EP1628089A2 - Device for cooling of a cryostat arrangement - Google Patents

Abstract

The cryogenic cooler (7) is attached to a cold head (10) which may be brought into contact with a workpiece. The cooler uses reflux flow of cryogenic gases and has a housing (8) surrounding a vacuum space (9). There are two cooling stages (11,12) in the vacuum chamber, protected by a radiation shield (13). There are two connections (14a,14b) to a cryostat (1) which have concentrically-arranged tanks (2a,2b) containing two different cryogenic fluids i.e. helium (18a) and nitrogen (18b).

Description

The invention relates to a cooling device for the re-liquefaction of cryogenic gases, with an outer shell defining a vacuum space, and a built-in cold head of a cryocooler having at least two cold stages and which is at least partially surrounded by a radiation shield.

Possibilities for the cryogenic loss-free cooling of a superconducting magnet system with a cryocooler are described, for example, in EP0905436, EP0905524, WO03036207, WO03036190, US5966944, US5563566, US5613367, US5782095, US2002 / 000283, US2003 / 230089.

The example two-stage cold head of the cryocooler is usually installed in a separate, vacuum-cladding tube (as described for example in US5613376) or directly into the vacuum space of a cryostat (as described for example in US5563566) so that the first cold stage of the cold head fixed with a radiation shield and the second cold stage is thermally conductively connected via a fixed thermal bridge or directly to the helium vessel where the superconductive magnet is in liquid helium. By recondensation of the helium evaporating by heat from the outside at the cold contact surface in the helium container, the entire heat input to the helium container can be compensated and a loss-free operation of the system can be made possible. Alternatively, the cold head may be inserted into a neck tube connecting the outer vacuum envelope of the cryostat to the helium vessel and correspondingly filled with helium gas, as described, for example, in US2002 / 0002830A1. The first cold stage of the two-stage cold head is again solidly contacted with a radiation shield, the second cold stage hangs freely in the helium atmosphere and liquefies directly evaporated helium.

However, these variants have certain disadvantages: The structure and construction of the cryostat becomes more complex and complicated. Furthermore, the installation of the additional, the cold head of the cryocooler receiving cladding leads to an additional heat input to the cold head. When using an additional neck tube for the cold head occurs by heat conduction in the helium gas column and in the pipe wall and possibly by convection in the helium gas to a further heat input to the helium tank or the cold head of the radiator. In addition, fixed, rigid or flexible thermal connection elements between the cold head and the cryostat can transmit vibrations of the cold head to the cryostat. In addition, because in the regenerator of the second stage of the cold head of cryocoolers, such as pulse tube coolers or Gifford-McMahon coolers, in the temperature range below 10 K usually magnetic regenerator materials are used and the regenerator may be relatively close to the magnetic center of the NMR magnet system, the regenerator must be shielded usually so that the magnetic field at the location of NMR sample is not disturbed and vice versa, the function of the regenerator is not affected. Finally, in case of failure of the cryocooler, an unstable state, in particular, the temperatures of cryostat components, such as the radiation shield, change constantly to a new equilibrium state. In a magnet system for high-resolution nuclear magnetic resonance (NMR) spectroscopy, this can mean that NMR measurements are no longer possible because the shim state of the magnet changes continuously or, in the worst case, the magnet runs dry and quenches.

One way of avoiding some of these drawbacks while still achieving a partial cryogenic loss-free system is to use a cryocooler cooled device that can be used to re-liquefy a single vaporized cryogen. In a hitherto conventional cryostat arrangement for, for example, a superconducting magnet system, the magnet is usually installed in a container filled with liquid helium of 4.2 K. The He container is usually surrounded by an exhaust-cooled radiation shield and another, cooled with liquid nitrogen shield, so that the heat input is minimized to the helium container from the outside. Passive cooling by the evaporating cryogens causes liquid helium and nitrogen to be replenished at certain intervals.

In JP11257770 and JP2000283578 it is therefore proposed to introduce into the existing neck or suspension tubes of a nitrogen container of a cryostat assembly a heat transfer device in the form of a heat pipe which is connected to the cold head of a cryocooler and liquefies vaporized nitrogen (see also: Advances of Cryogenic Engineering , 45, 41-48). Here, the condenser is flanged directly to the cold head of the single-stage pulse tube cooler. This consists of a thin tube in which the nitrogen vapor rises, is liquefied at a contacted with the cold head cold surface and then runs along the pipe wall down. This very thin, in the upper part still surrounded by a vacuum envelope tube can be inserted directly into a nitrogen neck tube or suspension tube and thus prevents evaporation of nitrogen or reduces nitrogen losses. However, the helium losses are not affected since only the nitrogen is liquefied again.

Similarly, the re-liquefaction of helium on its own in a helium storage vessel with the two-stage cold head of a cryocooler has already been carried out.

In both cases (nitrogen or helium liquefier), the cold head of the cryocooler is located in an outer jacket which limits a vacuum space. When using multi-stage cryocoolers, it is common that parts of the cold head are surrounded by a radiation shield, which is contacted with a (but not the coldest) cold stage, so that the cold head is well insulated against heat radiation in the low temperature range.

However, as already mentioned above, various conventional cryostat arrangements, such as those used in magnetic systems for high-resolution nuclear magnetic resonance (NMR), do not have just one cryogen: in addition to a container filled with liquid helium and containing the magnet, for example, there is also a liquid Nitrogen cooled radiation shield. Thus, one would have to use both your own helium liquefier and its own nitrogen liquefier, if at the same time the losses of helium and nitrogen should be reduced or a loss-free operation should be achieved. This would mean a considerable additional expenditure on equipment and higher investment and operating costs.

It is therefore an object of the present invention to provide a cooling device with which an existing cryostat arrangement, which contains at least two cryogenic liquids, in particular a cryostat arrangement, which has a superconducting Magnet arrangement comprises, without great expenditure on equipment and without additional disadvantages can be retrofitted so that outwardly no or at least only minor losses of some or all existing cryogenic liquids occur as usual.

Starting from the prior art, this object is achieved in that at least two cold stages of the cold head of the cryocooler for each thermally conductively connected to a heat transmitting device, each in the neck or suspension tubes of a cryostat for storage of at least two different cryogenic Liquids can be introduced.

Such a cooling device offers the following advantages: existing cryostat arrangements, and in particular those containing superconducting magnets, can be retrofitted without (or with only minor) adaptations so that cryogenic loss-free operation is possible even with the use of multiple cryogens with a low outlay on equipment becomes. No redesign of the cryostat is necessary. The additional heat input into the cryostat resulting from the device is modest and relatively predictable with suitable design. The heat transferring devices in which the liquefaction of the cryogens takes place are designed so that they can be introduced without contact into the neck or suspension tubes of the cryostat assembly. The evaporating gas is liquefied thermodynamically efficient, because the steam is not overheated and therefore does not have to be cooled down again to condensing temperature. The coldhead of the cryocooler is so far away from the magnetic center of a superconducting magnet assembly incorporated in the cryostat that disturbances from the magnetic regenerator material to the magnet assembly are much less noticeable than if the coldhead were integrated directly into the cryostat. Conversely, the function of the cryocooler is less affected by the magnetic field of the magnet assembly. If the cryocooler fails or has to be shut down for maintenance, the cryostat assembly, for example, when used to cool a superconducting magnet assembly, still serves its purpose ensures a high level of operational safety. In addition, the user can freely determine the mode of operation (conventional or cryogenic loss-free).

In a particularly preferred embodiment of the cooling device according to the invention, at least one of the heat-transferring devices has a cavity, which is connected to an open line, in particular a pipeline. Through the line, the cryogen vaporized from the liquid tank of the cryostat is led into the cavity at the cold stage, where it is liquefied. The condensate then flows back through the pipeline into the liquid tank of the cryostat. In operation, the heat transfer device in this form corresponds to the heat pipes known from heat technology.

In a further preferred embodiment of the invention, at least one of the heat-transferring devices has a metallic compound which conducts heat very well, liquefied at the end of which cryogen has evaporated from the liquid tank of the cryostat and then flows back again into the liquid bath of the liquid tank of the cryostat. This connection is flanged at the other end to a cold stage of the cold head of the cryocooler. Any combinations of the heat transferring devices are possible. Thus, for example, at the first cold stage of a two-stage cold head, a metallic connection which conducts the heat very well can be flanged, while the second cold stage is connected to a pipeline.

In particular for high-resolution NMR methods, it is advantageous if the cryocooler is a pulse tube cooler, since pulse tube coolers can be operated with particularly low vibration. Pulse tube coolers are also very reliable and low maintenance.

However, the operation of the cooling device is also very well possible with a Gifford-McMahon cooler. A disadvantage of this cryocooler compared to a pulse tube cooler are the larger vibrations. This disadvantage does not apply if soft sealing elements are used between the cryocooler and the cryostat arrangement, as described below.

It is particularly advantageous if at least one connecting line open on both sides is provided, via which the cold head of the cryocooler can be connected to at least one neck or suspension tube of the liquid tank with the cryogenic cryogen into which no heat transferring device is introduced is thermally contacted with at least two cold stages of the cold head and possibly also with a regenerator above the coldest cold stage, and wherein the conduit opens after thermal contact with the coldest cold stage in the cavity mounted on the cold head or is guided along the metallic compound in the liquid tank. The gas in the line is cooled at the cold head of the cryocooler and liquefied at the coldest cold stage, so that due to the resulting suction, a flow in the line through the neck or suspension tubes to the cooling device is formed. The gas flow causes the neck or suspension tubes to be cooled by the gas being heated, thereby ideally completely compensating for the heat input via the neck or suspension tubes. By means of this circulating flow for cooling neck or suspension tubes, the heat input to the cryostat can be further reduced.

In a further development of this embodiment, a valve and / or a pump for regulating the gas flow is provided in the connecting line between the neck or suspension tubes and the cold head. As a result, if necessary, the gas flow throttled or the optimal gas flow can be adjusted when z. B. the suction effect on the cold head is so large that the gas flow is greater than it would be sufficient for the optimal cooling of the suspension or neck tubes.

It is particularly advantageous if helium can be liquefied at a temperature of 4.2 K or at a lower temperature at the coldest cold stage of the cold head, since this offers a multitude of possible uses in the lowest temperature range. Thus, the helium loss and the refilling operations can be reduced or can be achieved at sufficiently large cooling capacity of the cryocooler lossless operation.

Another advantageous aspect involves that at a cold stage of the cold head of the cryocooler liquid nitrogen at 77 K or at a lower temperature can be generated. By using the heat transferring devices in a cryostat arrangement with a container of liquid nitrogen, therefore, the nitrogen losses can be reduced or loss-free operation can be achieved with sufficiently large cooling capacity of the cryocooler.

In an advantageous embodiment, a cold stage of the cold head, which is not the coldest, is thermally conductively connected to the radiation shield at least partially surrounding the cold head. In this way, the heat input is substantially reduced by radiation to the colder components of the cold head.

Moreover, it is advantageous if the heat-transferring device at least partially comes to rest within the outer jacket of the cooling device, ie within the vacuum space. This is particularly relevant to the part of the heat transfer device which is connected to the cold head of the cryocooler. Thus, this part of the heat transfer device is very well insulated against heat conduction to the outside.

Furthermore, it is particularly advantageous if the heat-transmitting device is at least partially surrounded by a first tube in the area outside the outer jacket. This tube serves to heat-isolate the heat-transferring device. It may or may not have the same diameter along its entire length. For example, it may be cheaper by design to choose the smallest possible part for one part of the pipe and a larger one for the rest.

In a preferred embodiment, the first tube surrounding the heat-transferring device is open at one end and connected there to the vacuum space of the outer jacket, while at the other end it is gas-tightly connected to the pipeline or the metallic connection of the heat-transferring device. If the vacuum space of the cooling device is evacuated in this embodiment, the part of the heat-transmitting device surrounded by the first pipe is also under vacuum. The heat transferring device is then very well insulated in this area to the outside against heat conduction.

In another advantageous embodiment, the first tube surrounding the heat-transferring device is connected in a gastight manner at both ends to the pipeline or the metallic connection of the heat-transferring device and provided with a separate connection for evacuation. The interior of the tube can thereby be evacuated and the part of the heat-transferring device surrounded by the tube can be isolated very well to the outside against heat conduction.

It is particularly favorable if the pipeline or the metallic connection of the heat-transferring device is at least partially surrounded by a further, second tube, which is thermally conductively connected to the radiation shield. This tube is arranged within the first tube, which - as just described - the vacuum insulation is used. In this way, the part of the heat transferring device surrounded by the second tube is insulated very well from heat radiation.

It is particularly advantageous if the pipes described above, which surround the heat-transferring device, are at least partially flexible, in particular as bellows.

In addition, it proves to be very favorable, although the heat-transferring device is at least partially flexible, in particular as a bellows or in the form of interwoven wires to wires, is executed. Thus, an embodiment of the cooling device according to the invention can be realized, in which the heat-transferring device is flexible together with the surrounding tubes, which can facilitate their installation in the neck or suspension tubes of a Kryostatanordnung substantially.

In this context, it is also advantageous if the heat-transferring device and the surrounding pipes connect to each other at least one location by means of a gas-tight coupling and separate from each other to let. The coupling is constructed so that the functionality of the heat transmitting device is not affected, including the surrounding pipes. As a result, the attachment of the cooling device is made much easier on a Kryostatanordnung.

In a further embodiment of the invention, it is provided that the cooling device can be attached gas-tight to the cryostat for the storage of cryogenic liquids. This can be done either on the neck or suspension tubes or on the outer shell of the Kryostatanordnung.

Alternatively, and preferably, the cooling device may be external to the cryostat, e.g. on the ceiling or on a separate stand, be attached. The weight of the cooling device then does not load on the cryostat arrangement. This may increase the mechanical stability of the cryostat assembly.

In this context, it is particularly advantageous if a soft, vibration non-transmitting connecting element is provided for sealing between the cooling device and cryostat. In this way it is ensured that - especially for high-resolution NMR methods - no disturbing or only a few oscillations of the cooling device are transferred to the Kryostatanordnung.

Furthermore, it is possible to attach to the cold stages of the cold head of the cryocooler electric heaters. With an excess power, the heaters can be adjusted so that the cryocooler precisely compensates for the incidence of heat on the various containers of the Kryostatanordnung.

The advantages of the cooling device according to the invention are particularly effective when it is part of a Kryostatanordnung.

It is particularly advantageous if the cooling device is used for cooling a superconducting magnet arrangement, in particular if the superconducting magnet arrangement is part of an apparatus for nuclear magnetic resonance, in particular magnetic resonance imaging (MRI) or magnetic resonance spectroscopy (NMR).

Finally, it is possible for an electrical heater to be introduced into the liquid tank via a neck or suspension tube of at least one liquid tank in a cryostat arrangement provided with the cooling device according to the invention. With an excess power of the cooling head integrated in the cold head of the cryocooler thus the pressure in the liquid containers above the ambient pressure and can be kept constant. However, it is also conceivable that the performance of the cryocooler is controlled by its operating frequency and / or the amount of working gas in the cryocooler.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, the features mentioned above and those listed further can be used individually or in any combination. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Fig. 1

eine Kryostatanordnung mit zwei Flüssigkeitstanks für kryogene Flüssigkeiten;

Fig. 2a

eine erfindungsgemäße Kühlvorrichtung mit Wärme übertragenden Vorrichtungen, die einen Hohlraum aufweisen;

Fig. 2b

eine erfindungsgemäße Kühlvorrichtung mit Wärme übertragenden Vorrichtungen, die eine metallische, die Wärme sehr gut leitende Verbindung aufweisen;

Fig. 3

eine in einen Kryostaten eingebaute Kühlvorrichtung gemäß Fig. 2a;

Fig. 4

eine in einen Kryostaten eingebaute Kühlvorrichtung gemäß der vorliegenden Erfindung mit einer Verbindungsleitung, die den Kaltkopf des Kryokühlers mit einem Aufhängerohre eines Flüssigkeitstanks verbindet;

Fig. 5a

eine am Kryostaten befestigte Kühlvorrichtung gemäß der vorliegenden Erfindung;

Fig. 5b

eine an der Raumdecke befestigte Kühlvorrichtung gemäß der vorliegenden Erfindung; und

Fig. 5c

eine an einem Ständer befestigte Kühlvorrichtung gemäß der vorliegenden Erfindung

Show it:

Fig. 1

a cryostat assembly with two liquid tanks for cryogenic liquids;

Fig. 2a

a cooling device according to the invention with heat-transmitting devices having a cavity;

Fig. 2b

a cooling device according to the invention with heat-transmitting devices having a metallic, the heat very good conductive connection;

Fig. 3

a built in a cryostat cooling device of FIG. 2a;

Fig. 4

a cryostat integrated cooling device according to the present invention having a connection line connecting the cryocooler cold head to a suspension tube of a liquid tank;

Fig. 5a

a cryostat-mounted cooling device according to the present invention;

Fig. 5b

a ceiling-mounted refrigerator according to the present invention; and

Fig. 5c

a mounted on a stand cooling device according to the present invention

Fig. 1 shows a schematic representation of a cryostat 1 with a magnet assembly 5 , as is customary for MR applications used. The cryostat 1 comprises a helium-filled liquid tank 2a which is connected to suspension tubes 3a, with an outer casing 4 of the cryostat 1, and in which a magnet assembly 5 is arranged. A further liquid tank 2 b is arranged around the liquid tank 2 a, which contains nitrogen and is connected to the suspension tubes 3 b with the outer jacket 4 of the cryostat 1. The liquid tank 2b with nitrogen is thermally contacted with the hanger ears 3a. Between the two liquid tanks 2a, 2b, an exhaust-cooled radiation shield 6 is arranged, which in turn is thermally contacted with the suspension tubes 3a.

FIG. 2 a shows an embodiment of a cooling device 7 according to the invention. The cooling device comprises an outer jacket 8 , which delimits a vacuum space 9 , and a cold head 10 of a cryocooler, which has at least two cold stages 11, 12 and which is at least partially surrounded by a radiation shield 13 . The cold stages 11, 12 of the cold head 10 are each thermally conductively connected to a heat transfer device 14a, 14b . The heat-transferring devices 14a, 14b each have a cavity 15a, 15b , wherein the cavities 15a, 15b are each connected to a pipeline 16a, 16b .

FIG. 2b shows an alternative embodiment of the cooling device 7 according to the invention, in which the heat-transferring devices 14a, 14b have connections 17a, 17b which can conduct heat very well. These compounds may, for example, be in the form of cold fingers, which are generally in the form of metal rods. Such a metal bar should have the greatest possible Have cross-sectional area, so that the temperature difference across the rod remains as small as possible.

The piping 16a, 16b may be introduced into the hanger pipes 3a, 3b from the liquid tanks 2a, 2b of a cryostat 1. Fig. 3 shows a cooling device 7 according to the invention in the installed state. The pipelines 16a, 16b are located here in the cryogenic vapor above the liquid surface of the cryogens 18a, 18b located in the liquid tanks 2a, 2b. As shown in FIGS. 2a, 2b and 3, the heat-transferring devices 14a, 14b are each thermally conductively connected to a cold stage 11, 12 of the cryocooler. The cryogens 18a, 18b vaporized from the liquid tanks 2a, 2b of the cryostat 1 are passed through the conduits 16a, 16b into the cavity 15a, 15b at the respective refrigeration stage 12, 11 where the cryogens 18a, 18b condense and are thus liquefied then flow back into the liquid tanks 2a, 2b of the cryostat 1 through the pipes 16a, 16b. Alternatively, the helium vapor can also be liquefied at the end of a metallic, very good heat conductive connection 17a, 17b, which is contacted with the cold head 10, as shown in Fig. 2b.

In this case, the cryogen 18b boiling at a higher temperature is liquefied from the liquid tank 2b at the first cold stage 11 of the cold head 10, while the liquefaction of the lower-boiling cryogen 18a takes place at the second, colder cold stage 12 of the cold head 10. The invention also includes cooling devices with a multi-stage cold head 10, so that in principle any number of cryogens, corresponding to the number of cold stages of the cold head 10, can be liquefied.

In order to insulate the heat-transferring devices 14a, 14b from heat input, they are surrounded by a first tube 19a, 19b , which is connected to the vacuum space 9 of the outer jacket 8 of the cooling device 7 and can be evacuated together with the vacuum space 9 (see FIG , 2 B). To improve the thermal insulation against heat radiation penetrating from the outside, a second tube 20 is arranged inside the first tube 19a and is thermally conductively connected to the radiation shield 13. The diameter of the first Pipe 19b is not the same in Fig. 2a, 2b and Fig. 3 over the entire length. It may be necessary for the tube at the closed end to be reduced to a smaller diameter so that it can be inserted without contact into the suspension tube 3b of the liquid tank 2b. In order to make flexible the connection between the first tube 19b and the outer shell 8 of the cooling device 7, this is designed as a bellows. A bellows can also be inserted in each case between the first tube 19a and the outer jacket 8 and in a section of the second tube 20. Flexible connectors 21a, 21b (such as wire strands braided into strands) can be used to make the metallic connection 17a, 17b shown in Fig. 2b movable. With an excess power of the cryocooler, additional heaters (not shown) may be attached to the cold stages 11, 12 of the cold head 10 of the cryocooler. Alternatively or additionally, with an excess power of the cryocooler, the pressure in the liquid tanks 2a, 2b for the cryogens 18a, 18b with heaters 22a, 22b in the liquid tanks 2a, 2b, for example via still free neck or suspension tubes 3c, 3d be introduced, kept constant.

4 shows an advantageous variant of the cooling device according to the invention, in which a free neck or suspension tube 3c of the cryostat 1 via a line 23 open on both sides after thermal contact with the cold stages 11, 12 of the cold head 10 with the cavity 15a and thus also with the liquid tank 2a is connected. Such a connection can also be realized with a plurality of free neck or suspension tube 3c. The lines coming from the suspension tubes 3c are then first taken in a single line 23. This line 23 is then passed through the outer jacket 8 of the cooling device 7, which contains the cold head 10 and by means of the heat exchanger 24b, 24a with at least two cold stages 11, 12 of the cold head 10 and possibly also with a regenerator tube 25 above the coldest cold stage 12, z. B. by wrapping the regenerator tube 25, thermally contacted. After contact with the coldest cold stage 12, the conduit 23 opens into the cavity 15a mounted on the cold head 10 or is guided along the metallic connection 17a into the liquid tank 2a for the cryogen 18a (helium). The gas located in the conduit 23 is cooled at the cold head 10 and liquefied at the coldest cold stage 12, so that due to the resulting suction, a flow in the conduit 23 through the suspension tube 3c toward the cooling device 7 is formed. The gas flow causes the suspension tube 3c is cooled by the heating gas and thus, ideally, the heat input via the suspension tube 3c completely compensated, or at least reduced. Overall, the performance of the cryocooler decreases slightly due to the additional load, but the gain due to the lower incidence of heat is greater than the loss of cooling capacity. For systems with more massive neck or suspension tubes 3c, under certain circumstances a less powerful cryocooler can be used. It is conceivable that the heat transfer devices 14a, 14b (heat pipes or cold fingers) to make two or more parts, whereby they can be separated by means of gas-tight couplings (not shown). This makes a simpler installation and removal possible. In order to regulate the gas flow through the conduit 23 and thereby achieve an optimal gas flow, a valve 26 and a pump 27 are provided in the conduit 23. In principle, however, it is sufficient to equip the line 23 only with such a device (valve 26 or pump 27) or to leave entirely without such devices. In the embodiment presented in FIG. 4, as in the embodiment according to FIG. 3, heaters 22a, 22b are provided in the liquid tank 2a, 2b. For reasons of clarity, however, the connections were not shown in FIG. 4.

5a to 5c show various possibilities for fixing the cooling device 7. The vacuum container in which the cold head 10 of the cryocooler is either directly on the outer shell 4 of the cryostat 1, as shown in Fig. 5a, or externally, for example the ceiling 28 (Figure 5b) or on a separate stand 29 (Figure 5c). When attached to the cryostat 1, a seal 30 must be provided. Between the vacuum space 9 and the outer shell 4 of the cryostat 1, only soft sealing elements 31a, 31b are used with external suspension. This has the consequence that vibrations of the cryocooler are not transmitted or only very attenuated to the cryostat 1. This proves to be particularly favorable when the cooling device 7 is used for cooling a Kryostatanordnung containing a superconducting magnet assembly 5, in particular, when the superconducting magnet assembly 5 is part of a nuclear magnetic resonance apparatus, in particular Magnetic Resonance Imaging (MRI) or Magnetic Resonance (NMR) spectroscopy. Accordingly, with the cooling device according to the invention, high-resolution NMR methods can be realized.

In summary, results in a cooling device that allows existing Kryostatanordnungen, and in particular those containing superconducting magnets, without (or with only minor) adjustments so retrofit that even when using multiple cryogenics with a low equipment cost, a cryogenverlustfreier operation is possible ,

LIST OF REFERENCE NUMBERS

1

cryostat

2a, 2b

liquid tanks

3a, b, c, d

suspension tubes

4

Outer jacket of the cryostat

5

magnet assembly

6

Radiation shield of the cryostat

7

cooler

8th

Outer jacket of the cooling device

9

vacuum space

10

cold head

11

first cold stage

12

second cold stage

13

Radiation shield of the cooling device

14a, b

Heat transferring device

15a, b

cavity

16a, b

pipeline

17a, b

connection

18a, b

cryogenically

19a, b

first pipe

20

second pipe

21a, b

connecting element

22 a, b

heater

23

open line

24a, b

Heat exchangers

25

regenerator

26

Valve

27

pump

28

ceiling

29

stand

30

poetry

31a, b

sealing

Claims (26)

A cooling device (7) for the re-liquefaction of cryogenic gases, with an outer jacket (8) delimiting a vacuum space (9) and a built-in cold head (10) of a cryocooler having at least two cold stages (11, 12) and at least partially surrounded by a radiation shield (13),
characterized,
in that at least two cold stages (11, 12) of the cold head (10) are in each case thermally conductively connected to a heat-transmitting device (14a, 14b), each in neck or suspension tubes (3a, 3b) of a cryostat (1) Storage of at least two different cryogenic liquids (18a, 18b) can be introduced. Cooling device (7) according to claim 1, characterized in that at least one of the heat-transferring devices (14a, 14b) has a cavity (15a, 15b) which is connected to an open conduit, in particular a pipeline (16a, 16b), which directs the cryogen (18a, 18b) evaporated from a liquid tank (2a, 2b) of the cryostat (1) into the cavity at the cold stage, where it is liquefied, and then through the pipeline (16a, 16b) into the liquid tank (16). 2a, 2b) of the cryostat (1) to flow back. Cooling device (7) according to one of the preceding claims, characterized in that at least one of the heat-transferring devices (14a, 14b) has a metallic connection (17a, 17b) which conducts heat very well, at the end thereof from the liquid tank (2a, 2b) of the cryostat (1) vaporized cryogen (18a, 18b) is liquefied and then returned to a Liquid bath of the liquid tank (2a, 2b) of the cryostat (1) flows back. Cooling device (7) according to one of the preceding claims, characterized in that the cryocooler is a pulse tube cooler. Cooling device (7) according to one of claims 1 to 3, characterized in that the cryocooler is a Gifford-McMahon cooler. Cooling device (7) according to one of the preceding claims, characterized in that at least one open on both sides connecting line (23) is provided, via which the cold head (10) of the cryocooler with at least one neck or hanger ear (3c) of the liquid tank (2a) the low boiling cryogen (18a) into which no heat transferring device (14a) is introduced,
wherein the line (23) with at least two cold stages (11, 12) of the cold head (10) and possibly also with a regenerator tube (25) above the coldest cold stage (12) is thermally contacted, and wherein the conduit (23) by thermal Contact with the coldest cold stage (12) in the cold head (10) mounted cavity (15a) opens or along the metallic connection (17a) in the liquid tank (2a) is guided. Cooling device (7) according to claim 6, characterized in that in the connecting line (23) between the neck or suspension tubes (3c) and cold head (10), a valve (26) and / or a pump (27) is inserted. Cooling device (7) according to one of the preceding claims, characterized in that at the coldest cold stage (12) of the Kryokühler's helium can be liquefied at a temperature of 4.2 K or at a lower temperature. Cooling device (7) according to one of the preceding claims, characterized in that at a cold stage (11) of the cold head (10) of the cryocooler liquid nitrogen at 77 K or at a lower temperature can be generated. Cooling device (7) according to one of the preceding claims, characterized in that a cold stage (11) of the cold head of the cryocooler, which is not the coldest, with the cold head (10) at least partially surrounding radiation shield (13) is thermally conductively connected. Cooling device (7) according to one of the preceding claims, characterized in that the heat-transmitting device (14a, 14b) is at least partially disposed within the outer jacket (8). Cooling device (7) according to one of the preceding claims, characterized in that the heat-transferring device (14a, 14b) in the region outside the outer jacket (8) is at least partially surrounded by a first tube (19a, 19b). Cooling device (7) according to claim 12, characterized in that the first pipe (19a, 19b) surrounding the heat-transferring device (14a, 14b) is open at one end and connected there to the vacuum space (9) of the outer jacket (8), while at the other end it is gas-tightly connected to the pipeline (16a, 16b) or the metallic connection (17a, 17b) of the heat-transferring device (14a, 14b). Cooling device (7) according to claim 12, characterized in that the heat transfer device (14a, 14b) surrounding the first tube (19a, b) at both ends gas-tight with the pipe (16a, 16b) or the metallic connection (17a, 17b ) of the heat transferring device (14a, 14b) and provided with a separate port for evacuation. Cooling device (7) according to one of the preceding claims, characterized in that the pipeline (16a) or the metallic connection (17a) of the heat-transferring device (14a) is at least partially surrounded by a second tube (20) which communicates with the radiation shield (16). 13) is thermally conductively connected, wherein the second tube (20) within the first tube (19 a) is arranged. Cooling device (7) according to one of claims 12 to 15, characterized in that the heat transferring device (14a, 14b) surrounding tubes (19a, 19b, 20) are at least partially flexible, in particular as a bellows executed. Cooling device (7) according to one of the preceding claims, characterized in that the pipe (16a, 16b) or the metallic, the heat very good conductive connection (17a, 17b) of the heat transfer device (14a, 14b) at least partially flexible, in particular as a bellows or in the form of interwoven wires to wires, is executed. Cooling device (7) according to any one of claims 12 to 17, characterized in that the heat-transferring device (14a, 14b) including the surrounding tubes (19a, 19b, 20) connect and disconnect at least one location by means of a gas-tight coupling , Cooling device (7) according to one of the preceding claims, characterized in that the cooling device (7) on the cryostat (1) for storing cryogenic liquids (18a, 18b) can be attached in a gastight manner. Cooling device (7) according to one of claims 1 to 18, characterized in that the cooling device (7) outside the cryostat (1) can be fastened. Cooling device (7) according to claim 20, characterized in that for sealing between the cooling device (7) and cryostat (1) a soft, vibration non-transmitting connecting element (31 a, 31 b) is provided. Cooling device (7) according to one of the preceding claims, characterized in that electrical heaters are attached to the cooling stages (11, 12) of the cryocooler. Cryostat configuration characterized by a cooling device (7) according to any one of the preceding claims. Cryostat arrangement according to claim 23, characterized by a superconducting magnet arrangement (5), wherein the cooling apparatus (7) serves to cool the superconducting magnet arrangement (5). Cryostat arrangement according to claim 24, characterized in that the superconducting magnet arrangement (5) is part of an apparatus for nuclear magnetic resonance, in particular magnetic resonance imaging (MRI) or magnetic resonance spectroscopy (Nuclear Magnetic Resonance, NMR). Cryostat arrangement according to one of Claims 23 to 25, characterized in that an electric heater (22a, 22b) can be introduced into the liquid tank (2a, 2b) via a suspension or neck tube (3c) of at least one liquid tank (2a, 2b).

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