JPH0621031Y2 - Superconducting magnetometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a superconducting magnetometer (skid magnetometer), and more particularly to a superconducting magnetometer characterized by a connection mechanism between a skid element and a pickup coil.

(B) Conventional Technology In general, a superconducting magnetometer detects micro magnetism with a detection unit which is housed in a cryogenic container and includes a skid element and a pickup coil. As shown in FIG. 4, the skid element of this type of superconducting magnetometer has an input coil 2, J
It is composed of a J element 3 and a tank circuit 4. The input coil 2 of the skid element 1 is connected to the pickup coil 7 by a connecting wire 6 composed of two thin wires. Conventionally, in the connecting wire 6, two thin wires 6a and 6b are twisted together as shown in FIG. 5 in order to reduce the inductance. Further, the connecting wire 6 is covered with a superconducting shield pipe 8 in order to prevent invasion of external magnetism.

(C) Problems to be solved by the device In the above conventional superconducting magnetometer, two thin wires are twisted together to connect the skid element and the pickup coil. As a result, there is a problem that a signal from the pickup coil may not be transmitted to the input coil of the skid element due to insulation failure.

Also, if the pickup coil is placed as close as possible to the object to be detected and the pickup coil is to be installed outside the inner tank composed of the FRP in order to increase the sensitivity of the magnetometer, the inner tank will be removed from the space between the shield pipe and the connecting line. There was a problem that the cryogen (liquid helium) in the inside leaked and the degree of vacuum between the inner tank and the outer tank was deteriorated.

In consideration of the above, this device has a small inductance,
Moreover, it is an object of the present invention to provide a superconducting magnetometer having a connection mechanism between a skid element and a pickup coil in which contact between wires does not occur and, if necessary, cryogen does not leak.

(D) Means and Actions for Solving Problems The superconducting magnetometer of the present invention is a cryogenic container comprising an inner tank and an outer tank, in which a skid element and a pickup coil are housed. A cryogen is placed inside, a skid element is placed in the cryogen, and the pickup coil is placed at the bottom between the inner tank and the outer tank. A coaxial tubular material made of a conductive material and a connecting wire made of a low temperature molding material filled between the center line and the coaxial tubular material are penetrated into the bottom of the inner tank wall,
This connection line connects the skid element and the pickup coil.

In this connection mechanism, since the center line and the coaxial tubular member are both made of a superconductor, magnetic noise is prevented from entering from the outside, and the inductance can be reduced without twisting the connection lines. It is possible to avoid the occurrence of insulation failure of the connection line. Further, since the molding material is filled between the center line and the coaxial cylinder, the cryogen does not leak from the inner tank to the outer tank.

(E) Embodiment Hereinafter, the present invention will be described in detail with reference to an embodiment.

FIG. 2 is a sectional view of a cryogenic container of a superconducting magnetometer showing an embodiment of the present invention.

The cryogenic container 11 has a double structure of an outer tank 12 and an inner tank 13, and both the outer tank wall 14 and the inner tank wall 15 are made of FRP (glass fiber reinforced plastic). Inner tank 1
Liquid helium 16 is filled in the chamber 3, and a skid element 17 is housed therein. Further, the outer tank 12 is kept in a vacuum, and a pickup coil 18 is disposed in the tank 12 below the skid element 17 in order to increase detection sensitivity, that is, to bring the object to be detected as close as possible.

The internal circuit of the skid element 17 is similar to that shown in FIG. 4, and the input coil 18 of this skid element 17 is connected by a connecting wire 19 penetrating the inner tank wall 15.

The connecting line 19 has a center line 2 as shown in the enlarged view of FIG.
0, a coaxial cylindrical body 21 provided coaxially with being separated from the center line 20, and a low temperature molding material 22 such as stycast which is filled between the center line 20 and the coaxial cylindrical body 21. The center line 20 and the coaxial cylinder 21 are both made of a superconducting material such as niobium. In addition, the top 20 having the same diameter as the coaxial cylindrical body 21 is provided at both upper and lower ends of the center line 20.
a and 20a are provided. Two lines of the input coil are connected to the center line 20 and the coaxial cylindrical body 21 at the upper end of the connection line 19, and two lines of the pickup coil 18 are connected to the center line 2 at the lower end.
0 and the coaxial cylindrical body 21.

Now, when the magnetic flux Φx enters the pickup coil 18, the inductance of the pickup coil 18 Lp, Lin inductance of the input coil, the inductance Ld of the connection line 19, the shielding current i _s i which is inversely proportional to these inductance pickup coil 18 _s = Φx / (Lp + Ld + Lin) is induced. By flowing through the shielding current i _s is the input coil, the magnetic flux Φs is generated and transmitted to the skid elements 17.

In general, the external magnetic flux [Phi] x is desirably enters only the pickup coil 18, the external magnetic flux entering the connecting line section and the input coil unit, shielding current is _{'is, is' = i s + Δi} s = Φx / (Lp + Ld + Lin) + ΔΦx / (Lp + Ld + Lin) becomes, so that the error signal .DELTA.i _s is generated.

However, in the superconducting magnetometer of this embodiment, since the connecting line 19 is composed of the center line 20 and the coaxial cylindrical body 21 and the superconducting material is used, the intrusion of external magnetic noise can be prevented. Therefore no induced current is generated such as .DELTA.i _s, errors can be suppressed small. Further, since the low temperature molding material 22 is filled between the center line 20 and the coaxial cylindrical body 21, the fluid helium 16 in the inner tank 13 does not leak to the outer tank 12. In addition, the cryogenic temperature in the inner tank 13 is the same as the connection line 1
Since it is transmitted to the pickup coil 18 through 9,
The pickup coil 18 can be kept at a required low temperature.

(F) Effect of the Invention As described above, according to this invention, the connecting line composed of the center line made of the superconducting material and the coaxial cylinder is used to connect the skid element and the pickup coil. Therefore, unlike the conventional method, twisting of thin wires is not performed, and there is no risk of short-circuiting between wires, and since the external magnetic nozzle is blocked by the superconducting material, the error can be reduced accordingly. Further, since the pickup coil is arranged outside the inner tank, it is possible to prevent liquid leakage by filling the low temperature molding material between the center line and the coaxial cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged view of a connecting line portion which is a main part of a superconducting magnetometer according to an embodiment of the present invention, and FIG. 2 is a cross section of a cryogenic container of the superconducting magnetometer. FIG. 3 is a diagram showing an internal circuit of the skid element, and FIG. 4 is a diagram for explaining a conventional example. 17: skid element, 18: pickup coil, 19: connection line, 20: center line, 21: coaxial cylindrical body, 22: low temperature molding material.

Claims (1)

[Scope of utility model registration request] 1. A superconducting magnetometer in which a skid element and a pickup coil are housed in a cryogenic container consisting of an inner tank and an outer tank. A cryogen is placed in the inner tank, and the skid element is placed in the cryogen. In addition, the pickup coil is arranged at the bottom between the inner tank and the outer tank, and a center line made of a superconducting material, a coaxial cylindrical member made of a superconducting material surrounding the center line, and a coaxial line with the center line. A superconducting magnetometer characterized in that a connecting wire made of a low-temperature mold material filled between tubular materials is penetrated into the bottom of the inner tank wall, and the skid element and the pickup coil are connected by this connecting wire.