order to prevent leakage of shaking noise, for example, Non-Patent Document 1 discloses a three-layer structure in which an amorphous layer around which a shaking coil is wound is covered with an aluminum layer, and further, the inner side of the aluminum layer is covered with an amorphous layer without magnetic shaking. Has proposed. However, even with such a three-layer structure measure, shaking noise exceeding 10 nT is measured near the inner wall of the magnetic shield space. In addition, noise countermeasures such as a three-layer structure have a problem that leads to an increase in the construction cost of the magnetic shield. In order to realize a magnetic shield space of 1 nT or less by magnetic shaking, it is necessary to shake the inside of the magnetic material evenly and reduce shaking noise.

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

  Referring to the embodiment of FIG. 1, a low-leakage shaking type open magnetic shield structure according to the present invention has a plurality of parallel planes Pz1 intersecting a first direction axis Az penetrating the magnetic shield target space 1 at a predetermined interval dz. , Pz2,..., PZ2,... Each of the ring-band magnetic plate 10 provided so as to surround the magnetic shield target space 1 with a predetermined band width W (see FIGS. 1A and 1B). The coil unit 20 is wound around and attached to a plurality of portions distributed in the direction of the annular axis substantially perpendicularly to the annular axis, and is drawn out with both ends 22a and 22b adjacent to each other in parallel (FIGS. 1C and 1D). And a coil driving device 30 that applies a shaking current I1 having a predetermined frequency to the lead portions 22a and 22b of each conductor coil unit 20, and a magnetic field generated by each conductor coil unit 20 In which more ring band magnetic plate 10 formed by magnetic shaking.

  In a preferred embodiment, as shown in FIG. 1 (E), both ends 22a and 22b of each conductor coil unit 20 are pulled out while twisting each other. In a more preferred embodiment, as shown in FIG. 10A, each conductor coil unit 20 is wound around each stage of the ring-shaped magnetic plate 10 so as to be the same right-handed or left-handed, and the coil drive devices 30a, 30b Reverse-direction shaking currents I1 and I2 are applied to each adjacent stage of the belt-like magnetic plate 10. Alternatively, as shown in FIG. 10B, each conductor coil unit 20 is wound so as to be reversed right-handed or left-handed for each adjacent stage of the annular belt-shaped magnetic plate 10, and the annular drive magnetic plate is formed by the coil driving device 30. The shaking current I1 in the same direction may be applied to each of the ten stages.

  In a preferred embodiment, as shown in FIGS. 1 and 10, adjacent parallel-arranged input / output loop conductors 23a for connecting a plurality of conductor coil units 20 at each stage of the ring-shaped magnetic plate 10 to a coil driving device 30 in parallel. 23b is provided, and the leakage magnetic field of the input / output loop conductors 23a, 23b is canceled by the reverse input / output current. In another preferred embodiment, as shown in FIG. 11, a coupling conductor 26 for connecting a plurality of conductor coil units 20 at each stage of the ring-shaped magnetic plate 10 in series in the annular axial direction, and adjacent to the coupling conductor 26. A loop conductor 27 is provided in parallel arrangement to pass a reverse current, 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, and the leakage magnetic field of the coupling conductor 26 and the loop conductor 27. Is canceled by the reverse current. The mutual interval T between the winding portions of the conductor coil unit 20 at each stage of the ring-shaped magnetic plate 10 can be set so that the shaking magnetic field induced inside the ring-shaped magnetic plate 10 is uniform.

  The low leakage shaking type open type magnetic shield structure according to the present invention has magnetic shields on a plurality of parallel planes Pz1, Pz2,... Intersecting a first direction axis Az penetrating the magnetic shield target space 1 at a predetermined interval dz. An annular belt-shaped magnetic plate 10 is provided so as to surround the target space 1 with a predetermined band width W, and a conductive wire coil unit is disposed substantially perpendicularly to the annular shaft at a plurality of portions dispersed in the annular axial direction of each stage of the annular belt-shaped magnetic plate 10. 20 is wound and attached, and both ends 22a and 22b are pulled out in parallel, and a magnetic field generated by applying a shaking current I1 of a predetermined frequency to the lead-out portions 22a and 22b of each conductor coil unit 20 by the coil driving device 30. Thus, since the ring-shaped magnetic plate 10 is magnetically shaken, the following advantageous effects can be obtained.

(A) A coil unit 20 is wound around each stage of the ring-shaped magnetic plate 10 in a direction substantially perpendicular to the annular axis, and currents of the same size and substantially opposite directions are point-symmetrical around the annular axis of the ring-shaped magnetic plate 10 To generate a uniform shaking magnetic field along the axial direction on the inner side of the ring-shaped magnetic plate 10, and a leakage magnetic field (shaking noise) from the conducting coil unit 20 due to the canceling effect of the reverse current flowing in a point-symmetric manner. Can be reduced.
(B) By generating a uniform shaking magnetic field along the annular axis on the inner side of the ring-shaped magnetic plate 10, the magnetic properties inside the magnetic body can be evenly shaken to efficiently improve the magnetic characteristics.
(C) Further, by pulling out the ends 22a and 22b of the conducting wire coil unit 20 wound around the ring-shaped magnetic plate 10 so as to be adjacent to each other in parallel, other than the winding portion due to the cancellation effect of the reverse current flowing through the leading portions 22a and 22b. Leakage magnetic field (shaking noise) can be reduced.

(D) Further, by pulling out both ends 22a and 22b of the conductor coil unit 20 while twisting each other, the effect of canceling the reverse current flowing through the lead portions 22a and 22b is enhanced, and the leakage magnetic field from the conductor coil unit 20 is extremely small. Can be suppressed.
(E) 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 conductive coil unit 20 is reversed, and the reverse direction leaks from the conductive coil unit 20 of the adjacent stage. By mutually canceling each other's magnetic field, the leakage magnetic field (shaking noise) can be further reduced.
(F) The magnetic properties inside the ring-shaped magnetic plate 10 are evenly swayed to improve the magnetic characteristics efficiently, and the magnetic field leaking to the magnetic shield space (shaking noise) is suppressed to a small size, thereby making the open magnetic shield structure It can be expected that the shielding performance is surely and greatly 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 the Example of the shaking type | mold open type | mold magnetic shield structure by this invention which wound the conducting wire coil unit 20 to the several site | part disperse | distributed to the annular-axis direction of each step of the ring-shaped magnetic plate 10 in the direction substantially orthogonal to the annular axis, respectively. It is. FIG. 3 is an explanatory view of a shaking type open magnetic shield structure in which conductive coil 25 is attached to each stage of the ring-shaped magnetic plate 10 independently at a predetermined pitch T interval. 3 is an explanatory view of an embodiment of a shaking type open magnetic shield structure in which a conductive coil 25 is continuously wound around each stage of the ring-shaped magnetic plate 10 at a predetermined pitch T. FIG. It is an experimental result which shows the leakage magnetic field distribution of the evaluation object area | region R by the shaking current of the magnetic shield structure of FIG. It is an experimental result which shows the leakage magnetic field distribution of the evaluation object area | region R by the shaking current of the magnetic shield structure of FIG. 2 is an explanatory view of a shaking type open magnetic shield structure in which conductor coils 25 are attached independently of each other at a predetermined pitch T interval across a plurality of stages of the ring-shaped magnetic plate 10. FIG. It is an experimental result which shows the leakage magnetic field distribution of the evaluation object area | region R by the shaking current of the magnetic shield structure of FIG. FIG. 3 is an explanatory diagram of a shaking type open magnetic shield structure in which a conductive coil 25 is continuously wound at a predetermined pitch T across a plurality of stages of an annular magnetic plate 10. It is an experimental result which shows the leakage magnetic field distribution of the evaluation object area | region R by the shaking current of the magnetic shield structure of FIG. It is explanatory drawing of the Example of the shaking type | mold open type | mold magnetic shield structure by this invention which made the direction of the shaking current reverse for every adjacent step of the ring-shaped magnetic board 10, or made the winding direction of the conducting wire coil unit 20 reverse. . It is explanatory drawing of the Example of the shaking type | mold open type | mold magnetic shield structure by this invention which connected the conducting wire coil unit 20 wound around the several site | part of each step of the ring-shaped magnetic board 10 in series (connection) sequentially. It is explanatory drawing of the three-layer shaking type | mold open-type magnetic shield structure 5x, 5y, 5z arrange | positioned in a nesting form. It is explanatory drawing of the application method of the shaking current with respect to the shaking type | mold open-type magnetic shield structure 5z of FIG. It is explanatory drawing of the conventional open type | mold magnetic shield structure. It is explanatory drawing of the magnetic shielding member using the conventional shaking.

  FIG. 1 shows an embodiment of a shaking type open type magnetic shield structure of the present invention arranged around a magnetic shield target space 1 (for example, a magnetic shield room). An open type magnetic shield structure 5z in FIG. 1A is formed on a plurality of parallel planes Pz1, Pz2,... Intersecting a first direction axis Az penetrating the center point O of the magnetic shield target space 1 at a predetermined interval dz. An annular belt-like magnetic plate 10 is disposed so as to surround the space with a predetermined belt width W (for example, 50 mm), and the magnetic shield target space 1 is enclosed by a plurality of annular belt-like magnetic plates 10 as in FIG. 14B. FIG. 1B shows an XY plan view including an annular belt-like magnetic plate 10 at any stage of the open type magnetic shield structure 5z, and an enlarged plan view and an enlarged side view of the ellipse C portion are shown in FIG. Shown in (D). In the illustrated example, the first direction axis Az that is the central axis of each ring-shaped magnetic plate 10 is the vertical direction 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 Y-axis penetrating 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 crossing angle may be other than orthogonal.

  For example, as shown in FIG. 14A, the ring-shaped magnetic plate 10 has a band width W and an appropriate length along the intersection line between the plane Pz intersecting the first direction axis Az and the inner surface of the target space. The plurality of strip-shaped conductor plates 2 are formed by joining the edges in a flat polygonal shape (for example, a cross-girder shape). The ring-shaped magnetic plate 10 can be made using a magnetic material that can be expected to improve magnetic properties by magnetic shaking, for example, cobalt-based and iron-based amorphous, permalloy, electromagnetic steel plate, etc., especially in the weak magnetic field region. It is desirable to use a cobalt-based amorphous material whose magnetic permeability is much higher than others. Generally, cobalt-based amorphous is provided as a ribbon-like magnetic plate with a maximum width of about 50 mm, and no wider material is provided. Therefore, in a sealed magnetic shield structure, a plurality of amorphous ribbons are paralleled as shown in FIG. However, in the open type magnetic shield structure, the annular belt-like magnetic plate 10 can be formed using the thin belt-like magnetic plate as it is, so that the magnetic material suitable for the open type magnetic shield structure is used. 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 type magnetic shield structure 5z, A coil driving device 30 for applying a shaking current having a predetermined frequency to the conducting wire coil unit 20 is provided. The conducting coil unit 20 is not continuously wound around the entire ring-shaped magnetic plate 10 but is distributed and wound around a plurality of portions separated in the annular axial direction of the ring-shaped magnetic plate 10. In order to improve the magnetic properties of the annular belt-shaped magnetic plate 10, it is effective to excite a uniform shaking magnetic field inside the annular belt-shaped magnetic plate 10, and a conductive coil is continuously wound around the entire annular belt-shaped magnetic plate 10. It is also possible to 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 unit 20 dispersed in the direction of the annular axis of the ring-shaped magnetic plate 10, a uniform magnetic field is generated inside the ring-shaped magnetic plate 10 and a leakage magnetic field (shaking noise) can be reduced relatively easily. can do.

  As shown in the enlarged plan view and the enlarged side view of FIGS. 1C and 1D, the conductor coil unit 20 of the illustrated example has an intermediate portion on a ring-shaped magnetic plate 10 substantially perpendicular to the annular axis. Winding is performed, and both ends 22a and 22b are drawn out in parallel and connected to the coil driving device 30. For example, by winding an intermediate portion of the conductor coil unit 20 around the annular belt-shaped magnetic plate 10 having a belt width of 50 mm at a pitch of about 1 to 2 mm, the angle formed by the conductor coil unit 20 (current direction) with respect to the annular axis of the annular belt-shaped magnetic plate 10 is increased. It is about 89 °. As shown in FIG. 1 (D), the conducting coil unit 20 wound substantially perpendicularly to the annular axis is shaken at a point-symmetrical position with respect to the center of gravity of the cross section (the cross section of the magnetic circuit) intersecting the annular axis. By flowing a current, a uniform shaking magnetic field can be generated along the axial direction inside the ring-shaped magnetic plate 10, and the magnetic flux inside the ring-shaped magnetic plate 10 can be evenly shaken to exhibit a magnetic shaking effect. .

  In addition, the conducting coil unit 20 wound substantially perpendicularly to the annular shaft has a leakage magnetic field to the outside of the ring-shaped magnetic plate 10 due to the effect of canceling the reverse current flowing symmetrically with respect to the center of gravity of the cross section of the magnetic circuit. (Shaking noise) can be kept low. Further, by pulling out the lead portions 22a and 22b of the conductor coil unit 20 in parallel, the leakage magnetic field (shaking noise) from other than the winding portion is 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 twisting the lead portions 22a and 22b of the conductor coil unit 20 to each other, it is possible to enhance the reverse current cancellation effect and further suppress the leakage magnetic field. As described above, the lead coil unit 20 in the illustrated example can easily perform uniform shaking inside the magnetic body and reduce shaking noise outside the magnetic body. Therefore, the open type magnetic shield structure is compared with the sealed type magnetic shield structure. Thus, a significant improvement in shielding performance by magnetic shaking can be expected.

  1 applies a shaking current I1 having a predetermined frequency to the lead portions 22a and 22b of each conductor coil unit 20 in parallel. That is, the conductor coil unit 20 is wound around each stage of the ring-shaped magnetic plate 10 so as to be the same right-handed or left-handed, and the input / output loop conductors 23a and 23b having substantially the same diameter as the ring-shaped magnetic plate 10 are adjacent to each other. Arranged in parallel, one lead portion 22a of each lead coil unit 20 is connected to an input loop lead (or output loop lead) 23a, and the other lead 22b is connected to an output loop lead (or input loop lead) 23b. By doing so, each conducting wire coil unit 20 is connected in parallel with the coil driving device 30 via the loop conducting wires 23a and 23b.

  In the embodiment of FIG. 1, magnetic field leakage from the input / output loop conductors 23a and 23b connecting the conductor coil units 20 can also be a problem, but the input / output loop conductors 23a and 23b are adjacent to each other in parallel as in the illustrated example. By disposing, the generated magnetic field can be canceled by the reverse input / output current, and the leakage magnetic field from the input / output loop conductors 23a, 23b can be kept small. If necessary, the cancellation effect can be enhanced by twisting the input / output loop conductors 23a and 23b. Note that it is not necessary to provide a plurality of input / output loop conductors 23a, 23b corresponding to each stage of the ring-shaped magnetic plate 10, and as shown in FIG. 10 (B), via the individual input / output loop conductors 23a, 23b. The shaking current I1 can be applied in parallel to the multi-stage conducting wire coil unit 20.

  Further, the connection between the coil driving device 30 and each conductor coil unit 20 is not limited to the parallel connection as shown in FIG. 1, and for example, as shown in FIG. It is also possible to sequentially connect (connect) the portions 22 a and 22 b in series, and apply the shaking current I 1 in series to the lead portions 22 a and 22 b of each conductor coil unit 20 by the coil driving device 30. In the embodiment of FIG. 11 (A), the conducting coil unit 20 is wound around each of the plurality of portions of each step of the ring-shaped magnetic plate 10 in a direction substantially perpendicular to the annular shaft, and the lead portions 22a at both ends of each conducting coil unit 20 are wound. , 22b are drawn adjacently in parallel, and the lead portions 22a, 22b of the respective conductive wire coil units 20 adjacent to each other in the annular axial 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 ellipse C portion.

  In the embodiment shown in FIG. 11, magnetic field leakage from the coupling conductor 26 connecting the conductor coil units 20 in series can be a problem, but the coupling conductor is connected to each stage of the ring-shaped magnetic plate 10 as shown in FIG. 26 are arranged in parallel to each other so as to pass a reverse current and are connected in series to the coil driving device 30 via the coupling conductor 26 and the loop conductor 27, so that the coupling conductor 26 is connected. The magnetic field generated from the can be canceled out and the leakage magnetic field can be kept small. It is also possible to enhance the cancellation effect by twisting the coupling conductor 26 and the loop conductor 27 as necessary.

  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 terminating end portion by the coupling conductor 26, and the annular axial direction from the terminating portion to the starting end portion is connected. The conducting wire (return conducting wire) returning in the opposite direction is a loop conducting wire 27, and the shaking current I1 from the coil driving device 30 is sequentially applied to each conducting coil unit 20 from the starting end portion to the terminating portion via the coupling conducting wire 26, and the terminating end. It returns to the coil drive device 30 from the part through the loop conducting wire 27 and the starting end part. In the illustrated example, one conducting wire is continuously wound around a plurality of stages of the ring-shaped magnetic plate 10, but the conducting coil units 20 at different stages are not necessarily connected to each other, and at least one conducting wire is provided. It is sufficient if the coil units 20 are connected in series. For example, it is also possible to individually apply a shaking current to the conductive coil unit 20 that is provided with a coil driving device 30 for each stage and is 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 coil 25 is wound around the ring-shaped magnetic plate 10 of each stage of the open type magnetic shield structure 5z. In order to confirm the leakage magnetic field in this case, a model experiment as shown in FIG. 2 was performed. In this experiment, as shown in FIG. 2 (A), four belt-like magnetic plates having a width of 50 mm, a length of 1000 mm, and a thickness of 5 mm were joined in a cross-beam shape to form an annular belt-like magnetic plate 10 (magnetic circuit) having an outer shape of 950 mm. The ring-shaped magnetic plate 10 is arranged in five stages at a predetermined interval dz = 200 mm to form an open-type magnetic shield structure 5z, and each of the ring-shaped magnetic plates 10 at each stage is arranged in a direction perpendicular to the annular axis. Was wound at a predetermined pitch T, and a shaking current (frequency: 200 Hz) was applied. The size of the outer shape of the ring-shaped magnetic plate 10 represents the length of the central axis of the annular magnetic circuit.

  2B shows a plan view parallel to the XY plane of the open type magnetic shield structure 5z, and FIG. 2C shows a cross-sectional view parallel to the YZ plane of the open type magnetic shield structure 5z. 2D is a schematic plan view of the coil current obtained by enlarging the ellipse D portion of FIG. 2B, and FIG. 2E is a schematic side view of the coil current viewed from the annular axis direction of the ring-shaped magnetic plate 10. The figure is shown. As shown in FIGS. 2B and 2D, the conductive coil 25 in this case is not continuous with each other, and a closed circuit independent of each other at each winding position at a predetermined pitch T interval is assumed. Each coil 20 (hereinafter also 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 circuit in consideration of the canceling effect of the generated magnetic field. The cross-sectional size is 50 mm × 5 mm.

  For comparison, as shown in FIG. 6, a conducting coil 25 is wound around a five-step annular magnetic plate 10 (magnetic circuit) of an open magnetic shield structure 5z and wound at a predetermined pitch T to obtain 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 at each winding position with a predetermined pitch T interval. Is 50 mm × 805 mm. Shaking currents were applied to the 1-stage coil of FIG. 2 and the 5-stage coil of FIG. 6, respectively, 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 make the shaking strength of the magnetic circuit uniform between the one-stage coil shown in FIG. 2 and the five-stage coil shown in FIG. 6, the one-stage coil so that the magnetic flux densities induced inside the annular magnetic plate 10 match. The shaking current of the coil and the 5-stage coil was set. That is, when a 1 A shaking current is applied to the 1-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 1-A shaking is applied to the 5-stage coil of FIG. The magnetic flux density at the center of each stage of the magnetic circuit at each stage when current is applied is 38.7 mT in the first and fifth stages, and 57.8 mT in the second to fourth stages. It became bigger. This is due to the fact that the 5-stage coil straddles between the magnetic circuit of each stage and the current path is long. For this reason, the current value of the shaking current applied to the 5-stage coil was set to 0.339 A so that the magnetic flux density of the second to fourth stages coincided with 19.6 mT of the first-stage coil.

  4 (A) and 4 (B) show the magnetic field distribution of the magnetic field distribution in the evaluation target region R inside the open type magnetic shield structure shown in FIGS. 2 (B) and 2 (C). It is represented as a figure / vector diagram. FIGS. 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 region R. FIG. 4 and 7 each show a leakage magnetic field when only a coil having no magnetic circuit is arranged. When a magnetic circuit is present, the magnetic field generated from the magnetic material magnetized by the shaking current is shown. Is superimposed, the magnetic field distribution in the evaluation target region R becomes large. However, the superimposed value varies depending on the type, thickness (number of stacked layers), size, etc. of the magnetic material. Therefore, in order to evaluate only the magnetic field generated from the shaking coil, It is effective to consider the leakage magnetic field.

  Comparing the magnetic field distribution of FIG. 4 produced by the single-stage coil with the magnetic field distribution of FIG. 7 produced by the five-stage coil, it can be seen that the single-stage coil is about 1/13 smaller. In either case, the leakage magnetic field is only the horizontal component, and it can be seen that the magnetic field in the vertical direction hardly leaks. The reason for this is that the currents Ia, Ib, Ic, Id flowing through the coil are point-symmetric with respect to the center of gravity of the cross section of the magnetic circuit, as can be seen from the schematic diagrams of the coil currents shown in FIGS. Because it is in a position (a point-symmetrical position when viewed from the annular axis direction), and has the same magnitude and different directions, the magnetic fields (vertical components) generated from the currents Ia and Ic cancel each other and become zero, and are generated from the currents Ib and Id. This is because only the magnetic field (horizontal component) to be leaked to the evaluation target region R. Although the 5-stage coil has a small current value, the leakage magnetic field is large because the vertical current path for inducing the horizontal component of the magnetic field is long. Of course, the leakage magnetic field in the vertical direction is relatively large in the vicinity of the coil (periphery of the evaluation target area R), but 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 getting smaller at once.

  From 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 belt-like magnetic plate 10 of each stage of the open magnetic shield structure 5z along the annular axis, and a shaking current is applied. Thus, it can be seen that the magnetic field (shaking noise) leaking to the outside of the conductor coil 25 can be sufficiently reduced. When the sealed magnetic shield structure is 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 compared to the sealed magnetic shield structure. It can be said that there is an advantage. In addition, as shown in FIG. 2E, a single-stage coil wound around a point-symmetrical 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 ring-shaped magnetic plate is evenly swayed.

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

  For comparison, as shown in FIG. 8, the conductor coil 25 is put together on a five-stage annular belt-like magnetic plate 10 (magnetic circuit) of the open type magnetic shield structure 5z, and the conductive coil 25 is turned at a predetermined pitch T (100 mm width, one turn). An experiment was performed in which a magnetic field generated inside the coil and a leakage magnetic field outside the coil were respectively obtained by numerical simulation by applying a shaking current by continuously winding the belt-shaped magnetic plate on each side (900 mm, 9 turns). In order to align the magnetic flux density induced inside the ring-shaped magnetic plate 10 with that of Experimental Example 1 (in the case of the single-stage coil in FIG. 2), the current value of the shaking current applied to the single-stage coil in FIG. The current value of the shaking current applied to the 5-stage coil of FIG. 8 was set to 0.339A.

  5A and 5B show the leakage magnetic field outside the first stage coil of FIG. 3 as a contour diagram / vector diagram of the magnetic field distribution in the evaluation target region R inside the open type magnetic shield structure. FIGS. 9A and 9B show the leakage magnetic field outside the five-stage coil of FIG. 8 as a contour diagram and vector diagram of the magnetic field distribution in the evaluation target region R. FIG. 5 and 9 also show the leakage magnetic field when only the coil having no magnetic material circuit is arranged in order to avoid the superposition of the magnetic field generated from the magnetic material, as in the case of FIGS. Show.

  Comparing the magnetic field distribution of FIG. 5 made by the single-stage coil with the magnetic field distribution of FIG. 9 made by the five-stage coil, the leakage magnetic field has a dominant vertical component, and the single-stage coil is about 30 times larger. I understand that The reason for this is that, 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 out the vertical component of the generated magnetic field is insufficient. In the five-stage coil of FIG. 9, the currents Ia and Ic are separated, so that a certain amount of cancellation effect is seen. However, the vertical component of the leakage magnetic field is large in the one-stage coil of FIG. The positions of the currents Ib and Id flowing through the coils are also shifted in the Y-axis direction, but the influence on the leakage magnetic field (horizontal component) is relatively small.

  From the comparison of the magnetic field distributions in FIGS. 5 and 9, when a conducting current is applied by continuously winding the conducting coil 25 at a predetermined pitch T (one turn with a width of 100 mm) around a magnetic circuit having an open type magnetic shield structure, It can be seen that the leakage magnetic field of the first 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 one-stage coil for passing a shaking current at a point-symmetrical position when viewed from the annular axis direction of the ring-shaped magnetic plate 10 uniformly shakes the magnetic flux inside the ring-shaped magnetic plate 10 to achieve the magnetic shaking effect. However, there is a concern that the magnetic environment may deteriorate due to the leakage magnetic field (shaking noise) accompanying the shaking current.

  In the open type magnetic shield structure 5z shown in FIG. 3, the conductive coil 25 is continuously wound around the annular belt-like magnetic plate 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, leakage of the magnetic field from the input / output lines 20a and 20b together with the coil 20 wound around the magnetic circuit at each stage may be a problem, but the input / output lines 20a and 20b are adjacent to each other in parallel as in the illustrated example. By disposing, the magnetic field generated in the input / output lines 20a and 20b can be canceled by the input / output current in the reverse direction, and the leakage magnetic field can be kept small. It is also effective to enhance the cancellation effect by twisting the output lines 20a and 20b as necessary. However, the conductor coil 25 does not need to be continuously wound around the plurality of stages of the annular belt-like magnetic plate 10 as in the illustrated example, and it is sufficient if it 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 coil 25 for each stage.

[Experiment 3]
As shown in FIG. 3, in the open type magnetic shield structure 5z continuously wound around the conductor coil 25 at a predetermined pitch T around each side of the annular belt-like magnetic plate 10 in each step, the predetermined shown in FIGS. 3 (D) and 3 (E). If the coil currents Ia and Ic of the conductor coil 25 having the pitch T are brought close to each other on the XY plane like the coil currents Ia and Ic of the conductor coil 25 shown in FIGS. It can be expected that the magnetic field distribution of FIG. 5 made by the coil 20 is brought close to the magnetic field distribution of FIG. 4 made by the single-stage coil 20 of FIG. 2 to reduce the leakage magnetic field. Therefore, the predetermined pitch T of the conductive coil 25 continuously wound around each side (900 mm) of the ring-shaped magnetic plate 10 of FIG. 3 is (a) 100 mm (900 mm width 9 turns), (b) 50 mm (900 mm width) 18 turns), (c) 20 mm (45 turns for a 900 mm width), and (d) 10 mm (90 turns for a 900 mm width), and the experiment for sequentially obtaining the leakage magnetic field in the evaluation target region R by numerical simulation was repeated.

  Regardless of the predetermined pitch T of the conductor coil 25, when the magnetic flux density induced in the ring-shaped magnetic plate 10 is aligned with that of Experimental Example 1 (in the case of the one-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 is 1.118 A, (c) 20 mm is 1.020 A, and (d) 10 mm is 1.005 A. Moreover, since the number of turns (the number of turns) increases when the predetermined pitch T is reduced, it is expected that the leakage of the shaking noise can be further reduced by reducing the current value of the shaking current as the number of turns increases.

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

  The column of 5-step coil (continuous) in Table 1 shows the leakage magnetic field in the evaluation target region R of the conductive coil 25 continuously wound around the 5-step ring-shaped magnetic plate 10 at a predetermined pitch of 100 mm as shown in FIG. In addition, the average value field of the leakage magnetic field of the first stage coil (continuous) in Table 1 shows the leakage of the evaluation target area R when the predetermined pitch T of the first stage 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 in the average value in the vertical plane are shown. As can be seen from the ratio column with the 5-stage coil (continuous) in Table 1, both the horizontal and vertical leakage magnetic fields produced by the 1-stage coil in FIG. 3 are leaked from the horizontal and vertical planes produced by the 5-stage coil in FIG. Although it is larger than the magnetic field, if the predetermined pitch T of the one-stage coil is decreased (the number of turns is increased), the coil currents Ia and Ic approach in the XY plane (see FIGS. 3D and 3E). It is possible to increase the cancellation rate and reduce both the horizontal and vertical leakage magnetic fields.

  From Table 1, a wire coil (one-stage coil) 20 is wound around each step of the ring-shaped magnetic plate 10 surrounding the magnetic shield space 1 along the axial direction at a predetermined pitch T so that the leakage magnetic field outside the wire coil 25 is canceled out. By setting a predetermined winding pitch T of the conductive coil 25, the magnetic properties inside the ring-shaped magnetic plate 10 are evenly swayed to improve the magnetic characteristics efficiently and at the same time, the leakage magnetic field (shaking) to the magnetic shield space 1 is improved. It can be seen that (noise) can be kept small. However, even if the predetermined pitch T of the first stage coil is reduced to 10 mm, the leakage magnetic field does not become smaller than that of the five-stage coil having a predetermined pitch of 100 mm. Therefore, in order to further reduce the leakage magnetic field, measures other than the pitch setting are required. Is required.

  However, Table 1 shows the simulation result of the leakage magnetic field by the model experiment of FIG. 3, and the leakage magnetic field differs depending on the model. Although the model experiment of FIG. 3 is relatively small, the leakage magnetic field is large. However, when the size of the magnetic shield space 1 is changed, the leakage magnetic field is reduced by 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 conductor coil 25 is appropriately set according to the design conditions and the required performance, the conductor coil 25 is continuously wound around each stage of the ring-shaped magnetic plate 10 at the predetermined pitch T as shown in FIG. The shaking type open type 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 conductive coil 25 is continuously wound around each stage of the ring-shaped magnetic plate 10 surrounding the magnetic shield space 1 generates relatively large shaking noise (vertical component). 1A. As shown in FIG. 1A, each ring has an open magnetic shield structure 5z in which an annular band-shaped magnetic plate 10 (magnetic circuit) having an outer shape (the length of the central axis) of 950 mm is arranged in five stages. A plurality of predetermined portions (three portions on each side) dispersed in the direction of the annular axis of the belt-like magnetic plate 10 are attached by winding the conductive coil unit 20 by three turns with the same right or left turn substantially perpendicular to the annular shaft. , Both ends 22a and 22b of the winding part are pulled out adjacent to each other in parallel, and a shaking current I1 (frequency: 200 Hz) in the same direction is applied by the coil driving device 30. Leakage magnetic field when (shaking noise) Experiments were conducted to determine the numerical simulation. The lead portions 22a and 22b of each conductor coil unit 20 were drawn out as stranded wires and connected in parallel to the coil driving device 30 as shown in FIG.

  Also in this experiment, the shaking current (excitation current) was set so that the ampere turn (AT) coincided with 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). The current value was set. That is, in FIG. 1A, since there are 9 turns per side (900 mm) of the ring-shaped magnetic plate 10, the shaking current (excitation current) is 9AT as in Experimental Example 1 and Experimental Example 3. The current value flowing through each conductor coil unit 20 was set to 1A. When changing the magnitude of the shaking current, it can be adjusted by the value of the current passed through each conductor coil unit 20, but it can also be adjusted by the number of turns (number of turns) of the conductor coil unit 20 at each predetermined part. It can also be adjusted by increasing or decreasing the attachment site of the conductive wire coil unit 20 in the ring-shaped 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 field of the leakage magnetic field of the coil dispersion (upper and lower two columns) in Table 1 is a conducting coil that is distributed and attached in the direction of the annular axis of each ring-shaped magnetic plate 10 as shown in FIG. The change of the average value in the horizontal plane of the leakage magnetic field of the evaluation object area | region R when the shaking current I1 of the same direction is applied to the unit 20 is shown, respectively. As can be seen from the ratio column with the 5-stage coil (continuous) in Table 1, the leakage magnetic field produced by the conductive coil unit 20 dispersed in the ring-shaped magnetic plate 10 as shown in FIG. 8 is 0.02 or less (1/50 or less) of the leakage magnetic field produced by the five-stage coil of FIG. 8, and compared with the leakage magnetic field produced by the conductive coil 25 continuously wound around the ring-shaped magnetic plate 10 as shown in FIG. It can be made small enough.

  According to this experiment, the conducting coil unit 20 is wound around a plurality of portions dispersed in the direction of the annular axis of the annular magnetic plate 10 in a direction substantially perpendicular to the annular axis, and a shaking current I1 is caused to flow, whereby the shaking of the annular magnetic plate 10 is performed. It was confirmed that the leakage magnetic field (shaking noise) associated with the can be greatly reduced. The conducting coil unit 20 wound substantially perpendicularly to the annular axis of the magnetic circuit effectively cancels the shaking noise from the winding part by a reverse current that flows symmetrically with respect to the center of gravity of the cross section of the magnetic circuit. This is considered to be because the shaking current from other than the winding portion can be effectively canceled by the reverse current flowing through the lead portions 22a and 22b drawn adjacently in parallel.

  From this experimental result, according to the shaking type open-type magnetic shield structure of FIG. 1, the magnetic field inside the magnetic material is evenly swayed to improve the magnetic characteristics efficiently, and the leakage magnetic field into the magnetic shield room is made sufficiently small. The shielding performance can be surely and greatly improved. Further, if the size of the magnetic shield space 1 is changed, the leakage magnetic field is reduced due to the distance attenuation effect. Therefore, it is considered that the leakage magnetic field when applied to a magnetic shield room of a normal medical facility or research facility is extremely small. By appropriately setting the winding part (mounting pitch), the number of windings (number of turns), the current value and direction of the applied shaking current according to the 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, as shown in FIG. 1, the conducting coil unit 20 is wound around each stage of the ring-shaped magnetic plate 10 in a direction substantially perpendicular to the annular shaft, and the shaking current I1 is caused to flow, so that the shaking noise can be suppressed sufficiently small. However, if the shaking noise leaking at each adjacent stage of the ring-shaped magnetic plate 10 is reversed, the leakage of the shaking noise to the magnetic shield space 1 is further reduced by canceling out the leakage magnetic fields at the adjacent stages. You can expect to. In order to confirm this, as shown in FIG. 10 (A), the conductor coil unit 20 is wound around each stage of the ring-shaped magnetic plate 10 so as to be the same right-handed or left-handed, and then the coil driving device 30a, An experiment was performed to apply the shaking currents I1 and I2 (frequency 200 Hz) in opposite directions to the adjacent stages of the ring-shaped magnetic plate 10 by 30b, and to obtain the leakage magnetic field in the magnetic shield space 1 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 field of the leakage magnetic field of the coil dispersion (the lower column among the upper and lower columns) in Table 1 is the shaking current I1, which is reversed 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 region R when I2 is applied are shown. As can be seen from the ratio column with the five-stage coil (continuous) in Table 1, the leakage magnetic field in FIG. 10 (A) is 0.05 or less of the leakage magnetic field produced by the five-stage coil in FIG. As shown in FIG. 1A, the leakage magnetic field (shaking noise) is reduced to about 1/4 compared to the case where the shaking current I1 in the same direction is applied to each stage of the ring-shaped magnetic plate 10 as shown in FIG. It shows that it can be made smaller.

  Further, as shown in FIG. 10B, the conductive coil unit 20 is wound around the adjacent stages of the ring-shaped magnetic plate 10 so as to be reversed right-handed or left-handed, and then the coil driving device 30 forms the ring-band-shaped. 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 in the magnetic shield space 1 was obtained by numerical simulation. The result of this experiment was also the same as the coil dispersion in Table 1 described above (the lower column of the upper and lower columns). From these experimental results, the direction of the shaking current I1 applied to each stage of the ring-shaped magnetic plate 10 surrounding the magnetic shield space 1 or the winding direction of the lead coil unit 20 wound around each stage of the ring-shaped magnetic plate 10 is reversed. By doing so, it was confirmed that the leakage of shaking noise to the magnetic shield space 1 can be reduced by canceling out the leakage magnetic fields of adjacent stages.

  Thus, it is possible to achieve the “low leakage shaking type open magnetic shield structure capable of suppressing the leakage of shaking noise”, which is an object of the present invention.

  The open magnetic shield structure 5z in FIG. 1 is mainly intended for shielding a disturbance magnetic field in one or two directions in the XY plane, but in a magnetic shield target space 1 in which the direction of the disturbance magnetic field is not determined, the three-way disturbance magnetic field is shown. Can be an open type magnetic shield structure in which a plurality of units as shown in FIGS. 12A to 12C are combined with the structure of FIG. 1 as a basic unit. FIG. 12 shows an example of a cube-shaped open magnetic shield room having a basic size of 2550 mm each outside dimension installed in a medical facility or research facility.

  FIG. 12A shows that the target space 1 is surrounded by a predetermined band width W on a plurality of parallel planes Pz intersecting the first direction axis Az (Z axis) penetrating the magnetic shield target space 1 at a predetermined interval dz. An open type magnetic shield structure 5z similar to that shown in FIG. 1 provided with an annular magnetic plate 10 is shown. FIG. 12B shows the target space 1 with a predetermined band width W on a plurality of parallel planes Px intersecting the second direction axis Ax (X axis) penetrating the magnetic shield target space 1 at a predetermined interval dx. An open type magnetic shield structure 5x provided with a ring-shaped magnetic plate 10 so as to surround is shown. FIG. 12C shows a plurality of crossing with a third direction axis Ay (Y axis) penetrating the magnetic shield target space 1 at a predetermined interval dy. An open type magnetic shield structure 5y is shown in which a ring-shaped magnetic plate 10 is provided so as to surround the target space 1 with a predetermined band width W on each of the parallel planes Py. Three open type magnetic shield structures 5z, 5x, 5y are arranged in a nested manner around the magnetic shield target space 1, or any two of the open type magnetic shield structures 5z, 5x, 5y are selected and nested. It is possible to provide a magnetic shield room that shields disturbance magnetic fields in three directions by arranging and integrating them.

  12 (A) to 12 (C), each of the annular belt-shaped magnetic plates 10 is formed by arranging strips of cobalt-based amorphous (thickness 23 μm × 20 layers, width 50 mm) in a cross-beam shape, for example, a predetermined interval dz = The open magnetic shield structures 5z, 5x, and 5y can be formed by arranging 12 stages at 200 mm. Open-type magnetic shield structures 5z and 5x are provided with openings surrounded by door frames 14a, 14b, 14c and 14d made of the same strip-shaped magnetic plate (cobalt-based amorphous) 10, and PC permalloy plates ( A door 12 having a two-layer structure (inner side and outer side) having a thickness of 1 mm × two layers is attached.

  As in the case of FIGS. 1, 10 and 11, the annular magnetic plate 10 at each stage of the open type magnetic shield structure 5z, 5x, 5y has an annular shaft and substantially a plurality of portions dispersed in the annular axial direction. The conductive wire coil unit 20 is wound in a direction perpendicular to the upper side, and both ends 22a and 22b thereof are drawn out in parallel and connected to the coil driving device 30. The coil driving device 30 applies a shaking current of a predetermined frequency to each conductive wire coil unit 20. Then, the magnetic shielding structures 5z, 5x and 5y are magnetically shaken. The winding part (mounting pitch), the number of windings (number of turns), and the current value and direction of the shaking current applied to the conductive coil unit 20 are appropriately determined according to design conditions and required performance (required magnetic field environment). Can be determined.

[Experimental Example 6]
FIG. 13A shows an example of a method of attaching the conductive wire coil unit 20 to the annular belt-like magnetic plate (magnetic circuit) 10 in each stage of the open type magnetic shield structure 5y without 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 in the ring-shaped magnetic plate 10 due to 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 confirmed. (A) 150 mm (15 winding parts on one side), (b) 300 mm (8 winding parts on one side), (c) 525 mm (5 winding parts on one side), (d) 1050 mm (3 winding parts on one side) An experiment was conducted to obtain the distribution of the magnetic flux density induced inside the ring-shaped magnetic plate 10 by numerical simulation.

  In this experiment, regardless of the mutual interval T, the winding coil unit 20 is wound around each winding part in a direction substantially perpendicular to the annular shaft (turning number = 8T), as shown in FIGS. 1C and 1D. , 8 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 part. Further, since the magnetic flux density induced in the ring-shaped magnetic plate 10 is uniform regardless of the mutual interval T, the shaking current (excitation current) per side of the ring-shaped magnetic plate (magnetic circuit) 10 becomes 12AT. (A) When the mutual interval T = 150 mm, the current value of the shaking current I1 is 0.1 A, (b) 0.1875 A when 300 mm, (c) 0.3 A when 525 mm, (d) When it was 1050 mm, it set to 0.5A. The results of this experiment are shown in Table 2.

  The column of magnetic flux density in Table 2 excludes the corner portion when the shaking current is applied to the conductive coil unit 20 while switching the mutual interval T in the ring-shaped magnetic plate (magnetic circuit) 10 of FIG. The maximum value, minimum value, and minimum value of the magnetic flux density induced inside the magnetic material are shown. As can be seen from Table 2, the variation in the induced magnetic flux density (ratio of (maximum value−minimum value) to the average value) increases as the mutual interval T between the winding portions of the conductor coil unit 20 increases. Is 525 mm or less, the variation in magnetic flux density is about 6% or less, and it can be said that there is no problem from the viewpoint of obtaining a magnetic shaking effect by uniformly shaking the inner side of the ring-shaped magnetic plate 10. On the other hand, when the mutual interval T is 1050 mm, the variation in the magnetic flux density exceeds 30%, and it is difficult to evenly shake the inside of the ring-shaped magnetic plate 10.

  According to this experiment, the mutual interval T between the winding portions of the conductor coil unit 20 at each stage of the ring-shaped magnetic plate 10 is within a range where the shaking magnetic field induced inside the ring-shaped magnetic plate 10 is uniform, for example, variation in magnetic flux density. It was confirmed that it was desirable to set the value to be 6% or less. Accordingly, as shown in FIG. 13A, for example, a plurality of ring-shaped magnetic plates 10 around which the conductive wire coil units 20 are wound at a mutual interval T of 525 mm intersect with the third direction axis Ay (Y axis) at a predetermined interval dy. By disposing each on the parallel planes Py of the steps, an open magnetic shield structure 5y without an opening can be constructed. The open-type magnetic shield structures 5z and 5x having an opening can be similarly configured.

  FIG. 13B shows an example of a method of attaching the conductor coil unit 20 to the ring-shaped magnetic plate 10 of the open magnetic shield structure 5z having an opening at a predetermined mutual interval (attachment pitch) T. In the illustrated example, the conductor coil unit 20 is attached only to the side where the door 12 is located among the sides of the ring-shaped magnetic plate 10, but the conductor coil unit 20 is similarly attached to the other three sides at a predetermined mutual interval T. It is done. The ring-shaped magnetic plate 10 of the open type magnetic shield structure 5x having an opening can be similarly configured.

  13A and 13B, the both ends 22a and 22b of each conductor coil unit 20 attached to the annular belt-like magnetic plate 10 are pulled out in parallel and adjacent, for example, FIG. 1A, FIG. As shown in FIG. 10B, the coil driving device 30 is connected, and the coil driving device 30 applies a shaking current I1 in parallel to the lead portions 22a and 22b of each conductor coil unit 20. Alternatively, as shown in FIG. 11A, the lead-out portions 22a and 22b of the respective conductive wire coil units 20 are connected in series by the combined conductive wire 26, and the shaking current I1 is applied in series by the coil driving device 30, and the combined conductive wire 26 and A reverse current (-I1) is passed through the loop conductor 27 arranged adjacent and parallel.

DESCRIPTION OF SYMBOLS 1 ... Magnetic shield object space 2 ... Strip | belt-shaped magnetic board 3 ... Shield housing 5 ... Open type 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 ... Lead-out part 23a, 23b ... Input / output loop conductor 24a, 24b ... Input / output line 25 ... Conductor coil 26 ... coupling | bonding Conductor 27 ... Loop conductor 30 ... Coil driving device 40 ... Magnetic shield member 41 ... Base materials 42a, 42b ... Magnetic ribbon 43 ... Conductor 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 target area T ... pitch W ... band width of ring-shaped magnetic plate

Claims (9)

A ring-shaped magnetic plate provided on a plurality of parallel planes intersecting the first direction axis passing through the magnetic shield target space at a predetermined interval so as to surround the space with a predetermined band width, and each step of the ring-shaped magnetic plate A plurality of portions distributed in the direction of the annular axis and wound around the annular shaft in a substantially right angle direction, attached to the lead coil unit with the both ends thereof being adjacent to each other in parallel, and a predetermined frequency at the lead portion of each of the lead coil units. A low-leakage shaking type open magnetic shield structure comprising a coil driving device for applying the above-described shaking current and magnetically shaking an annular belt-shaped magnetic plate with a magnetic field generated by each of the conductive wire coil units. 2. A low-leakage shaking type open-type magnetic shield structure according to claim 1, wherein the lead-out portions of the conductor coil units are pulled out while being twisted with each other. 3. The structure according to claim 1, wherein each of the conductor coil units is wound around each step of the ring-shaped magnetic plate so as to be wound in the same right-handed or left-hand direction, and is reversed every adjacent step of the ring-shaped magnetic plate by the coil driving device. A low-leakage shaking type open magnetic shield structure that applies a shaking current in the direction. 3. The structure according to claim 1 or 2, wherein each conductor coil unit is wound so as to be reversed right-handed or left-handed for each adjacent step of the ring-shaped magnetic plate, and is wound on each step of the ring-shaped magnetic plate by the coil driving device. A low-leakage shaking type open magnetic shield structure that applies a shaking current in the same direction. 5. The structure according to claim 1, wherein a plurality of conductor coil units at each stage of the ring-shaped magnetic plate are provided in parallel with input / output loop conductors arranged in parallel to connect to a coil driving device. A low-leakage shaking type open magnetic shield structure in which the leakage magnetic field of the conductor is canceled by the input / output current in the reverse direction. 5. The structure according to claim 1, wherein a plurality of conductor coil units at each stage of the ring-shaped magnetic plate are connected in series in the annular axial direction, and oppositely arranged in parallel with the joint conductor. Is formed by connecting a series of coil units to the coil driving device via the coupling conductor and the loop conductor, and canceling the leakage magnetic field of the coupling conductor and the loop conductor by a reverse current. Leaky shaking type open magnetic shield structure. 7. The structure according to claim 1, wherein a mutual spacing of the winding coil unit winding portions of each step of the ring-shaped magnetic plate is made uniform so that a shaking magnetic field induced inside the ring-shaped magnetic plate is uniform. Low leakage shaking type open magnetic shield structure. 8. The structure according to claim 1, wherein each space is provided on a plurality of parallel planes intersecting with a second direction axis passing through the magnetic shield target space at a predetermined interval so as to surround the space with a predetermined band width. A group of second annular belt-like magnetic plates and a plurality of portions distributed in the annular axial direction of each stage of the second annular belt-like magnetic plate are attached by being wound substantially perpendicularly to the annular shaft, and both ends thereof are adjacent in parallel. A second conducting wire coil unit is provided, and an annular belt-like magnetic plate group and a second annular belt-like magnetic plate group are arranged in a nested manner around the target space, and each conducting coil unit is predetermined by the coil driving device. A low-leakage shaking type open-type magnetic shield structure obtained by magnetically shaking each band-shaped magnetic plate group by applying a frequency-shaking current. 9. The structure according to claim 8, wherein a third annular belt-like magnet is provided on each of a plurality of parallel planes intersecting with a third direction axis passing through the magnetic shield target space at a predetermined interval so as to surround the space with a predetermined band width. A group of plates and a plurality of portions of the third ring-shaped magnetic plate dispersed in the direction of the annular axis are attached by being wound substantially perpendicularly to the annular axis, and drawn out with their both ends adjacent to each other in parallel. A three-conductor coil unit is provided, and an annular belt-like magnetic plate group, a second annular belt-like magnetic plate group, and a third annular belt-like magnetic plate group are arranged in a nested manner around the target space, and each conductor coil is arranged by the coil driving device. A low-leakage shaking type open-type magnetic shield structure obtained by applying a shaking current of a predetermined frequency to the unit to magnetically shake each ring-shaped magnetic plate group.