JPH01411A - superconducting pressure sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides the ability to operate in cryogenic environments without temperature compensation or calibration by combining a superconductor with a normal conductor coil or spring that does not exhibit superconducting properties. The present invention relates to a highly sensitive and highly accurate superconducting pressure sensor that can be used for.

[Prior Art] A typical example of a pressure displacement detector (hereinafter referred to as a sensor) that operates in a normal temperature environment is a stosine gauge. There are piezoelectric sensors, electrostatic and electromagnetic transducers, etc. A strain gauge is a high/low antibody with a high gauge factor made of a so-called advanced alloy made of copper and nickel, and by forming a bridge, it is possible to detect displacement from the change in resistance. In addition, piezoelectric sensors utilize polarized charges generated by pressure displacement, and as is well known, electrostatic and electromagnetic transducers detect pressure displacement from changes in electric flux density and magnetic flux density, respectively. It is something to do.

(Problems to be solved by the invention) These conventional pressure sensors operate at room temperature;
Therefore, when this sensor is used in an extremely low temperature environment, the material properties and electrical properties of the sensor material change, causing the sensor function number to disappear. For this reason, there is a drawback that conventional sensor technology cannot be extended to the extremely low temperature region.

The present invention was made in view of the above points, and an object thereof is to provide a superconducting pressure sensor that can detect pressure displacement with high sensitivity and high accuracy in a cryogenic environment without temperature compensation or calibration. It is something to do.

[Means for solving problems]

The superconducting pressure sensor of the present invention applies a current below the critical current or a magnetic field below the critical magnetic field to a medium having a critical current and critical magnetic field inherent to the superconductor, and then A magnetic field facing in an arbitrary direction is applied as an external magnetic field from a normal conductor spring or coil that does not exhibit superconducting characteristics, and this applied magnetic field is changed by displacement of the normal conductor coil, and this magnetic field change causes superconductivity. The main feature is that pressure displacement is detected using the characteristic that the critical current of the body changes, and it is characterized by satisfying the following equation (1).

Ic=f (Hc, H8(δ))
(1) (In the above equation (1), Ic is the critical current of the superconductor + HC is the critical magnetic field of the superconductor, H, (δ) is a normal state that does not exhibit superconducting characteristics including pressure displacement δ as a parameter. (The magnetic field of the conduction coil is shown.) Therefore, the detection of pressure displacement in the cryogenic region, where conventional sensors could not function, can be easily achieved in the cryogenic region by satisfying the condition of equation (1) above. This is a major difference from the conventional technology.

[Example 1] FIG. 1 is a diagram illustrating a first example of the present invention,
1 is a rod-shaped superconductor, 2 is a normal conductor coil, and 3 is a critical current detector. This embodiment is a superconductor pressure sensor in which a magnetic field is applied perpendicularly to the axis of the superconductor by a normal conductor coil.

Next, the operating principle of this pressure sensor will be explained.

FIG. 2 shows some of the components of the present invention. A coil made of a normal conductor (such as copper) that does not exhibit superconducting properties, where d is the diameter of the coil material, α is the pitch angle of the coil, n is the number of turns of the coil, P is the pressure, and R is the radius of the coil. . When a current I8 is passed through this coil, a magnetic field H0 is generated by the normal conductor coil as shown in FIG. Now, in FIG. 3, when the coil (or spring) is pulled with a pressure P, a displacement δ occurs. Since δ occurs almost uniformly throughout the coil, this δ causes the magnetic field H
8 changes. In other words, H8 is a function of δ, and H, = H
, (δ).

In the case of FIG. 3, δ due to P is generally expressed by the following equation.

δ=Kseccr(cos”cr+4155in2α)
(2) K is a mechanical property term including shear modulus G, etc., G = 64 P R3n / (Gd')
(3). Further, H is the magnetic field at the center of FIG. 3. Therefore, H, (δ) can be obtained by eliminating δ from equations (2) and (4), and approximately (α<1) can be obtained by the following equation (5):
becomes.

Next, as shown in Figure 1, a critical current ■ is applied to the superconductor 1. Let the following current ■ flow through. If superconductor 1 is a round bar with radius a, and the magnetic field due to superconductor l is Hl, then 15 = 2 x a Hs
(6) In addition, the normal conductor coil 2 receives a magnetic field H due to the current IN.
, (δ).

Combined magnetic field H when H, (δ) and II act at right angles
8 is H,”=H,(δ)”+II,”
(7). Therefore, the change in the critical current ゎ of the superconductor 1 due to the displacement δ is expressed by formulas (5) and (6), (
11 of the equation obtained by substituting into 7). to HC, and I, to■
. It can be found by , =f (Hc, H, (δ) )
(8) As is clear from equation (8), ■ due to the displacement δ. If the change in is detected by the detector 3, pressure can be detected in an extremely low temperature environment.

[Embodiment 2] FIG. 4 is a diagram illustrating a second embodiment of the present invention, in which magnetic fields H, (δ) and H act in parallel to the axis of the superconductor 1. The composite magnetic field IIL in this case is expressed as follows.

Re=H0(δ)+H, (9) Therefore, the IC at this time is as shown in the following equation.

2〇〇) is determined by IIC and 11° (δ) as in equation (8).

〔Effect of the invention〕

As explained above, the superconducting pressure sensor that combines the superconductor of the present invention and a normal conductor coil that does not exhibit superconducting properties has a critical magnetic field characteristic (Meissner As the technology applies the following: (effect) and can be used in cryogenic conditions, it is possible to detect pressure displacement with high sensitivity and accuracy without temperature compensation in cryogenic regions outside the application range of conventional sensors. This is a big advantage.

[Brief explanation of drawings]

FIG. 1 shows the first embodiment of the present invention. FIG. 2 shows the configuration of a normal conductor coil. FIG. 3 shows the magnetic field generated in the coil when a current is passed through the normal conductor coil. Example 2 is shown below. 1... Rod-shaped superconductor 2... Normal conductor coil 3... Critical current detector

Claims (1)

[Claims] A rod-shaped superconductor and a normal conductor coil through which a current I_N flows,
A superconducting pressure sensor characterized by having a means for detecting a change in the magnetic field due to displacement of a normal conductor coil as a change in a critical current I_C, which is arranged at a position where both magnetic fields interact.