JPS59182512A - Cryostat - Google Patents

Abstract

PURPOSE:To obtain a container wall for liquid helium which has sufficient rigididity and minimize the permeation of helium by a method wherein an inside container for liquid helium and a coil bobbin are commonly composed of a solid fiber reinforced plastic body. CONSTITUTION:A cylindrical bobbin 5 is made of fiber reinforced plastic. A superconductive wire 6 is wound around the cylindrical bobbin 5 in a solenoid shape to form a coil proper. Auxiliary coils for magnetic field correction are formed by winding superconductive wires 9 on annular bobbins 8 and provided to both sides of the coil proper. An outside container 1 for liquid helium is connected airtightly to both ends of the fiber reinforced plastic bobbin 5 so as to make the bobbin 5 serve as an inside container for liquid helium as well. With this constitution, the container wall for liquid helium which has sufficient rigidity while minimizing the permeation of helium can be obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a cryostat, and relates to a cryostat with extremely high uniformity, such as a computer image processing diagnostic system (CT) used for nuclear magnetic resonance (NMR). It relates to a cryostat containing a superconducting solenoid coil for obtaining a high static magnetic field.

[Background of the invention]

Generally, superconducting solenoid coils used in NMR-CT and the like need to be able to generate an extremely highly uniform magnetic field. In the Seven Tanu, the bobbin of the coil body is thick and rigid, and has a thick-walled cylinder. Superconducting wire is wound around the outer periphery of such a bobbin at a precise pitch to form a coil body, and then covered with a binding layer. A pair of separately prepared auxiliary coils is placed on both sides of the coil body, but the auxiliary coils were initially made so that they could slide in the axial direction, and the whole was placed in a separately manufactured cryostat for testing. Then, the coil body and the auxiliary coil are energized, and the optimum position of the auxiliary coil is determined while measuring the uniformity of the magnetic field. After that, let it return to room temperature and fix it to the bobbin and the bobbin of the auxiliary coil.

If the cylindrical bobbin is made of all metal, the material will be stainless V.
In the case of steel, the elastic modulus is large (approximately 20,000 kg/m
m'), so it can be relatively thin, but it is not desirable because it is locally magnetized by bath contact or machining, and the uniformity of the magnetic field is disturbed to the extent that it cannot be corrected by the auxiliary coil. Therefore, generally when NMR-CTJ=I=1, an aluminum alloy bobbin is used. Since aluminum alloy has good electrical conductivity, an external alternating magnetic field, for example, in NMR-CT, a magnetic field created by a high frequency coil for measurement and a pulse coil for generating a gradient magnetic field generates eddy ftl flow, which disturbs the uniformity of the magnetic field and causes ,
Heat is generated and the amount of liquid helium evaporates increases. therefore,
The cylindrical bobbin is preferably made of non-metal. In addition, conventionally, an inner cylindrical container was prepared separately along with the outer container of the liquid helium container, and a coil was formed around the cylindrical bobbin to correct the uniformity of the magnetic field. It is accommodated. In this case, the inner container may be thin as long as helium does not pass therethrough. However, to support the coil i in liquid helium,
If you insert a spacer between the tiller and the coil bobbin, it will need to be thick enough to support the weight of the coil.

[Invention 9) Purpose] The present invention was developed in view of the above-mentioned points, and its purpose is to simplify the structure so that it has sufficient rigidity as a wall of a liquid helium container, and to prevent the permeation of helium. There are very few cryostats on offer.

[Summary of the invention]

In the present invention, the inner liquid helium container and the coil bobbin are entirely made of fiber-reinforced plastic.
It was designed to achieve the intended purpose.

[Practice of the invention ψ1]] The present invention will be explained below based on the embodiments shown in the drawings.

The figure shows a cryostat that is an embodiment of the present invention. In the figure reading, IJj: an outer container for containing liquid helium 3, 2 is a vacuum container, and between the outer container 1 and the vacuum container 2 there is a laminated solid-walled thermal insulation layer 4, so that the liquid helium enters the liquid helium container from the outside. It keeps the heat to an extremely low level. In this embodiment, five cylindrical bobbins are made of fiber-reinforced plastic, and a superconducting wire 6 is placed around the cylindrical bobbin 5.
The coil body is formed by winding it in a V-nod shape.

7 is a binding layer that prevents the coil body from moving due to electromagnetic force. On both sides of the coil body, there are provided auxiliary coils for magnetic field correction, which are formed by winding a superconducting wire 9 around a ring-shaped bobbin 8. The outer container 1 for liquid helium is hermetically joined to both ends of a bobbin 50 made of fiber-reinforced plastic, and the bobbin 5 is made to rest on the metal part of the inner container for liquid helium.

The structure of this embodiment simplifies the structure and reduces the overall cost. Is it possible to achieve this, and is the coil bobbin itself sufficiently rigid? Since it is made thick enough to hold water, it has sufficient rigidity to serve as a container wall for liquid helium, and furthermore, it is possible to minimize the permeation of helium.

〔Effect of the invention〕

According to the cryostat of the present invention described above, the coil bobbin is made entirely of fiber-reinforced plastic, and the outer container of the liquid helium container is joined to both ends of the coil bobbin, so that the structure is simplified and the liquid helium It is possible to obtain a stray lyostat which has a sufficient structure as a container wall and has extremely low helium permeation.

[Brief explanation of the drawing]

The figure is a cross-sectional view of an embodiment of the cryostand of the present invention.

Claims (1)

[Claims] 1. A superconducting solenoid coil formed by winding around the outer periphery of a cylindrical coil bobbin, and a superconducting solenoid coil that accommodates the superconducting solenoid coil, and a superconducting solenoid coil? A liquid helium container that is cooled to an extremely low temperature with liquid helium, and a Makabe container that pumps water through a heating section throughout the liquid helium container? In the cryostand equipped with the coil bobbin, the coil bobbin is made of fiber-reinforced plastic, the outer container of the liquid helium container is joined to the end of the coil bobbin, and the fiber-reinforced plastic coil bobbin also serves as the inner container wall of the liquid helium container. A cryostat is characterized by the following features: