JPS5992336A - Realizing device for fixed point of temperature - Google Patents

Abstract

PURPOSE:To measure quantitatively the magnetic field in the space where a sample is present when the sample becomes superconduction by utilizing the sample at a fixed point of temperature itself as a magnetic field sensor. CONSTITUTION:The device consists of fixed-point samples 1, 2, and 3, a superconductor 4 wound around the samples to constitute a superconductive loop having higher transition temperature than the fixed-point samples, a switch 5, and a coil 6 coupled with a superconductive quantum interference element. Magnets 7 and 8 are arranged outside of the device. The switch 5 is turned on when the fixed-point samples 1, 2, and 3 are in normal conduction states to cool the samples. When the sample 1 becomes superconduction firstly at the transition temperature, the magnetic flux in the space where the sample 1 is present is dischrged, but the magnetic flux in the superconduction loop is unchanged, so the discharged magnetic flux is transferred to the coil 6 and detected by a fluxmeter coupled with the coil. The temperature at which its variation is detected is the transition temperature of the sample 1 and the extent of the variation is proportional to the magnetic flux where the sample 1 is present.

Description

DETAILED DESCRIPTION OF THE INVENTION Recently, it has become common to realize a fixed temperature point below IK by superconducting transition of a superconductor. However, the reproducibility is still only about 1 mK, which is still insufficient.

The cause of the distortion in reproducibility is presumed to be due to the residual magnetic field, but since it is impossible to have a highly sensitive magnetic field sensor and temperature fixed point element function simultaneously in close proximity, there is no prospect of improvement. do not have.

The present invention uses the sample itself at a temperature fixed point as a magnetic field sensor, so that the magnetic field in the space where the sample exists just when the sample reaches the superconductor temperature τ using the temperature fixed point realizing device of the present invention. High - (The configuration used to realize a temperature fixed point is a temperature fixed point material that becomes superconducting at a certain temperature, and a superconducting wire that has a higher transition temperature than the fixed point material wrapped around it.

and a switch that constitutes a superconducting loop, and a coil that also constitutes a superconducting loop and is coupled to a magnetometer typified by a 5QLJID (superconducting quantum interference device). In particular, if a fixed temperature point in a zero magnetic field is required, a magnetic field is applied and an actual device is added.

The principle of the present invention is when a fixed point substance becomes superconducting.

The magnetic field is emitted from the substance (Meissner effect)
It depends on If the temperature fixed point realizing device of the present invention is used,
The magnetic flux emitted from a fixed point material at the transition temperature can be determined by the action of a superconducting loop using a magnetometer connected to a coil that forms part of the loop. Through this measurement, it is possible to simultaneously know the transition temperature of the fixed point material and the magnitude of the residual magnetic field in the space where the fixed point material existed during the transition, making it possible to accurately compensate for the effects of the residual magnetic field. .

Furthermore, it is also possible to cancel the residual magnetic field by applying a magnetic field so that the magnetic field becomes 0, thereby realizing superconducting transition in a situation where the residual magnetic field is extremely small.

The embodiment of the present invention uses a fixed point sample of 1°2.3 as shown in FIG.
and constitute a superconducting loop with a higher transition temperature than the fixed point sample. Superconducting wire 4° switch 5, 5Q wrapped around the sample
It consists of a coil 6 coupled to the UID.

A magnet 7°8 is placed outside of it.

First, when the fixed point samples 1, 2.3 are in the normal conduction state, switch 5
to cool the sample. When 1 first becomes superconducting at the transition temperature, the magnetic flux in the space where ■ existed is discharged, but the magnetic flux in the superconducting loop does not change, so the discharged magnetic flux is transferred to the coil 6.

It is detected as shown in FIG. 2 by a magnetometer coupled to the coil. The temperature at which the change is detected is the transition temperature of the sample 1, and the magnitude of the change is proportional to the magnetic field at the location where the sample 1 is present. Since the magnitude of the magnetic field in the sample 1 can be directly known in this way, it is possible to accurately correct the fixed point temperature.

On the other hand, by following the steps below, it is also possible to observe transitions in a zero magnetic field in a situation where the magnetic field is canceled out. To do this, after performing the above measurements and measuring the magnetic field, the temperature is raised to return the sample 1 to normal conduction, and after a magnetic field sufficient to cancel the magnetic field is applied by the magnet 8, the switch 5 is turned off. This is 1
The magnetic field at the location becomes extremely close to O. After turning on the switch 5, it is cooled down, but in the zero magnetic field, the second
Since the signal shown in the figure cannot be obtained, another magnet 9 is used to apply a very weak alternating magnetic field to find the transition temperature. The alternating magnetic field is detected by a magnetometer through the action of a superconducting loop, and an alternating current signal is obtained, and the amplitude of this signal changes due to the superconducting transition, as shown in Figure 3. This allows us to know the transition temperature. In this case, if the residual magnetic field is caused by some reason, a DC component as shown in FIG. 2 will be superimposed on the change in the transition temperature of the output, and an output as shown in FIG. 4 will be obtained. Therefore, the existence of a residual magnetic field can be immediately known, and the transition point at zero magnetic field can always be determined.

In this way, the present invention not only makes it possible to accurately correct the influence of the residual magnetic field on the transition temperature of a fixed-point sample, but also makes it possible to transition the fixed-point sample to superconductivity in a space with an extremely small residual magnetic field, and in this case, the residual magnetic field is always It is easy to keep checking the size of As described above, the present invention can greatly improve the reproducibility of the current temperature fixed point.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment, and FIGS. 2, 3, and 4 are diagrams showing characteristics. 1.2.3 Sample 4 transitioning to superconductivity
Superconducting wire 5 Switch 6 5 Coil connected to QUID 7.8
Magnet 9.10 Power supply designated agent

Claims (1)

[Claims] 1. A device for realizing a fixed temperature point, characterized in that a superconducting wire is arranged around a substance that becomes superconducting at a certain temperature, and a device for making the superconducting wire part of a superconducting loop is added.