JPH08110372A - Squid flux meter - Google Patents

Abstract

PURPOSE: To obtain a superconducting quantum interference device(SQUID) flux meter having a pick-up coil which is highly accurate and steady in a mechanical structure by a constitution wherein the pick-up coil is formed on a surface of a core member by a pattern-forming method. CONSTITUTION: A core member 1 is made of a material that is a paramagnetism material and an electric insulator in an ultralow temperature condition and has the durability in the temperature cycle of a normal temperature and cryogenic temperature, e.g. a glass, an epoxy resin, a ceramic material or the like. A super-condition this film is formed on the core member 1 by a sputtering method or a vacuum evaporation method. After that, a pick-up coil 5 is formed by a photolithography technology. Thereby, it is possible to make a differentiation type pick-up coil 5 with high accuracy compared to a manually wound pick-up coil. Because of its steady structure, it is not deformed by an normal impulsive force and it can maintain the high accuracy in a mechanical structure after the production. The shape of the core member 1 is not limited to a rectangular solid in the case where a first loop face 3 and a second loop face 2 are in parallel to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SQUID magnetometer used for measuring biomagnetism, and more particularly to the structure of a pickup coil.

[0002]

2. Description of the Related Art In SQUID magnetometers, SQUID
The ring allows a flux transformer to be used to guide more flux. A differential pickup coil is well known as a pickup coil portion of a magnetic flux transformer for the purpose of canceling an environmental noise magnetic field. The differential pickup coil includes an axial pickup coil and a flat pickup coil. FIG. 8 shows a shaft type pickup coil.

In order to construct such an axial pickup coil, conventionally, (1) a method of winding a superconducting wire around a core material having a cylindrical shape or another shape. (2) A method of forming a pickup coil pattern on a flexible substrate and then fixing it to a desired shape. Was used.

The primary differential type pickup coil cancels a uniform magnetic field by winding two loops in opposite directions. Since the ambient magnetic field is generally more uniform than the magnetic field generated by the signal source to be observed, such pickup coils selectively remove the ambient magnetic field. However, due to the mechanical accuracy of the pickup coil,
The uniform magnetic field cannot be completely removed. The cause is that each loop is not completely flat, the areas of the two loops are not the same, and the two loops are not parallel. For example, a uniform magnetic field of 10 ^-7 [T / √H
z], the sensitivity of SQUID is about 10 ⁻¹⁴ [T / √Hz], and the shielding ratio of the shield room is 10 ⁻³ , the uniform magnetic field that cannot be removed and remains is about 10 ⁻ of the uniform magnetic field after shielding. It must be ⁴ times or less. To achieve this, the difference in the area of each loop is a times the loop area,
When the angle between the two loops is α, a + 1-cos
It is necessary that (α) be ^less than 10 ⁻⁴ . a = 5 × 1
0 ⁻⁵ , α = 5 × 10 ⁻⁵ , α = 0.57 [deg] is an example of a value satisfying this.

Further, in order to constantly maintain the above-mentioned mechanical accuracy, the pickup coil is required to be robust so as not to be deformed by vibration or shock which is usually expected. Normally, geomagnetism is not observed in SQUID because it has little temporal variation, but when the pickup coil oscillates, the magnetic field interlinking the pickup coil changes, so an oscillating magnetic field that should not be there is observed. . For this reason also, the pickup coil needs to have a mechanically strong structure so as not to cause vibration. Above 1
Although the mechanical accuracy and robustness required for the second-order differential type pickup coil have been described, the same can be said for the zero-order differential type or higher-order partial type pickup coil.

[0006]

As described above, the conventional method (1) has a drawback in that the high mechanical precision desired for biomagnetic measurement cannot be obtained. Further, the method (2) has a drawback that it is not mechanically robust.

The present invention has been made in order to solve such a conventional problem, and an object thereof is to provide an SQUID magnetometer having a mechanically highly accurate and mechanically robust pickup coil. To do.

[0008]

In order to achieve the above object, the present invention has a pickup coil for measuring a magnetic flux generated in a subject, and a magnetic field distribution based on the magnetic flux measured by the pickup coil. In the SQUID magnetometer, the pickup coil is characterized in that it is formed on the surface of a three-dimensional core material by a pattern forming method.

[0009]

According to the present invention configured as described above, since the pickup coil is formed on the solid core material by using the pattern forming method such as the photolithography technique, the pickup coil can be formed with high accuracy and solidity. You will be able to.

[0010]

FIG. 1 shows the first embodiment of the present invention. The core material 1 shown in the figure is a material that is paramagnetic in a cryogenic state, is an electrical insulator in a cryogenic state, and can withstand a temperature cycle between room temperature and cryogenic temperature, such as glass or epoxy. It is made of resin, fluorine resin-based plastic, or FRP and ceramics using them. A superconducting thin film is formed on this core material by sputtering or vacuum evaporation. afterwards,
The pickup coil 5 is formed by the photolithography technique. According to the present embodiment, the differential type pickup coil can be produced with higher accuracy than the case where the pickup coil 5 is wound manually. Further, since the structure is solid, it is not deformed by a normal impact even after being manufactured, and high mechanical accuracy can be maintained.

Although the core material 1 is shown as a rectangular parallelepiped in FIG. 1, other shapes may be used as long as the first loop surface 3 and the second loop surface 2 are parallel to each other. In particular, a mechanism for attaching the pickup coil 5 to the support may be added. This has the advantages that the pickup coil 5 can be mounted in a precise position, and the pickup coil 5 can be easily mounted and replaced. FIG. 2 shows a configuration example in which an attachment mechanism is added to the core material and the support body. In this example, the core 1 is provided with a hole 1a having a countersink, the support 6 is provided with a conical projection 6a, and both are fixed and fixed with a screw 8. At this time, the dish fir portion 1a and the conical portion 6a are provided with projections and depressions so that the pickup coil 5 faces the determined direction so that the pickup coil 5 cannot be mounted in a direction other than the determined direction. The pickup coil 5 according to the present embodiment can be mounted with high accuracy without causing a positional deviation during mounting. In addition, there is no misalignment, deformation, or loss even after installation,
System reliability is improved.

FIG. 3 shows a structural example in which a curved plate is used as the support. The core material 1 and the support body 7 have holes through which screws are inserted, and the ring 21 is sandwiched between these holes to fix them with the screws 8. The material of the ring 21 needs to be a non-magnetic material and an insulator, and the same material as the core material can be used.
By sandwiching the ring 21 between the pickup coil 5
Vibration is prevented and installation accuracy is secured.

FIG. 4 shows an example of another fixing method. In this example, a hole is formed through the core material 1 and a recess 1b is provided in the hole. On the other hand, the support body 10 is provided with the claws 22, and the core material 1 is fixed to the support body 10 so that the claws 22 and the recesses 1b are aligned with each other. According to this method, since the pickup coil 5 can be fixed by simply fitting it without using a screw, the labor of mounting can be reduced.

The pickup coil 5 and external wiring can be connected by, for example, soldering, bonding, pressure contact with a pressing means such as a screw or a spring. Also, SQU
The ID chip may be attached to the core material 1, and the pickup coil 5 and the SUQ ID chip may be directly connected by the above-described connecting method. FIG. 5 shows an example in which the pickup coil and the SQUID chip 14 are connected by bonding. According to this example, the pickup coil 5 and the input coil are connected to each other by using the bonding wire 13.
It is sufficient to connect between 1 and 12, and the wiring can be shortened, so the inductance in the wiring can be suppressed to a small value,
The magnetic flux interlinking the pickup coil 8 can be efficiently guided to the input coil. Moreover, since the number of parts can be reduced, the failure rate can be reduced and the system reliability can be improved.

6 and 7 show a modification of the present invention.
Shows a pickup coil for simultaneous measurement of three axes, and FIG. 7 shows a pickup coil for simultaneous measurement of two axes. In either case, the magnetic field gradient near the center of the core material can be measured. By replacing part or all of the pickup coil for uniaxial measurement used in the multi-channel magnetometer with the biaxial and triaxial pickup coils shown in this embodiment, measurement having more information than before can be performed. You can get the data. In the device that estimates the position of the magnetic field source from the measurement data,
Alternatively, it is effective to use most of the pickup coils as one axis and partially as two axes rather than the three-axis pickup coil.

[0016]

As described above, according to the present invention, it is possible to form a pickup coil having a rigid structure with high accuracy, which leads to improvement in reliability and accuracy of the SQUID magnetometer. Further, since the mounting accuracy of the pickup coil is improved by providing the core member with the mounting mechanism to the supporting body, the accuracy of position information of the magnetometer is improved.
In addition, since the replacement can be easily performed, the maintainability is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an SQUID magnetometer according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state in which a core material is fixed to a support portion.

FIG. 3 is an explanatory view showing another example of fixing the core material to the support portion.

FIG. 4 is an explanatory view showing still another example of fixing the core material to the support portion.

FIG. 5 is an explanatory diagram showing a connection between a pickup coil and an input coil.

FIG. 6 is a configuration diagram of a pickup coil for simultaneous measurement of three axes.

FIG. 7 is a configuration diagram of a pickup coil for two-axis simultaneous measurement.

FIG. 8 is a configuration diagram of a general pickup coil.

[Explanation of symbols]

1 core material 2 2nd loop surface 3 1st loop surface 5 coil pattern 6,7,10 support 8
Screws 11, 12 Connection part 13 Bonding wire 14 SQUID chip 21 Ring 22 Claw

Claims (3)

[Claims] 1. A SQUID magnetometer having a pickup coil for measuring a magnetic flux generated in a subject and measuring a magnetic field distribution based on the magnetic flux measured by the pickup coil, wherein the pickup coil is three-dimensional. SQU characterized by being formed on the surface of various core materials by a pattern forming method
ID magnetometer. 2. The S according to claim 1, wherein a plurality of the pickup coils are formed on one core material.
QUID magnetometer. 3. The SQ according to claim 1 or 2, wherein the core material is made of a paramagnetic insulating material.
UID magnetometer.