JPS5990069A - Magnetic field measuring method - Google Patents

Abstract

PURPOSE:To measure a magnetic field with extremely high sensitivity by utilizing the discharge of magnetic flux proportional to the magnetic field in the space wherein a material is present preceding the material becomes superconductive in the magnetic field. CONSTITUTION:A superconductor 5 is coiled around a sample 4 and a coil 7 coupling with SQUID through a switch 6 and the superconductor 5 constitute a superconduction loop. The switch 6 is closed when the sample is normally conductive to cool the sample 4. Magnetic flux penetrating the superconduction loop is held constant, so a current flows through the loop as the magnetic flux is discharged; the current is detected with high sensitivity by the coil 7 coupling with the SQUID and its output varies as shown by a graph. The magnetic field is known from the variation. Further, plural samples 8, 9, and 10 are arranged in parallel to three axes X, Y, and Z and coils wound around them are connected in series; and both their terminals are connected to a fluxmeter or voltmeter 11 and the samples are made superconductive successively to measure magnetic fields on the three axes with high sensitivity.

Description

[Detailed Description of the Invention] Currently, when measuring a DC magnetic field, except when using a Hall element tube that utilizes physical properties, a change in magnetic flux is created by changing the relative position of the detection coil and the magnetic field. This has been done by measuring the deformation debris. but,
Its sensitivity was not sufficient, and the device tended to be large due to the presence of mechanically moving parts.

On the other hand, current changes in magnetic flux can be measured using superconducting quanta from SQU. Therefore, if a direct current magnetic field can be converted into changes in magnetic flux, magnetic fields can be measured with extremely high sensitivity.

What is required for the single measurement method is a substance that becomes superconducting Ii at a certain appropriate temperature, and a measurement system that measures the magnetic flux emitted from the substance when it becomes superconducting.

The principle of the present invention is that when a substance becomes superconducting, the magnetic field is ejected from the substance, which is due to the Smyessner effect. Since a proportional magnetic flux is discharged, the magnitude of the original magnetic field can be determined from the magnitude of the magnetic flux.

The embodiments of the present invention differ greatly depending on whether or not an SQU is used to measure magnetic flux changes.

FIG. 1 shows an example in which a conductive wire 2 is not used, and a conductive wire 2 is wound in a coil around a sample 1, and both ends thereof are connected to a voltage source 13. By cooling the sample 1, the sample 1 transitions to a superconducting state, and magnetic flux is discharged from the superconductor. As it is discharged, an electromotive force is generated in the coil 2, and a voltage appears at both ends thereof. When the output is shown as a function of time, it changes as shown in Figure 2. By integrating the voltage over time, the magnetic flux, and thus the magnetic field, can be measured.

On the other hand, if 5QUID, which is currently available for high-resolution magnetic flux, is used, it becomes possible to measure magnetic fields with higher sensitivity. In that case, as shown in Fig. 7, superconducting wire 5 is wound around sample 4 in the shape of a coil (b), and this 5 and coil 7 are connected to SQU through +1? and Inochiro to form 5 superconducting loops. When sample 4 is normally conducting, switch 6 is connected to cool sample 4. The magnetic flux passing through the superconducting/loop remains constant, so as the magnetic flux is discharged, current flows through the loop. The current is detected with high sensitivity by the coil 7 connected to the SQU, and its output changes as shown in Fig. 4. The magnetic field can be determined by the amount of change.

In addition, multiple samples 8.9.10 to X, Y as shown in Figure 5
, 2, are placed parallel to the three axes, and the three films wound around them are connected in series, and both ends are read directly by a magnetic flux meter or a voltmeter (11-) to make the sample superconducting one after another. ,
3-axis magnetic field, 1 field number can be measured.

°: In this way, according to the present invention, it is possible to make changes in the magnetic flux of the SQU. Furthermore, since the detection element is made of only superconductors and is li-, it can be made small, and it is also possible to know the magnitude of the local magnetic field. Furthermore, since it has no mechanically movable parts, it is expected to have a very wide range of application, and at the same time, it is easy to detect the three components of the magnetic field as described above.

[Brief explanation of drawings]

1, 3 and 5 are configuration diagrams of the embodiment, and FIGS. 2 and 4 are diagrams showing its characteristics. 1.4.8, 9, 10 ・Sample 2 that transitions to superconductivity, e** door wire 3, ... 5 for voltage, ... superconducting wire 6, ... switch 7, +1.・Coil 11 connected to SQU,...
Coil connected to voltage plate or SQU 31 Figure 2 Freezing 3 times 4 Figure 1 gate

Claims (1)

[Claims] 1. A magnetic field measurement method that detects the magnetic field in the space where a substance existed before it became a superconductor by measuring the magnetic flux emitted by a substance when it transitions to a superconductor state.