JPH0283476A - Cryostat for SQUID - 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 The present invention is characterized by the fact that an element and a pickup coil are cooled by refrigerants having different temperatures, and a first refrigerant that cools the element and a first refrigerant whose temperature is higher than that of the first refrigerant. A SQUID with a vacuum layer provided between it and the second refrigerant that cools the pink-up coil.
5QtJiD (il conduction quantum interferometer) is attracting attention as an application of the Josephson junction to cryostat applications. This 5QLIID is capable of measuring minute magnetic fields, and is being applied to research in medical fields such as magnetocardial measurement and magnetoencephalography, as well as exploration of minerals and geothermal sources. The above-mentioned SQUID is composed of an element made of a superconductor (SC) such as Hb and a pickup coil. Conventionally, both the element and the pickup coil were cooled with liquid helium.

Incidentally, oxide superconductors have been discovered in recent years, and attempts have been made to manufacture SQUIDs using them.

This oxide superconductor becomes superconducting when cooled with liquid nitrogen, which has a higher temperature and lower cost than liquid helium, so if it is used in a SQUID, running costs can be reduced. However, since the pickup coil operates in a superconducting state, it can be cooled with liquid nitrogen, but the noise generated by the element increases as the temperature rises (noise increases in proportion to the temperature to the 473rd power). , the device needed to be cooled using low-temperature liquid helium. Therefore, the first cooling layer stores liquid helium to cool the element, the second cooling layer stores liquid nitrogen to cool the pickup coil, and the first vacuum layer insulates the second cooling layer from the outside air. , a SQUID having a second vacuum layer that insulates the first cooling layer and the second cooling layer.
It is conceivable to use a commercial cryostat.

With this structure, the distance between the pickup coil and the object to be measured can be shortened, so the SQUID
It has advantages such as being able to improve the measurement accuracy of liquid helium, and reducing the amount of heat entering into liquid helium, thereby reducing its consumption.

However, when transmitting electrical signals from the pickup coil to the element, if the two are directly connected with a superconducting wire, heat will enter the liquid helium through the superconducting wire. For this reason, there has been a problem in that the amount of liquid helium consumed cannot be sufficiently reduced, and the running cost of the SQUID cannot be sufficiently reduced.

Therefore, an object of the present invention is to provide a cryostand for a SQUID that can significantly reduce the running cost of a SQUID by sufficiently reducing the amount of liquid helium consumed.

In order to achieve the above object, the present invention is such that an element and a pickup coil are cooled with refrigerants having different temperatures, and a first refrigerant that cools the element and a first refrigerant whose temperature is higher than that of the first refrigerant are used to cool the pickup coil. In a SQUID cryostat in which a vacuum layer is provided between a second refrigerant that cools a coil, an output coil superconductingly bonded to the pickup coil and an input coil superconductively bonding to the element are provided in the vacuum layer. It is characterized by being

Sakuji - Moon - With the above configuration, since the output coil superconductingly bonded to the pickup coil and the input coil superconductingly bonding to the element are provided in the second vacuum layer, the element and the pickup coil are disposed in the second vacuum layer. is not directly connected. therefore,
Since there is no thermal conduction from the pickup coil to the element, the amount of vaporization of the first refrigerant is reduced, and the amount of consumption of the first refrigerant can be reduced.

Next-1" L-1 square [First embodiment] The first embodiment of the present invention is based on FIGS. 1 to 3,
This will be explained below.

As shown in FIG. 1, the SQUID cryostat of the present invention has an outer tank 1 and an inner tank 2 both made of FRP. The outer tank 1 is composed of an outer case 3 for an outer tank and an inner case 4 for an outer tank, while the inner tank 2 is composed of an outer case 5 for an inner tank and an inner case 6 for an inner tank. At the lower portions of the outer case 3 for the outer tank and the inner case 4 for the outer tank, convex portions 3a and 4a are formed that project toward the object to be measured (not shown).

Here, a first vacuum layer 7 for heat insulation is formed in the space between the outer case 3 for the outer tank and the inner case 4 for the outer tank,
In order to form this first vacuum layer 7, a vacuum valve 8 is provided on the side wall of the outer case 3 for the outer tank. The inner space of the convex portion 4a of the inner case 4 for the outer tank is filled with YBaCuO (Tc 94K).
) is provided with a pick amplifier coil 12 consisting of
This pickup coil 12 is supported by a support 13 fixed to the bottom wall of the outer case 5 for the inner tank.

In addition, liquid nitrogen 9 for cooling the pickup coil 12 is stored in the inner case 4 for the outer tank, and liquid nitrogen 9 is stored in the inner case 4 for the outer tank on the upper wall 4b of the inner case 4 for the outer tank. A liquid nitrogen supply port 10 that supplies vaporized liquid nitrogen 9
A gaseous nitrogen outlet 11 is provided for discharging gaseous nitrogen. On the other hand, a second vacuum layer 14 for heat insulation is formed in the space between the outer case 5 for the inner tank and the inner case 6 for the inner tank. A vacuum valve 15 is provided on the side wall of the case 5.

Inside the inner case 6 for the inner tank is an element 1 made of YBaCuO.
6 is provided, and this element 16 and the pickup coil 12 are connected by an element side lead wire 31, a pickup coil side lead 33, an input coil 40, and an output coil 41, which will be described later. In addition, the inner case 6 for the inner tank
Liquid helium 17 for cooling the element 16 is stored inside. A liquid helium supply port 1 is provided on the upper wall 6b of the inner case 6 for the inner tank to supply liquid helium into the inner case 4 for the outer tank.
8 and a gaseous helium outlet 19 for discharging vaporized liquid helium, and a pressure valve 20 is provided on the side wall of the inner case 6 for the inner tank.

By the way, the element side lead wire 31 and the pickup coil side lead wire 34 pass through the bottom wall 5c of the outer case 5 for the inner tank and the bottom wall 6c of the inner case 6 for the inner tank, and are connected to the pink-up coil 12 and the element. 16, the detailed structure of which is shown in FIGS. 2 and 3. A through hole 25 and a through hole 26 are formed in both the bottom walls 5c and 6c, respectively. Each of these through holes 25 and 26 has a board fixing stand 2.
7 and a substrate fixing stand 28 are fixed, and this fixing method is to machine the side substrate fixing stands 27 and 28 and the through holes 25 and 26 by punching and then sealing them with a low-temperature adhesive such as epoxy resin. Notches 27b and 28b are formed in the opposing surfaces of the side substrate fixing bases 27 and 28, respectively, and substrates 42 and 43 are fixed to these notches 27b and 28b.

Note that the substrate fixing stands 27 and 28 and the substrates 42 and 43 are fixed with adhesive. In addition, the above-mentioned side board fixing bases 27 and 28
A through hole 27a and a through hole 28a are formed in the vicinity of the ends thereof, respectively, and the through holes 27a and 28a are filled with an epoxy resin 29 and an epoxy resin 30, respectively. An element side lead wire 31 connected to the element is inserted into the epoxy resin 29, and the input coil 40 is formed at the end of the element side lead wire 31. On the other hand, a pickup coil side lead wire 33 connected to the pickup coil 12 is inserted into the epoxy resin 30, and an output coil 41 facing the input coil 40 is attached to the end of the pickup coil side lead wire 33. is formed. Here, the input coil 40 and the output coil 41 are made of YBaCuO or Bt.
The substrates 42 and 4 are made of SrCaCuO-based oxide.
It is formed on the opposing surface of 3. In addition, both coils 40.
41 is formed by a screen printing method.

In the above configuration, when the SQUID of the present invention is operated, the signal obtained by the pickup coil 12 is applied to the element 16 via the pickup coil side lead wire 33, the output coil 41, the input coil 40, and the element side lead wire 31. After that, a signal is output from the element 16 to the control circuit.

By the way, if the output coil 41 which is superconductingly bonded to the pickup coil 12 and the human-powered coil 40 which is superconductively bonded to the element 16 are provided in the second vacuum JiilA as described above, the element 16 and the pickup coil 12 are directly connected to each other. Not connected. Therefore, pink up coil 1
Since there is no thermal conduction from 2 to element 16, element 16
The amount of vaporized liquid helium 17 that cools the liquid helium 17 decreases, and the consumption amount of liquid helium 17 can be reduced.

Furthermore, since the element side lead wire 31 and the pickup coil side lead wire 33 pass through the epoxy resin 29 and the epoxy resin 30 having elastic force, it is possible to completely seal the second vacuum layer 14. Can be done.

[Second Embodiment] The second embodiment of the present invention is based on FIGS. 4 and 5.
This will be explained below. Incidentally, the same members as in the first embodiment are given the same reference numerals and their explanations will be omitted.

An input coil core 52 and an output coil core 53 are fixed to the through holes 25 and 26 formed in both bottom walls 5c and 6c. A recess 60 is formed on the opposing surface of the input coil core 52, while a protrusion 61 having a slightly smaller diameter than the recess 60 is formed on the opposing surface of the output coil core 53. The inner periphery of the recess 60 and the outer periphery of the protrusion 61 are arranged to face each other, and the inner periphery of the recess 60 and the outer periphery of the protrusion 61 are wound like a solenoid (3 to 10 turns). An input coil 32 and an output coil 34.4 are provided. The element side leader wire 31 connected to the input coil 32 is inserted through the epoxy resin 29 provided in the through holes 52a and 52b of the input coil core 52, and the pickup coil 31 connected to the output coil 34 The side lead wire 33 is made of epoxy resin 30 provided in the through holes 53a and 53b of the output coil core 53.
It has a structure that allows it to be inserted through.

Even with this structure of the second embodiment, the same effects as those of the first embodiment can be achieved.

As described above, according to the present invention, since there is no heat conduction from the pickup coil to the element, the consumption amount of the first refrigerant can be reduced. Therefore, it is possible to dramatically reduce the running cost of the SQUID.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the SQUID cryostat of the first embodiment, FIG. 2 is a plan view of the input coil and output coil,
Fig. 3 is a sectional view showing the relationship between the input coil and the output coil, Fig. 4 is a plan view of the input coil and output coil of the second embodiment, and Fig. 5 is a cross-sectional view showing the relationship between the input coil and the output coil of the second embodiment. FIG. 7... First vacuum layer, 9... Liquid nitrogen, 12... Pickup coil, 14... Second vacuum layer, 16...
Element, 17...Liquid helium, 32.40...Input coil, 34.41...Output coil. Patent applicant: Sanyo Electric Co., Ltd.

Claims (1)

[Claims] (1) The element and the pickup coil are cooled with refrigerants having different temperatures, and a vacuum layer is formed between a first refrigerant that cools the element and a second refrigerant that is higher in temperature than the first refrigerant and that cools the pickup coil. A cryostat for SQUID, characterized in that an output coil superconductingly bonded to the pickup coil and an input coil superconductively bonding to the element are provided in the vacuum layer.