JPH03131782A - Superconduction magnetometer - Google Patents

Abstract

PURPOSE:To adhere and fix SQUID sensors orthogonally with high accuracy by adhering SQUIDs of respective axes of X, Y, and Z to surfaces of a sensor block which contain 90 deg. highly accurately by using an adhesive to which microbeads are added. CONSTITUTION:The three mutually orthogonal planes of the sensor block 1 to which the X-axis SQUID 2, Y-axis SQUID 3, and Z-axis SQUID 4 are adhered are obtained by cutting, for example, a silicon wafer by dice cutting, etc., and adhered and fixed to the three orthogonal planes of a sensor block 1 made of ceramic, fused quartz, etc. In this case, microbeads for uniformizing the thickness of an adhesion layer between the X-axis SQUID 2 and sensor block 1 are added to the adhesion layer and the height in the adhering direction is controlled with the microbeads to uniformize the thickness of the adhesion layer, thereby joining the surface of the SQUID 2 and the surface of the sensor block with highly accurate collimation.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to superconducting quantum interference devices (Supercondu...
c-ting Quantum engineering interferenc
e Device, hereinafter referred to as 5QUID)
This paper relates to a method for manufacturing a highly sensitive superconducting magnetometer, especially for use in magnetic exploration.

[Conventional technology]

FIGS. 2 to 5 are diagrams showing conventional devices.

FIG. 2 is a diagram showing the senna portion of the superconducting magnetic detection device. For example, on three mutually perpendicular surfaces of a sensor block (1) made of fused quartz glass.

X-axis 8Qσ engineering H21, 7-axis day Q U m D (
3).

2-axis SQ, (4) is arranged from σ. The sensor block (1) is supported by a long boat support pipe (5) made of non-magnetic and non-conductive material and is placed near the bottom inside the liquid helium container (6). The support tube 15+ is hollow, and a sensor is driven inside it.

Also included is a coaxial cable (7) for taking out the output.

The support pipe is connected to a liquid helium container (
6) open to the outside atmosphere; t21. from the X-axis sqσ attached to the sensor block i1).
(3) from the y-axis sqσ and (4) from the z-axis &QU perform multiple operations by being cooled in the liquid helium.

First, the operation from the SQU will be explained using the X-axis 8QσrD (21) as an example.

FIG. 3 shows an example of a drive circuit for driving the X-axis QU and the X-axis SQ [7] used in the superconducting magnetic detection device. In Figure 3, (2) is the X-axis 5QUID
(This is an example of a plan view of 21. To operate (2) from the SQU, first, cool it by immersing it in liquid helium to transform it into a superconducting state, and place it in the magnetic field to be measured. At this time, Quantization conditions for 7-laxoid in superconducting ring α [and Josephson element Ql of superconducting ring α value)
, 5sc due to the DC Josephson effect in Qa
Maximum value of superconducting current that can flow between terminals A and B of tσID+21 without creating a potential difference. is a function of the detected magnetic flux φ passing through the superconducting ring α. If we consider the inductance L8-0 of the superconducting ring α1, then φ and engineering.

The relationship with (!) is as follows. is φ for φ
It changes with a period of 0.

φ IB=2Iccasπ stone...4...(
In Rikoζ, IC is the critical current value of each of the Josephnon elements Qυ and α2. Also, φ0 is a magnetic flux quantum.

Its value is 2.07×10 ωb. Actually L8
Since ≠0, The function of and φ deviates from equation (1) and is Although the minimum value of is not zero, in this case also the
changes with a period of φ0. In response to the change in the above-mentioned m, SQ, UID (2+ current-voltage (r-v)
Characteristics too. The detected magnetic flux φ changes with a period of magnetic flux quantum φ0. FIG. 4(a) shows the knee V characteristic of (2) from sQa, υ, φ−nφ0. φ−(n+1/
2) When φ0, the curve C1 curves, and changes continuously between these curves depending on the value of φ. however,
n is an integer.

In the figure, construction m1. Each m2 is φ−nφ. , φ−(n+
172) Maximum value of superconducting current at φ0. Furthermore, when a DC bias current that is slightly larger than the current value m1 is applied and the potential difference V between terminals A and B is measured with respect to φ, the magnetic flux quantum φ is determined as shown in FIG. 4 (1)). The input/output characteristics with period is obtained.

The above is the principle of magnetic force detection based on SQU (2), and the driving method of the 9th order superconducting magnetometer will be explained.

In FIG. 3, Ω is an example of a drive circuit from the above BQσ. The above drive circuit is generally FLL (Flux −
This is a well-known circuit called a Locked-Loop circuit, and is composed of the following components. Namely.

DC current source 0. Phase shifter α4. Preamplifier Q9. multiplier a
n, an integrator consisting of an integrator switch αn and an integrating amplifier aυ +113. They are an oscillator (A), a modulation feedback coil QD, and a modulation feedback resistor @. The above drive circuit is 5QU as shown below.
Drive ID. That is, first, a bias current of, for example, Ib-1, 11°1 is applied from the DC current source 0. At this time, it is assumed that the integrator switch αη is closed. Next, a modulation signal H is applied from the oscillator (1) via the modulation feedback coil CID. - As an example, this modulation signal H has an amplitude of @1/
2φ[, (1)-1)) and a sine wave with a frequency of f-100 KHz. At this point, if the detected magnetic flux φ is φ-nφ0 or φ-(n+1/2)φ0, the operating point from sQa is point E or point F in FIG. 4(b).

At the minimum or maximum position, the frequency component of the output voltage generated between terminals A and B of 8QUIDf2> is zero. When the detected magnetic flux φ changes and the operating point shifts, a component of frequency f appears, φ-(n+1/4)φ.

It reaches its maximum at point G or point H, which corresponds to .

However, the phase of the component of one frequency f becomes opposite between the G point and the H point. After amplifying the output voltage of the 5 QUID (2) with a preamplifier (c), the frequency f is increased in the 9 multiplier αQ.
The reference signal S and the multiplication signal are combined for phase detection. Next, when the integrator switch (Iη is opened, the output of the multiplier (IQ) is output from the integrator α
After being integrated by 9, there is a feedback resistance.

5QU as the residual current f flowing through the modulation feedback coil GD
Negative feedback is provided to ID (2), and the operating point is φ-nφ. , or φ−(n+1/2)φ. The magnetic flux is locked to the position of . After the magnetic flux is locked, the detected magnetic flux at the time when the integrator switch αη is opened, that is, the initial magnetic flux, is set as the origin of zero output, and a voltage vout proportional to the relative change amount Δφ of the detected magnetic flux from there is outputted. The relationship between △φ and VOut is f Δφ−Mf− 工f −′ Yout ・・・Song・
・It is f2J5. However, 1M is the mutual inductance between the modulation feedback coil Qυ and the superconducting ring α value, and Rf is the value of the feedback resistance α. Further, an output voltage Δvx proportional to the amount of change Δφ in the magnetic flux interlinking with the superconducting loop is output to the drive circuit @. Assuming that the area of the superconducting loop is 8, the amount of change ΔBx in the external magnetic field X component corresponding to ΔvX is.

ΔBX-Δφ machining/8K ・・・・・・・・・
・+3). external magnetic field y component,
The amount of change in the two components, ΔBz, is found in the same way.

The amount of change in the three-axis direct variable components of the magnetic field is independently detected.

Furthermore, the amount of change ΔB in the external magnetic field strength is calculated as ΔB=((△Bxzo+(△By)2+(ΔBz)2)'
Calculate using -.-f41.

In addition, in the above embodiment, an SQU is arranged on each of the 3+ planes that are perpendicular to each other, but the SQU
The twists may be arranged on 3+ planes that are not parallel to each other. At this time, three sQ[7 to t-8Qff to 1
, EIQ, from U2. Set as 3 from SQU, 8QUI
D1. 2 from E3QU. It is assumed that 3 from BqU is sensitive to the magnetic field in the direction perpendicular to 2. The changes in the magnetic field obtained from these outputs are calculated as ΔB1.
Let ΔB2 and ΔB3 be the angles between the y-axis, I from EIQU, SQ from σ, 2 from σ, and 3 from BqU, respectively.

When θ2 is assumed, the amount of change in the external magnetic field X component, y component, and two components ΔBX +ΔBy, ΔBX are.

ΔB1=ΔB! -Residence θe・・・・・・・・・
・(5)ΔB2−ΔBy−Residenceθy・・・・
・・・・・・+6)ΔB5−ΔB2・■θ2
. . . (7) The amount of change in the three-axis direct variable components of the nine magnetic fields is independently detected.

FIG. 5 is a diagram showing the angle θ between such an external magnetic field X component and the base, and in FIG. 91, (2) is 1 from SQ and σ.

[Problem to be solved by the invention]

The conventional device as described above has the following problems. In other words, in order to independently detect the amount of change in the three-axis direct variable components of the magnetic field and calculate the amount of change ΔB in the external magnetic field strength using equation (4), the error that occurs in the three-axis composite calculation must be minimized. However, on the other hand, if the angle between the sensors deviates from 90° with respect to each SQσ, there is an inconvenience that the error in the value of the detected magnetic field after calculating the three-axis composite becomes large. Therefore, in order to obtain a predetermined required accuracy for the desired value of the detected magnetic field.

There is also a method of measuring the angles that the TID sensors make with each other with high precision and making calculation corrections when calculating the 3-axis composite, but the angles that the sensors make with each SQ and U are 90°. This error caused by deviation from
Each SQσ becomes larger as the deviation of the angle between the sensors from 90° increases. Another possible method is to provide an adjustment mechanism on the surface on which the sensors are placed or on the block itself from SQ [7], and to precisely adjust the orthogonal arrangement of the sensors from each SQU in advance. Considering the current situation where devices are used at high temperatures, it is extremely difficult to provide an adjustment mechanism in such a portion. In other words, when constructing a magnetometer such as the one according to the present invention, it is necessary to hold senna from 8Ql in a non-magnetic and non-conductive material. Since the sensor is normally used at liquid helium temperature, thermal expansion is small in order to minimize the thermal stress applied to the sensor during cooling from room temperature to liquid helium temperature.

For example, it was necessary to use materials such as quartz glass or ceramics. However, it is impossible to process such materials, and each
It has been virtually impossible to provide an adjustment mechanism for accurately adjusting the orthogonal arrangement accuracy of the sensors due to Qσ. For the reasons mentioned above, there is a problem in that the sensor itself must be adhesively disposed on each orthogonal surface of the block with extremely high precision.

[Means to solve the problem]

This invention was made to solve this problem, and the sensor is fixed with high precision orthogonally from 8Qσ,
The adhesive must be non-magnetic and non-conductive, and must withstand thermal cycling from 4K to room temperature.

For example, an epoxy adhesive may be used as long as it satisfies these conditions. At this time, micro beads are added to the adhesive to prevent unevenness in the thickness of the adhesive layer, thereby adhesively fixing IQ and σ to the senna block.

Furthermore, in order to solve the problem that when micro beads are added, it is necessary to press the sensor more often than 8QU, which adheres with the force of kasb, the present invention uses an adhesive with a viscosity of 1000 cps or less. Micro-beads are added, thereby allowing the 9sQUID sensor to be adhesively fixed to the sensor block from the SQU orthogonally with high precision.

[Effect]

In the superconducting magnetometer according to the present invention, micro beads are added to the adhesive, and the 9sQtr is adhesively fixed to the sensor block, thereby the sensor is adhesively fixed orthogonally to the SQU with high precision. This is an attempt to solve the problem of not being able to do so. Furthermore, a superconducting magnetometer according to the present invention is provided.

Micro-beads are added to a non-magnetic, non-conductive adhesive with a viscosity of 1000 cpa or less.
By adhesively fixing the QU to the sensor block, the sensor is intended to be adhesively fixed perpendicularly to the SQU with high precision, and by using these micro beads, υ
The thickness of the adhesive layer can be made uniform. In other words, when the adhesive with micro beads attached is sandwiched and pressed against the sensor block from the SQU, the micro beads line up horizontally on the adhesive surface, making the height, that is, the thickness of the adhesive layer uniform. It has this effect. On the other hand, by using an adhesive with a viscosity of 1000 cpθ or less, if the conventional force is not applied, the advantage of adding micro beads to the adhesive can be used to make the sensor more accurate and orthogonal than +3Q [T]. This is an attempt to solve the problem that adhesive fixation is not possible. In the first place, when micro beads are used, this is not utilized and SQ [
The reason for the insufficient orthogonality accuracy between the JID sensor and the sensor block is thought to be the insufficient pressing force during adhesion, but this is due to the fact that all the micro- It should take more force to press the beads to line up horizontally between the bonding surfaces of the senna and senna block than the 5Qff, but in actual bonding work, the size of the sensor is smaller than the 5QtT to be bonded and fixed. is small, and the surface on which the superconducting ring is formed has only a small surface on which pressure can be applied for the purpose of adhesion, so it is not possible to apply enough pressing force to obtain the desired orthogonal accuracy. This is due to this. Therefore, in the present invention, an adhesive with a viscosity of 1000 cps or less is used as the adhesive to which micro-beads are added, so that all the micro-beads added to the adhesive are SQ
Pressing from U to align horizontally between each adhesive surface of the sensor block reduces the force, resulting in
It can be adhesively fixed with good parallelism on each orthogonal surface of the sensor block, and the sensors can be arranged orthogonally with high precision from each 8QU.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention, and is shown in FIG.

+1) is the sensor block, (2) is from the X-axis SQ[7, (3) is from y@BQσ, (4) is the 2-axis SQU
It's better.

From X-axis sclσ (21, from 7-axis 8Qσ (31r
From z @ S Qσ, (4) is fixed on three mutually orthogonal planes of a sensor block (1) made of 9 ceramic fused silica or the like. 3C@SQUX
D(2), from 7-axis Bqσ (31, z-axis 8Q[7I
The three mutually orthogonal planes of the Senna block (1) to which D (41 is attached) are !@5QuID+21.7 The angles formed by (3) from the axis 8Qσ and (4) from the z-axis SQU are arranged at right angles with high precision. For ease of use, the 3,000 planes of the Senna block (1) that are orthogonal to each other are machined with high precision so that they are at right angles.
Axis 8QUID (3), Z-axis SQ, U (4) are 1, for example, sensor blocks (1) cut out from a silicon wafer by dicing, etc., and made of reed, ceramic, fused silica, etc. ) are adhesively fixed on three mutually orthogonal planes.

In the superconducting magnetic detection device configured as above,
Sensor block fil, +21° from x-axis 8QU, y-axis 8Q, from tJ (3), z-axis 5QUIDf41
is cooled to transition to a superconducting state, and the amount of change ΔB in external magnetic field strength is calculated using equation (4). In the embodiment of the present invention, micro beads are added to the adhesive layer between I By regulating the height of the direction by the microzease, the thickness of the adhesive layer becomes uniform, and from 5Qtr (2)
The surface of the sensor block can be joined with high parallelism to the surface of the sensor block. For example, an epoxy adhesive may be used as the adhesive. Further in the embodiments of the present invention.

From z-axis 8 QU (2) and Senna block +1+ are bonded using an adhesive with a viscosity of 1000Cp9 or less and micro beads to make the thickness of the adhesive layer uniform, and from tsci, tr (2) ) by pressing the surface of the sensor block against the viscosity of the adhesive, all the microbeads added to the adhesive
Since the bonding surfaces of D(2+ and sensor block) are lined up horizontally, the height in the bonding direction is not restricted by the micro beads, and the thickness of the bonding layer is uniform. , θQ[7, the surface of (2) and the surface of the sensor block can be joined with high parallelism.

〔Effect of the invention〕

As explained above, according to the present invention, for the surface of the sensor block (1) in which the orthogonal surface has a right angle with high precision,
X-axis 5QU using adhesive added with micro beads
ID (2), from 7-axis BQU (31, from g-axis 8QU (
4)), and each surface of the senna block (1) in the e 79 m direction and *x@sQσworkingn
(21+ From y-axis 8Qσ (3), from z-axis 8QU (
4) with each plane including each superconducting ring, and as a result, (21
, from y-axis 8QU (3) s ts 41] 8 Q
[r] The mutual orthogonality accuracy between (4) is maintained higher than r, and the change ΔB in the external magnetic field strength can be calculated with high accuracy using equation (4).

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIGS. 2 to 5 are diagrams showing the operating principle and configuration of a conventional device. In the figure, (l) is the Senna block, (2) is from the X-axis SQU, (3) is from the y-axis SQσ, (41 is g$1
From 1sQU, +61 is a liquid helium container, 01 is a superconducting ring, (Iυα is a Josephson element, αn is an integrator switch, αJ is a DC current source, c!0 is an oscillator,
21 is a modulation feedback coil or an integrating amplifier, a[9 is a multiplier, aI is an integrator, @ is a modulation feedback resistor, (to) is a drive circuit, and (goods) is an adhesive. In addition, in FIG. 9, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] a superconducting quantum interference device; a sensor block for fixing the superconducting quantum interference device on three orthogonal planes or on a determined plane that is not parallel to each other and forming a certain angle; and the superconducting quantum interference device and the sensor. It has a liquid helium container for immersing the block in liquid helium, a support tube for supporting the sensor block in the liquid helium container, and the output of the superconducting quantum interference element fixed on the three planes is controlled on three axes. A superconducting magnetometer that performs vector synthesis and detects the strength of a magnetic field to be measured, characterized in that micro beads are added to an adhesive, thereby adhesively fixing the sensor block and the superconducting magnetometer. Conduction magnetometer.