Pre-cooling circuit and method for helium cooling supply

Abstract

A pre-cooling circuit is provided for the helium cooling supply to at least one load (72) to be cooled, comprising a feed pipe (30) and a return pipe (32) interconnected via a low-temperature discharge device (10) designed for heat exchange with the at least one load to be cooled, a helium refrigeration device (2) designed for discharging heat to the environment, compressing the returning helium and directing the compressed helium to the feed pipe, a first cooling tank vessel (34) and a second cooling tank vessel (36), the feed pipe passing through a first heat exchanger (40) arranged in the bottom space of the first cooling tank vessel (34) and then in the direction of the low-temperature discharge device, the second cooling tank vessel (36) and the feed pipe passing through a first heat exchanger (40) arranged in the bottom space of the first cooling tank vessel (34) and then through a second cooling tank vessel (36) in the direction of the low-temperature discharge device. a first cooling tank vessel (34) and a second cooling tank vessel (36) extending through a second heat exchanger (42) disposed in the bottom space of the first cooling tank vessel (36), the top space of the first cooling tank vessel being connected to the helium refrigeration system via a return supply pipe (18), and an ejector (50) having a driving flow opening connected to the return pipe, a suction opening connected to the top space of the second cooling tank vessel, and a discharge opening connected to the top space of the first cooling tank vessel, the ejector designed to suck helium vapor from the second cooling tank vessel and raise it to the pressure of the first cooling tank vessel by using the helium flowing back from the cryogenic discharge device as a driving flow.

Description

[Technical field]

[0001] The present invention relates to a pre-cooling circuit and method for providing helium cooling supply to at least one load to be cooled. [Background technology]

[0002] In fundamental research, such as for cooling quantum computers, cooling temperatures well below 1 K are required. For this, according to the current state of the art, mixed cryostats are used, which are precooled in the range of 3-4 K with pulse tube, Stirling or Gifford-McMahon refrigerators. The low precooling temperature is a prerequisite for the efficiency of the mixed cryostats. The cooling power of these precoolers, including an additional cooling power of 50 K as shield cooling, is in the range of only a few watts. Therefore, mixed cryostats are equipped, for example, with two pulse tube refrigerators each.

[0003] With the progress of research, especially in quantum computers, the power requirements for pre-cooling have increased significantly. However, the efficiency of the above-mentioned pre-cooling systems is very low. This is not particularly important for relatively small applications, where the generally high initial cost of the mixing cryostat becomes a determining factor. However, if several pre-cooling systems are deployed, the resulting operating costs become significant, since the energy consumption rises linearly. Moreover, this problem becomes even more severe if several mixing cryostats are operated, for example for several quantum computers.

[0004] Thus, there is a need for an efficient pre-cooling system that allows one or more mixing cryostats to refrigerate at the lowest possible temperatures, particularly helium refrigeration, and, especially in the case of multiple mixing cryostats, it is desirable to have variable cooling supply or capacity. DISCLOSURE OF THEINVENTION

[0005] This problem is solved by a pre-cooling circuit and a method for helium cooling supply of at least one load to be cooled with the features of the independent claims. The dependent claims relate to preferred embodiments.

[0006] A (closed) pre-cooling circuit for providing helium cooling supply to at least one load to be cooled comprises a feed pipe and a return pipe, which are interconnected via a low-temperature discharge device designed to exchange heat with at least one load to be cooled, a helium refrigeration device designed to discharge heat to the environment, compress the returning helium and guide the compressed helium to the feed pipe, a first cooling tank vessel and a second cooling tank vessel, the feed pipe running through a first heat exchanger arranged in the bottom space of the first cooling tank vessel and then through a second heat exchanger arranged in the bottom space of the second cooling tank vessel in the direction of the low-temperature discharge device, a first cooling bath vessel and a second cooling bath vessel, the head space of the first cooling bath vessel being connected to a helium refrigeration system via a return supply pipe to supply the helium to the helium refrigeration system, and an ejector having a driving flow opening connected to the return pipe, a suction opening connected to the head space of the second cooling bath vessel, and a discharge opening connected to the head space of the first cooling bath vessel, the ejector being designed to suck in helium vapor from the second cooling bath vessel and raise it to the pressure of the first cooling bath vessel by using the helium flowing back from the cryogenic discharge device through the return pipe as a driving flow. The term "bottom space" is also known as "sump space".

[0007] The pre-cooling circuit according to the invention allows the helium compressed by the compressor system to be introduced to the load in a supercritical state, thus avoiding the generation of a difficult-to-control two-phase mixture (gaseous and liquid helium). In this case, the helium still has sufficient pressure even after passing the load in order to raise the helium vapor of the second cooling tank vessel to the pressure of the first cooling tank vessel by means of an ejector. In short, the use of a multi-stage tank cooling section is realized, so that low temperatures can be achieved.

[0008] Preferably, the at least one load to be cooled is a mixed cryostat.

[0009] Preferably, a secondary return line is provided, which is branched off from the return line downstream of the load, runs through a fourth heat exchanger arranged in the bottom space of the first cooling tank vessel and opens into the return line upstream of the drive flow opening of the ejector, in which case it is further preferred that at least one valve is arranged in the secondary return line and / or in the return line parallel to the secondary return line to control the flow through the secondary return line, which allows partial load operation of the pre-cooling circuit, so that in particular a variable number of loads can be supplied with low temperature.

[0010] Preferably, the pre-cooling circuit includes a third cooling tank vessel, in which the feed pipe runs from the second cooling tank vessel through a third heat exchanger arranged in the bottom space of the third cooling tank vessel, and the head space of the third cooling tank vessel is connected to a vacuum pump designed to pump helium vapor from the head space and supply it to a helium refrigerator, preferably provided with a compressor to increase the pressure level of the pumped helium to the pressure level of the helium refrigerator, thereby achieving a lower temperature.

[0011] Preferably, the first cooling bath vessel is designed to contain liquid helium in the bottom space in equilibrium with helium vapor in the head space, with a second equilibrium pressure preferably in the range of 0.4 to 0.65 bar, and optionally, the third cooling bath vessel is designed to contain liquid helium in the bottom space in equilibrium with helium vapor in the head space, with a third equilibrium pressure preferably in the range of 0.1 to 0.3 bar. In the two-stage case, temperatures of up to 3.6 K can be achieved. In the three-stage case, temperatures below 3 K can be achieved.

[0012] Preferably, the helium refrigerator includes at least one compressor and is designed to compress the helium to a pressure in the range of 7 to 18 bar, preferably in the range of 10 to 15 bar. The high pressure can prevent the formation of a two-phase helium mixture.

[0013] Preferably, the helium refrigeration system includes a heat exchanger system, in which case the returning helium is guided through the heat exchanger system in a counter-flow direction to the compressed helium.

[0014] More preferably, the cryogenic discharge device includes a shield circulation system and the helium refrigerator is designed to provide a helium shield flow, whereby the helium shield flow is guided from the helium refrigerator to the shield circulation system and from the shield circulation system back to the helium refrigerator, thereby providing external shield cooling of the load.

[0015] Advantageously, the low temperature discharge device is designed for heat exchange with a number of loads to be cooled, in which case the loads can be connected and disconnected independently of one another to the feed and return pipes, i.e. a variable number of loads is realized.

[0016] The cryogenic apparatus according to the invention comprises a (closed) pre-cooling circuit according to the invention and at least one mixing cryostat connected to a cryogenic discharge device as at least one load to be cooled, the cryogenic discharge device being preferably designed such that a feed pipe and a return pipe are connected to at least one helium bath of the at least one mixing cryostat.

[0017] In the cryogenic method according to the invention, at least one sample is placed in at least one mixing cryostat of the cryogenic apparatus according to the invention and cooled to a temperature below 1K.

[0018] A method according to the invention for providing a helium cooling supply to at least one load to be cooled comprises the steps of compressing the returning helium, guiding the compressed helium through a first cooling tank and a subsequent second cooling tank to obtain helium in a supercritical state, guiding the helium in the supercritical state to a cryogenic discharge device for heat exchange with at least one load to be cooled, guiding the returning helium flow from the cryogenic discharge device to a driving flow opening of an ejector, sucking in a second helium vapor in equilibrium with the second cooling tank by means of the ejector and feeding it to a first helium vapor in equilibrium with the first cooling tank, and directing the first helium vapor to obtain the returning helium flow.

[0019] Preferably, the method further comprises branching at least a portion of the return flow to form a secondary return flow, and directing the secondary return flow through the first cooling tank and subsequently into the return flow.

[0020] Among other things, the method includes directing the compressed helium through a third cooling vessel downstream from the second cooling vessel.

[0021] For simplicity, reference will be made herein to "cooling supply" or "cold temperature output" by the pre-cooling circuit, or to "cooling being supplied to the load" or "cold temperature being output to the load", which will be understood to mean that heat from the load is absorbed or rejected, respectively, by the pre-cooling circuit (by means of the respective heat exchange device).

[0022] The term "pipe" or "guide" relates to a pipe for a fluid, in particular helium, especially gaseous helium. That is, a tube means a tube. Similarly, the term "connected" relates to the existence of a fluid connection via a (tube) pipe. In both cases, valves may be provided to influence or control the fluid flowing through the pipe.

[0023] The present invention will now be described in detail with reference to the accompanying drawings which illustrate the invention and its features relative to the prior art. [Brief description of the drawings]

[0024] [Figure 1] 1 shows a pre-cooling circuit with two-stage bath cooling according to a preferred embodiment of the present invention. [Diagram 2] 1 shows a pre-cooling circuit with a variably designed two-stage bath cooling section according to another preferred embodiment of the present invention. [Diagram 3] 4 shows a pre-cooling circuit with three-stage bath cooling according to another preferred embodiment of the present invention. [Figure 4] 1 shows a pre-cooling circuit with a variably designed three-stage bath cooling section according to another preferred embodiment of the present invention. [Diagram 5] 1 shows a cryogenic discharge device connected to a load to be cooled, in particular a mixing cryostat. [Figure 6] 1 illustrates a method according to the present invention according to a preferred embodiment. EMBODIMENTS OF THE PRESENTINVENTION

[0025] 1 shows a pre-cooling circuit 100 with two-stage bath cooling according to a preferred embodiment of the invention. The pre-cooling circuit comprises a helium refrigeration device 2, which comprises a compressor system 4 or a compressor system and a heat exchanger system 6, and a bath cooling system 8, which comprises a first cooling bath vessel 34 and a second cooling bath vessel 36. Together with a low-temperature discharge device 10, which is designed for heat exchange with at least one load to be cooled, a closed pre-cooling circuit (for the load to be further cooled) is formed, in which helium is used as the refrigerant.

[0026] The compressor system 4 comprises at least one compressor 16, which compresses the helium flowing back through a return supply line 18. The pressure of the returning helium is typically about 1.05 bar. The pressure of the compressed helium is typically in the range of 7 to 18 bar, in particular 10 to 15 bar. Furthermore, in or on the compressor system, a heat rejection device, not shown in detail, may be provided, which is able to reject heat to the surroundings.

[0027] Compressed helium is supplied via supply line 20 to feed line 30. Return supply line 18 and supply line 20 extend through heat exchanger system 6 so that heat exchange is achieved between the returning helium and the compressed helium flowing in the countercurrent direction.

[0028] Furthermore, one or more turbines 22 may be provided in the refrigeration device 2, by means of which compressed helium taken from the supply line at a point in the heat exchanger system 6 is reduced in pressure to the pressure level of the supply line and is again fed at a point (possibly another point) in the heat exchanger system to the helium flowing back in the return supply line, thus forming, in principle, a Brayton cycle.

[0029] The feed pipe 30 running through the bath cooling system 8 firstly passes through a first heat exchanger 40 arranged in the bottom space of the first cooling bath vessel 34 and then through a second heat exchanger 42 arranged in the bottom space of the second cooling bath vessel 36. Each cooling bath vessel is designed such that in the bottom space there is a helium bath, i.e. helium in liquid form, and in the top space there is helium vapor in equilibrium with the liquid helium in the bottom space. This means that the pressure in the cooling bath vessel, i.e. the equilibrium pressure, can be associated with a corresponding temperature (corresponding to the vapor pressure curve). In the first cooling bath vessel 34 the pressure is in particular about 1.25 bar, i.e. the pressure is in the range of 1.0 bar to 1.5 bar. In the second cooling bath vessel 36 the pressure is in particular about 0.5 bar, i.e. the pressure is in the range of 0.4 bar to 0.65 bar. The bottom space of the first cooling tank vessel 34 is connected via a pipe to the second cooling tank vessel 36 or its top space, thereby allowing helium to be supplied to the second cooling tank vessel 36 or its top space, in which case a valve 54 is provided in the pipe so that this helium supply can be controlled.

[0030] Overall, the two-stage bath cooling (in the first and second cooling bath vessels 34, 36) allows the temperature of the helium supplied to the cryogenic discharge device 10 to be reduced to below 3.6K.

[0031] Helium is supplied to the cryogenic discharge device 10 via a feed line 30 and, after being used by the cryogenic discharge device to cool at least one load, the helium is conducted from the cryogenic discharge device to a return line 32 .

[0032] The return line 32 is connected to the ejector 50, so that the helium guided back from the cryogenic discharge device via the return line can be used as a driving flow in the ejector, so that helium vapor can be sucked in from the second cooling bath vessel 36, brought up to the pressure of the first cooling bath vessel 34 and discharged into the first cooling bath vessel 34. Correspondingly, the driving flow opening of the ejector is connected to the return line, the suction opening of the ejector is connected (via a tube) to the head space of the second cooling bath vessel and the discharge opening of the ejector is connected (via a tube) to the head space of the first cooling bath vessel. In this way, further liquefaction of helium can be avoided in the pre-cooling circuit. The connecting pipe between the head space of the second cooling bath vessel 36 and the ejector 50 or its suction opening is provided, inter alia, with a valve 52 in order to be able to control the vapor flow from the head space of the second cooling bath vessel to the ejector.

[0033] The head space of the first cooling bath vessel 34 is connected to the return supply pipe 20 of the refrigeration system 2 so that the helium circulation is closed.

[0034] Furthermore, a shield cooling flow can be provided which can be used by the load for external cooling. For this purpose, for example, a shield flow feed pipe 80 and a shield flow return pipe 82 are provided, via which compressed helium taken from the heat exchanger system 6 or the supply pipe 18 is guided to the load, and via the shield flow return pipe 82 helium is fed back to the heat exchanger system 6, for example via the turbine 22.

[0035] The components of the pre-cooling circuit, except for the compressor system 4, are located inter alia within the freezer box 12. That is to say, the components of the pre-cooling circuit, except for the compressor system 4, are surrounded by insulated walls. Similarly, the piping to and from the cryogenic discharge device 10 are also surrounded by insulated walls, each of which is indicated by a dashed line.

[0036] Figure 2 shows a pre-cooling circuit 200 with a variably designed two-stage bath cooling section according to another preferred embodiment of the invention. This embodiment largely corresponds to the embodiment shown in Figure 1. Therefore, substantially only different or additional elements will be described below, without repeating the description of elements already described in connection with Figure 1.

[0037] 1, here there is additionally provided an auxiliary return pipe 58. The auxiliary return pipe is connected to a branch of the return pipe 32 so that a part of the helium coming from the cryogenic discharge device 10 can be diverted from the return pipe. The auxiliary return pipe and the return pipe are provided with valves 60, 62 in order to be able to control the helium flow into the auxiliary return pipe or into the return pipe.

[0038] The secondary return line 58 is guided through a fourth heat exchanger 46 arranged in the bottom space of the first cooling tank vessel 34 and subsequently rejoins the return line 32 upstream of the ejector 50. By cooling a portion of the helium guided through the secondary return line, the temperature of the drive flow opening of the ejector can be influenced, which allows for an adjustment of the operating point of the ejector 50 (indirectly by means of valves 60, 62 in the secondary return line or in the return line). The pre-cooling circuit can thus be used with various loads, since the helium flow is essentially determined by the operating point of the ejector. For example, a number of different loads to be cooled can be supplied with low temperature via the low temperature discharge device 10.

[0039] Figure 3 shows a pre-cooling circuit 300 with a three-stage bath cooling section according to another preferred embodiment of the invention. This embodiment largely corresponds to the embodiment shown in Figure 1. Therefore, substantially only different or additional elements will be described below, without repeating the description of elements already described in connection with Figure 1.

[0040] This embodiment additionally includes a third cooling tank vessel 38, in which the feed pipe 32 is guided through a third heat exchanger 44, which is arranged in the bottom space of the third cooling tank vessel 38, downstream of the second cooling tank vessel 36. In the third cooling tank vessel 38 too, liquid helium in the bottom space and helium vapor in the top space are in equilibrium. The pressure is in particular about 0.2 bar, i.e. the pressure is in the range from 0.1 bar to 0.3 bar. In this way, a further temperature reduction of the helium supplied to the cryogenic discharge device via the feed pipe can be achieved. For example, temperatures below 3 K can be achieved.

[0041] A vacuum pump 64 is connected via a pipe to the head space of the third cooling bath vessel 38 and is designed to pump helium vapor from the head space. The pumped helium is guided to the return supply pipe 18 of the refrigeration system 2 via a pipe 68 in which a compressor 66 is located. The compressor is used to increase the pressure of the helium to the level in the return supply pipe.

[0042] The bottom space of the first cooling tank vessel 34 is connected via a tube to the third cooling tank vessel 38 or its top space so that helium can be supplied to the third cooling tank vessel 38 or its top space, in which case a valve 56 is provided in the tube so that this helium supply can be controlled.

[0043] It is likewise possible to combine the embodiments of figures 2 and 3, i.e. in the embodiment according to figure 2, it is also possible to additionally provide a third cooling stage according to figure 3, i.e. a third cooling tank vessel, a vacuum pump, a compressor and corresponding pipes / valves. A corresponding pre-cooling circuit 400 is shown in figure 4, all elements of which have already been described in connection with figures 1 to 3.

[0044] Figure 5 shows a cryogenic discharge device 10 connected to a load 72 to be cooled, in particular a mixed cryostat. This cryogenic discharge device 10 can in particular be used in any of the embodiments corresponding to figures 1, 2 and 3. The correspondence of the connections is represented in the figures by arrows marked with the letters "A", "B", "C" and "D".

[0045] The cryogenic discharge device 10 includes a number of (here, for example, three) valve groups 74, each of which is provided with a line to an individual load or load group 72, which is connected to the feed line 32 or the return line 34. The lines are provided with valves in the valve groups so that helium can be directed from the feed line to the individual loads and from the loads to the return line in a targeted manner. That is, the loads 72 can be connected and disconnected independently of each other to the feed line ("A") and the return line ("B"). This is particularly advantageous in connection with the pre-cooling circuits 200, 400 of Figures 2 and 4, which realize partial load operation.

[0046] Valve group 74 is likewise provided with pipes and valves for the shield cooling flow, through which it can be guided from a shield flow feed pipe ("C") to the load and back to a shield flow return pipe ("D"), thus forming a shield circulation system.

[0047] In particular, here too one or more freezing boxes are provided, inside which the valve groups and also in particular the load, in particular the mixing cryostat, are arranged.

[0048] Figure 6 shows the method according to the invention according to a preferred embodiment. The individual steps are part of a circulation through which helium passes. In step 602, the returning helium is compressed (for example using a compressor system). The pressure achieved here is in the range of 7 to 18 bar, preferably 10 to 15 bar.

[0049] In step 604, the compressed helium is guided through a first cooling tank and a subsequent second cooling tank to obtain helium in a supercritical state. In preferred step 606, after passing through the second cooling tank, the helium is guided to a third cooling tank, which is in equilibrium with the corresponding first, second or third helium vapor. In this case, the equilibrium pressure corresponds to the pressure previously described in relation to the first, second or third cooling tank vessel, respectively.

[0050] In step 610, the supercritical helium is directed to a cryogenic discharge device where it exchanges heat with at least one load to be cooled.

[0051] A return flow of helium is directed from the cryogenic ejector to a motive flow opening of the ejector, step 612. Optionally, at least a portion of the return flow is branched to form a secondary return flow, step 614, which is directed through a first cooling tank and subsequently to the return flow.

[0052] In step 616, a second helium vapor in equilibrium with the second cooling reservoir is drawn in by an ejector and fed to the first helium vapor in equilibrium with the first cooling reservoir.

[0053] In step 618, the first helium vapor is induced to obtain the flow-back helium compressed in step 602, thereby completing the circulation system.

Claims

1. In a precooling circuit (100, 200, 300, 400) for performing a helium cooling supply to at least one load (72) to be cooled, a feed pipe (30) and a return pipe (32) which are interconnected via a low-temperature discharge device (10) designed to effect heat exchange with at least one load to be cooled, a helium refrigeration device (2) designed to release heat to the surroundings, compress the returned helium, and guide the compressed helium to the feed pipe, a first cooling tank container (34) and a second cooling tank container (36), wherein the feed pipe passes through a first heat exchanger (40) arranged in a bottom space of the first cooling tank container (34) and then extends through a second heat exchanger (42) arranged in a bottom space of the second cooling tank container (36) in the direction of the low-temperature discharge device, and a top space of the first cooling tank container is connected to the helium refrigeration device via a return supply pipe (18), whereby the returned helium is supplied to the helium refrigeration device, the first cooling tank container (34) and the second cooling tank container (36), an ejector (50) having a drive flow opening connected to the return pipe, a suction opening connected to a top space of the second cooling tank container, and a discharge opening connected to the top space of the first cooling tank container, the ejector (50) being designed to use the helium flowing back from the low-temperature discharge device through the return pipe as a drive flow to suck helium vapor from the second cooling tank container and raise the pressure to that of the first cooling tank container, a precooling circuit (100, 200, 300, 400), characterized by comprising.

2. On the downstream side of the load, a sub-return pipe (58) branched from the return pipe (32) extends through a fourth heat exchanger (46) arranged in a bottom space of the first cooling tank container (34) and opens into the return pipe upstream of the drive flow opening of the ejector, At least one valve (60, 62) is arranged in the sub-return pipe and / or the return pipe parallel to the sub-return pipe to control the flow passing through the sub-return pipe, the precooling circuit (200, 400) according to claim 1.

3. Including a third cooling tank container (38), the feed pipe (30) extends through a third heat exchanger (44) disposed in the bottom space of the third cooling tank container following the second cooling tank container, the top space of the third cooling tank container is connected to a vacuum pump, the vacuum pump is designed to suck up helium vapor from the top space and supply it to the helium refrigeration device, and a compressor (66) is provided to raise the pressure level of the sucked-up helium to the pressure level of the helium refrigeration device. The precooling circuit (300, 400) according to claim 1 or 2 is characterized by this.

4. The first cooling tank container (34) is designed to accommodate liquid helium in equilibrium with helium vapor in the top space in the bottom space, and is in the range of 1.0 bar (0.10 MPa) to 1.5 bar (0.15 MPa). The second cooling tank container (36) is designed to accommodate liquid helium in equilibrium with helium vapor in the top space in the bottom space, and the second equilibrium pressure is in the range of 0.4 bar (0.04 MPa) to 0.65 bar (0.065 MPa). The precooling circuit (100, 200, 300, 400) according to claim 1 or 2 is characterized by this.

5. The third cooling tank container (38) is designed to accommodate liquid helium in equilibrium with helium vapor in the top space in the bottom space, and the third equilibrium pressure is in the range of 0.1 bar (0.01 MPa) to 0.3 bar (0.03 MPa). The precooling circuit (100, 200, 300, 400) according to claim 3 is characterized by this.

6. The helium refrigeration device (2) includes at least one compressor (16) and is designed to compress helium to a pressure in the range of 7 bar (0.7 MPa) to 18 bar (1.8 MPa). The precooling circuit (100, 200, 300, 400) according to claim 1 or 2 is characterized by this.

7. The helium refrigeration device (2) includes at least one compressor (16) and is designed to compress helium to a pressure in the range of 10 bar (1.0 MPa) to 15 bar (1.5 MPa). The precooling circuit (100, 200, 300, 400) according to claim 1 or 2 is characterized by this.

8. The pre-cooling circuit (100, 200, 300, 400) according to claim 6, wherein the helium refrigeration device (2) includes a heat exchanger system (6), and the returned helium is guided through the heat exchanger system in a flow direction opposite to that of the compressed helium.

9. The pre-cooling circuit (100, 200, 300, 400) according to claim 7, wherein the helium refrigeration device (2) includes a heat exchanger system (6), and the returned helium is guided through the heat exchanger system in a flow direction opposite to that of the compressed helium.

10. The cryogenic release device (10) includes a shield circulation system. The helium refrigeration device is designed to supply a helium shield flow, and the helium shield flow is guided from the helium refrigeration device to the shield circulation system and then back to the helium refrigeration device. The pre-cooling circuit (100, 200, 300, 400) according to claim 1 or 2 is characterized in that.

11. The cryogenic release device (10) is designed to exchange heat with a plurality of loads (72) to be cooled, and the loads are independently connectable and disconnectable to the supply pipe and the return pipe. The pre-cooling circuit (100, 200, 300, 400) according to claim 1 or 2 is characterized in that.

12. A cryogenic device including a closed pre-cooling circuit according to claim 1 or 2, and at least one hybrid cryostat connected to the cryogenic release device as at least one load to be cooled, wherein the cryogenic release device is designed such that the supply pipe and the return pipe are connected to at least one helium tank of the at least one hybrid cryostat.

13. A cryogenic method, wherein at least one sample is disposed in the at least one hybrid cryostat of the cryogenic device according to claim 12 and is cooled to a temperature below 1K.

14. In a method for performing a helium cooling supply to at least one load to be cooled, a step of compressing the returned helium; a step of guiding the compressed helium through a first cooling tank (34) and a subsequent second cooling tank (36) to obtain supercritical helium. Guiding the supercritical helium to a low-temperature discharge device (10) that exchanges heat with at least one load to be cooled; Guiding the return flow of the helium from the low-temperature discharge device to the driving flow opening of an ejector (50); Using the ejector to suck second helium vapor in equilibrium with the second cooling tank and supply it to first helium vapor in equilibrium with the first cooling tank; Inducing the first helium vapor to obtain the returned helium. A method characterized by comprising the steps.

15. Forming a sub-return flow by branching at least a part of the return flow; Guiding the sub-return flow through the first cooling tank and then guiding it to the return flow. The method according to claim 14, characterized by comprising the steps.

16. The method according to claim 14 or 15, including the step of guiding the compressed helium through a third cooling tank downstream of the second cooling tank.

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