JPH07263759A - Cryostat - Google Patents

Abstract

PURPOSE:To measure more accurately a weak calculating object at a lower bottom by positioning and fixing a SQUID magnetic sensor easily and ensuring rigidity of the bottom so that the SQUID magnetic sensor does not move or vibrate. CONSTITUTION:A positioning recessed part 2d for positioning the lower end part of a probe at the bottom of the inner container 2, is provided in a cryostat that comprises a bottomed inner container 2 of a cylindrical shape, that contains a SQUID magnetic sensor provided at the lower end of the probe and cooling medium 12, and a lid 4 which covers the open end of the inner container 2, an insertion hole for allowing the probe to be inserted into the inner container 2 and for positioning the upper end of the probe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention accommodates a SQUID (superconducting quantum interference device) magnetic sensor for isolating the inside from the outside environment and maintaining a very low temperature environment with a cooling medium to measure weak magnetism with high accuracy. The present invention relates to a cryostat, which is one of the storage containers.

[0002]

2. Description of the Related Art In recent years, SQUIDs, which have been studied to detect weak magnetism, utilize the quantum interference effect to reduce the magnetic quantum flux φ ₀ (1.5 × 10 ⁻¹⁵ Wb) to 1 / 100,000. The magnetic flux is converted into a voltage and measured. Therefore,
The SQUID is useful for measuring weak magnetism, and is applied to biomagnetic measurement, physical constant measurement, nondestructive inspection, and the like. The SQUID magnetic sensor composed of such a SQUID is housed in a cryostat whose interior is isolated from the external environment and maintained in an ultra-low temperature environment by a cooling medium, and is maintained in a superconducting state.

A conventional cryostat has a bottomed cylindrical outer container, a bottomed cylindrical inner container housed in the outer container, and a vacuum space formed by the inner container and the outer container. It is composed of a radiation shield housed and a lid that covers the open end of the inner container. Then, the lid has an insertion hole for inserting the probe having the SQUID magnetic sensor attached thereto, and an SQUID.
A supply / exhaust hole is provided for supplying a cooling medium for transferring the ID magnetic sensor to a superconducting state and maintaining the superconducting state into the inner container, and for discharging the cooling medium from the inner container. The inner surface of the bottom of the inner container is flat.

When the probe is inserted into the cryostat constructed as described above to position the SQUID magnetic sensor, the probe is inserted into the insertion hole from the lower end portion of the probe and the SQUID magnetic sensor is positioned.
The QUID magnetic sensor is dipped in a cooling medium and the upper end of the probe is supported by a lid. Then, the mounting base of the probe on which the SQUID magnetic sensor is arranged is kept away from the bottom of the inner container.

[0005]

Since the conventional cryostat is constructed so as to support the probe in a cantilever state, when an external force such as vibration acts, the probe mount, that is, the SQUID magnetic sensor resonates due to the vibration. Therefore, an error is added to the measured value. Then, when a plurality of probes are inserted into the cryostat to accommodate a plurality of SQUID magnetic sensors, even if external force such as vibration does not act, the interaction of the SQUID magnetic sensors causes 10 Hz.
Since it vibrates at the natural frequency of the order, it gives an error to the measured value. Furthermore, if the bottom is made thicker to secure the strength of the inner container, the SQUID magnetic sensor is far from the bottom of the inner container, so if there is a weak measurement target, such as a human body, below the bottom, the magnetic field fluctuations of the human body will occur. There were inconveniences such as difficulty in measurement.

The present invention has been made in order to eliminate the above-mentioned inconvenience, and the SQUID magnetic sensor can be easily positioned and fixed so as not to move or vibrate.
Provided is a cryostat capable of more accurately measuring a weak measurement target below the bottom with an SQUID magnetic sensor while ensuring the strength of the bottom.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a bottomed cylindrical container for accommodating a SQUID magnetic sensor and a cooling medium disposed at the lower end of a probe, and an open end of the container are covered so that the probe is inside the container. In a cryostat having at least a lid that can be inserted into the container and is provided with an insertion hole for positioning the upper end of the probe, a positioning recess for positioning the lower end of the probe is provided on the inner surface of the bottom of the container. It is desirable that the peripheral surface of the positioning recess be an inclined surface that expands inside the container.

[0008]

In the cryostat according to the present invention, the lower end of the probe is positioned by the positioning recess and the upper end of the probe is positioned by the lid by the positioning recess provided on the inner surface of the bottom of the container. Then, the lower end of the probe is guided and positioned by the inclined surface of the positioning recess.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a partially cutaway side view of a cryostat which is a first embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of a positioning recess, and FIG. 3 is a sectional view of an inner container taken along the line AA of FIG. FIG. 4 is a cross-sectional view showing the half of the bottom, and FIG. 4 is a plan view showing the half of the lid of FIG. In these figures, reference numeral 1 denotes an outer container made of glass epoxy (glass fiber kneaded with epoxy resin) and having a cylindrical shape with a bottom, and a flange 1f formed around the open end is formed.

Reference numeral 2 denotes an inner container which is made of glass epoxy and has a cylindrical shape with a bottom. The inner container is accommodated in the outer container 1 and has an orbiting flange 2f mounted on the flange 1f at its open end. A plurality of cylindrical positioning recesses 2d are formed on the inner surface of the bottom. Reference numeral 3 denotes an aluminum vapor deposition mylar as a radiation shield, which is housed in a vacuum state space formed by the outer container 1 and the inner container 2 so as to surround the inner container 2 in a laminated state.

Reference numeral 4 denotes a lid for covering the open end of the inner container 2, which corresponds to the positioning recess 2d, and has a plurality of insertion holes 4h for inserting a probe 11 which will be described later and a cooling medium 12 supplied into the inner container 2. In addition, a supply / discharge tube portion 4p for discharging the cooling medium 12 from the inside of the inner container 2 and discharging the gas of the evaporated cooling medium 12 is provided. The outer container 1
The inner container 2 and the inner container 2 are flange portions 1f and 2f, and are fastened with bolts having hexagonal holes (not shown), and the inner container 2 and the lid 4 are fastened with bolts 5 having hexagonal holes.

Reference numeral 11 denotes a probe, which is a positioning recess 2d.
The SQUID magnetic sensor is arranged on the mounting base 11a having the same diameter as that of the lower end and protected from damage, and the connector 11b at the upper end is fitted into the insertion hole 4h of the lid 4 on the lower side. The lower surface of the upper side is in contact with the upper surface of the lid 4, and the pipe 11c connects the mounting base 11a and the connector portion 1 to each other.
It is configured to connect with 1b. The signal line is arranged in the pipe 11c. Reference numeral 12 denotes a cooling medium such as liquid helium, which causes the SQUID magnetic sensor to transition to a superconducting state and maintain the superconducting state.

Next, the positioning of the SQUID magnetic sensor will be described. First, by inserting the mounting base 11 a of the probe 11 through the insertion hole 4 h of the lid 4, the mounting base 1 a
Since 1a is immersed in the cooling medium 12, the SQUID magnetic sensor is cooled and transitions from the normal conducting state to the superconducting state. Then, the mount 11a is further lowered to move the inner container 2
When it is inserted into the positioning recess 2d of
Since the lower side of b is fitted in the insertion hole 4h, the mounting base 11a is positioned by the positioning recess 2d, and the connector portion 11b is positioned by the lid 4. Therefore, the probe 11 is positioned in a double-supported state in which the top and bottom are fixed.

As described above, according to the first embodiment of the present invention, since the positioning recess 2d is provided in the inner container 2, the upper and lower sides of the probe 11 are fixed by the lid 4 and the positioning recess 2d. When an external force such as vibration acts on the mounting base 11a on which the sensor is arranged, the mounting base 11a vibrates together with other parts and does not vibrate at the natural frequency due to the interaction of the SQUID magnetic sensor. Therefore, there is an error in the measured value of the SQUID magnetic sensor. It will not occur.

The strength of the bottom of the inner container 2 can be ensured by reducing the thickness of the bottom portion of the inner container 2 having the positioning recess 2d and increasing the thickness of the other bottom portion. Therefore, since the SQUID magnetic sensor can be brought close to the weak measurement target below the bottom, for example, the human body, the weak magnetic field can be measured more accurately.

Embodiment 2 FIG. 5 is a partially enlarged perspective view showing a major part of a cryostat according to a second embodiment of the present invention in a broken manner.
The same or corresponding parts are designated by the same reference numerals and the description thereof will be omitted. In FIG. 5, the positioning recess 2 d provided on the bottom of the inner container 2 has an inclined surface that expands into the inside of the inner container 2 and has a truncated cone shape.

Also in the second embodiment shown in FIG. 5,
The same effect as the first embodiment can be obtained, and the positioning recess 2 is provided.
Since the peripheral surface of d is expanded upward (inside the inner container 2), the mount 11a of the probe 11 can be easily inserted, and the mount 11a, that is, the SQUID magnetic sensor can be easily positioned.

In the first and second embodiments described above,
Although the example in which the positioning recess 2d has a cylindrical shape or a truncated cone shape and the mounting base 11a has a cylindrical shape has been described, other shapes may be used as long as they can be fitted and positioned.

[0019]

As described above, according to the present invention, since the positioning recess is provided in the container, the upper and lower portions of the probe can be fixed by the lid and the positioning recess, so that even if an external force such as vibration is applied, the SQUID magnetic field is applied. The sensor vibrates with other parts. Then, the SQUID magnetic sensor does not vibrate at the natural frequency due to the interaction. Therefore, the SQUID
No error occurs in the measured value of the magnetic sensor.

The strength of the bottom of the container can be ensured by reducing the thickness of the bottom of the inner container having the positioning recess and increasing the thickness of the other bottom. Since the SQUID magnetic sensor can be brought close to the weak measurement target below, the weak magnetic field can be measured more accurately. Furthermore, since the peripheral surface of the recess is an inclined surface that expands into the interior of the container, the probe mount can be easily inserted into the recess, and the SQUID magnetic sensor can be easily positioned.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a cryostat according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of a positioning recess.

3 is a cross-sectional view showing the bottom half of the inner container taken along the line AA in FIG.

FIG. 4 is a plan view showing a half of the lid of FIG.

FIG. 5 is a partially enlarged perspective view showing a main part of a cryostat according to a second embodiment of the present invention in a cutaway manner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 outer container 2 inner container 2d positioning recess 4 lid 4h insertion hole 4p supply / discharge barrel 11 probe 11a mount 11b connector 11c pipe 12 cooling medium

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Thread ▲ Zaki ▼ Hideo 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works Co., Ltd.

Claims (2)

[Claims] 1. A SQUID disposed at the lower end of the probe
A bottomed cylindrical container for containing the magnetic sensor and the cooling medium, and a lid which covers the open end of the container, allows the probe to be inserted into the container, and has an insertion hole for positioning the upper end of the probe. A cryostat comprising at least: a positioning recess for positioning the lower end of the probe at the bottom of the container. 2. The cryostat according to claim 1, wherein a peripheral surface of the positioning recess is an inclined surface that expands into the inside of the container.