Magnetic shield device

Abstract

To provide a magnetic shield device for shielding magnetism from the outside, which maintains a low magnetic field environment in the magnetic shield device (magnetic shield space) and reduces a fluctuation amount of a magnetic field by suppressing temperature fluctuation of the magnetic shield device itself causing magnetic field fluctuation (maintaining temperature stability).SOLUTION: The magnetic shield device 1 includes two or more layers of magnetic shield members 11,12, a thermally conductive member 13 which can accommodate a magnetic sensor and a test object therein, is disposed outside the innermost magnetic shield member 11, and is in thermal contact with substantially the entire surface of the innermost magnetic shield member 11, and a thermally conductive member temperature stabilizing means (here, a constant-temperature fluid 14, a constant-temperature fluid passage 15, a constant-temperature fluid delivery function, and a heat insulating layer 19) for maintaining the thermally conductive member 13 at a constant temperature.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a magnetic shield device that shields against external magnetism and can house a magnetic sensor and a test object inside. [Background technology]

[0002] Conventionally, biomagnetic measurements using magnetic sensors, such as magnetoencephalography, have used SQUIDs (Superconducting Quantum Interference Devices), which are highly sensitive magnetic sensors that detect weak magnetic fields. When using such highly sensitive magnetic sensors, a magnetic shielding device that shields against external magnetism is used, as disclosed in Patent Document 1 (JP 2007-311523 A), for example. In recent years, optically pumped magnetometers (OPMs, hereafter referred to as OPM sensors in this specification) have been proposed as highly sensitive magnetic sensors to replace SQUIDs. Unlike SQUIDs, OPM sensors do not require cryogens such as liquid helium, and have the advantage of being able to achieve magnetic sensitivity comparable to that of SQUIDs at room temperature. Research is being conducted into their application to various biomagnetic measurements (e.g., magnetoencephalography). OPM sensors require an even lower magnetic field environment than conventional sensors as an operating condition, so they must be used within a magnetic shielding device that sufficiently blocks (reduces) external magnetic fields (external magnetic fields), including geomagnetism, and the residual magnetic field within the magnetic shielding device must be maintained below a certain value. In order to reduce the residual magnetic field, for example, as disclosed in Patent Document 2 (JP Patent Publication No. 11-243294), a magnetic field that decays over time is temporarily applied to the magnetic shield wall, thereby obtaining a low magnetic field (demagnetization) that satisfies the operating conditions of the OPM sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2007-311523 [Patent Document 2] Patent Publication No. 11-243294 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the inventors have come to the realization that temperature changes in the magnetic shield device (magnetic shield material) due to changes in the outside air temperature and heat generation from the magnetic sensors and test subject within the magnetic shield device will cause (measure) residual magnetic field fluctuations that cannot be ignored, particularly in biomagnetic measurements using OPM sensors. Specifically, when biomagnetic measurements were performed using an OPM sensor in a conventional magnetic shielding system, the inventors first noticed unexpected magnetic field fluctuations and resulting malfunctions of the OPM sensor. They investigated the possibility that the temperature dependency of the OPM sensor was the cause. This idea was conceived because, unlike conventional SQUID sensors, the OPM sensor does not require a cryogen such as liquid helium and can operate at room temperature. Specifically, as shown in FIG. 6 , an OPM sensor 102 and a temperature sensor 103 were housed in a thermally insulated duct 101 within a magnetic shielding system 100. Temperature-adjusting air was circulated through the thermally insulated duct 101 (indicated by the white arrow in FIG. 6 ), causing a temperature change only in the OPM sensor 102, and the residual magnetic field (magnetism) within the magnetic shielding system 100 was measured. The results are shown in FIG. 7 . As shown in FIG. 7 , slight temperature dependency (changes in the residual magnetic field (magnetism) due to temperature changes) was confirmed (measured) in the OPM sensor, but it was determined that this was not a major cause of malfunctions of the OPM sensor. Based on these results, the inventors conducted further intensive research and came to the conclusion that the temperature dependence of the shielding device itself may have a significant effect. Therefore, as shown in Fig. 8, a temperature sensor 103 was installed in magnetic shielding device 100, an OPM sensor 102 was housed in thermal insulation duct 101, and temperature-adjusting air was circulated within magnetic shielding device 100 excluding the thermal insulation duct 101 (indicated by the hollow arrows in Fig. 8), thereby applying a temperature change only to magnetic shielding device 100 and measuring the residual magnetic field (magnetism) within magnetic shielding device 100. The results are shown in Fig. 9. As shown in Fig. 9, it was found that the temperature dependence of the magnetic shielding device (changes in the residual magnetic field (magnetism) due to temperature changes) was greater than that of the OPM sensor. The inventors' verification as described above revealed that the residual magnetic field within the magnetic shielding device fluctuates over time due to temperature changes in the magnetic shielding device itself, which could narrow the dynamic range of the OPM sensor's operating range (the ratio and range of the maximum and minimum values ​​of the signal that the OPM sensor can process and reproduce). Furthermore, such temporal fluctuations in the residual magnetic field can cause problems when using the magnetic shielding device to perform characteristic tests on the OPM sensor, particularly DC stability tests and temperature characteristic tests, or when using the OPM sensor to perform biomagnetic measurements on a test subject. Therefore, an object of the present invention is to provide a magnetic shielding device that shields against external magnetic fields, which suppresses temperature fluctuations in the magnetic shielding device itself, which are the cause of magnetic field fluctuations (maintains temperature stability), thereby maintaining a low magnetic field environment within the magnetic shielding device (magnetically shielded space) and reducing the amount of magnetic field fluctuation. [Means for solving the problem]

[0005] The above objectives are achieved by the following: (1) A magnetic shield device that includes two or more layers of magnetic shielding material that shields against external magnetism and can accommodate a magnetic sensor and a test object therein, a thermally conductive member disposed outside the innermost magnetic shield member and in thermal contact with substantially the entire surface of the innermost magnetic shield member; a heat conductive member temperature stabilization means for maintaining the heat conductive member at a constant temperature; A magnetic shielding device comprising:

[0006] The above objectives are also achieved by the following: (2) A magnetic shield device that includes two or more layers of magnetic shielding material for shielding against external magnetism and can accommodate a magnetic sensor and a test object therein, a thermally conductive member disposed outside the innermost magnetic shield member and in thermal contact with substantially the entire surface of the innermost magnetic shield member; a constant temperature fluid passage through which a constant temperature fluid can flow and which brings the constant temperature fluid into thermal contact with the heat conductive member; a constant temperature fluid delivery function for continuously delivering the constant temperature fluid to the constant temperature fluid passage; A magnetic shielding device comprising:

[0007] The above objectives are also achieved by the following: (3) A magnetic shield device for biomagnetic measurement using an OPM sensor, which includes two or more layers of magnetic shielding material that shields against external magnetism and can accommodate an OPM sensor and a subject whose biomagnetic field is to be measured by the OPM sensor, a thermally conductive member disposed outside the innermost magnetic shield member and in thermal contact with substantially the entire surface of the innermost magnetic shield member; a constant temperature fluid passage through which a constant temperature fluid can flow and which brings the constant temperature fluid into thermal contact with the heat conductive member; a constant temperature fluid delivery function for continuously delivering the constant temperature fluid to the constant temperature fluid passage; A magnetic shielding device comprising:

[0008] (4) The magnetic shield device according to (2) or (3) above, wherein a heat insulating layer is provided on substantially the entire inner surface of the innermost magnetic shield member. (5) The magnetic shield device according to any one of (2) to (4) above, wherein a heat insulating layer is provided outside the innermost magnetic shield member. (6) The magnetic shield device includes a constant-temperature fluid circulation function that continuously sends the constant-temperature fluid to the constant-temperature fluid passage and continuously receives the constant-temperature fluid from the constant-temperature fluid passage, and a constant-temperature fluid temperature adjustment function that adjusts the temperature of the received constant-temperature fluid, The magnetic shield device according to any one of (2) to (5) above, wherein the constant temperature fluid circulation function and the constant temperature fluid temperature adjustment function are electrically and vibrationally insulated from the innermost magnetic shield member. (7) The magnetic shield device has a constant temperature fluid generating function for generating the constant temperature fluid, The magnetic shield device according to any one of (2) to (6) above, wherein the constant temperature fluid generating function is electrically and vibrationally insulated from the magnetic shield member of the innermost layer. (8) a second thermally conductive member disposed outward of the innermost magnetic shield member and in thermal contact with substantially the entire surface of the outer magnetic shield member; a second constant-temperature fluid passage through which a second constant-temperature fluid can flow and which brings the second constant-temperature fluid into thermal contact with the second thermally conductive member; a second constant-temperature fluid delivery function for continuously delivering the second constant-temperature fluid to the second constant-temperature fluid passage; The magnetic shield device according to any one of (2) to (7) above, comprising: (9) The magnetic shield device according to any one of (1) to (8) above, further comprising a demagnetizing function for demagnetizing the innermost magnetic shield member. [Effects of the Invention]

[0009] The magnetic shield device of the present invention is a magnetic shield device that has two or more layers of magnetic shield members that shield against external magnetic fields and can accommodate a magnetic sensor and a test object inside, and is equipped with a thermally conductive member that is arranged outside the innermost magnetic shield member and is in thermal contact with almost the entire surface of the innermost magnetic shield member, and a thermally conductive member temperature stabilization means for maintaining the thermally conductive member at a constant temperature. This suppresses temperature fluctuations in the magnetic shield device itself, which are the cause of magnetic field fluctuations (maintains temperature stability), thereby maintaining a low magnetic field environment within the magnetic shield device (magnetically shielded space) and reducing the amount of magnetic field fluctuation.

[0010] Furthermore, the magnetic shield device of the present invention is a magnetic shield device that has two or more layers of magnetic shield members that shield against external magnetism and can accommodate a magnetic sensor and a test subject inside, and is equipped with a heat conductive member that is arranged outside the innermost magnetic shield member and is in thermal contact with almost the entire surface of the innermost magnetic shield member, a constant temperature fluid passage through which a constant temperature fluid can flow and which brings the constant temperature fluid into thermal contact with the heat conductive member, and a constant temperature fluid delivery function that continuously delivers the constant temperature fluid to the constant temperature fluid passage. This suppresses temperature fluctuations in the magnetic shield device itself, which are the cause of magnetic field fluctuations (maintains temperature stability), thereby maintaining a low magnetic field environment within the magnetic shield device (magnetically shielded space) and reducing the amount of magnetic field fluctuation.

[0011] Furthermore, the magnetic shield device of the present invention is a magnetic shield device for biomagnetic measurement using an OPM sensor, which has two or more layers of magnetic shielding members that shield from external magnetism and can accommodate an OPM sensor and a subject whose biomagnetic field is to be measured by the OPM sensor inside, and is equipped with a heat conductive member that is arranged outside the innermost magnetic shielding member and is in thermal contact with almost the entire surface of the innermost magnetic shielding member, a constant temperature fluid passage through which a constant temperature fluid can flow and which brings the constant temperature fluid into thermal contact with the heat conductive member, and a constant temperature fluid delivery function that continuously delivers the constant temperature fluid to the constant temperature fluid passage. This suppresses temperature fluctuations in the magnetic shield device itself, which are the cause of magnetic field fluctuations (maintains temperature stability), thereby maintaining a low magnetic field environment within the magnetic shield device (magnetically shielded space) and reducing the amount of magnetic field fluctuation. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an embodiment of a magnetic shield device according to the present invention. [Figure 2] 2 is a front vertical cross-sectional view of the device main body of the magnetic shield device shown in FIG. [Figure 3] FIG. 3 is a front vertical cross-sectional view of a device main body showing an embodiment of the magnetic shield device of the present invention. [Figure 4] FIG. 4 is a front vertical cross-sectional view of the device main body showing another embodiment of the magnetic shield device of the present invention. [Figure 5] FIG. 5 is a front vertical cross-sectional view of the device main body showing another embodiment of the magnetic shield device of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view of an apparatus for measuring the temperature dependence of an OPM sensor. [Figure 7] FIG. 7 is a graph showing the temperature dependence of the OPM sensor measured using the apparatus of FIG. [Figure 8] FIG. 8 is a schematic cross-sectional view of an apparatus for measuring the temperature dependency of the magnetic shield device. [Figure 9] FIG. 9 is a graph showing the temperature dependence of the magnetic shield device measured using the device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] The magnetic shield device of the present invention will be described with reference to an embodiment shown in the drawings. As shown in Figures 1 and 2, the magnetic shield device 1 of the present invention is a magnetic shield device 1 that has two or more layers of magnetic shield members (here, two layers of magnetic shield members 11 and 12) that shield against external magnetism and can accommodate a magnetic sensor (not shown) and a test subject (not shown) inside, and is equipped with a heat conductive member 13 that is arranged outside the innermost magnetic shield member 11 and is in thermal contact with almost the entire surface of the innermost magnetic shield member 11, a constant temperature fluid passage (heat transfer fluid flow path) 15 through which a constant temperature fluid 14 can flow and which brings the constant temperature fluid (heat transfer fluid) 14 into thermal contact with the heat conductive member 13, and a constant temperature fluid delivery function (fluid delivery function) that continuously delivers the constant temperature fluid 14 to the constant temperature fluid passage 15.

[0014] The magnetic shield apparatus 1 of this embodiment is a magnetic shield apparatus 1 for biomagnetic measurement using an OPM sensor that can accommodate an OPM sensor (not shown) and a subject (not shown) whose biomagnetic properties are to be measured by the OPM sensor. That is, the magnetic shield device 1 is a magnetic shield device 1 for biomagnetic measurement using an OPM sensor that has two or more layers of magnetic shield members (here, two layers of magnetic shield members 11 and 12) that shield against external magnetism, and can accommodate an OPM sensor and a subject whose biomagnetic measurement is to be performed by the OPM sensor inside, and is equipped with a heat conductive member 13 that is arranged outside the innermost magnetic shield member 11 and is in thermal contact with almost the entire surface of the innermost magnetic shield member 11, a constant temperature fluid passage (heat transfer fluid flow path) 15 through which a constant temperature fluid 14 can flow and which brings the constant temperature fluid 14 (heat transfer fluid) into thermal contact with the heat conductive member 13, and a constant temperature fluid delivery function (fluid delivery function) that continuously delivers the constant temperature fluid 14 to the constant temperature fluid passage 15.

[0015] The magnetic shield device 1 is for shielding (reducing or blocking) external magnetism. In this embodiment, the magnetic shield device 1 includes a box-shaped device main body 10, and a magnetically shielded space 16 is formed inside the device main body 10 (inside the innermost magnetic shield member 11). Although not described in detail, as shown in FIG. 1, the device main body 10 of the magnetic shield device 1 is provided with an entrance / exit section for entering and exiting the magnetically shielded space 16, and a door 17 that can open and close the entrance / exit section. A measuring tool (not shown) may be installed in the magnetically shielded space 16. The magnetic shield device 1 may also include a function (device) for maintaining a constant temperature in the magnetically shielded space 16.

[0016] The magnetic shield device 1 includes two or more layers of magnetic shield members. Specifically, the device main body 10 of the magnetic shield device 1 of this embodiment includes two layers of magnetic shield members 11 and 12, including an innermost magnetic shield member (a box-shaped innermost shield wall portion formed by the innermost magnetic shield member) 11 that defines a magnetic shield space 16, and an outer magnetic shield member (a box-shaped outer magnetic shield wall portion formed by the outer magnetic shield member) 12 that is adjacent to the innermost magnetic shield member 11 on the outside and spaced a predetermined distance from the innermost magnetic shield member 11 so as to surround the innermost magnetic shield member 11. Although not described in detail, it is preferable that the magnetic shield members (the innermost and outer shield wall portions) 11 and 12 are configured so as to have as few gaps as possible between them in order to prevent magnetic penetration. Furthermore, it is preferable that each magnetic shield member (innermost layer shield wall portion and outer layer shield wall portion) 11, 12 has a structure with as few openings as possible, but openings may be provided as necessary (for example, to pull in various measurement cables, etc.).

[0017] In this embodiment, each of the magnetic shield members 11 and 12 is composed of a plate-shaped member made of a highly magnetically permeable material. Examples of materials for the magnetic shield members 11 and 12 include iron and permalloy, with permalloys with a relatively high nickel content (e.g., permalloy C) being particularly preferred. Permalloy is a metallic material with high magnetic permeability that is primarily composed of nickel and iron, and has a nickel content of 35 to 80%. The permalloy that constitutes the magnetic shield members 11 and 12 in the magnetic shield device 1 of this embodiment preferably has a nickel content of 75 to 82%. The thickness of the magnetic shield members 11 and 12 (the thickness of the plate-shaped members that constitute the magnetic shield members 11 and 12) is preferably 1 to 2 mm.

[0018] Although the magnetic shield device 1 of this embodiment includes two layers of magnetic shield members 11 and 12, the number of layers of the magnetic shield members may be increased depending on the surrounding magnetic environment, etc. For example, the number of layers of the magnetic shield members in the magnetic shield device is preferably 3 to 4.

[0019] Although not described in detail, it is preferable that the innermost magnetic shield member 11 is supported by (the bottom wall of) the outer magnetic shield member 12 via a base 18, with no supports or the like supporting the lateral direction or the ceiling surface. It is also preferable that the innermost magnetic shield member 11 is supported in a vibrationally insulated state with respect to the outer magnetic shield member 12 (a state in which vibrations from the outside or the outer magnetic shield member 12 are less likely to be transmitted).

[0020] The magnetic shield device 1 is provided with a thermally conductive member 13 that is disposed outside the innermost magnetic shield member 11 and inside the magnetic shield member (outer layer magnetic shield member 12) adjacent to the innermost magnetic shield member 11 on the outside, and that is in thermal contact with almost the entire surface of the innermost magnetic shield member 11.

[0021] Specifically, the device main body 10 of the magnetic shield device 1 of this embodiment is provided with plate-shaped heat-conductive members 13 that are provided so as to contact substantially the entire surface of each outer surface of the innermost magnetic shield member 11. Note that "contacting substantially the entire surface" here means making the contact area as large as possible, excluding parts that are unavoidably incapable of contact due to the structure, and does not necessarily have to be in contact over the entire surface.

[0022] In this embodiment, the thermally conductive member 13 is a plate-shaped member made of a material with a relatively high thermal conductivity. The thermally conductive member 13 preferably has a higher thermal conductivity than the innermost magnetic shield member 11. Examples of materials that can be used to make such a thermally conductive member 13 include metal materials such as aluminum and copper. The thermally conductive member may also be made of a resin material with a high thermal conductivity.

[0023] The thickness of the thermally conductive member 13 (the thickness of the plate-like member that constitutes the thermally conductive member) is preferably 2 to 10 mm. The thickness of the thermally conductive member 13 is preferably greater than the thickness of the magnetic shield member 11 that is the innermost layer described above.

[0024] Furthermore, when the thermally conductive member 13 is made of a metal material with high thermal conductivity, such a metal material also has high electrical conductivity and is prone to generating thermal noise (magnetic field fluctuations due to temperature changes), so it is preferable not to place it inside the magnetic shield device 1 (inside the innermost magnetic shield member 11). Note that in order to reduce the generation of the thermal noise described above, the thickness of the thermally conductive member 13 can be reduced or the thermally conductive member 13 can be made into a mesh (punched metal).

[0025] The thermally conductive member 13 being in "thermal contact" with the innermost magnetic shield member 11 means that heat can be transferred (heat exchanged) between the innermost magnetic shield member 11 and the thermally conductive member 13. Specifically, in this embodiment, the innermost magnetic shield member 11 and the thermally conductive member 13 are connected with bolts and nuts (not shown), and the outer surface of the innermost magnetic shield member 11 and the inner surface of the thermally conductive member 13 are in physical contact, allowing heat to be transferred (heat exchanged) between the innermost magnetic shield member 11 and the thermally conductive member 13. The innermost magnetic shield member 11 and the thermally conductive member 13 may also be in thermal contact via a thermally conductive adhesive or the like.

[0026] The magnetic shield device 1 includes a constant temperature fluid passage 15 through which a constant temperature fluid 14 can flow and which brings the constant temperature fluid 14 into thermal contact with the heat conductive member 13 .

[0027] 1, the magnetic shielding device 1 includes a constant-temperature fluid device 3, which has a constant-temperature fluid delivery (circulation) function, a constant-temperature fluid generation function, and a constant-temperature fluid temperature adjustment function, which will be described later. Preferably, the constant-temperature fluid device 3 (the constant-temperature fluid delivery function, constant-temperature fluid generation function, and constant-temperature fluid temperature adjustment function provided by the constant-temperature fluid device 3) is disposed in an electrically and / or vibrationally insulated state with respect to the device main body 10 of the magnetic shielding device 1 (a state in which electricity and vibrations generated by the operation of the constant-temperature fluid device 3 (various functions) are not easily transmitted to the device main body 10).

[0028] In this embodiment, constant temperature water (liquid (tap water, pure water, ethylene glycol, etc.) adjusted to a predetermined temperature) is used as the constant temperature fluid 14. In this embodiment, constant temperature water adjusted to a predetermined temperature is generated by the constant temperature fluid generation function of the constant temperature fluid device 3 of the magnetic shield device 1. In this embodiment, since the OPM sensor used for biomagnetic measurement using the magnetic shield device 1 can operate at room temperature, it is preferable that the constant temperature fluid (constant temperature water) 14 be adjusted to room temperature (the temperature of the environment in which the magnetic shield device 1 is used) or a temperature higher than room temperature to prevent condensation.

[0029] The constant temperature fluid is preferably a non-magnetic fluid. The term "non-magnetic fluid" refers to a fluid that does not have magnetism, in other words, a fluid that is not attracted to a magnet and does not generate a magnetic field. However, the term also includes fluids with relatively weak magnetism (for example, fluids that inevitably generate a magnetic field (magnetism) that does not cause problems in biomagnetic measurement by an OPM sensor using a magnetic shield device, and fluids whose inevitably generated magnetic field (magnetism) can be shielded (reduced) by the innermost magnetic shield member 11).

[0030] In this embodiment, the constant-temperature fluid passage 15 is a tubular member through which the constant-temperature fluid (constant-temperature water) 14 can flow. In this embodiment, the constant-temperature fluid 14 and the heat-conductive member 13 are in thermal contact via the constant-temperature fluid passage (tubular member) 15. Such a constant-temperature fluid passage (tubular member) 15 is preferably made of a material with high thermal conductivity (e.g., aluminum, copper, etc.). Furthermore, it is preferable that the constant-temperature fluid passage (tubular member) 15 be in contact with as wide an area of ​​the heat-conductive member 13 as possible.

[0031] The constant-temperature fluid passage 15 brings the constant-temperature fluid 14 into "thermal contact" with the heat-conductive member 13. Here, "thermal contact" means that heat can be transferred (heat exchanged) between the constant-temperature fluid 14 and the heat-conductive member 13. Specifically, in this embodiment, the constant-temperature fluid passage (tubular member) 15 is provided (wrapped around) the heat-conductive member 13 so as to be in physical contact with the outer surface of the heat-conductive member 13, allowing heat to be transferred (heat exchanged) between the constant-temperature fluid 14 and the heat-conductive member 13. More specifically, in this embodiment, the constant-temperature fluid 14 can exchange heat with the constant-temperature fluid passage (tubular member) 15, and the constant-temperature fluid passage (tubular member) 15 can exchange heat with the heat-conductive member 13. As a result, the constant-temperature fluid 14 is in thermal contact with the heat-conductive member 13 via the constant-temperature fluid passage (tubular member) 15.

[0032] Furthermore, in this embodiment (see Figure 2), the constant temperature fluid 14 (constant temperature fluid passage 15) is in thermal contact with the heat conductive member 13 except for the upper and lower portions, but the constant temperature fluid 14 (constant temperature fluid passage 15) may be configured to be in thermal contact with the upper and lower heat conductive members 13.

[0033] In the magnetic shield device 1, the heat conductive member 13 is made of a material with high thermal conductivity. As a result, even when the constant temperature fluid 14 is in partial physical contact with the heat conductive member 13 via the constant temperature fluid passage (tubular member) 15, as in this embodiment, the heat of the constant temperature fluid 14 is quickly transferred to the entire heat conductive member 13, and the temperature of the entire heat conductive member 13 can be maintained constant.

[0034] The magnetic shielding device 1 has a constant temperature fluid delivery function for continuously delivering the constant temperature fluid 14 to the constant temperature fluid passage 15. In this embodiment, the constant temperature fluid device 3 of the magnetic shielding device 1 has a constant temperature fluid delivery function (constant temperature fluid circulation function).

[0035] Specifically, as shown in FIG. 1 , the constant-temperature fluid device 3 is connected to both ends of the constant-temperature fluid passage 15 via two tubes (a delivery tube 31 and a receiving tube 32). The constant-temperature fluid 14 is continuously delivered from one end (the constant-temperature fluid delivery side) of the constant-temperature fluid passage 15 to the constant-temperature fluid passage 15, and is continuously received from the other end (the constant-temperature fluid receiving side) of the constant-temperature fluid passage 15. The constant-temperature fluid device 3 (constant-temperature fluid delivery (circulation) function) of this embodiment has a constant-temperature fluid temperature adjustment function that adjusts (maintains) the constant-temperature fluid 14 received (returned) from the constant-temperature fluid passage 15 to a predetermined temperature. This allows the constant-temperature fluid 14 circulating through the magnetic shield device 1 (constant-temperature fluid passage 15) to be maintained at a predetermined temperature, and the constant-temperature fluid 14 at the predetermined temperature can be continuously delivered (circulated).

[0036] The magnetic shield device is not limited to a configuration in which a constant-temperature fluid is circulated as described above, and may be configured to sequentially discharge the constant-temperature fluid sent to the constant-temperature fluid passage by the constant-temperature fluid sending function. In other words, the constant-temperature fluid sending function may be any function that can maintain a constant temperature of the thermally conductive member that is in thermal contact with the innermost magnetic shield member by continuously sending the constant-temperature fluid to the constant-temperature fluid passage.

[0037] 2, the magnetic shield device 1 of this embodiment includes a heat insulating layer 19 provided inside the innermost magnetic shield member 11. In this embodiment, the heat insulating layer 19 is provided over substantially the entire surface inside the innermost magnetic shield member 11. Note that "substantially the entire surface" here means that the heat insulating layer is provided over as wide an area as possible, excluding areas where it is unavoidable to form a heat insulating layer due to the structure, and it is not necessarily necessary to provide the heat insulating layer over the entire surface.

[0038] In this embodiment, the heat insulating layer 19 is a layer having heat insulating properties and formed to a predetermined thickness. Examples of materials that can be used for the heat insulating layer 19 include glass wool, cellulose fiber, rock wool, and urethane foam. In particular, when the constant temperature fluid is adjusted to a temperature close to room temperature as described above, it is preferable to use urethane foam.

[0039] According to the magnetic shield device 1 of this embodiment, the temperature of the innermost magnetic shield member 11 can be maintained uniformly and constantly, thereby achieving magnetic stability in the innermost magnetic shield member 11 and, ultimately, in the magnetically shielded space 16. That is, by bringing a constant-temperature fluid (constant-temperature water) 14 into thermal contact with the innermost magnetic shield member 11 via the thermally conductive member 13, it is possible to suppress magnetic field fluctuations (stabilize the magnetic field) in the magnetic shield device 1 (device main body 10) (magnetically shielded space 16).

[0040] Furthermore, in the magnetic shield device 1 of this embodiment, because the material such as permalloy that constitutes the innermost magnetic shield member 11 has low thermal conductivity, external temperature changes and the influence of internal (inside the magnetic shield space 16) heat sources (magnetic sensors and test objects) can impair the thermal uniformity of the innermost magnetic shield member 11 (causing temperature variations depending on the location), which can result in partial magnetic changes (fluctuations in the magnetic field).In response to this, by thermally contacting the outer side of the innermost magnetic shield member 11 with a thermally conductive member 13 made of a material with high thermal conductivity (aluminum, copper, etc.), the thermal uniformity of the innermost magnetic shield member 11 can be ensured, and not only temporal magnetic fluctuations but also spatial fluctuations in magnetic distribution can be suppressed.

[0041] Furthermore, in the magnetic shield device 1 of this embodiment, by providing an insulating layer 19 inside the innermost magnetic shield member 11, heat generated by the equipment housed within the magnetic shield device 1 (magnetic shield space 16), the target subject, etc. is less likely to be transmitted to the innermost magnetic shield member 11, thereby ensuring higher thermal uniformity.

[0042] Although not shown, the magnetic shield device may be provided with a configuration for stabilizing the temperature of not only the innermost magnetic shield member but also the outermost magnetic shield member. That is, the magnetic shield device may include a second thermally conductive member in thermal contact with substantially the entire surface of the outermost magnetic shield member disposed outward of the innermost magnetic shield member, a second constant-temperature fluid passage through which a second constant-temperature fluid can flow and which brings the second constant-temperature fluid into thermal contact with the second thermally conductive member, and a second constant-temperature fluid delivery function for continuously delivering the second constant-temperature fluid to the second constant-temperature fluid passage.

[0043] As shown in FIG. 3, in the magnetic shield device 1, a heat insulating layer 20 may be provided outside the innermost magnetic shield member 11 (and the thermally conductive member 13). More specifically, in the magnetic shield device 1 shown in FIG. 3, the heat insulating layer 20 is provided on substantially the entire surface of the inner side of the adjacent magnetic shield member (the outer-layer magnetic shield member 12) outside the innermost magnetic shield member 11. This reduces the penetration of heat from the outside (outside the innermost magnetic shield member 11 and the thermally conductive member 13) and further improves the heat uniformity effect. As a result, the magnetic field inside the magnetic shield device 1 (magnetically shielded space 16) can be further stabilized.

[0044] The magnetic shield device of the present invention may be a magnetic shield device that has two or more layers of magnetic shielding members that shield against external magnetism and can accommodate a magnetic sensor (OPM sensor) and a test subject inside, and may also be equipped with a thermally conductive member that is arranged outside the innermost magnetic shielding member and is in thermal contact with almost the entire surface of the innermost magnetic shielding member, and a thermally conductive member temperature stabilization means for maintaining the thermally conductive member at a constant temperature.

[0045] That is, in the magnetic shield device 1 of the above-described embodiment, the thermally conductive member temperature stabilization means is constituted by the constant temperature fluid 14, the constant temperature fluid passage 15, the constant temperature fluid delivery function, and the heat insulating layer 19. Note that the thermally conductive member temperature stabilization means may not include the heat insulating layer.

[0046] Furthermore, the thermally conductive member temperature stabilization means may be one that maintains the thermally conductive member and the innermost magnetic shield member that is in thermal contact with the thermally conductive member at a constant temperature without relying on a constant temperature fluid, and may, for example, utilize the latent heat generated by the phase change of a specified substance, or may use an electrical constant temperature device (such as a Peltier element).

[0047] In the present invention, since the thermal conductivity of the innermost magnetic shielding member is relatively low, a thermally conductive member is provided between the innermost magnetic shielding member and the constant temperature source (constant temperature fluid, etc.). However, if a magnetic shielding member (material) with excellent thermal conductivity is realized in the future, it is thought that a configuration in which the innermost magnetic shielding member and the constant temperature source (constant temperature fluid, etc.) are in direct thermal contact with each other without the thermally conductive member may be adopted.

[0048] Next, another embodiment of the magnetic shield device of the present invention will be described using the example shown in the drawings. In the following description, the same components as those in the magnetic shield device 1 described above will be designated by the same names and reference numerals, and detailed description thereof will be omitted.

[0049] In the magnetic shield device 1a shown in FIG. 4, constant-temperature air is used as the constant-temperature fluid, and the space between the innermost magnetic shield member (a box-shaped innermost shield wall portion formed by the innermost magnetic shield member) 11 and the outer-layer magnetic shield member (a box-shaped outer layer shield wall portion formed by the outer layer magnetic shield member) 12 adjacent to the innermost magnetic shield member 11 and spaced a predetermined distance from the innermost magnetic shield member 11 on the outside so as to surround the innermost magnetic shield member 11 is configured as a constant-temperature fluid passage 15a.

[0050] 4, the outer magnetic shield member 12 is provided with a constant temperature air supply port 21 and a constant temperature air exhaust port 22, and constant temperature air generated by the constant temperature fluid generating function of the constant temperature fluid device is sent from the constant temperature air supply port 21 to the constant temperature fluid passage 15a by the constant temperature fluid sending function of the constant temperature fluid device. Note that in such a magnetic shield device 1a, a constant temperature fluid (constant temperature air) may be circulated.

[0051] In the magnetic shield device 1a of this embodiment, the constant-temperature fluid (constant-temperature air) in the constant-temperature fluid passage 15a is in direct (thermal) contact with the heat-conductive member 13. Furthermore, the constant-temperature fluid (constant-temperature air) in the constant-temperature fluid passage 15a is in direct (thermal) contact with the outer magnetic shield member 12. Although not shown, the magnetic shield device 1a of this embodiment may be provided with a structure (e.g., fins) that promotes heat exchange with the constant-temperature fluid (constant-temperature air) on the heat-conductive member 13 (and the outer magnetic shield member 12). Furthermore, a heat-conductive member may be provided on the inner side (the side that comes into contact with the constant-temperature fluid) of the outer magnetic shield member 12.

[0052] In the magnetic shield device 1a of this embodiment, the temperature of the innermost magnetic shield member 11 can also be stabilized (kept uniform and constant), and magnetic field fluctuations within the magnetic shield device 1a (magnetic shield space 16) can be suppressed.

[0053] Furthermore, in the magnetic shield device 1a described above, constant temperature air generated outside the magnetic shield device 1a may be sent to the constant temperature fluid passage 15a. For example, when the magnetic shield device 1a is used by being placed in a constant temperature bath that functions separately from the magnetic shield device 1a, the constant temperature air in the constant temperature bath (constant temperature air generated by the constant temperature bath) can be sent to the constant temperature fluid passage 15a of the magnetic shield device 1a. In this case, the constant temperature fluid device of the magnetic shield device 1a only needs to have a constant temperature fluid sending function, and does not need to have a constant temperature fluid generating function or a constant temperature fluid temperature adjusting function.

[0054] In addition, in a magnetic shielding device using constant-temperature air as the constant-temperature fluid, a configuration for promoting heat transfer (heat exchange) between the constant-temperature fluid (constant-temperature fluid passage) and the thermally conductive member may be provided. For example, in the above-described magnetic shielding device 1a, fins may be provided inside the constant-temperature fluid passage 15a (the outer surface of the thermally conductive member 13 constituting the constant-temperature fluid passage 15a) to increase the contact area with the constant-temperature fluid (constant-temperature air).

[0055] 5, the magnetic shield device 1b may also be provided with a degaussing function (demagitator 23) for reducing the residual magnetic field of the magnetic shield members 11 and 12. Note that "demagitating" refers to the operation of temporarily applying an intentionally generated magnetic field (magnetic field) (an electric alternating magnetic field, a magnetic field that decays over time) to a target member (here, the magnetic shield members 11 and 12) to reduce the residual magnetic field of the target member. Although not described in detail, the degaussing device 23 of the magnetic shield device 1b of this embodiment includes a degaussing cable (coil) 24 and a degaussing power supply (a power supply for supplying electricity to the degaussing cable 24) 25 disposed near the innermost magnetic shield member 11, and is capable of reducing the residual magnetic field of at least the innermost magnetic shield member 11 through a predetermined degaussing operation.

[0056] When using a magnetic shield device with a demagnetization function, it is preferable to demagnetize the magnetic shield material using the demagnetization function after the temperature of the magnetic shield device (magnetic shield material) has stabilized after starting the constant temperature fluid delivery function. The mechanism behind this is not entirely clear, but it is thought that, for example, the dimensions of the structure change while the temperature of the magnetic shield device (magnetic shield material) is stabilizing, which in turn changes the gaps between the components and causes fluctuations in the internal magnetic field due to magnetostriction (a phenomenon in which a magnetic field is generated when a component is distorted). [Explanation of symbols]

[0057] 1. Magnetic shielding device 10 Device main body 11 Innermost layer magnetic shielding material (innermost layer shielding wall portion) 12 Outer layer magnetic shielding material (outer layer shielding wall) 13 Thermally conductive material 14 Constant temperature fluid (heat transfer fluid) 15 Constant temperature fluid passage (heat transfer fluid passage) 16 Magnetically shielded space 19 Insulation layer 20 Insulation layer 23 Degaussing device 3 Constant temperature fluid equipment 100 Magnetic shielding device 101 Insulated duct 102 OPM sensor 103 Temperature Sensor

Claims

1. A magnetic shield device comprising two or more layers of magnetic shield members for shielding against external magnetism, and capable of accommodating a magnetic sensor and a test object therein, a thermally conductive member disposed outside the innermost magnetic shield member and in thermal contact with substantially the entire surface of the innermost magnetic shield member; a heat conductive member temperature stabilization means for maintaining the heat conductive member at a constant temperature; A magnetic shield device comprising:

2. A magnetic shield device comprising two or more layers of magnetic shield members for shielding against external magnetism, and capable of accommodating a magnetic sensor and a test object therein, a thermally conductive member disposed outside the innermost magnetic shield member and in thermal contact with substantially the entire surface of the innermost magnetic shield member; a constant temperature fluid passage through which a constant temperature fluid can flow and which brings the constant temperature fluid into thermal contact with the heat conductive member; a constant temperature fluid delivery function for continuously delivering the constant temperature fluid to the constant temperature fluid passage; A magnetic shield device comprising:

3. A magnetic shield device for biomagnetic measurement using an OPM sensor, comprising two or more layers of magnetic shielding material for shielding against external magnetism, and capable of accommodating an OPM sensor and a subject whose biomagnetic field is to be measured by the OPM sensor, a thermally conductive member disposed outside the innermost magnetic shield member and in thermal contact with substantially the entire surface of the innermost magnetic shield member; a constant temperature fluid passage through which a constant temperature fluid can flow and which brings the constant temperature fluid into thermal contact with the heat conductive member; a constant temperature fluid delivery function for continuously delivering the constant temperature fluid to the constant temperature fluid passage; A magnetic shield device comprising:

4. 4. The magnetic shield device according to claim 2, wherein a heat insulating layer is provided on substantially the entire inner surface of the innermost magnetic shield member.

5. 4. The magnetic shield device according to claim 2, wherein a heat insulating layer is provided outside the innermost magnetic shield member.

6. the magnetic shield device includes a constant-temperature fluid circulation function that continuously sends the constant-temperature fluid to the constant-temperature fluid passage and continuously receives the constant-temperature fluid from the constant-temperature fluid passage, and a constant-temperature fluid temperature adjustment function that adjusts the temperature of the received constant-temperature fluid, 4. The magnetic shield device according to claim 2, wherein the constant temperature fluid circulation function and the constant temperature fluid temperature adjustment function are electrically and vibrationally insulated from the magnetic shield member of the innermost layer.

7. the magnetic shield device has a constant temperature fluid generating function for generating the constant temperature fluid, 4. The magnetic shield device according to claim 2, wherein the constant temperature fluid generating function is electrically and vibrationally insulated from the magnetic shield member of the innermost layer.

8. a second thermally conductive member disposed outward of the innermost magnetic shield member and in thermal contact with substantially the entire surface of the outer magnetic shield member; a second constant-temperature fluid passage through which a second constant-temperature fluid can flow and which brings the second constant-temperature fluid into thermal contact with the second thermally conductive member; a second constant-temperature fluid delivery function for continuously delivering the second constant-temperature fluid to the second constant-temperature fluid passage; The magnetic shield device according to claim 2 or 3, comprising:

9. 4. The magnetic shield device according to claim 2, further comprising a demagnetizing function for demagnetizing the innermost magnetic shield member.

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