EP3938721B1 - Cryostat - Google Patents

Description

Technical area

The present invention relates to a cryostat according to claim 1 for experiments at temperatures in the range of less than 2 K.

Cryostats and in particular demixing cryostats for temperatures in the range of less than 2 K are currently mainly required and built for the development of quantum computers and quantum communication devices. The arrangement of the individual temperature levels or cold plates and thus also the arrangement of experimental stations is given by the vertical arrangement of conventional cryostats.

Fig. 7a and 7b show schematically a state-of-the-art demixing cryostat with a suspended, vertical structure. The demixing cryostat according to Fig.7 comprises six cooling stages 2-1 to 2-6 with four experimental stations 4-1 to 4-4. The room temperature area is not equipped as an experimental station. The temperature levels of the six cooling stages 2-i are provided by three unspecified cooling devices.

A first cooling device (not shown in detail), e.g. a first stage of a GM cooler, comprises a first cold plate 8-1 with the first experimental station 4-1 arranged under the first cold plate 8-1. The first cooling stage 2-1 provides a temperature level of approximately 50 K for the first experimental station 4-1.

A second cooling device (not shown in detail), e.g. a second stage of the GM cooler, comprises a second cooling device arranged under the first experimental station 4-1. Cold plate 8-2. The second cold plate 8-2 or the second cooling stage 2-2 is at a temperature level of approximately 4 K. The second experimental station 4-2 is arranged under the second cold plate 8-2 at the temperature level of the second cooling stage 2-2. A third cold plate 8-3 of a third cooling stage 2-3 with a temperature level of approximately 1 K is arranged under the second experimental station 4-2, which is cooled by a third cooling device (not shown in detail), e.g. a Joule-Thomson stage.

A fourth cooling device (not shown in detail), e.g. a ³ He/ ⁴ He demixing cooler, provides the temperature levels of the fourth, fifth and sixth cooling stages 2-4, 2-5 and 2-6. The third experimental station 4-3 is provided on the fourth cooling stage 2-4 between the fourth cold plate 8-4 and the fifth cold plate 8-5. A sixth cold plate 8-6, the lowest cooling stage 2-6, is provided below the third experimental station 4-3 and below the fifth cold plate 8-5. The temperature level of the fourth cold plate 8-4 is in the range between 500 and 700 mK, the temperature level of the fifth cold plate 8-5 is between 100 and 200 mK and the lowest temperature level of the sixth cold plate 8-6 and the fourth experimental station 4-4 arranged below it is in the range <100 mK.

The entire arrangement is arranged in a vacuum container 10. In the vacuum container 10, all six cooling stages 2-1 to 2-6 are enclosed by a first heat shield 12-1. Within the first heat shield 12-1, the second to sixth cooling stages 6-2 to 6-6 are enclosed by a second heat shield 12-2. Within the second heat shield 12-2, the fourth to sixth cooling stages 2-4 to 2-6 are enclosed by a third heat shield 12-3. The deepest, sixth cooling stage 2-6 is shielded by a fourth heat shield 12-4.

This conventional arrangement has the advantage that the individual temperature levels lie inside each other like onion skins and are easy to manufacture - see Fig. 7b However, due to the increasing requirements in terms of experimental space on the individual stages, these known cryostats are becoming relatively large and, above all, high and long. This means that the heat shields are becoming longer and longer and you either have to split them or you have to install a heat shield underneath the device. A lot of space must be provided to be able to remove these heat shields in order to access the experiment stations. Furthermore, all structures on the individual levels must be suspended, as experiment stations are provided within the heat shields under the cold plate of the corresponding temperature level.

From the WO2010/106309 A2 is a cryostat with an experimental area accessible only from above and from the WO 2009/000629 A2 A cryostat with only one experimental station accessible from the side is known.

From the article by Kurt Uhlig "Concepts for a low-vibration and cryogen-free tabletop dilution refrigerator" in Cryogencis 87 (2017) 29-34 A so-called tabletop demixing cryostat is described, which allows a smaller construction volume due to the arrangement of the still and mixing chamber, but has the same disadvantage as the state of the art according to Fig.7 namely that the individual cold plates or experimental stations are only accessible from the side.

From the EN 102014015665B4 An optical table is known which has a single cold plate integrated into the table top.

From the DE102016214731B3 , the DE102005041383A1 and also the DE102011115303A1 NMR apparatuses or cryogenic devices are known in which probe head components are arranged one above the other or below one another at different temperature levels when viewed from above. DE102011115303A1 It can be seen from the drawing that two probe heads are arranged horizontally and vertically offset from each other. DE102016214731 B3 discloses a cryostat according to the preamble of claim 1.

It is therefore an object of the present invention to provide a cryostat which enables improved accessibility of the experimental stations and at the same time requires a smaller construction volume.

This problem is solved by the features of claim 1.

Because the experiment stations are arranged next to each other rather than one below the other, they are accessible from above and from the side after removing the respective heat shields, whereas with the current technology they are only accessible from the side. This simplifies various experiments and generally the handling of the cryostat in use. By arranging the experiment stations next to each other, the height of the cryostat is also significantly reduced and it is possible to operate the cryostat in laboratory rooms with a standard height, which is not possible with cryostats with a vertically hanging arrangement. Although arranging the experiment stations next to each other can lead to larger heat shields, this disadvantage (increased cooling capacity of the various coolers is necessary for operation) is accepted by the possibility of use in laboratory rooms with a standard height.

According to the advantageous embodiment of the invention according to claim 2 or 3, several cooling stages are served by a mixing cooler.

The advantageous embodiments of the invention according to claims 4 to 6 relate to suitable cooling devices for the cryostat.

The advantageous embodiment of the invention according to claim 7 represents a simple juxtaposition of the experimental stations, whereby these are still at different temperature levels.

The advantageous embodiment of the invention according to claim 8 provides experimental stations arranged next to one another, which are located at approximately the same height.

Further details, features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention.

Short description of the characters

• Fig. 1a and 1b show schematically the basic idea of the present invention;
• Fig. 2a and 2b show the geometric structure of a first embodiment of the invention;
• Fig.3 shows the geometric structure of a second embodiment of the invention;
• Fig.4 shows the arrangement of the heat shields in the embodiments according to Fig. 2 and 3 ;
• Fig.5 shows a third embodiment of the invention with the experimental stations arranged next to each other on one level;
• Fig.6 shows a fourth embodiment of the invention in which a GM cooler penetrates the vacuum vessel from below, and
• Fig. 7a and 7b show a state-of-the-art cryostat.

The Figures 1a and 1b show schematically the basic principle of the present invention, the juxtaposition of five experimental stations 4-1 to 4-5 on the cold plates 8-1 to 8-5 in one plane. The five experimental stations 4-1 to 4-5 are located on the cooling stages 2-1 to 2-5 with the associated temperatures, room temperature 50 K, 4 K, 700 mK and 100 mK.

Fig. 1a shows the experiment stations arranged next to each other from the side and thus the volume of the experiment stations 4-1 to 4-5 above the respective cold plate 8-1 to 8-5 and Fig. 1b shows a top view of the representation according to Fig.1 .

Fig. 2a and 2b show a first embodiment of the invention, in which the cryostat according to the invention has a rectangular cross-sectional shape and the individual experimental stations 4-1 to 4-5 are arranged next to each other on one level and are nested in an L-shape; with the fifth experimental station 4-5 as a cube.

Fig.3 shows a second embodiment of the invention, in which the basic structure is circular or cylindrical and the individual experimental stations 4-1 to 4-5 surround each other.

Fig.4 represents a possible arrangement of four heat shields 32-1 to 32-4 for the individual embodiments according to Fig. 2 and 3 represents.

Fig.5 shows a third embodiment of the invention. The individual components of the cryostat are arranged in a vacuum container 10. The vacuum container 10 comprises a base plate 20 on which a side border 22 is arranged, resulting in a tub 24. On the left side of the tub 24, a pulse tube cooler 26 extends into the tub 24. The right side of the side border 22 supports a first partial cold plate 30-1 at room temperature. A first experimental station 4-1 is arranged on the first partial cold plate 30-1. The first experimental station 4-1 is surrounded by a first heat shield 32-1 and is at room temperature. The entire vacuum container 10 represents the first heat shield 32-1.

A second cold plate 8-2 is provided at a distance from the base plate 20 by support elements 28, which is in thermal contact with the pulse tube cooler 26 and also has a lateral border 22. In the right edge area of the second cold plate 8-2, a support element 28 supports a second partial cold plate 30-2 which is offset upwards and is located in the plane of the first partial cold plate 30-1. The second cold plate 8-2 and the second partial cold plate 30-2 are at a second temperature level of approximately 50 K. A second experimental station 4-2 is located on or above the second partial cold plate 30-2. Starting from the second cold plate 8-2, a second heat shield 32-2 encloses the second experimental station 4-2.

Again spaced apart by support elements 28, a third cold plate 8-3 is arranged on the second cold plate 8-2, which in turn is thermally coupled to the pulse tube cooler 26 and provides a temperature level of approximately 4 K. A support element 28 on the right side of the third cold plate 8-3 carries a third partial cold plate 30-3 offset upwards. The third partial cold plate 30-3 is located in the plane of the second and first partial cold plates 30-1 and 30-2. A third experimental station 4-3 with a temperature level of approximately 4 K is arranged on or above the third partial cold plate 30-3. Starting from the third cold plate 8-3, a third heat shield 32-3 encloses the third experimental station 4-3.

Again spaced apart by support elements 28, a fourth cold plate 8-4 is arranged above the third cold plate 8-3, on which the components of a ³ He/ ⁴ He demixing cooler 34 are arranged. On the right side of the fourth cold plate 8-4, a support element 28 supports a fourth partial cold plate 30-4 offset upwards at the height level of the other partial cold plates 30-1 to 30-3.

By means of further support elements or support walls 28, a fifth cold plate 8-5 is arranged above the fourth cold plate 8-4 at the same height as the partial cold plates 30-i at the lowest temperature level of approximately 30 mK. A fifth experimental station 4-5 is arranged above or on the fifth cold plate 8-5. Starting from the fifth cold plate 8-5, a fifth heat shield 32-5 encloses the fifth experimental station 8-5.

The ³ He/ ⁴ He demixing cooler 34 between the fourth and fifth cold plates 8-4, 8-5 comprises a still 36 with concentric heat exchanger 38, a mixing chamber 40 and connections 42. The still is thermally coupled to the fourth cold plate 8-4 and the fourth partial cold plate 30-4. The mixing chamber 40 is thermally coupled to the fifth cold plate 8-5.

The thermal coupling of the individual cold plates 8-i with the partial cold plates 30-i and the pulse tube cooler 26 or the ³ He/ ⁴ He demixing cooler 34 is achieved via heat conductors 44. The pulse tube cooler 26 is mounted in the vacuum vessel 10 via a vibration decoupling device 46.

Fig.6 shows a fourth embodiment of the invention, which differs from the third embodiment according to Fig.5 differs in that instead of a pulse tube cooler that penetrates the vacuum container 10 from the side, a GM cooler 48 penetrates the vacuum container 10 from below approximately in the middle of the fifth cold plate 8-5. The GM cooler 48 also penetrates an opening in the second cold plate 8-2 so that the thermal coupling with the third heat plate can take place. By installing the GM cooler 48 from below, a somewhat narrower, but somewhat higher design is obtained.

As can be seen from the sectional views in Fig.5 and 6 As can be seen, the arrangement of the experiment stations 4-i next to each other enables a significantly lower design. The low height of the cryostat makes it possible to operate the cryostat in standard height laboratory rooms, which is not possible with cryostats with a vertically hanging arrangement. Although the arrangement of the experiment stations next to each other can lead to larger heat shields, this disadvantage (increased cooling capacity of the various coolers is necessary for operation) is accepted by the possibility of use in standard height laboratory rooms.

List of reference symbols:

2-i

Cooling levels

4-i

Experimental areas

8-i

Cold plates

10

Vacuum container

12-i

Heat shields

20

Base plate

22

side border of 20, 8-2

24

Tub

26

Pulse tube cooler

28

Support elements

30-i

Partial cold plate

32-i

Heat shield

34

³ He/ ⁴ He demixing cooler

36

Still

38

concentric heat exchanger

40

Mixing chamber

42

Connections of 34

44

Heat conductor

46

Vibration decoupling

48

GM Radiator

Claims (8)

1. A cryostat, comprising

   a plurality of cooling levels (2-i) having different temperature levels, having cooling devices (26, 34) associated therewith,

   a plurality of experimentation places (4-i) at the temperature levels of the cooling levels (2-i),

   a plurality of heat shields (32-i) for the cooling levels (2-i) enclosing the experimentation places (4-i), and

   a vacuum chamber (10) in which the plurality of cooling levels (2-i) are arranged, characterized in that the experimentation places (4-i) are arranged side by side when viewed from above, and

   in that the experimentation places (4-i) are arranged side by side in such a way that they are each accessible from above and from the side.
2. The cryostat according to claim 1, characterized in that a cooling device (26, 34) is associated with several cooling levels (2-i).
3. The cryostat according to claim 2, characterized in that the cooling device for the cooling levels (2-4, 2-5) with the two lowest temperature levels is a ³He/⁴He dilution refrigerator (34) comprising a still (36) and a mixing chamber (40).
4. The cryostat according to one of claims 1 to 2, characterized in that the cooling device for the cooling level (2-4, 2-5) with the lowest temperature level is a Joule-Thomson cooler, a 1-K pot, and/or a ³He level.
5. The cryostat according to one of claims 1 to 2, characterized in that the cooling device for the cooling level (2-4, 2-5) with the lowest temperature level is an ADR cooler.
6. The cryostat according to one of the preceding claims, characterized in that the cooling devices for the cooling levels (2-1, 2-2, 2-3) with higher temperature levels are pulse tube refrigerators, GM coolers, Stirling coolers, and/or Joule-Thomson coolers.
7. The cryostat according to one of the preceding claims, characterized in that

   at least two of the cooling levels (2-i) comprise a cold plate (8-i) at the temperature level of the respective cooling level (2-i),

   in that the individual cold plates (8-i) are designed on top of each other and protruding laterally over each other, so that the laterally protruding part of the cold plates (8-i) is accessible from above, and

   in that experimentation places (4-i) are formed above the laterally protruding parts of the cold plates (8-i).
8. The cryostat according to claim 7, characterized in that

   on the laterally protruding parts of the cold plates, partial cold plates (30-i) which are offset upwards are provided, which are mechanically supported on the protruding parts of the cold plates,

   in that the vertically offset partial cold plates (30-i) are connected by thermal couplings (44) to the protruding parts of the cold plates at the respective temperature level, and

   in that the experimentation places (4-i) are formed above the cold plate (8-5) at the lowest temperature level and the partial cold plates (30-i).

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