Patent Application
20220299580
The present invention relates to a magnetic-field measuring apparatus.
Measurement of a weak magnetic field, such as magnetism of a living body, is implemented typically using superconducting quantum interference devices (SQUIDs) in a magnetically shielded room (MSR). Hereinafter, a superconducting quantum interference device will be also referred to as a SQUID. SQUIDs have non-linear responses to magnetic fields, and the non-linear responses are linearized using flux-locked loop (FLL) circuitry to measure the magnetic fields. As FLL circuitry, an analog FLL system, which includes exclusively analog circuitry, and a digital FLL system, which converts analog signals into digital signals and converts the digital signals back into analog signals after signal processing, are known.
Magnetic-field signals measured by SQUIDs are weak and susceptible to noise. Therefore, a method for dividing control circuitry for controlling operation of SQUIDs into two sections is disclosed. The one of the two sections is installed in a magnetically shielded room and the other is installed outside the magnetically shielded room (see PTL 1).
For example, in a case where a cooling system including SQUIDs and headsets including preamplifiers are directly connected, the distance between the SQUIDs and the preamplifiers can be minimized, thereby enabling to improve the noise robustness with respect to the signals that are output from the SQUIDs to be amplified by the preamplifiers. However, long cables are used to connect the preamplifiers with control circuitry that is outside the magnetically shielded room. In particular, longer cables are used in the magnetically shielded room than the corresponding cables of a case where the preamplifiers are provided away from the cooling system.
The cables connecting the preamplifiers and the control circuitry include not only signal cables for transmitting the signals amplified by the preamplifiers but also power cables for supplying power to the preamplifiers. Therefore, if the longer cables are used in the magnetically shielded room, greater radiant magnetic field noise is generated in the magnetically shielded room, and thus, greater radiant magnetic field noise is detected by the SQUIDs. Therefore, even if the noise robustness with respect to the signals before being amplified by the preamplifiers is improved, the pream-plifiers amplify the radiant magnetic field noise detected by the SQUIDs together with the biomagnetic field signals.
An aspect of the present invention has been devised in view of the above-described problem and is intended to provide a magnetic-field measuring apparatus capable of reducing radiant magnetic field noise generated in a magnetically shielded room.
In order to solve the above described problem, a magnetic-field measuring apparatus according to the aspect of the present invention includes a SQUID; and flux-locked loop circuitry including first circuitry that includes an amplifier connected to an output of the SQUID, and second circuitry connected to the first circuitry. The first circuitry is along an inner surface or an outer surface of a shielding material that separates an inside of a magnetically shielded room from an outside of the magnetically shielded room, the magnetically shielded room including the SQUID. The second circuitry is in the outside of the magnetically shielded room.
Thus, the magnetic-field measuring apparatus capable of reducing radiant magnetic field noise generated in a magnetically shielded room can be provided.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the ac-companying drawings.
Now, embodiments will be described with reference to the drawings. In each drawing, the same elements are indicated by the same reference numerals and duplicate descriptions may be omitted.
The magnetic-field measuring apparatus 100A includes a SQUID 10, a digital FLL circuitry 20, and a feedback coil 36. The SQUID 10 is a highly sensitive magnetic sensor that detects a magnetic field (magnetic flux), generated from a living body, passing through a superconducting ring having Josephson junctions. For example, in the SQUID 10, Josephson junctions are provided at two positions of the super-conducting ring.
The SQUID 10 generates a voltage that varies periodically with a change in a magnetic flux passing through the superconducting ring. Therefore, a magnetic flux passing through the superconducting ring can be detected by measuring a voltage across the superconducting ring with a bias current applied to the superconducting ring. Hereinafter, the characteristic of a periodic voltage change generated by the SQUID 10 is also referred to as a Φ-V characteristic.
The digital FLL circuitry 20 includes an amplifier 31, an analog-to-digital converter 32, a digital integrator 33, a digital-to-analog converter 34, and a voltage-to-current converter 35. In the digital FLL circuitry 20, the amplifier 31 and the voltage-to-current converter 35 are included in first circuitry 21; and the analog-to-digital converter 32, the digital integrator 33 and the digital-to-analog converter 34 are included in second circuitry 22. A feedback coil 36 near the SQUID 10 is physically apart from the digital FLL circuitry 20, but may be included in the functional block of the digital FLL circuitry 20.
A plurality of electrical cables FLC, such as power supply cables 37 and control signal lines (an amplifier output line 38 and a voltage line 39) are installed between the first circuitry 21 and the second circuitry 22. A plurality of electrical cables SQC are installed to connect the SQUID 10 and the feedback coil 36 with the first circuitry 21. Hereinafter, the electrical cables SQC and FLC are also simply referred to as cables SQC and FLC.
In the present embodiment, the first circuitry 21, which does not include digital circuitry, is located in the magnetically shielded room MSR, together with the SQUID 10 and the feedback coil 36. The second circuitry 22, including digital circuitry, is located outside the magnetically shielded room MSR. Therefore, it is possible to prevent radiant magnetic field noise, generated by operation of digital circuitry operating in synchronization with a clock signal, for example, from being transmitted in the magnetically shielded room MSR. This prevents the SQUID 10 from detecting radiant magnetic field noise generated by digital circuitry.
Further, because the first circuitry 21 includes only minimum circuitry, the volume of the first circuitry 21 housed by the magnetically shielded room MSR can be minimized, and the magnetically shielded room MSR can be effectively used.
Herein, the term “magnetically shielded room” means a space formed by using, as a shielding material (wall material), a magnetic material or a material having a high electrical conductivity alone or in a lamination to reduce an influence of environmental magnetic field noise on the inside.
A magnetic field emitted from a living body is very weak, ranging from 10−10 to 10−14 T (tesla). Therefore, in order to accurately detect a magnetic field using the SQUID 10, it is desired to reduce urban noise (environmental magnetic field noise). Therefore, the magnetically shielded room is required to reduce environmental magnetic field noise by approximately 60 dB. Hereinafter, an example of the magnetically shielded room will be described, but there is no limitation to the example.
The magnetically shielded room MSR is formed by covering an internal space SIN, in which the SQUID 10 is installed, with a shielding member (indicated by an alternate long and short dash line) that shields magnetism. The shielding member corresponds to a shielding material (wall material) that separates the inside of the magnetically shielded room MSR from the outside of the magnetically shielded room MSR. As a result, the internal space SIN which is the inside of the magnetically shielded room MSR in which the SQUID 10 is installed is magnetically shielded from an external space SOUT which is the outside of the magnetically shielded room MSR. By placing the SQUID 10 in the magnetically shielded room MSR, it is possible to reduce an influence of an environmental magnetic field such as a geomagnetic field.
The amplifier 31 amplifies an output voltage, generated by the SQUID 10 from a magnetic flux passing through the SQUID 10, to output the amplified output voltage to the analog-to-digital converter 32 via an amplifier output line 38. The analog-to-digital converter 32 converts the analog signal output by the amplifier 31 into a digital signal (voltage value), by sampling the analog signal at a predetermined sampling frequency, to output the digital signal to the digital integrator 33.
The digital integrator 33 integrates a change in the voltage of the SQUID 10 (precisely, the amplified voltage output from the amplifier 31) from a working point, which is a starting point of each cycle with respect to the Φ-V characteristic, and outputs the integrated voltage value to the digital-to-analog converter 34.
The digital integrator 33 outputs the integrated voltage value to a data processor 70 such as a computer. The data processor 70 calculates a value of a biomagnetic field signal, which is a magnetic flux emitted by a living body (a brain, a heart, a nerve, or the like) to be measured, based on the voltage value from the digital integrator 33.
The digital-to-analog converter 34 converts the integrated voltage value (the digital signal) of the digital integrator 33 to a voltage and outputs the converted voltage to the voltage-to-current converter 35 via the voltage line 39. The voltage-to-current converter 35 converts the voltage received from the digital-to-analog converter 34 into a current and outputs the converted current to the feedback coil 36.
The feedback coil 36 generates a magnetic flux due to the current received from the voltage-to-current converter 35 and feeds the generated magnetic flux back to the SQUID 10 as a feedback magnetic flux. As a result, the voltage generated by the SQUID 10 can be maintained near the working point (linear zone) with respect to the Φ-V characteristic, and thus, the biomagnetic field signal can be accurately obtained.
The configuration illustrated in
In the following description, it is assumed that, for example, eight cables SQC are installed for each channel from the SQUID 10 and the feedback coil 36 to the first circuitry 21, and eight cables FLC are installed for each channel between the first circuitry 21 and the second circuitry 22. That is, the magnetic-field measuring apparatus 100A with the 128 channels has 1024 cables SQC and 1024 cables FLC. The cables SQC and FLC include cables for control in addition to the cables illustrated in
With regard to the magnetically shielded room MSR, the shielding material 90 (wall material) that separates the internal space SIN from the external space SOUT is formed by laminating of, for example, a plate material made of permalloy or the like as a high magnetic permeability material and a plate material made of an electrical conductor such as copper or aluminum. The magnetically shielded room MSR, as illustrated in
For example, the first circuitry 21 is installed on a shelf 80 installed at an upper section of an inner wall (inner surface) of the shielding material 90 of the magnetically shielded room MSR obliquely above the dewar 13. That is, the first circuitry 21 is located at the upper section of the inner wall of the magnetically shielded room MSR and higher than the top surface of the dewar 13.
The internal space SIN of the magnetically shielded room MSR can be effectively used by installing of the first circuitry 21 on the shelf. In addition, by placing the first circuitry 21 at a higher position than the top surface of the dewar 13, the cables SQC can be introduced to a cable insertion opening of the dewar 13 due to gravity, thereby reducing the influence of the load of the cables SQC applied to the cable insertion opening.
The plurality of cables SQC are installed to connect the first circuitry 21 with the SQUIDs 10 and the feedback coils 36 (not illustrated) disposed inside the dewar 13. For example, the cables SQC are inserted into the dewar 13 through the cable insertion opening formed at the top of the dewar 13.
In addition, the first circuitry 21 and the second circuitry 22 installed in the external space SOUT of the magnetically shielded room MSR are connected to each other through the cables FLC which pass through a through hole provided in a wall of the magnetically shielded room MSR. The first circuitry 21 may be placed on the floor surface in contact with or near the inner wall of the magnetically shielded room MSR. However, in order to prevent the cables FLC from being exposed to the internal space SIN and to prevent the radiant magnetic field noise generated from the cables FLC from being radiated to the internal space SIN, it is desirable that the first circuitry 21 be in contact with the inner wall (see
In this regard, the shielding material 90 may be protected by protection materials 91 as depicted in
With regard to the cables FLC connecting the first circuitry 21 and the second circuitry 22, the length of the cables FLC from the first circuitry 21 to the inner surface of the shielding material 90 is smaller than the length of the cables SQC connecting the SQUIDs 10 and the feedback coils 36 with the first circuitry 21. That is, the length of the cables FLC from the first circuitry 21 to the inner surface of the shielding material 90 is smaller than the length of the cables SQC from the dewar 13 to the first circuitry 21.
As to the cables SQC and FLC, for example, 136-core cord-assembled-type cables are used. Hereinafter, a cable in which 136 cables SQC (or FLC) are assembled will also be referred to as cables SQC (or FLC). With regard to the 1024 cables SQC and 1024 cables FLC, the number of cord-assembled-type cables SQC and the number of cord-assembled-type cables FLC used in the internal space SIN and the external space SOUT is eight each.
The cord-assembled-type cables SQC and FLC are thicker and have greater flexural rigidity than individual cables SQC and FLC. Therefore, for example, it is desirable that the first circuitry 21 be positioned so as to minimize the bending of the cables SQC and prevent the load of the cables SQC from concentrating at the cable insertion opening of the dewar 13. In this regard, the first circuitry 21 is desirably located obliquely above the dewar 13.
For example, the first circuitry 21 is provided in a form of at least one printed circuit board housed in a housing illustrated as having a rectangular parallelepiped shape in
In the following description, the state where the first circuitry 21 is in contact with or near an inner wall or the like means a state where a part of the first circuitry 21 facing the inner wall or the like is in contact with or near the inner wall or the like. For example, when the first circuitry 21 includes the rectangular parallelepiped housing, the state where the first circuitry 21 is in contact with or near an inner wall or the like means a state where a side, top or bottom surface of the housing facing the inner wall or the like is in contact with or near the inner wall or the like.
The second circuitry 22 is provided in a form of at least one printed circuit board housed in a housing such as a rack illustrated as having a rectangular parallelepiped shape in
In the present embodiment, because the first circuitry 21 is installed along the inner wall of the shielding material 90 of the magnetically shielded room MSR, it is possible to prevent the cables FLC including the power supply cables 37 (see
The first circuitry 21 may be installed directly to the inner wall of the magnetically shielded room MSR above the dewar 13 or the first circuitry 21 may be installed to the inner wall via a mounting panel or the like. As indicated by the dashed-line box A in
For example, the magnetic-field measuring apparatus 100A illustrated in
Similar to
The first circuitry 21 may be installed directly to the inner wall of the magnetically shielded room MSR above the dewar 14 or may be installed to the inner wall via a mounting panel or the like. Similarly to
With regard to the cables FLC connecting the first circuitry 21 and the second circuitry 22, the length of the cables FLC brought from the first circuitry 21 to the inner surface of the shielding material 90 is smaller than the length of the cables SQC connecting the SQUIDs 10 and the feedback coils 36 with the first circuitry 21. That is, the length of the cables FLC brought from the first circuitry 21 to the inner surface of the shielding material 90 is smaller than the length of the cables SQC brought from the dewar 14 to the first circuitry 21.
That is, in the magnetic-field measuring apparatus 100B, the cables SQC pass through a through-hole formed in a wall of the magnetically shielded room MSR. For example, the magnetic-field measuring apparatus 100B uses a digital FLL system and may be applied to a magnetoencephalograph, a magnetospinograph, a magnetocardiograph, a magnetomyograph, or the like.
In
In this regard, the shielding material 90 may be protected by protection materials 91 as depicted in
The cables SQC from the dewar 13 are connected to the first circuitry 21 through a through hole formed obliquely above the dewar 13. The cables FLC connecting the first circuitry 21 and the second circuitry 22 are installed in the external space SOUT outside the magnetically shielded room MSR.
With regard to the cables SQC connecting the SQUIDs 10 and the feedback coils 36 with the first circuitry 21, the length of the cables SQC brought from the first circuitry 21 to the outer surface of the shielding material 90 is smaller than the length of the cables SQC brought from the SQUIDs 10 and the feedback coils 36 to the inner surface of the shielding material 90. That is, the length of the cables SQC brought from the first circuitry 21 to the outer surface of the shielding material 90 is smaller than the length of the cables SQC brought from the dewar 13 to the inner surface of the shielding material 90.
Similarly to
Even in a case where the first circuitry 21 and the second circuitry 22 are thus installed outside the magnetically shielded room MSR, the first circuitry 21 and the second circuitry 22 are housed in separate housings. Therefore, in the external space SOUT, the degree of freedom of installing the first circuitry 21 and the second circuitry 22 can be increased.
For example, the first circuitry 21 may be placed in contact with or near an outer wall of the shielding material 90, regardless of the position where the second circuitry 22 is installed. The length of the cables SQC can be minimized when the first circuitry 21 is placed in contact with or near the outer wall. When the first circuitry 21 is placed in contact with the outer wall, the cables SQC are not exposed to the external space SOUT. This prevents the minute signals output from the SQUIDs 10 and transmitted through the cables SQC from being affected by radiant noise transmitted through the external space SOUT outside the magnetically shielded room MSR.
In
This allows for effective use of the internal space SIN of the magnetically shielded room MSR, similar to the examples of
With regard to the cables SQC connecting the SQUIDs 10 and the feedback coils 36 with the first circuitry 21, the length of the cables SQC brought from the first circuitry 21 to the outer surface of the shielding material 90 is smaller than the length of the cables SQC brought from the SQUIDs 10 and the feedback coils 36 to the inner surface of the shielding material 90. That is, the length of the cables SQC brought from the first circuitry 21 to the outer surface of the shielding material 90 is smaller than the length of the cables SQC brought from the dewar 14 to the inner surface of the shielding material 90.
Similarly to the example of
In a case of applying a wiring route WR1, the first circuitry 21 is placed on the top surface of the dewar 13 and the cables SQC are installed between the first circuitry 21 and the inside of the dewar 13. The cables FLC are brought installed downward from the first circuitry 21 to the floor along a side wall of the dewar 13 and then are installed around the bed 12. The cables FLC are then connected to the second circuitry 22 which is installed in the external space SOUT through a through hole, provided in a side wall of the magnetically shielded room MSR, near the floor. In the case of applying the wiring route WR1, the length of the cables SQC can be made smallest, but the length of the cables FLC in the magnetically shielded room MSR is great.
In the cases of applying wiring routes WR2, WR3, and WR4, the first circuitry 21 is placed on the floor surface in contact with or near the inner wall of the magnetically shielded room MSR (
In the case of applying the wiring route WR2, the cables FLC are installed from the first circuitry 21 over the bed 12 at a position facing the front surface of the dewar 13, and then are installed around the bed 12. The cables FLC are then connected to the second circuitry 22 which is installed in the external space SOUT through a through hole provided in a side wall of the magnetically shielded room MSR near the floor. In the case of applying the wiring route WR2, the length of the cables FLC is great as in the case of applying the wiring route WR1.
In the case of applying the wiring route WR3, the cables FLC are installed upward along the inner wall of the magnetically shielded room MSR from the first circuitry 21, then are installed downward along an inner wall to a through hole, pass through the through hole, and are connected to the second circuitry 22 which is installed in the external space SOUT. In the case of applying the wiring route WR3, the length of the cables FLC is great as in the cases of applying the wiring routes WR1 and WR2, but are installed away from the dewar 13.
In the case of applying the wiring route WR4, the cables FLC are installed on the floor surface from the first circuitry 21 up to a through hole, pass through the through hole, and are connected to the second circuitry 22 which is installed in the external space SOUT. In the case of applying the wiring route WR4, the length of the cables FLC can be minimized. For example, the length of the cables FLC in the case of applying the wiring route WR3 is 8 m, and the length of the cables FLC in the case of applying the wiring route WR4 is 1 m. For example, the size of the magnetically shielded room MSR is 2 m high by 3.6 m wide (at the wall surface having the through hole) by 2.3 m deep.
With reference to
In the case of applying the wiring route WR5, the cables FLC are brought from the first circuitry 21 into the internal space SIN through a through hole formed in a wall of the magnetically shielded room MSR near the floor. The cables FLC thus brought into the internal space SIN are installed around the bed 12, then, pass through the through hole again, and are installed up to the second circuitry 22 which is installed in the external space SOUT. In the case of applying the wiring route WR5, as in the case of applying the wiring route WR2 of
In the case of applying the wiring route WR7, the first circuitry 21 is installed on a shelf 80 installed to an inner wall of the magnetically shielded room MSR obliquely above the dewar 13, similar to the case illustrated in
In the waveforms of
In each of the cases of the wiring routes WR1, WR2, and WR5 where the cables FLC are installed near the dewar 13, magnetic field noise of 168 Hz was clearly observed. Also in the case of applying the wiring route WR3 where the cables FLC are installed for a long distance in the magnetically shielded room MSR, very small magnetic field noise of 168 Hz was observed.
On the other hand, magnetic field noise of 168 Hz was not observed in the case of applying the wiring route WR4 where the length of the cables FLC is small in the magnetically shielded room MSR and in each of the cases of applying the wiring routes WR6 and WR7 where the cables FLC are not installed in the magnetically shielded room MSR.
Thus, it can be seen that the nearer to the dewar 13 the cables FLC are installed, and the longer the cables FLC are installed in the magnetically shielded room MSR, the more likely the SQUIDs 10 detect magnetic field noise. That is, it can be seen that the positional relationships between the cables FLC and the dewar 13 correlate with magnetic field noise detected by the SQUIDs 10. It can be also seen that the length of the cables FLC in the magnetically shielded room MSR correlate with magnetic field noise detected by the SQUIDs 10.
For example, when the first circuitry 21 is positioned on the top surface of the dewar 13, as in the case of the wiring route WR1, the installation area of the first circuitry 21 can be made to overlap with the installation area of the dewar 13, and the inside of the magnetically shielded room MSR can be efficiently used. However, magnetic field noise is generated when the cables FLC are installed near the dewar 13 as a result of the first circuitry 21 being installed near the dewar 13. In this regard, if the dewar 13 is installed away from the cables FLC to avoid influence of magnetic field noise, the installation position of the dewar 13 becomes limited.
The minute signals output from the SQUIDs 10 through the cables SQC are not likely to be a source of noise because a change in amplitude is gentler than a change in amplitude of a digital signal. On the other hand, the length of the cables SQC is desirably as small as possible because the minute signals transmitted through the cables SQC are likely to be affected by radiation noise or the like.
Accordingly, it is desirable that the cables FLC are not installed in the magnetically shielded room MSR and that the length of the cables SQC be as small as possible in order to reduce magnetic field noise caused by the magnetic-field measuring apparatus 100A or 100B. To prevent the cables FLC from being installed in the magnetically shielded room MSR, it is desirable that the first circuitry 21 be located near or in contact with an inner or outer wall of the magnetically shielded room MSR.
In addition, when the first circuitry 21 is placed in the magnetically shielded room MSR, it is desirable that the first circuitry 21 is in contact with an inner wall of the magnetically shielded room MSR in order to prevent the cables FLC from being exposed to the inside of the magnetically shielded room MSR. When the first circuitry 21 is installed outside the magnetically shielded room MSR, the first circuitry 21 is desirably in contact with an outer wall of the magnetically shielded room MSR in order to prevent the cables SQC from being exposed to the external space SOUT.
For example, as a result of the installation position of the first circuitry 21 being determined in accordance with either one of the cases of the wiring routes WR4 and WR7 each satisfying these conditions, the magnetic-field measuring apparatus where magnetic field noise detected by the SQUIDs 10 can be minimized can be implemented. According to either one of the cases of applying the wiring routes WR4 and WR7, the length of the cables FLC (0 m or 1 m) brought from the first circuitry 21 to an inner wall (or a through hole) of the magnetically shielded room MSR is to be smaller than the length of the cables SQC (10 m), and consequently, the first circuitry 21 is to be placed near a wall of the sealing room.
Therefore, the measurement accuracy of biomagnetic field signals by the SQUIDs 10 can be improved. For example, by installing the first circuitry 21 at the position illustrated in any one of
The magnetic-field measuring apparatus 100C includes, for each channel, a SQUID 10, analog FLL circuitry 40, and a feedback coil 36. The analog FLL circuitry 40 includes, for each channel, an amplifier 31, an integrator 43, an analog-to-digital converter 44, and a voltage-to-current converter 35. The feedback coil 36 disposed near the SQUID 10 may be included in the analog FLL circuitry 40.
In the analog FLL circuitry 40, the amplifier 31 and the voltage-to-current converter 35 are included in the first circuitry 21 as in the example illustrated in
For example, the first circuitry 21 is disposed in the magnetically shielded room MSR together with the SQUID 10, and the second circuitry 42 is disposed outside the magnetically shielded room MSR. Similar to the example illustrated in
The integrator 43 is analog circuitry and has a function similar to the function of the digital integrator 33 illustrated in
In the magnetic-field measuring apparatus 100C, an installation example of the first circuitry 21 and the second circuitry 42 is the same as any one of the installation examples illustrated in
This allows the magnetic-field measuring apparatus 100C of the present embodiment to reduce magnetic field noise generated in the magnetically shielded room MSR, similar to the above-described magnetic-field measuring apparatuses 100A and 100B, and prevents the SQUIDs 10 from detecting magnetic field noise. As a result, the measurement accuracy of biomagnetic field signals by the SQUIDs 10 can be improved.
In the above-described embodiments, the examples in which the first circuitry 21 is installed on an inner wall (inner surface) or an outer wall (outer surface) of the shielding material 90 of the magnetically shielded room MSR have been described, but the first circuitry 21 may be installed on a ceiling of the shielding material 90 of the magnetically shielded room MSR. In this case, the first circuitry 21 may be installed either inside (i.e., an inner surface of the shielding material 90) or outside (i.e., an outer surface of the shielding material 90) of the magnetically shielded room MSR.
Further, the first circuitry 21 may be located under the floor (i.e., an outer surface of the shielding material 90) when there is a space under the floor of the shielding material 90 of the magnetically shielded room MSR.
For example, the FLL circuitry 50 is digital FLL circuitry and includes first circuitry 21 and second circuitry 22 illustrated in
The FLL circuitry 50 is connected to the dewar 13 via cables SQC. The FLL circuitry 50 is also connected to a power supply 60 and a data processor 70 which are located outside of the magnetically shielded room MSR via a plurality of electrical cables PCC including signal cables and power supply cables. Hereinafter, the electrical cables PCC will be simply referred to as cables PCC.
In the configuration illustrated in
On the other hand, the cables SQC connecting the SQUIDs 10 and the amplifiers 31 of the FLL circuitry 50 can be made to have a length equivalent to the length of the cables SQC illustrated in any one of
In addition, when the FLL circuitry 50 is thus installed in the magnetically shielded room MSR, the available space in the internal space SIN becomes smaller. When the size of the magnetically shielded room MSR is increased accordingly, this increases the cost of a magnetic-field measuring system including the magnetic-field measuring apparatus 110A and the magnetically shielded room MSR.
The cables SQC connected to the SQUIDs 10 (not illustrated) in the dewar 13 pass through a through hole formed in a wall of the magnetically shielded room MSR and are then connected to the FLL circuitry 50. The FLL circuitry 50 is connected to a power supply 60 and a data processor 70 located outside of the magnetically shielded room MSR, through a plurality of cables PCC including signal cables and power cables.
In the configuration illustrated in
Although the magnetic-field measuring apparatuses have been described with reference to the embodiments, embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.
The present application is based on and claims priority to Japanese patent application No. 2019-182193 filed on Oct. 2, 2019 and Japanese patent application No. 2019-188211 filed on Oct. 11, 2019. The entire contents of Japanese priority application No. 2019-182193 and Japanese priority application No. 2019-188211 are hereby incorporated herein by reference.
[PTL 1] Japanese Unexamined Patent Application Publication No. 11-118893
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-182193 | Oct 2019 | JP | national |
| 2019-188211 | Oct 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/036142 | 9/24/2020 | WO |
