US3385072A

US3385072A - Cryostat

Info

Publication number: US3385072A
Authority: US
Inventors: Marsing Helmut
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1965-08-07
Filing date: 1966-08-08
Publication date: 1968-05-28
Anticipated expiration: 1985-05-28
Also published as: CH461554A; DE1501304A1; DE1501304B2; GB1156833A; NL6610445A

Description

H. MARSING May 28, 1968 CRYOSTAT 2 Sheets-Sheet l Filed Aug.

Fig.1

y 28, 1968 H. MARSING 3,385,072

CRYOSTAT Filed Aug. 8. 1966 2 Sheets-Sheet 2 United States Patent 3,385,072 CRYOSTAT Helmut Marsing, Hetzles, Germany, assignor to Siemens Aktiengesellschaft, Berlin, Germany, a corporation of Germany Filed Aug. 8, 1966, Ser. No. 571,117 Claims priority, application Germany, Aug. 7, 1965, S 98,717 10 Claims. (Cl. 6245) ABSTRACT OF THE DISCLGSURE In a cryostat adapted to house a structure such as a superconductive magnetic coil and provided with a substantially horizontal tubular inner chamber accessible from the outside there is an outer horizontal hollow container of cylindrical configuration and an inner horizontal hollow container of cylindrical configuration situated within said outer container, and vertically extending tubular means connected to and carrying said outer and inner containers and including at least an outer tube connected to said outer container and an inner tube situated within said outer tube and connected to said inner container, said outer container including a ring fixed to said outer tube and a pair of cylindrical walls, said ring and said cylindrical walls having means for removably connecting said cylindrical walls respectively with said ring, said cylindrical walls respectively extending in opposite directions from the latter.

My invention relates to cryostats.

Cryostats which are provided with horizontal inner hollow chambers which are accessible from the outside are required for various technical and scientific purposes. Such devices are required primarily for cooling cryostat coils, particularly superconductive coils which serve to provide a magnetic field filling a horizontally extending chamber which is accessible from the outside. Such coils can be used particularly where charged particles, such as ions, electrons, or other elementary particles, for example, are to be subjected to the influence of a magnetic field. Such a magnetic coil can be used, for example, as a magnet for a magnetohydrodynamic generator or for achieving an intense axially extending magnetic field which is to enclose plasma.

Various difficulties are encountered in the construction of cryostats of the above type. Thus, such cryostats should be as easy as possible to disassemble, so that access may be had in a simple way to the coil which is situated in the interior of the cryostat. On the other hand, there should be as few connections as possible between the inner part of the cryostat, which is at a low temperature, and an outer chamber of the cryostat, in particular the outer wall of the cryostat which is at room temperature, since such connections will provide transfer of heat from the outer chamber to the inner part of the cryostat with the result that there will be a high consumption of the cooling medium. Furthermore, the cryostat must have a high mechanical strength, which can only be achieved with difficulty because of the great weight of the magnetic coil.

It is thus a primary object of my invention to provide a cryostat of the above general type which will avoid the above difiiculties.

In particular, it is an object of my invention to provide a cryostat capable of solving the above problems while at the same time being adapted to house a superconductive magnetic coil and having a horizontal approximately tubular inner chamber which is accessible from the outside.

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It is furthermore an object of my invention to provide a cryostat in which the possibility of transfer of heat between an outer chamber and an inner container of the cryostat is very greatly reduced.

It is also an object of my invention to provide a cryostat construction of high mechanical strength which at the same time will reduce to a minimum the extent of heat-conducting contact between the cryostat and its supporting structure.

The objects of my invention also include the provision of a cryostat which can be very easily disassembled so that easy access may be had to a coil situated in an inner container of the cryostat.

It is especially an object of my invention to provide a construction where easy access may be had to a coil in an inner container of the cryostat without requiring any change in the position of the coil.

Thus, the cryostat of my invention is particularly adapted to house a superconductive magnetic coil and is provided with an inner hollow horizontal chamber which is accessible from the outside. This cryostat of my invention include-s an outer hollow horizontal cylindrical container and an inner horizontal hollow cylindrical container situated within the outer container, as well as vertically extending tubular means fixed to the inner and outer containers and carrying the latter. This tubular means of my invention includes an outer tube which is connected to the outer container and an inner tube which is connected to the inner container. At least the outer container of the cryostat of my invention includes a ring which is fixed to the outer tube of the tubular means and a pair of cylindrical walls which are respectively removably connected with the ring and respectively extend in opposite directions therefrom.

My invention is illustrated by way of example in the accompanying drawings which form part of the application and in which:

FIG. 1 is a schematic longitudinal sectional elevation of one possible embodiment of a cryostat according to my invention;

FIG. 2 illustrates schematically in a longitudinal sectional elevation another embodiment of an inner container of the cryostat of FIG. 1; and

FIG. 3 shows in a longitudinal sectional elevation a further embodiment of an inner container for the cryostat of FIG. 1.

Referring now to FIG. 1, the cryostat illustrated therein serves to refrigerate a superconductive magnetic coil. This cryostat of my invention includes three elongated hollow horizontal containers arranged one within the other and all having a common horizontal axis. The outer container 1 serves to provide the cryostat with an evacuated space in which structure within the outer container is situated. The intermediate container 2 forms a heat-shielding means. The inner container 3 serves to house the coil as well as the liquid refrigerating bath which surrounds this coil and which is in the form of liquid helium. A tubular means 4 is provided to carry the containers 1-3 of the cryostat of my invention, and this tubular means 4 includes an outer vertical tube 41 and an inner vertical tube 42. In the illustrated example this inner tube 42 has a pair of tubular sections which are connected to each other in the manner shown in FIG. 1. The outer tube 41 and the inner tube 42 of the tubular means are connected to each other at the top end of the tubular means. The inner tube 42 is surrounded by an intermediate tube 43 made of a material of good thermal conductivity. This intermediate tube 43 is in good heat-conducting contact with the inner tube 42 approximately midway between the ends thereof, which is to say at the connection between the sections of the inner tube 42.

In accordance with my invention, the outer container 1 includes a ring 44 which is fixed to the outer tube 41 and which is coaxial with the remainder of the cylindrical outer container 1. In this way the ring 44 serves to fix the outer container 1 to the outer tube 41, and it will be noted that the tube 41 communicates with the interior of the outer container 1. This outer container 1 has a pair of cylindrical walls 11 and 12 which are respectively removably connected with the ring 44 and which respectively extend in opposite directions therefrom. For example, the cylindrical walls 11 and 12 may have a threaded connection with the ring 44. A discshaped end wall 13 of the container 1 is permanently fixed with the cylindrical wall 11 thereof as by being welded thereto. In a corresponding way, an opposed discshaped end wall 14 is permanently fixed with the cylindrical wall 12 as by being welded thereto.

The outer container 1 includes an inner tubular wall 15 which extends into central openings which are formed in the

end walls

13 and 14. This inner tubular wall 15 of the outer container 1 is fixed to the end wall 13, as by being welded thereto, and has a removable connection with the end wall 14. For example, the tubular wall 15 may have a threaded connection with the end wall 14.

The intermediate container 2, which forms the heatshielding means, is fixed to and hangs from the intermediate tube 43. This intermediate container 2 includes a ring 45 which co'axially surrounds the axis of the cryostat and which is connected with the tube 43. The intermediate container 2 includes a pair of double-walled

cylinders

21 and 22 which are respectively fixed removably to and respectively extend in opposite directions from the ring 45, these double-

walled cylinders

21 and 22 having, for example, a threaded connection with the ring 45. Each of the double-walled

cylinders

21 and 22 is formed by a pair of cylindrical walls which define between themselves a space which during operation of the cryostat is filled with liquid nitrogen or liquid air. The filling of the double-walled

cylinders

21 and 22, in the space between the walls thereof, can take place through a suitable conduit which is guided through the tubular means 4 of the cryostat and which communicates with a suitable connection provided at the outer cylindrical wall of each of the double-walled

cylinders

21 and 22. The double-walled cylinder 21 is fixed at its outer end of a disc-shaped end wall 23, while the double-walled cylinder 22 is fixed at its outer end to a disc-shaped end wall 24.

The intermediate container 2 includes an inner tubular wall which extends into central openings formed in the

end walls

23 and 24. This tubular inner wall 25 I of the intermediate container 2 coaxially surrounds the inner wall 15 of the outer container 1, as indicated in FIG. 1. Inasmuch as, during the operation of the cryostat, the space within which the intermediate container 2 is located is evacuated, so that the space within and without the container 2 is at a certain degree of vacuum, the tube 25 need not be welded or threaded to the

end walls

23 and 24. It need only extend into the central openings of these end walls. However, there should be a good heat-conductive contact between the

end walls

23 and 24 and the tube 25.

The inner container 3 includes a single cylindrical wall 31 which is permanently fixed with the inner tube 42 of the tubular means 4 as by being welded thereto. A disc-shaped end wall 32 is welded to the right end of the cylinder 31, as viewed in FIG. 1. The inner container 3 includes, in addition to the single cylindrical wall 31 and the end wall 32, an inner tubular wall 33 which coaxially surrounds the inner wall 25 of the intermediate container 2. Also, the inner container 3 includes an end wall 34 which is opposed to the end wall 32 and which is of a disc-shaped configuration. The inner tubular Wall 33 of the inner container 3 is welded with the end wall 34 so as to be permanently fixed therewith. It will be noted that the inner tubular wall 33 of the inner container 3 is in alignment with central openings of the

end walls

32 and 34. The inner tube 33 is rcmovably connected with the end wall 32 as by being threaded to the latter. The superconductive coil which is situated in the interior of the inner container 3 can be fixed either to the inner tube 33 or to the end wall 34 or to both the inner tube 33 and the end wall 34.

It is thus apparent that the cryostat of my invention can be very easily disassembled and reassembled so as to give ready access to a coil in the inner container 3. For this purpose it is only necessary to remove the walls 11 and 12 of the outer container 1 from the ring 44, and one of the end walls can also be simultaneously removed from the tube 15 or the tube 15 can be removed with one of the end walls from the outer end wall. In this way access may be had to the intermediate container 2. Then the double-walled cylinder 21 together with the and wall 23 and the double-walled cylinder 22 together with the end wall 24 are removed from the ring 45, thus giving access to the inner container 3, and now the end wall 34 together with the tube 33 can be displaced from the interior of the cylindrical wall 31 so as to give ready access to a coil carried by the inner container 3 in the interior thereof.

The tube 43 which is in good thermal contact with the outer wall of the container 2 and with the tube 42 and which also serves to carry the intermediate container 2 serves simultaneously as a heat shield for the inner tube 42 of the tubular means and as a structure for precooling the inner tube 42.

A tubular fitting 46 is operatively connected with the outer tube 41 and is adapted to be placed in communication with a suitable vacuum pump or the like for the purpose of evacuating the cryostat. The interior space of the tube 41 communicates with the interior of the outer container 1 as well as with the interior of the intermediate container 2, this space of the tube 41 which communicates with the interiors of the outer and

intermediate containers

1 and 2 being defined between the tube 41 and the upper portion of the tube 42 as well as the tube 43. In order to evacuate the space between the heat shield and the inner container 3 as well as the space between the

tubes

42 and 43, the

end walls

23 and 24 of the intermediate container 2 are provided with a plurality of small openings. The tube 43 may also be provided with such small openings.

. The cover 47 of the tubular means of the croystat of my invention is provided with passages for the conduits through which the refrigerating mediums flow to the inner container 3 as well as the space in the double Walls of the intermediate container 2, and also the cover 47 is provided wtth a passage for the power-supply conductors which are connected electrically with the coil.

During assembly of the cryostat of my invention, the tubular means 4 together with the

rings

44 and 45 as well as the outer wall 31 of the inner container 3 and the end wall 32 thereof form a mounting frame. Initially the end wall 34 and inner tube 33 of the inner container 3, which carry the coil, are threaded to the wall 31 and the end wall 32, respectively. Then the intermediate container 2 is assembled, and finally the outer container 1 is assembled.

The intermediate container 2, including its ring 45, and also including the intermediate tube 43, which is in direct heat-conducting contact with the intermediate container 2, are preferably made of copper. The material for the other containers, tubes, and rings of the containers is preferably antimagnetic chrome-nickel steel 18/8 (V A-steel The horizontal innermost tubular space of the cryostat, this space being surrounded by and situated within the inner tube wall 15 of the outer container 1, is accessible from both ends of the cryostat. In FIG. 2 another embodiment of an inner container of the cryostat of my invention is shown. In this case the outer cylindrical wall of the inner container 3 is made up of a pair of

cylindrical walls

35 and 36. These walls are threaded to a ring which is fixed to the inner end of the tube 42 of the tubular means. The remainder of the structure of the embodiment of FIG. 2 is the same as that of FIG. 1. Thus, with the embodiment of FIG. 2 it becomes possible to remove either of the

walls

35 and 36. When the wall 36 is removed together with the end wall 32, access may be had to the coil without changing its position.

FIG. 3 shows a further embodiment of an inner container of a cryostat of my invention. In this embodiment the coil-carrying body which carries the winding of the magnetic coil, forms the inner tubular wall of the inner container 3. The outer wall of the container 3 of this embodiment also includes a pair of

cylindrical walls

35 and 36 which are threaded with the ring 48 which is fixed to the inner tube 42. The disc-shaped

end walls

32 and 34 of the inner container 3 of this embodiment are welded to the

cylindrical walls

35 and 36 of the inner container 3. The inner tubular wall of the container 3 of FIG. 3 is formed by the coil-carrying body 37 on which the winding 38 of the magnetic coil is wound. This coil-carrying body 37 is removably connected with the

end walls

32 and 34 as by being threaded therewith.

During operation of the cryostat the coil within the inner container 3 is situated in a bath of a refrigerating medium such as liquid helium with which the inner container 3 is filled, so that in this way the entire coil is submerged within the refrigerating bath. The surface 50 of the liquid cooling medium is shown in FIG. 3 within the inner tube 42.

The cryostat of my invention is particularly suited for refrigerating cylindrical coils where the axis of the coil extends in the same direction as the axis of the container in which the coil is situated. Thus, with this construction there will be provided within the inner tubular inner chamber of the cryostat a magnetic field which extends parallel to the axis of the inner chamber.

Also, the cryostat of my invention is suitable for refrigerating coils which have windings composed of a pair of saddle-shaped components, such windings serving to achieve in the tubular interior chamber of the cryostat a magnetic field which extends perpendicularly with respect to the axis of the container. Coils of this latter type are particularly suited for magnetohydrodynamic generators.

Thus, it will be seen that with the cryostat of my invention, the cylindrical containers are carried by the tubular means. In particular, the inner container, which serves to receive the coil and the refrigerating medium, hangs freely from the inner tube of the tubular means and is in communication with the outer chamber only by way of this inner tube. The chrome-nickel-steel used for this inner tube has a very poor thermal conductivity, so that with this construction of my invention the extent of transfer of heat between the inner container and the outer chamber is very greatly reduced. Further reduction in this transfer of heat is brought about by the precooling of the inner tube. It will be noted that there ar no other supporting connections between the inner containers of the cryostat of my invention. At the same t m the suspension of the individual containers from the tubes of the tubular means provides a high mechanical strength, while reducing the thermal contact between the components to a minimum. The removable conn ct ons of the cylindrical walls of the outer container with the ring 44 thereof provides the cryostat of my invention with the possibility of easy access to the interior of the cryostat, and thus with the cryostat of my invention it is possible in a simple way to have access to the interior of the inner container where the coil is situated.

Thus, with the cryostat of my invention, removable connections are provided wherever required so as to give the cryostat a simple and convenient assembly and disassembly, whereas components which do not have to be assembled and disassembled are welded together in a vacuum-tight manner.

It is to be noted that it is also possible to provide the coil-carrying body, such as the body 37, with parts which form the end walls of the inner container 3.

Because the space between the inner container, which houses the coil and refrigerating medium, and the outer container, which forms the outer wall of the cryostat, is evacuated, together with the space between the outer and inner tubes which carry the outer and inner containers, the possibility of thermal conductivity between the inner and outer containers is avoided.

Of course, the shielding means formed by the inter mediate container functions to prevent to a very large extent radiation of heat through the outer chamber to the inner container. The suspension of the intermediate container from the intermediate tube 43 which is in good heat-conducting contact with the inner tube 42 and the formation of the tube 43 as well as the intermediate container from a metal such as copper of good thermal conductivity provide the cryostat of my invention with particularly favorable features. Inasmuch as this intermediate container 2 is made of a material of good thermal conductivity, the entire container assumes the temperature of the refrigerating medium which is situated within the double walls of the intermediate container. Thus, the heat which radiates inwardly from the outer chamber is absorbed by the walls of the intermediate container and does not radiate all the way through to the inner container wihch is at an even lower temperature than the intermediate container walls inasmuch as the inner container contains liquid helium.

This refrigerating medium which is situated in the space within the double walls of the intermediate container serves to pre-cool the inner tube 42. Since this inner tube is surrounded by the tube 43 from which the intermediate container is suspended and since this intermediate tube 43 is made of a material of good thermal conductivity, the inner tube 42 at its connection with the intermediate tube 43 is also maintained approximately at the temperature of the outer double-wall of the intermediate container, which is to say at the temperature of the cooling medium therein, such as liquid nitrogen or liquid air. Further pre-cooling of the inner tube of the tubular means is provided by use of the vapor of the cooling medium which is situated in the interior of the inner container and which rises up into the inner tube to the elevation 50 shown in FIG. 3. The conduit for the refrigerant, this conduit serving to fill and empty the inner container, and also the power-supply conductors for the magnetic coil extend along the interior of the inner tube of the tubular means, and of course these components are cooled in the same way by the vapor of the cooling medium. The conduits for delivering the cooling medium to the interior of the double walls of the intermediate container as well as any tubular connections for evacuating the cryostat can advantageously extend along the interior of the tubular means in the space between the inner and outer tubes.

I claim:

1. In a cryostat which is adapted to house a structure such as a superconducitive magnetic coil and is provided with a substantially horizontal tubular inner chamber which is accessible from the outside, an outer horizontal hollow container of cylindrical configuration and an inner horizontal hollow container of cylindrical con-figuration situated within said outer container, and vertically extending tubular means connected to and carrying said outer and inner containers and including at least an outer tube connected to said outer container and an inner tube situated within said outer tube and connected to said inner container, said outer container including a ring fixed to said outer tube and a pair of cylindrical walls, said ring and said cylindrical walls having means for removably connecting said cylindrical walls respectively with said ring, said cylindrical walls respectively extending in opposite directions from the latter.

2. In a cryostat as recited in claim 1, said inner container including only a single cylindrical wall which is welded to said inner tube.

3. In a cryostat as recited in claim 1, said inner container including a ring fixed to said inner tube and a pair of cylindrical walls respectively fixed removably to said ring and extending in opposite directions therefrom, respectively.

4. In a cryostat as recited in claim 1, heat-shielding means situated between said inner and outer containers and including a hollow cylindrical container situated between said outer and inner containers and forming an intermediate container in which said inner container is located, and said intermediate container being situated within said outer container.

5. In a cryostat as recited in claim 4, said tubular means including an intermediate tube of good thermal conductivity situated between said outer and inner tubes and extending part of the way along the length of said inner tube and being in good heat-conducting relationship therewith, said intermediate container also being made of a material of good thermal conductivity and being fixed to said intermediate .tube.

6. In a cryostat as recited in claim 5, said intermediate container including a ring fixed to said intermediate tube and a pair of double-walled cylinders respectively fixed removably to and extending in opposite directions from said ring, respectively, each of said double-walled cylinders having a pair of walls which define between themselves a space for receiving a cooling medium.

7. In a cryostat as recited in claim 5, said materials of said intermediate tube and intermediate container which are of good thermal conductivity being copper.

8. In a cryostat as recited in claim 7, said inner and outer containers and said inner and outer tubes being made of antimagnetic chrome-nickel-steel.

9. In a cryostat as recited in claim 1, a winding of a magnetic coil situated in said inner container, and a coilcarrying body carrying said Winding of said magnetic coil and forming part of said inner container.

10. In a cryostat as recited in claim 9, said coil-carrying body forming an inner wall of said inner container.

References Cited UNITED STATES PATENTS 3,133,144 5/1964 Cottingham et al. 62-514 3,176,473 4/1965 Andonian 62-45 3,242,418 3/1966 Mela et al. 62514 3,262,279 7/1966 Moore 6245 3,320,757 5/1967 Pauliukonis 6245 LLOYD L. KING, Primary Examiner.