JP4700287B2 - Active magnetic shield device - Google Patents

Description

  The present invention relates to an active magnetic shield device used for biomagnetism measurement, an electron beam drawing apparatus, and an electron beam mask drawing apparatus.

  Instead of the magnetic shield room (MSR) that has been used for biomagnetism measurement, electron beam drawing apparatus, and electron beam mask drawing apparatus, an active magnetic shield apparatus that is inexpensive, lightweight, and easy to disassemble and relocate recently. Have been used in biomagnetic measurements, electron beam drawing apparatuses, and electron beam mask drawing apparatuses. This active magnetic shield device senses magnetic noise in the measurement space by sensors provided for the x, y, and z axes, feeds back the sensed signal, and in the measurement space for each of the x, y, and z axes. A shielding effect is exhibited by generating a magnetic field in a reverse direction in a pair of canceling coils (hereinafter referred to as CC) disposed on two opposing surfaces to cancel magnetic noise.

  The primary differential type coil used as an input coil for the differential SQUID (Superconducting Quantum Interference Devices) magnetometer for biomagnetism measurement does not sense a magnetic field with uniform spatial distribution, so magnetic noise with uniform spatial distribution (zero order noise) ) Is not a problem, but since a magnetic field having a constant gradient is sensed, magnetic noise (primary noise) having a constant gradient is sensed as a large noise. Therefore, if there is magnetic noise having a gradient, the measurement will be hindered. In addition, since the secondary differential coil used as an input coil in the differential SQUID magnetometer does not sense a magnetic field with a uniform spatial distribution or a magnetic field having a constant gradient, the presence of zero-order noise or primary noise becomes a problem. However, in order to sense a magnetic field having a secondary gradient, magnetic noise having a secondary gradient (secondary noise) is detected as a large noise. Therefore, there is a problem that if there is a magnetic noise having a second-order or higher gradient, the measurement is hindered.

  Therefore, as described in Non-Patent Document 1, by arranging coils having the same size as the CC for each of the x, y, and z axes to form a triple coil, a quadruple coil, and a five-coil, Magnetic noise having the following gradient is effectively reduced to realize a magnetic field having a uniform spatial distribution. Thereby, especially in the triple coil, the differential SQUID magnetometer using the primary differential coil that senses the primary noise as noise can effectively measure.

R. merit, C. Purcell, and G. stroink, "Uniform Magnetic Field Produced by Three, Four, and Five Square Coils.", Rev. Sci. Instrim, .54 (7) (1983) 879-882.

  However, when a triple coil, a quadruple coil, and a five-coil coil are arranged in the measurement space as the CC, a plurality of CCs are laid vertically and horizontally on each surface of the measurement space, which hinders access to the measurement space. In addition, a part of the CC is laid directly under the device installed in the measurement space, and the device is in a state of stepping on the CC. In order to avoid this, it is conceivable to devise a door for entering and exiting the measurement space, or to make the floor of the measurement space a double bottom, but the structure becomes complicated.

  The present invention has been made in view of the above problems, and its purpose is that the canceling coil does not hinder access to the measurement space, and the canceling coil is not laid directly under the device, An active magnetic shield device having high shielding performance is provided.

Means and effects for solving the problems

The active magnetic shield device of the present invention includes a sensor for detecting magnetic noise in a measurement space, a first canceling coil disposed on one surface of the two opposing surfaces in the measurement space or in the vicinity thereof, The second canceling coil which is disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forms a first pair with the first canceling coil, and on one surface of the two opposing surfaces or in the vicinity thereof A third canceling coil that is concentric with the first canceling coil and disposed on the other surface of the two opposing surfaces or in the vicinity thereof, and forms a second pair with the third canceling coil. the second canceling coil concentric fourth canceling coils, based before the magnetic noise xenon capacitors senses, is the first to fourth canceling coil A current flowing through the first to fourth canceling coils is generated so as to generate a magnetic field that reduces magnetic noise in the measurement space, and the generated current is supplied to the first to fourth canceling coils. A circuit , wherein the sensor is capable of sensing magnetic noise with a uniform spatial distribution, the circuit passes a first current in a positive direction through the first canceling coil, and the second canceling coil A second current in the positive direction is supplied, a third current in the negative direction is supplied to the third canceling coil, and a fourth current in the negative direction is supplied to the fourth canceling coil .

  According to the present invention, since the first to fourth canceling coils are arranged on the two opposing surfaces of the measurement space or in the vicinity thereof, the entry / exit to the measurement space is obstructed, or a part of the coil is directly under the device. The measurement space can be shielded from external magnetic noise without being laid.

In addition , by setting the directions of the first to fourth currents flowing through the first to fourth canceling coils, the first to fourth canceling coils can secure a magnetic field having a uniform spatial distribution over a wide region. Therefore, magnetic noise with a uniform spatial distribution in the measurement space can be effectively erased by the reverse magnetic field formed by the first to fourth canceling coils.

In the present invention, a sensor for detecting magnetic noise in the measurement space, a first canceling coil disposed on one surface of the two opposing surfaces in the measurement space or in the vicinity thereof, and the two opposing electrodes Disposed on the other surface of the surface or in the vicinity thereof, the second canceling coil that forms a first pair with the first canceling coil, and disposed on one surface of the two opposing surfaces or in the vicinity thereof, A third canceling coil concentric with the first canceling coil; and the second canceling coil disposed on or near the other surface of the two opposing surfaces, and forming a second pair with the third canceling coil. Based on the fourth canceling coil concentric with the canceling coil and the magnetic noise sensed by the sensor, the first to fourth canceling coils generate magnetic fields in the measurement space. To generate a magnetic field to reduce the noise, current generates a flow in the first to fourth canceling coils, and a circuit for supplying the generated current to the first to fourth canceling coils, the sensor Can sense a magnetic field having a gradient, and the circuit passes a first current in the positive direction through the first canceling coil, a second current in the negative direction through the second canceling coil, and the third the canceling coil flows a third current in the positive direction, and wherein the flowing a fourth current in the negative direction on the fourth canceling coil. According to this, since the first to fourth canceling coils are arranged on the two opposing surfaces of the measurement space or in the vicinity thereof, the entry / exit to the measurement space is obstructed, or a part of the coil is laid directly under the device. The measurement space can be shielded from external magnetic noise without being done. In addition, since the direction of the first to fourth currents flowing through the first to fourth canceling coils is set, a magnetic field having a constant gradient can be secured over a wide region by the first to fourth canceling coils. Magnetic noise having a constant gradient in the measurement space can be effectively eliminated by the reverse magnetic field formed by the first to fourth canceling coils.

In the present invention, a sensor for detecting magnetic noise in the measurement space, a first canceling coil disposed on one surface of the two opposing surfaces in the measurement space or in the vicinity thereof, and the two opposing electrodes Disposed on the other surface of the surface or in the vicinity thereof, the second canceling coil that forms a first pair with the first canceling coil, and disposed on one surface of the two opposing surfaces or in the vicinity thereof, A third canceling coil concentric with the first canceling coil; and the second canceling coil disposed on or near the other surface of the two opposing surfaces, and forming a second pair with the third canceling coil. Based on the fourth canceling coil concentric with the canceling coil and the magnetic noise sensed by the sensor, the first to fourth canceling coils generate magnetic fields in the measurement space. To generate a magnetic field to reduce the noise, current generates a flow in the first to fourth canceling coils, and a circuit for supplying the generated current to the first to fourth canceling coils, the sensor A first sensor capable of sensing magnetic noise with a uniform spatial distribution and a second sensor capable of sensing a magnetic field having a gradient, and the circuit passes through the first to fourth canceling coils. For each canceling coil, as the current, the first to fourth canceling coils generate a magnetic field that reduces even-order magnetic noise in the measurement space based on the magnetic noise sensed by the first sensor. Based on the determined even-order noise reduction current and the magnetic noise sensed by the second sensor, the first to fourth canceling coils are connected to the odd-order in the measurement space. Generating a combined current with the odd-order noise reduction current determined for each canceling coil so as to generate a magnetic field that reduces magnetic noise, and the even-order noise reduction current according to the first to fourth canceling coils, Currents flowing in the positive direction, the positive direction, the negative direction, and the negative direction, respectively, and the odd-order noise reduction currents related to the first to fourth canceling coils are respectively the positive direction, the negative direction, the positive direction, and the negative direction. characterized in that it is a current flowing through. According to this, since the first to fourth canceling coils are arranged on the two opposing surfaces of the measurement space or in the vicinity thereof, the entry / exit to the measurement space is obstructed, or a part of the coil is laid directly under the device. The measurement space can be shielded from external magnetic noise without being done. Further, since the current flowing through the first to fourth canceling coils is a combined current of the even-order noise reduction current and the odd-order noise reduction current, the space in which the even-order magnetic field is reduced by the first to fourth canceling coils. A magnetic field with a uniform distribution can be secured over a wide area, and a magnetic field with a constant gradient with a reduced odd-order magnetic field can be secured over a wide area, and the spatial distribution in the measurement space can be kept constant with a uniform magnetic noise. Magnetic noise having a gradient can be effectively erased by a reverse magnetic field formed by the first to fourth canceling coils.

In the present invention, a sensor for detecting magnetic noise in the measurement space, a first canceling coil disposed on one surface of the two opposing surfaces in the measurement space or in the vicinity thereof, and the two opposing electrodes Disposed on the other surface of the surface or in the vicinity thereof, the second canceling coil that forms a first pair with the first canceling coil, and disposed on one surface of the two opposing surfaces or in the vicinity thereof, A third canceling coil concentric with the first canceling coil; and the second canceling coil disposed on or near the other surface of the two opposing surfaces, and forming a second pair with the third canceling coil. Based on the fourth canceling coil concentric with the canceling coil and the magnetic noise sensed by the sensor, the first to fourth canceling coils generate magnetic fields in the measurement space. To generate a magnetic field to reduce the noise, current generates a flow in the first to fourth canceling coils, and a circuit for supplying the generated current to the first to fourth canceling coils, the sensor A first sensor capable of sensing magnetic noise with a uniform spatial distribution and a second sensor capable of sensing a magnetic field having a gradient, and passing a first current in a positive direction through the first canceling coil. First, a second current in the positive direction is supplied to the second canceling coil, a third current in the negative direction is supplied to the third canceling coil, and a fourth current in the negative direction is supplied to the fourth canceling coil. In this state, a first current in the positive direction is supplied to the first canceling coil, a second current in the negative direction is supplied to the second canceling coil, and a third current in the positive direction is supplied to the third canceling coil. Flushed, characterized in that it further comprises a switching means for switching selectively the circuit to one of the second state to flow a fourth current in the negative direction on the fourth canceling coil. According to this, since the first to fourth canceling coils are arranged on the two opposing surfaces of the measurement space or in the vicinity thereof, the entry / exit to the measurement space is obstructed, or a part of the coil is laid directly under the device. The measurement space can be shielded from external magnetic noise without being done. Further, if the measurement space distribution is remarkable uniform magnetic noise in the space, and the direction of the current flowing through the first to fourth canceling coil in a first state, the first to fourth canceling coil A magnetic field with a uniform spatial distribution is ensured over a wide area, and magnetic noise with a uniform spatial distribution in the measurement space is effectively erased by the reverse magnetic field formed by the first to fourth canceling coils, If magnetic noise having a constant gradient in the measurement space is significant, the direction of the current flowing through the first to fourth canceling coils is set to the second state, and the first to fourth canceling coils have a constant gradient. The magnetic field is ensured over a wide area, and magnetic noise having a constant gradient in the measurement space is effectively erased by the reverse magnetic field formed by the first to fourth canceling coils. Cancel The magnetic noise in the measurement space can be erased selectively by Ngukoiru.

In the present invention, a sensor for detecting magnetic noise in the measurement space, a first canceling coil disposed on one surface of the two opposing surfaces in the measurement space or in the vicinity thereof, and the two opposing electrodes Disposed on the other surface of the surface or in the vicinity thereof, the second canceling coil that forms a first pair with the first canceling coil, and disposed on one surface of the two opposing surfaces or in the vicinity thereof, A third canceling coil concentric with the first canceling coil; and the second canceling coil disposed on or near the other surface of the two opposing surfaces, and forming a second pair with the third canceling coil. Based on the fourth canceling coil concentric with the canceling coil and the magnetic noise sensed by the sensor, the first to fourth canceling coils generate magnetic fields in the measurement space. To generate a magnetic field to reduce the noise, current generates a flow in the first to fourth canceling coils, and a circuit for supplying the generated current to the first to fourth canceling coils, the sensor A first sensor capable of sensing magnetic noise having a uniform spatial distribution and a second sensor capable of sensing a magnetic field having a gradient, and are arranged on one surface of the two opposing surfaces or in the vicinity thereof. A fifth canceling coil that is arranged on the other surface of the two opposite surfaces or in the vicinity thereof, and a sixth canceling coil that forms a third pair with the fifth canceling coil, and the opposite two A seventh canceling coil concentric with the fifth canceling coil, disposed on one surface of the two surfaces or in the vicinity thereof, and disposed on the other surface of the two opposing surfaces or in the vicinity thereof. And further comprising an eighth canceling coil concentric with the sixth canceling coil that forms a fourth pair with the seventh canceling coil, wherein the circuit is based on magnetic noise sensed by the first sensor. The first to fourth canceling coils determine the even-order noise reduction current determined for each canceling coil so as to generate a magnetic field that reduces even-order magnetic noise in the measurement space. The fifth to eighth canceling coils generate a magnetic field that reduces odd-order magnetic noise in the measurement space based on the magnetic noise sensed by the second sensor while flowing through the four canceling coils. The odd-order noise reduction current determined for each canceling coil is passed through the fifth to eighth canceling coils, and the first to fourth keys are passed. The even-order noise reduction currents related to the canceling coil are currents flowing in the positive direction, the positive direction, the negative direction, and the negative direction, respectively, and the odd-order noise reduction currents related to the fifth to eighth canceling coils are respectively , positive, negative, and wherein the forward direction, a current flows in the negative direction. According to this, since the first to fourth canceling coils are arranged on the two opposing surfaces of the measurement space or in the vicinity thereof, the entry / exit to the measurement space is obstructed, or a part of the coil is laid directly under the device. The measurement space can be shielded from external magnetic noise without being done. In addition, since the first to fourth canceling coils can secure a uniform magnetic field over a wide area in which the even-order magnetic field is reduced, the magnetic noise with the uniform spatial distribution in the measurement space can be The magnetic field can be effectively erased by the reverse magnetic field formed by the fourth canceling coil, and at the same time, the magnetic field having a constant gradient in which the odd-order magnetic field is reduced by the fifth to eighth canceling coils is widened. Since the crossing can be ensured, magnetic noise having a constant gradient in the measurement space can be effectively eliminated by the reverse magnetic field formed by the fifth to eighth canceling coils.

  In the present invention, it is preferable that the ratio of the current flowing through the third pair to the current flowing through the fourth pair is 7:17. According to this, since the magnetic field having a constant gradient can be efficiently formed by the fifth to eighth canceling coils, the fifth to eighth canceling coils form magnetic noise having a constant gradient in the measurement space. It is possible to effectively erase the magnetic field in the opposite direction.

  In the present invention, the fifth canceling coil and the sixth canceling coil are squares having the same size, and the seventh canceling coil and the eighth canceling coil are having the same size, and the fifth canceling coil has the same size. The seventh canceling coil is disposed closer to the inside than the fifth canceling coil, and the eighth canceling coil is disposed closer to the inside than the sixth canceling coil. A distance a between the fifth canceling coil and the sixth canceling coil; a distance b between the seventh canceling coil and the eighth canceling coil; a length c of one side of the fifth canceling coil; The length d of one side of the seventh canceling coil is a: b: c: d = 1.4: 1: 0.74: 1. It is preferably set to 5. According to this, since the magnetic field having a constant gradient can be efficiently formed by the fifth to eighth canceling coils, the fifth to eighth canceling coils form magnetic noise having a constant gradient in the measurement space. It is possible to effectively erase the magnetic field in the opposite direction.

  In the present invention, it is preferable that the fifth to eighth canceling coils are provided in at least two directions of the x-axis, the y-axis, and the z-axis, respectively. According to this, the shielding effect can be obtained in at least two directions of the x, y, and z axes by the fifth to eighth canceling coils respectively disposed in at least two directions of the x, y, and z axes.

  In the present invention, the ratio of the magnitude of the current flowing through the first pair to the magnitude of the current flowing through the second pair is preferably 7:17. According to this, since the first to fourth canceling coils can efficiently form a magnetic field having a uniform spatial distribution or a magnetic field having a constant gradient, magnetic noise having a uniform spatial distribution in the measurement space or Magnetic noise having a constant gradient can be effectively erased by a reverse magnetic field formed by the first to fourth canceling coils.

  In the present invention, the first canceling coil and the second canceling coil are the same size square, and the third canceling coil and the fourth canceling coil are the same size, and the first canceling coil is the same as the first canceling coil. A square that is larger than a ring coil, the third canceling coil is disposed closer to the inside than the first canceling coil, and the fourth canceling coil is disposed closer to the inside than the second canceling coil, A distance a between the first canceling coil and the second canceling coil, a distance b between the third canceling coil and the fourth canceling coil, a length c of one side of the first canceling coil, The length d of one side of the third canceling coil is a: b: c: d = 1.4: 1: 0.74: 1. It is preferably set to 5. According to this, since the first to fourth canceling coils can efficiently form a magnetic field having a uniform spatial distribution or a magnetic field having a constant gradient, magnetic noise having a uniform spatial distribution in the measurement space or Magnetic noise having a constant gradient can be effectively erased by a reverse magnetic field formed by the first to fourth canceling coils.

  In the present invention, it is preferable that the first to fourth canceling coils are provided in at least two directions of the x-axis, the y-axis, and the z-axis, respectively. According to this, a shielding effect can be obtained in at least two directions of the x, y, and z axes by the first to fourth canceling coils arranged in at least two directions of the x, y, and z axes, respectively.

  Hereinafter, embodiments of an active magnetic shield device according to the present invention will be described with reference to the drawings.

[First Embodiment]
The configuration of the active magnetic shield device according to the first embodiment of the present invention will be described with reference to FIGS.
The active magnetic shield device 1 includes x1 to x4 canceling coils (x1 to x4CC) 11 to 14 which are first to fourth canceling coils arranged in the x-axis direction, and first to first arranged in the y-axis direction. Y1 to y4 canceling coils (y1 to y4CC) 21 to 24, which are fourth canceling coils, and z1 to z4 canceling coils (z1 to z4CC), which are first to fourth canceling coils arranged in the z-axis direction. ) 31-34.
In addition, the active magnetic shield device 1 includes a sensor 3 disposed substantially at the center of the measurement space 2 formed by x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34, and each of the measurement space 2 in the x, y, and z axis directions. Sensors 4x, 4y, 4z, 5x, 5y, 5z arranged on the surface.
The active magnetic shield device 1 is provided outside the measurement space 2 and is based on magnetic noise sensed by the sensor 3 or the sensors 4x, 4y, 4z, 5x, 5y, and 5z, x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31. ~ Z4CC34 generates currents that flow through x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34 so that magnetic noise in the measurement space 2 is reduced, and the generated currents are x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 It has the circuit 6 which supplies to z4CC34.

  In FIG. 1, a measurement space 2 is a substantially rectangular space, and a biomagnetism measurement, an electron beam drawing device, an electron beam mask drawing device, etc. (not shown) are installed in the measurement space 2, and a subject and a test object are magnetically measured. Or electron beam drawing is performed.

  The sensor 3 is arranged at substantially the center in the measurement space 2, detects magnetic noise (zero order noise) in the measurement space 2 with a uniform spatial distribution, and feeds back the signal to the circuit 6. The circuit 6 generates current based on the signal, and supplies the generated current to x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34, so that zero-order noise is generated by x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34. A magnetic field in the reverse direction is generated in the measurement space 2. The number of sensors 3 is not limited to one, and the position where the sensors 3 are arranged may be outside the measurement space 2 as long as the magnetic field inside the measurement space 2 can be measured.

  In FIG. 3, sensors 4x, 4y, 4z, 5x, 5y, and 5z are arranged at the center of each surface in the x, y, and z-axis directions of the measurement space 2, and a pair of the sensor 4x and the sensor 5x, and the sensor 4y and the sensor 5y. The magnetic noise (primary noise) having a constant gradient inside the measurement space 2 is sensed by measuring a magnetic field having a gradient, and used as a pair of the sensor 4z and the sensor 5z, and the signal is fed back to the circuit 6 To do. The circuit 6 generates current based on the signal, and supplies current to x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34, so that x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34 and reverse direction of primary noise. A magnetic field is generated in the measurement space 2. The number of sensors 4x, 4y, 4z, 5x, 5y, and 5z is preferably two each in the x, y, and z axis directions in order to measure a magnetic field having a gradient, but is limited to two. The arrangement position is not limited to the center of each surface, and may be outside the measurement space 2 as long as the magnetic field inside the measurement space 2 can be measured.

  As shown in FIG. 1, x1CC11 to x4CC14 that are the first to fourth canceling coils of the x axis, y1CC21 to y4CC24 that are the first to fourth canceling coils of the y axis, and the first to fourth canceling of the z axis. The coils z1CC31 to z4CC34 are square coils arranged on each surface of the measurement space 2 in the x, y, and z directions.

  Since the x-axis x1CC11 to x4CC14, the y-axis y1CC21 to y4CC24, and the z-axis z1CC31 to z4CC34 have the same configuration except for the axial direction, only the z-axis will be described with reference to FIGS. To do.

  In FIG. 2, z <b> 1 CC <b> 31 is a first canceling coil disposed on the lower surface of the measurement space 2. z3CC33 is a third canceling coil disposed on the lower surface of the measurement space 2 as with z1CC31, but is disposed closer to the inside of the measurement space 2 than z1CC31, and is larger than z1CC31. Z2CC32 is a second canceling coil disposed on the upper surface of the measurement space 2, and has the same size as z1CC31. z4CC34 is a fourth canceling coil arranged on the upper surface of the measurement space 2 like z2CC32, but is arranged closer to the inside of the measurement space 2 than z2CC32, and is larger than z2CC32, and has the same size as z3CC33. is there.

  z1CC31 and z2CC32 constitute a first pair and are arranged near the outside of the measurement space 2, and z3CC33 and z4CC34 constitute a second pair and are arranged near the inside of the measurement space 2. The arrangement relationship of the four CCs is set so that the action and effect of the CC can be appropriately executed. That is, the interval a between z1CC31 and z2CC32, the interval b between z3CC33 and z4CC34, the length c of one side of z1CC31 and z2CC32, and the length d of one side of z3CC33 and z4CC34 are a: b: c: d = 1. : 0.85: 0.85: 1, more preferably a: b: c: d = 1.4: 1: 0.74: 1.35. The second pair may be arranged on the outer side and the first pair may be arranged on the inner side. However, for the purpose of ensuring a wide working space and keeping the total volume of the system compact, the second pair is arranged. It is preferable to arrange the first pair closer to the outer side and closer to the outer side. Similarly, it is preferable that the four CCs are arranged on the outer periphery of each surface of the measurement space 2 for the purpose of ensuring a wide working space and keeping the total volume of the system compact.

  The circuit 6 includes an amplifier 41, a low-pass filter 42, an A / D converter 43, a digital signal processor 44, a D / A converter 45, a D / A converter 46, and a power amplifier (inverting amplifier) 47. Consists of. As shown in FIG. 1 or FIG. 3, the amplifier 41 amplifies the analog signal fed back from the sensors 3, 4x, 4y, 4z, 5x, 5y, 5z, and removes the high-frequency analog signal by the low-pass filter 42, thereby reducing the low frequency. The A / D converter 43 converts the low frequency analog signal into a digital signal. The digital signal processor 44 calculates the magnitude of the current required for each CC of the three sets of CCs, one set of four CCs arranged for each of the x, y, and z axes, and supplies it to each CC. Determine the current value. The digital signal processor 44 calculates current values such that three sets of CCs each generate a magnetic field that reduces magnetic noise in the measurement space 2. The digital signal output from the digital signal processor 44 is converted into an analog signal by the D / A converter 46, and the power amplifier (inverting amplifier) 47 inverts and amplifies the analog signal output from the D / A converter 46, Supply current to each CC. The digital signal processor 44 also outputs a digital signal to the D / A converter 45. The D / A converter 45 converts the digital signal into an analog signal and inputs the analog signal to the amplifier 41. The amplifier 41 compares the analog signal fed back from the sensors 3, 4 x, 4 y, 4 z, 5 x, 5 y, and 5 z with the analog signal output from the digital signal processor 44 and passed through the D / A converter 45. The difference between the two is calculated. The digital signal processor 44 controls so that the difference calculated by the amplifier 41 becomes zero.

First, the case where the circuit 6 supplies a current to the CC to effectively erase a magnetic field having a uniform spatial distribution will be described by limiting to the z axis.
In FIG. 2, the current flowing through the first pair is an even-order noise reduction current i11, and the current flowing through the second pair is an even-order noise reduction current i21.
If the direction of the current flowing through z1CC31 is clockwise (positive direction) as shown in FIG. 2, the direction of the current flowing through z2CC32 is clockwise (positive direction), and the direction of current flowing through z3CC33 is counterclockwise. (Negative direction), the direction of the current flowing through the z4CC 34 is set counterclockwise (negative direction). That is, the direction of the first pair of even-order noise reduction currents i11 is set clockwise (positive direction), and the direction of the second pair of even-order noise reduction currents i21 is set counterclockwise (negative direction). This set state is referred to as a first state for convenience. Even if the direction of the first pair of even-order noise reduction currents i11 is set to be counterclockwise (negative direction) and the direction of the second pair of even-order noise reduction currents i21 is set to be clockwise (positive direction). It goes without saying that it is good.

  In the first state, the second pair generates a magnetic field having a positive polarity as shown in FIG. On the other hand, the first pair generates a magnetic field having a negative polarity as shown in FIG. Needless to say, the polarity of the magnetic field formed by the second pair may be negative and the polarity of the magnetic field formed by the first pair may be positive. At this time, the ratio between the even-order noise reduction current i11 flowing through the first pair and the even-order noise reduction current i21 flowing through the second pair is set to 7:17. When the second pair and the first pair each form a magnetic field, a magnetic field obtained by combining a positive magnetic field and a negative magnetic field is generated in the measurement space 2, and the combined magnetic field is as shown in FIG. The even-order magnetic field, especially the secondary magnetic field is reduced, and a magnetic field having a uniform spatial distribution is secured over a wide area. Thereby, the circuit 6 supplies even-order noise reduction currents i11 and i21 to the first pair and the second pair, and the first pair is a magnetic field in the direction opposite to the zero-order noise sensed by the sensor 3. By generating a composite magnetic field formed by the second pair, zero-order noise can be effectively eliminated.

Next, a case where the circuit 6 supplies a current to the CC to effectively erase a magnetic field having a constant gradient will be described by limiting to the z axis.
In FIG. 4, the current flowing through the first pair is an odd-order noise reduction current i12, and the current flowing through the second pair is an odd-order noise reduction current i22. Here, assuming that the direction of current flowing through z1CC31 is clockwise (positive direction) as shown in FIG. 4, the direction of current flowing through z2CC32 is counterclockwise (negative direction), and the direction of current flowing through z3CC33 is clockwise. (Positive direction), the direction of the current flowing through the z4CC 34 is set counterclockwise (negative direction). That is, the current directions of z1CC31 and z2CC32 constituting the first pair are different from each other, the current directions of z3CC33 and z4CC34 constituting the second pair are different from each other, and z1CC31 and z3CC33 arranged on the lower surface of the measurement space 2 Are set such that the current directions coincide with each other, and z2CC32 and z4CC34 arranged on the upper surface of the measurement space 2 coincide with each other. This set state is referred to as a second state for convenience. The direction of current flowing through z1CC31 is counterclockwise (negative direction), the direction of current flowing through z2CC32 is clockwise (positive direction), the direction of current flowing through z3CC33 is counterclockwise (negative direction), and the current flows through z4CC34. It goes without saying that the direction may be set clockwise (positive direction).

  In the second state, the second pair generates a gradient magnetic field in which the gradient is saturated as the parameter increases or decreases, as shown in FIG. On the other hand, the first pair generates a gradient magnetic field in which the gradient increases as the parameter increases or decreases as shown in FIG. The second pair may generate a gradient magnetic field in which the gradient increases as the parameter increases or decreases, and the first pair may generate a gradient magnetic field in which the gradient is saturated as the parameter increases or decreases. At this time, the ratio of the odd-order noise reduction current i12 flowing through the first pair to the odd-order noise reduction current i22 flowing through the second pair is set to 7:17. As the second pair and the first pair each form a magnetic field, a gradient magnetic field (FIG. 6 (a)) and a parameter increase in which the gradient is saturated in the measurement space 2 as the parameter increases or decreases. Alternatively, a magnetic field is generated by synthesizing a gradient magnetic field (FIG. 6B) that increases in gradient with a decrease. As shown in FIG. 6C, an odd-order magnetic field, particularly a tertiary magnetic field is reduced. In this state, a magnetic field having a constant gradient is secured over a wide area. Thereby, the circuit 6 supplies odd-order noise reduction currents i12 and i22 to the first pair and the second pair, and the magnetic field in the direction opposite to the primary noise sensed by the sensors 4z and 5z that measure the magnetic field having a gradient. By generating a composite magnetic field formed by the first pair and the second pair, the primary noise can be effectively eliminated.

Next, the case where the circuit 6 supplies a current to the CC and effectively erases the magnetic field having a uniform spatial distribution and the magnetic field having a constant gradient at the same time will be limited to the z axis.
First, an even-order noise reduction current i11 that flows through the first pair when erasing a magnetic field having a uniform spatial distribution and an odd-order noise reduction current i12 that flows through the first pair when erasing a magnetic field having a constant gradient are serially connected. The combined current i1 is the combined current i1. Similarly, when the magnetic field having a uniform spatial distribution is erased, the even-order noise reduction current i21 flowing through the second pair and the magnetic field having a constant gradient are erased. The sum of the odd-order noise reduction currents i22 flowing through the pair is added as a series and is defined as a combined current i2.

  In order to effectively erase simultaneously a magnetic field having a uniform spatial distribution and a magnetic field having a constant gradient, the combined current i1 flows through the first pair and the combined current i2 flows through the second pair. Here, the ratio of the even-order noise reduction current i11 flowing through the first pair to the even-order noise reduction current i21 flowing through the second pair is set to 7:17, and the odd-order noise reduction flowing through the first pair is reduced. Since the ratio between the current i12 and the odd-order noise reduction current i22 flowing in the second pair is set to 7:17, the first-order sum of the even-order noise reduction current i11 and the odd-order noise reduction current i12 is added in series. The ratio of the combined current i1 flowing through the pair and the combined current i2 flowing through the second pair obtained by adding the even-order noise reduction current i21 and the odd-order noise reduction current i22 in series is 7:17. On the other hand, the direction of the current flowing through the z1CC31 to z4CC34 is not uniquely determined as in the first state and the second state described above, and differs from case to case. Taking z2CC32 as an example, a combined current obtained by adding in series the current flowing clockwise (positive direction) for eliminating zero-order noise and the current flowing counterclockwise (negative direction) for eliminating primary noise is z2CC32. Therefore, if the value of the current flowing clockwise (positive direction) is larger than the value of the current flowing counterclockwise (negative direction), the current flows clockwise (positive direction) and counterclockwise (negative direction) When the value of the current flowing in the direction is larger than the value of the current flowing in the clockwise direction (positive direction), the current flows in the counterclockwise direction (negative direction). A state in which the direction of the current flowing through z1CC31 to z4CC34 changes on a case-by-case basis is referred to as a combined current supply state for convenience. In this case, the circuit 6 supplies a composite current obtained by adding the even-order noise reduction current and the odd-order noise reduction current in series to the z1CC31 to z4CC34, thereby forming a magnetic field as shown in FIG. 7, for example. Accordingly, the combined magnetic field formed by the first pair and the second pair, which is a magnetic field in the direction opposite to the zeroth order noise sensed by the sensor 3, and the magnetic field in the direction opposite to the primary noise sensed by the sensors 4z and 5z. By generating a combined magnetic field formed by the first pair and the second pair, the zero-order noise and the primary noise can be effectively eliminated.

  Next, the operation of the active magnetic shield device having the above configuration will be described.

When a subject or test object is magnetically measured with a biomagnetism measuring device (not shown) installed inside the measurement space 2, for example, it is generated from an automobile or train traveling outside the measurement space 2, or an electronic device adjacent to the measurement space 2. Magnetic noise affects magnetic measurement by a device in the measurement space 2. Magnetic noise includes not only noise with a uniform spatial distribution but also noise with various gradients.
Therefore, first, a case will be described in which the zero-order noise sensed by the sensor 3 in FIG. 1 is erased by a reverse magnetic field generated by x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34.

  First, the direction of the current flowing through x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34 is set to the first state (see FIGS. 1 and 2). The sensor 3 senses zero-order noise in the measurement space 2 and feeds back the signal to the circuit 6. The circuit 6 generates a current based on the signal and supplies the even-order noise reduction current to the x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34. The first pair and the second pair of each of x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34 generate a magnetic field, and the even-numbered magnetic field, in particular, the secondary magnetic field is reduced by the combined magnetic field. A magnetic field with a uniform spatial distribution is formed over a wide area. As a result, the x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34 generate a magnetic field in the opposite direction to the zeroth order noise sensed by the sensor 3 to effectively erase the zeroth order noise in the measurement space 2. To do. Thereby, the shielding effect with respect to the 0th-order noise is exhibited in the measurement space 2, and the subject and the test object can be effectively magnetically measured by the biomagnetic measurement using the differential SQUID magnetometer using the secondary differential coil. Further, even in an electron beam drawing apparatus and an electron beam mask drawing apparatus having a sample chamber / electron optical system cylinder made of a ferromagnetic material (permalloy), fluctuations in electron beam drawing can be reduced.

  Next, in FIG. 3, the primary noise sensed by the sensors 4x, 4y, 4z, 5x, 5y, and 5z capable of sensing a magnetic field having a gradient is generated in the reverse direction generated by the x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34. The case of erasing with the magnetic field will be described.

  First, the direction of the current flowing through x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34 is set to the second state (see FIGS. 3 and 4). The sensors 4 x, 4 y, 4 z, 5 x, 5 y, 5 z sense primary noise inside the measurement space 2 and feed back the signal to the circuit 6. The circuit 6 generates a current based on the signal and supplies an odd-order noise reduction current to the x1CC11 to x4CC14, the y1CC21 to y4CC24, and the z1CC31 to z4CC34. The first pair and the second pair of each of x1CC11 to x4CC14, y1CC21 to y4CC24, z1CC31 to z4CC34 generate a magnetic field, and the odd-order magnetic field, particularly the third-order magnetic field is reduced by the combined magnetic field. A magnetic field having a constant gradient is formed over a wide area. As a result, a magnetic field in the direction opposite to the primary noise sensed by the sensors 4x, 4y, 4z, 5x, 5y, and 5z is generated in the measurement space 2 by the x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34. The primary noise in is effectively canceled. Thereby, the shielding effect with respect to primary noise is exhibited in the measurement space 2, and a subject and a test object can be effectively magnetically measured by biomagnetic measurement using a differential SQUID magnetometer using a primary differential coil.

Next, the operation of shielding magnetic noise in this embodiment will be described.
As described above, magnetic noise includes noise having various gradients. Therefore, it is conceivable to obtain the 0th order noise shielding effect and the primary noise shielding effect by switching between the first state and the second state. However, when the state is switched to the second state, the 0th order noise shielding effect in the first state is obtained. When switched to the first state, the primary noise shielding effect of the second state cannot be obtained. Therefore, in this embodiment, the circuit 6 generates a combined current (in the case of z-axis, combined currents i1 and i2) obtained by adding together the currents necessary for obtaining the effects of the first state and the second state in series. It is in a combined current supply state that generates and supplies a combined current to x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34. Therefore, the circuit 6 supplies a combined current obtained by adding the even-order noise reduction current and the odd-order noise reduction current to the x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34, and the x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34 are sensors. 3 generates a magnetic field opposite to the zeroth order noise sensed in the measurement space 2 to effectively erase the zeroth order noise in the measurement space 2, and the x1CC11 to x4CC14, y1CC21 to y4CC24, and z1CC31 to z4CC34 are sensors. A magnetic field in a direction opposite to the primary noise sensed by 4x, 5x, sensors 4y, 5y, and sensors 4z, 5z is generated in the measurement space 2, and the primary noise in the measurement space 2 is effectively eliminated. Thereby, the shielding effect with respect to the 0th order noise and the primary noise can be exhibited simultaneously in the measurement space 2.

[Second Embodiment]
A configuration of an active magnetic shield device according to a second embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the description is abbreviate | omitted. The configuration of the second embodiment is different from the first embodiment in that x1CC31 to x4CC34, y1CC31 to y4CC34, z1CC31 to z4CC34 in the first state, and x1CC31 ′ to x4CC34 ′, y1CC31 ′ to y4CC34 ′ in the second state. , Z1CC31 ′ to z4CC34 ′ are provided in the same measurement space. FIG. 8 shows the arrangement state of CCs limited to the z-axis. According to this, among the z1CC31 to z4CC34 in the first state, the first canceling coil z1CC31 and the second canceling coil z2CC32 constitute the first pair and the third canceling coil. Due to the even-order noise reduction current flowing through the second pair formed by z3CC33 and the fourth canceling coil z4CC34, a magnetic field in the direction opposite to the 0th-order noise sensed by the sensor 3 is generated by z1CC31 to z4CC34. A second pair of z1CC31 ′ to z4CC34 ′ in the second state, which is configured by a first canceling coil z1CC31 ′ and a second canceling coil z2CC32 ′, Z3CC33 ′, which is a 3 canceling coil, and z, which is a fourth canceling coil A magnetic field in a direction opposite to the primary noise sensed by the second-order differential sensors 4z and 5z is generated by the z1CC31 ′ to z4CC34 ′ by the odd-order noise reduction current flowing through the fourth pair formed by the CC34 ′. Noise can be shielded. Further, as in the combined current supply state shown in the first embodiment, a combined current obtained by adding the even-order noise reduction current and the odd-order noise reduction current in series is supplied to the CC, and at the same time, the magnetic field has a uniform spatial distribution and a constant value. Unlike the circuit 6 that forms a magnetic field having a gradient, an even-order noise reduction current for generating a magnetic field having a uniform spatial distribution is generated, and the even-order noise reduction current is generated in the first pair and the second pair. A circuit for supplying even-order noise reduction current (not shown) for supplying an odd-order noise reduction current for generating a magnetic field having a constant gradient, and generating odd-order noise reduction currents for the third and fourth pairs. An odd noise reduction current supply circuit (not shown) for supplying is provided in parallel.
Since other points are the same as those of the first embodiment, description thereof is omitted.

As described above, the active magnetic shield device according to the present embodiment has a large current flowing through three sets of CCs each including four canceling coils (CC) arranged on each surface in the x-, y-, and z-axis directions. By setting the direction, magnetic noise having a high-order gradient is reduced, and the zero-order noise and the primary noise sensed by the sensor can be effectively shielded. In addition, a large work space can be secured inside the measurement space, and each CC does not hinder access to the measurement space or is laid directly under a biomagnetic measurement device or the like.
As a result, biomagnetic measurements such as cerebral magnetic field and cardiac magnetic field measurement using a SQUID magnetometer using primary and secondary differential coils, and a sample chamber / electron optical system cylinder made of ferromagnetic material (permalloy) In the electron beam drawing device and electron beam drawing device, the zero-order noise and the primary noise in the measurement space are effectively shielded so that magnetic measurement or electron beam drawing can be performed with high accuracy and the work space in the measurement space can be maximized. Available.

  Moreover, although this invention was demonstrated based on suitable embodiment, this invention can be changed in the range which does not exceed the meaning. In other words, the first embodiment may be configured to switch between the first state and the second state. In this case, with four CCs as one set, the direction of the current flowing through the CCs arranged on the x, y, and z axes at least one set is changed from the first state to the second state, and the second state. By providing the circuit with switching means capable of switching from the first state to the first state, the CC is first set to the first state, the zero-order noise is eliminated, and then the CC is set to the second state. The primary noise is eliminated, or the CC is first set to the second state and the primary noise is erased, and then the CC is set to the first state and the zeroth order noise is eliminated. By switching the current direction between the first state and the second state, it is possible to obtain a shielding effect against zero-order noise and primary noise.

  Further, in the first embodiment, the three sets of CCs and circuits provided on the x, y, and z axes, respectively, have a configuration in which the current direction is limited to the first state and only has a shielding effect against zero-order noise. Alternatively, the three sets of CCs and circuits respectively provided on the x, y, and z axes may have a configuration in which the current direction is limited to the second state and only a shielding effect against primary noise is provided.

It is the schematic diagram which showed the direction of the electric current which flows into the canceling coil which comprises the active magnetic shielding apparatus which concerns on 1st Embodiment of this invention, and a canceling coil, and the position of a sensor. It is the schematic which showed the direction of the electric current which flows into the z-axis direction canceling coil which comprises the active magnetic shielding apparatus which concerns on 1st Embodiment of this invention, the z-axis direction canceling coil, and the position of a sensor. It is another schematic diagram which showed the direction of the electric current which flows into the canceling coil which comprises the active magnetic shielding apparatus which concerns on 1st Embodiment of this invention, and a canceling coil, and the position of a sensor. It is another schematic diagram which showed the direction of the electric current which flows into the canceling coil of the z-axis direction which comprises the active magnetic shielding apparatus which concerns on 1st Embodiment of this invention, the canceling coil of az axis direction, and the position of a sensor. (A) is a graph showing the magnetic field formed by the canceling coil, (b) is a graph showing another magnetic field formed by the canceling coil, and (c) shows the magnetic field of (a). It is a graph showing the magnetic field which synthesize | combined the magnetic field of (b). (A) is a graph showing the magnetic field formed by the canceling coil, (b) is a graph showing another magnetic field formed by the canceling coil, and (c) shows the magnetic field of (a). It is a graph showing the magnetic field which synthesize | combined the magnetic field of (b). It is a graph showing the magnetic field which has the low-order gradient which four canceling coils form. It is the schematic which showed the direction of the electric current which flows into the canceling coil of the z-axis direction which comprises the active magnetic shielding apparatus which concerns on 2nd Embodiment of this invention, the canceling coil of az axis direction, and the position of a sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Active magnetic shield apparatus 2 Measurement space 3 Sensor 4x, 4y, 4z Sensor 5x, 5y, 5z Sensor 6 Circuit 11 x1 Canceling coil (x1CC)
12 x2 canceling coil (x2CC)
13 x3 canceling coil (x3CC)
14 x4 canceling coil (x4CC)
21 y1 canceling coil (y1CC)
22 y2 canceling coil (y2CC)
23 y3 canceling coil (y3CC)
24 y4 canceling coil (y4CC)
31 z1 canceling coil (z1CC)
32 z2 canceling coil (z2CC)
33 z3 canceling coil (z3CC)
34 z4 canceling coil (z4CC)

Claims (11)

A sensor for detecting magnetic noise in the measurement space;
A first canceling coil disposed on one surface of two opposing surfaces in the measurement space or in the vicinity thereof;
A second canceling coil disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forming a first pair with the first canceling coil;
A third canceling coil concentric with the first canceling coil, disposed on one surface of the two opposing surfaces or in the vicinity thereof;
A fourth canceling coil concentric with the second canceling coil, which is disposed on or near the other surface of the two opposing surfaces and forms a second pair with the third canceling coil;
Based before the magnetic noise xenon capacitors senses, the first to as fourth canceling coil for generating a magnetic field to reduce the magnetic noise in the measurement space, the first to fourth canceling A circuit for generating a current to flow through the coil and supplying the generated current to the first to fourth canceling coils ,
The sensor is capable of sensing magnetic noise with a uniform spatial distribution;
The circuit passes a first current in the positive direction through the first canceling coil, a second current in the positive direction through the second canceling coil, and a third current in the negative direction through the third canceling coil. An active magnetic shield device , wherein a fourth current in a negative direction is caused to flow through the fourth canceling coil . A sensor for detecting magnetic noise in the measurement space;
A first canceling coil disposed on one surface of two opposing surfaces in the measurement space or in the vicinity thereof;
A second canceling coil disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forming a first pair with the first canceling coil;
A third canceling coil concentric with the first canceling coil, disposed on one surface of the two opposing surfaces or in the vicinity thereof;
A fourth canceling coil concentric with the second canceling coil, which is disposed on or near the other surface of the two opposing surfaces and forms a second pair with the third canceling coil;
Based on the magnetic noise sensed by the sensor, the first to fourth canceling coils generate a magnetic field that reduces the magnetic noise in the measurement space. A circuit for generating a current to flow and supplying the generated current to the first to fourth canceling coils,
The sensor is capable of sensing a magnetic field gradient;
The circuit passes a first current in the positive direction through the first canceling coil, a second current in the negative direction through the second canceling coil, and a third current in the positive direction through the third canceling coil. flowing the fourth feature and to luer active magnetic shield that flow in canceling coil fourth current in the negative direction. A sensor for detecting magnetic noise in the measurement space;
A first canceling coil disposed on one surface of two opposing surfaces in the measurement space or in the vicinity thereof;
A second canceling coil disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forming a first pair with the first canceling coil;
A third canceling coil concentric with the first canceling coil, disposed on one surface of the two opposing surfaces or in the vicinity thereof;
A fourth canceling coil concentric with the second canceling coil, which is disposed on or near the other surface of the two opposing surfaces and forms a second pair with the third canceling coil;
Based on the magnetic noise sensed by the sensor, the first to fourth canceling coils generate a magnetic field that reduces the magnetic noise in the measurement space. A circuit for generating a current to flow and supplying the generated current to the first to fourth canceling coils,
The sensor includes a first sensor capable of sensing magnetic noise having a uniform spatial distribution, and a second sensor capable of sensing a magnetic field gradient,
As the current that the circuit passes through the first to fourth canceling coils, the first to fourth canceling coils generate even-order magnetism in the measurement space based on magnetic noise sensed by the first sensor. Based on the even-order noise reduction current determined for each canceling coil so as to generate a magnetic field that reduces noise and the magnetic noise sensed by the second sensor, the first to fourth canceling coils are in the measurement space. Generating a combined current with the odd-order noise reduction current determined for each canceling coil to generate a magnetic field that reduces the odd-order magnetic noise within the
The even-order noise reduction currents related to the first to fourth canceling coils are currents flowing in the positive direction, the positive direction, the negative direction, and the negative direction, respectively.
The first to odd noise reduction current of the fourth canceling coils, respectively, a positive direction, a negative direction, the positive direction, wherein a to luer active magnetic shield that the current flowing in the negative direction. A sensor for detecting magnetic noise in the measurement space;
A first canceling coil disposed on one surface of two opposing surfaces in the measurement space or in the vicinity thereof;
A second canceling coil disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forming a first pair with the first canceling coil;
A third canceling coil concentric with the first canceling coil, disposed on one surface of the two opposing surfaces or in the vicinity thereof;
A fourth canceling coil concentric with the second canceling coil, which is disposed on or near the other surface of the two opposing surfaces and forms a second pair with the third canceling coil;
Based on the magnetic noise sensed by the sensor, the first to fourth canceling coils generate a magnetic field that reduces the magnetic noise in the measurement space. A circuit for generating a current to flow and supplying the generated current to the first to fourth canceling coils,
The sensor includes a first sensor capable of sensing magnetic noise having a uniform spatial distribution, and a second sensor capable of sensing a magnetic field gradient,
A first current in the positive direction is passed through the first canceling coil, a second current in the positive direction is passed through the second canceling coil, a third current in the negative direction is passed through the third canceling coil, and A first state in which a fourth current in the negative direction flows through the four canceling coils, a first current in the positive direction through the first canceling coils, and a second current in the negative direction through the second canceling coils. For selectively switching the circuit to a second state in which a third current in the positive direction is supplied to the third canceling coil and a fourth current in the negative direction is supplied to the fourth canceling coil. features and to luer active magnetic shield, further comprising: a switching means. A sensor for detecting magnetic noise in the measurement space;
A first canceling coil disposed on one surface of two opposing surfaces in the measurement space or in the vicinity thereof;
A second canceling coil disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forming a first pair with the first canceling coil;
A third canceling coil concentric with the first canceling coil, disposed on one surface of the two opposing surfaces or in the vicinity thereof;
A fourth canceling coil concentric with the second canceling coil, which is disposed on or near the other surface of the two opposing surfaces and forms a second pair with the third canceling coil;
Based on the magnetic noise sensed by the sensor, the first to fourth canceling coils generate a magnetic field that reduces the magnetic noise in the measurement space. A circuit for generating a current to flow and supplying the generated current to the first to fourth canceling coils,
The sensor includes a first sensor capable of sensing magnetic noise having a uniform spatial distribution, and a second sensor capable of sensing a magnetic field having a gradient,
A fifth canceling coil disposed on one surface of the two opposing surfaces or in the vicinity thereof,
A sixth canceling coil disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forming a third pair with the fifth canceling coil;
A seventh canceling coil concentric with the fifth canceling coil, disposed on one surface of the two opposing surfaces or in the vicinity thereof;
And an eighth canceling coil concentric with the sixth canceling coil, which is disposed on the other surface of the two opposing surfaces or in the vicinity thereof and forms a fourth pair with the seventh canceling coil. And
Each canceling coil so that the circuit generates a magnetic field that reduces even-order magnetic noise in the measurement space based on magnetic noise sensed by the first sensor. The even-order noise reduction current determined for the first to fourth canceling coils is supplied to the first to fourth canceling coils, and the fifth to eighth canceling coils are moved in the measurement space based on the magnetic noise sensed by the second sensor. Flowing an odd-order noise reduction current determined for each canceling coil so as to generate a magnetic field that reduces the odd-order magnetic noise of the fifth to eighth canceling coils,
The even-order noise reduction currents related to the first to fourth canceling coils are currents flowing in the positive direction, the positive direction, the negative direction, and the negative direction, respectively.
The odd-order noise reduction current of the fifth to eighth canceling coils, respectively, a positive direction, a negative direction, the positive direction, wherein a to luer active magnetic shield that the current flowing in the negative direction. 6. The active magnetic shield device according to claim 5 , wherein the ratio of the magnitude of the current flowing through the third pair to the magnitude of the current flowing through the fourth pair is 7:17. The fifth canceling coil and the sixth canceling coil are squares having the same size, and the seventh canceling coil and the eighth canceling coil have the same size and are larger than the fifth canceling coil. The seventh canceling coil is disposed closer to the inside than the fifth canceling coil, the eighth canceling coil is disposed closer to the inner side than the sixth canceling coil, and the fifth canceling coil is disposed. A distance a between the coil and the sixth canceling coil, a distance b between the seventh canceling coil and the eighth canceling coil, a length c of one side of the fifth canceling coil, the seventh canceling coil Is set to a: b: c: d = 1.4: 1: 0.74: 1.35 Active magnetic shield apparatus according to claim 5 or 6. Wherein the x-axis fifth to eighth canceling coils, y-axis, the active magnetic shield device according to any one of claims 5 to 7, characterized in that it respectively provided in at least two directions of the z-axis. Active magnetic shield device according to any one of the first current flowing through the pair of size and the current flowing through said second pair ratio of the size is 7:17 claims 1 to 8. The first canceling coil and the second canceling coil are squares having the same size, and the third canceling coil and the fourth canceling coil have the same size and are larger than the first canceling coil. The third canceling coil is disposed closer to the inside than the first canceling coil, the fourth canceling coil is disposed closer to the inside than the second canceling coil, and the first canceling coil A distance a between the coil and the second canceling coil, a distance b between the third canceling coil and the fourth canceling coil, a length c of one side of the first canceling coil, the third canceling coil Is set to a: b: c: d = 1.4: 1: 0.74: 1.35 Active magnetic shield device according to any one of claims 1 to 9. Wherein the x-axis first to fourth canceling coils, y-axis, the active magnetic shield device according to any one of claims 1 to 10, characterized in that it respectively provided in at least two directions of the z-axis.

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