US20090293504A1

US20090293504A1 - Refrigeration installation having a warm and a cold connection element and having a heat pipe which is connected to the connection elements

Info

Publication number: US20090293504A1
Application number: US12/443,329
Authority: US
Inventors: Marijn Pieter Oomen; Peter van Hasselt
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2006-09-29
Filing date: 2007-09-05
Publication date: 2009-12-03
Also published as: EP2066991B1; ES2647681T3; EP2066991A1; CN101523136A; WO2008040609A1; KR20090077800A; KR101422231B1; DE102006046688B3

Abstract

The invention relates to a refrigerating arrangement (100) comprising a hot connection element and a cold connection element (101, 103) and a heat exchanger tube arranged between said connection elements (101, 103). The heat exchanger tube (105) is to be at least partially filled with a liquid (106) that can be circulated in the heat exchanger tube (105) by a thermosiphon effect. The parts (102) to be cooled of a device, especially used in superconductivity technology, are connected to the hot connection element (101), and a heat sink (104) is connected to the cold connection element (103). In order to thermally separate the connection elements (101, 103), the liquid (106) can be pumped out by means of a pipeline (107) connected to the inside of the heat exchanger tube (105).

Description

The invention relates to a refrigeration installation having at least

- one warm connection element, which is thermally connected to parts to be cooled of a device,
- a cold connection element, which is thermally connected to a heat sink,
- a heat pipe composed of poorly thermally conductive material, which is connected to the warm connection element at a first end and is connected to the cold connection element at a second end, and whose interior is at least partially filled with a fluid which can circulate on the basis of a thermosiphon effect.

A refrigeration installation having the features mentioned above is disclosed, for example, in DE 102 11 568 B4.
Cooling systems, for example cooling systems for superconducting magnets, often have so-called bath cooling. A fluid coolant, for example helium, at a typical temperature of 4.2 K can be used for bath cooling such as this. DE 10 2004 060 832 B3 discloses an NMR spectrometer, whose superconducting magnet coil system has bath cooling. The refrigeration installation of the NMR spectrometer is designed such that a circulating coolant covers various elements of the NMR spectrometer on its circulation route. A coolant circulation such as this allows a multiplicity of elements of the NMR spectrometer to be cooled with different temperature levels by means of a single refrigerator.
However, large amounts of the appropriate coolant are required for bath cooling. In the case of a superconducting magnet, it is also possible for this magnet to lose its superconducting characteristics, for example by exceeding a critical current for the corresponding superconducting material or a critical magnetic field. In a situation such as this, a large amount of heat is developed in a short time on the superconducting material. The heat which occurs leads to boiling of the coolant within the cryostat in the case of bath cooling. Gaseous coolant occurring in large amounts leads to a rapid rise in the pressure within the cryostat.
In order to overcome this problem and at the same time to reduce the costs for the coolant, cooling systems are designed without a coolant bath. Cooling systems such as these do not require any coolant. The refrigeration power is in this case introduced into the areas to be cooled solely by solid-body heat conduction. In the case of a cooling system such as this, the areas to be cooled may be connected by means of a so-called solid-body cryobus composed of copper, for example, to a refrigeration machine. A further option is to connect the areas to be cooled and the refrigeration machine to a closed pipeline system in which a small amount of coolant circulates. The advantage of cooling systems such as these without a coolant bath is also that they can be matched more easily to moving loads that have to be cooled than cooling systems which have a coolant bath. Cooling systems without a coolant bath are therefore particularly suitable for superconducting magnets on a so-called gantry, such as that used when using ion beam therapy for cancer treatment. The refrigeration power in the cooling systems described above can typically be provided by a refrigeration machine having a cold head, in particular a Stirling cooler.
A superconducting magnet in which the second stage of a cold head is mechanically and thermally connected directly to the holding structure of a superconducting magnet winding is disclosed, for example, in U.S. Pat. No. 5,396,206. The required refrigeration power in the case of the abovementioned superconducting magnet is introduced into the superconducting magnet windings directly by solid-body thermal conduction. However, if a cold head has to be replaced, for example for maintenance purposes, the abovementioned cooling apparatus for a superconducting magnet is subject to a critical technical problem. During the replacement process, air or other gases can freeze on the very cold contact surface, in this case the holding structure of the superconducting windings. Ice occurring at these points leads to a poor thermal connection between the cold head, which is then used again, and the holding structure of the winding.
In order to prevent gases from freezing on the very cold contact surfaces, they can be heated to about room temperature. In general, this leads to all of the parts to be cooled of a device, for example all of the superconducting windings of a magnet, having to be brought to room temperature before the cold head can be replaced. Particularly for large systems, a warming-up phase such as this and the subsequent cooling-down phase can take a long time. This leads to long system downtimes. Furthermore, the warming-up and cooling-down phases lead to a large increase in energy consumption.
Alternatively, the freezing of surrounding gases on the very cold contact surfaces can be prevented by deliberately flooding the area around these contact surfaces with gas. However, this is complex and leads to a large consumption of purging gas or of coolant that is vaporized for this purpose.
EP 0 696 380 B1 discloses a superconducting magnet having a cryogen-free refrigeration installation. The disclosed refrigeration installation has a thermal bus composed of highly thermally conductive material such as copper, which is connected to the superconducting magnet. The thermal bus can also be connected to two cold heads. The two cold heads are arranged symmetrically with respect to the thermal bus. They can each be moved to the thermal bus from opposite sides. In this way, one or both of the cold heads can be brought into thermal contact with the thermal bus. The refrigeration power is correspondingly introduced into the thermal bus by one or else both of the cold heads.
In order to replace one of the two cold heads in the known installation, it can be mechanically moved back from the thermal bus, as a result of which the corresponding cold head is likewise thermally isolated from the thermal bus. In this case, the refrigeration power is made available only by the one remaining cold head. The cold head that has been moved back can now be replaced without having to heat the superconducting magnet. In the refrigeration installation disclosed in EP 0 696 380 B1, the cold heads must, however, be designed such that they can be moved mechanically, and this requires a multiplicity of components which are compatible with low temperatures and a corresponding mechanical system, which may be susceptible to defects.
JP 2000-146333 A discloses an apparatus and a method for maintenance of a cryocooler. Before replacement of a cryocooler or cold head, a corresponding physically identical cold head is precooled in a bath with fluid nitrogen. The precooling of the physically identical cold head allows the components of the cold head to be brought to a temperature comparable to that of the corresponding components to be replaced. This allows the cryogenic conditions within an installation whose cold head is intended to be replaced to be maintained virtually unchanged.
DE 102 11 568 B4 discloses a refrigeration installation having two cold heads which are connected to the parts to be cooled of a device by a pipeline system in which a coolant can circulate on the basis of a thermosiphon effect. The pipeline system has a branch. A coolant area which is in each case connected to a cold head is located at the ends of each of the branches. Starting from one of these coolant areas, fluid coolant falls, driven by the force of gravity, to the parts to be cooled of a device, at which the heat transfer takes place. Gaseous coolant once again rises in the pipeline system to the two cold heads, where it is liquefied again. A coolant circuit such as this can be used in the pipeline system both in the situation in which just one cold head is operating and in the situation in which both cold heads are operating. If the refrigeration installation is designed such that a single cold head also applies the refrigeration power required for the parts to be cooled of the device, a further cold head can be replaced during operation of the refrigeration installation. In order to minimize thermal losses, the pipeline system between the branch and the coolant areas, which are each connected to a cold head, is produced from poorly thermally conductive material. This makes it possible to limit the losses resulting from solid-body thermal conduction. Gaseous coolant will, however, always also rise to the point at which no cold head or a switched-off cold head is located. The losses resulting from solid-body thermal conduction can thus admittedly be limited, but not the losses which are caused by circulating coolant.
DE 101 04 653 A1 discloses a mechanical thermal switch which comprises a first metal body, which is in the form of a pot and can surround a second metal body in an interlocking manner. For this purpose, the first metal body has a free end which can form an interlock together with the outer casing of the second metal body. A fourth metal body is introduced into the first metal body, which is in the form of a pot, and a third metal body surrounds the first metal body, which is in the form of a pot, on the outside. When the fourth metal body is heated, it expands and presses against the pot inner wall of the first metal body such that the free end of the first metal body is moved and thus releases the connection to the second metal body. This makes it possible to open the thermal contact between the first and the second metal body. When the first metal body is being cooled down, the third metal body, which is in the form of a ring and surrounds the first metal body, contracts and presses the free end of the first metal body against the second metal body. The thermal switch can be closed in this way.
The object of the present invention is to specify a refrigeration installation in which the parts to be cooled of a device are connected to a heat sink by means of a heat pipe in which a fluid can circulate on the basis of a thermosiphon effect, in which case the parts to be cooled of a device are intended to be able to be largely thermally decoupled from the heat sink, without being mechanically disconnected.
This object is achieved by the measures specified in claim 1. The present invention is in this case based on the following concepts: The heat exchange between the heat sink and the parts to be cooled of a device takes place essentially by means of the fluid which can circulate in the heat pipe on the basis of a thermosiphon effect. The heat pipe can be pumped out via a pipeline, which is connected to its interior, for thermal isolation of the heat sink from the parts to be cooled of a device. At the same time, the heat pipe should be produced from a poorly thermally conductive material. These measures decrease the thermal connection between the heat sink and the parts to be cooled of the device, except for a small amount which is defined by the solid-body thermal conductivity of the heat pipe. According to the invention, the refrigeration installation should contain at least one warm connection element, which is thermally connected to parts to be cooled of a device, and a cold connection element, which is thermally connected to a heat sink. A heat pipe composed of poorly thermally conductive material should be connected to the warm connection element at a first end and should be mechanically detachably connected to the cold connection element at a second end. The interior of the heat pipe should be at least partially filled with a fluid which can circulate on the basis of a thermosiphon effect. Furthermore, the refrigeration installation should comprise a pipeline which is connected at a first end to the interior of the heat pipe and is designed such that at least parts of the pipeline are geodetically higher than the liquid level. According to the invention, it should be possible to pump the fluid out of the heat pipe via the pipeline for thermal isolation of the connection elements.
The advantages of a refrigeration installation having the features mentioned above are, in particular, that any heat transfer via the heat pipe is considerably reduced in that the fluid is pumped out of the interior of the heat pipe. This allows the parts to be cooled of a device to be largely thermally decoupled from the heat sink without a second heat sink being required and without one or more heat sinks having to be mechanically moved. If the heat sink, which is mechanically detachably connected to the cold connection element, is removed from the refrigeration installation, the cold connection element can heat up within a short time to such an extent that, in particular, air or other gases contained in the surrounding atmosphere freeze only to a minor extent on the surface of the cold connection element. This makes it possible to very largely avoid ice formation on the contact surfaces between the cold connection element and the heat sink. As a result of the reduced ice formation, the thermal contact when the heat sink is inserted again will be considerably better than in the situation in which there is considerable ice formation on the contact surfaces. Furthermore, the cryogenic area in which the parts to be cooled of the device are located is protected by the thermal decoupling against heat flows entering this area. In this way, the parts to be cooled of a device remain at the desired low temperature even when the heat sink is being replaced. The measures stated above make it possible to specify a refrigeration installation which allows the heat sink to be replaced, or serviced, or to be temporarily removed, without any need to heat the parts to be cooled, even when using a single heat sink. The refrigeration installation according to the invention is particularly suitable for devices in the field of superconducting technology.
Advantageous refinements of the refrigeration installation according to the invention are specified in the claims which are dependent on claim 1. In this case, the embodiment as claimed in claim 1 can be combined with the features of one of the dependent claims, or preferably also those of a plurality of dependent claims. The refrigeration installation according to the invention can accordingly additionally also have the following features:

- The parts to be cooled of the device can be arranged in a cryostat which can be evacuated, and the second end of the pipeline can be located outside the cryostat. Very cold parts of a device can particularly advantageously be thermally isolated from their environment by means of a cryostat which can be evacuated. Thermal isolation such as this represents particularly effective isolation for very cold parts of a device. Particularly in the case of very cold parts such as these of a device, it is desirable to prevent ice formation on the contact surfaces of the cold connection element. The use of a refrigeration installation according to the above exemplary embodiment is therefore particularly advantageous, in particular for apparatuses with very cold parts.
- A multistage refrigeration machine having a first stage and a second stage can be provided, in which case the heat sink can be formed by the second stage and the first stage can be mechanically detachably connected to a heat shield which is arranged within the cryostat. A multistage refrigeration machine is particularly suitable for parts of a device which are to be cooled to very cold temperatures. It is particularly advantageous to use a heat shield as a further measure for thermal isolation. The thermal isolation according to the invention of the parts to be cooled of a device of the second stage of the refrigeration machine is particularly advantageous since, particularly in the case of mechanically complex cooling systems, this results in the advantage of thermal isolation without moving parts.
- At least parts of the refrigeration machine can be fitted replaceably in a maintenance area which can be evacuated and is separated from the cryostat which can be evacuated. The process of replacement of the refrigeration machine can be carried out without having to break the vacuum of the cryostat with the aid of a further maintenance area which can likewise be evacuated and is separated from the cryostat which can be evacuated. This allows the maintenance process to be carried out particularly easily and effectively.
- The fluid may be in the form of a two-phase mixture. If the fluid in the heat pipe is in two phases, then circulation of the fluid can occur in the heat pipe, by means of which gaseous fluid condenses at the cold end of the heat pipe, and liquid fluid vaporizes at the warm end of the heat pipe. This makes it possible to make use of the latent heat of the phase change for heat transport. However, a corresponding circulation can also occur in a single-phase fluid as a result of natural convection, based on density differences.
- The refrigeration installation can rotate about an axis which runs essentially parallel to an axis of symmetry of the heat pipe. The heat pipe can also have a larger cross section in a first area, which is connected to the warm connection element, than in a second area, which is connected to the cold connection element. Those parts of the heat pipe which connect the first area and the second area to one another can be designed such that coolant which has condensed in the second area can pass without any impediment under the influence of the force of gravity to the first area. A refrigeration installation having the features mentioned above can be used particularly advantageously for moving parts, which in this case are arranged such that they can rotate and are to be cooled, of a device. The specific configuration of the heat pipe means that the thermal contact between the refrigeration machine and the parts to be cooled of the device is ensured at all times, even during rotation of the parts to be cooled of a device.
- At its ends, close to the axis of symmetry of the heat pipe, the pipeline can be connected to the heat pipe and the outside of the cryostat. Furthermore, the pipeline may have, in the direction in which it runs at least one intermediate area which is close to the axis. A configuration of the pipeline as described above makes it possible, when the parts to be cooled of a device rotate, to prevent the coolant from passing through the pipeline to the warm end of the pipeline, which is mounted outside the cryostat. This prevents the coolant from circulating in the pipeline between the very cold area which is located within the heat pipe and the end of the pipeline which is fitted outside the cryostat. The configuration of the pipeline as described above allows heat losses resulting from circulation of the coolant as described above to be prevented in a particularly advantageous manner.
- The intermediate area of the pipeline may have a V-shaped profile in the direction of the axis A. A pipeline bent in a V-shape represents a particularly simple and effective embodiment of the pipeline.
- The heat pipe may be designed essentially in the form of a truncated cone. An embodiment of the heat pipe in the form of a truncated cone allows a particularly simple, low-cost and effective form of the heat pipe to be specified.
- The refrigeration installation may comprise an additional cooling system which has at least the following features: a coolant area which is connected to the cold connection element; a supply line through which the coolant area can be filled with a second coolant from a geodetically higher point outside the cryostat; a pipeline system which is thermally connected over a large area to the parts to be cooled of the device and in which the second coolant can circulate by means of a thermosiphon effect; an off-gas line, through which gaseous second coolant can escape from the pipeline system. An additional cooling system having the features mentioned above makes it possible to speed up the cooling-down phase, particularly when large masses have to be cooled. Since the coolant area is filled with a second coolant via the supply line from a geodetically higher point outside the cryostat, additional cooling power is provided for the parts to be cooled of a device. Any second coolant which vaporizes off can escape from the pipeline system via the off-gas line. This prevents the formation of an overpressure in the pipeline system. The second coolant can circulate on the basis of a thermosiphon effect within the pipeline system, thus ensuring effective cooling.
- The connection elements may be composed of a highly thermally conductive material, preferably of copper. The heat pipe may be composed of a material having a thermal conductivity lower than that of copper, preferably of stainless steel. A refinement to the connection elements such as this, composed of a highly thermally conductive material such as copper, makes it possible to achieve particularly effective thermal coupling both to the heat sink and to the parts to be cooled of the device. The thermal conductivity of the heat pipe is governed primarily by the coolant circulating within the heat pipe. If the heat pipe is itself produced from a poorly thermally conductive material such as stainless steel, a particularly major reduction in the thermal conductivity can be achieved by pumping out the coolant.
- The device may be a gantry apparatus for beam therapy, and the parts to be cooled may be the magnets of the gantry for deflection of a particle beam. The refrigeration installation according to the invention is particularly suitable for a gantry, since the magnets to be cooled are rotated about a rotation axis of the gantry.

Further advantageous refinements of the refrigeration installation according to the invention are specified in the claims which have not been mentioned above, and in particular will become evident from the drawing explained in the following text. Preferred refinements of the refrigeration installation according to the invention are indicated in a slightly schematic form in the drawing, in which, in this case:

FIG. 1 shows a cross section through a refrigeration installation,

FIG. 2 shows a cross section through a refrigeration installation which can rotate, and

FIG. 3 shows a cross section through a refrigeration installation which can rotate and has an additional cooling system.

Corresponding parts are each provided with the same reference symbols in the figures. Parts which are not mentioned in any more detail are general prior art.
FIG. 1 shows the schematic design of a refrigeration installation 100 according to one exemplary embodiment. The parts 102 to be cooled of a device are located in a cryostat 108. The parts 102 to be cooled of the device may, for example, be the magnet windings of a superconducting magnet or other parts from superconducting technology. A heat shield 112 is fitted within the cryostat 108, in order to improve the thermal isolation. The cooling power for the parts 102 to be cooled of the device is provided by a refrigeration machine 109, for example a cold head or a Stirling cooler. A cold head can preferably be used, operating on the Gifford-McMahon principle. According to the present exemplary embodiment, the first stage 111 of a two-stage refrigeration machine such as this can be thermally connected to the heat shield 112. The connection between the first stage 111 of the refrigeration machine 109 and the heat shield 112 can preferably be a detachable mechanical connection, for example a screw connection or clamping connection, which at the same time ensures a good thermal contact between the components. The second stage 110 of the refrigeration machine 109 represents the actual heat sink 104 of the refrigeration installation 100. The second stage 110 of the refrigeration machine 109 is thermally connected to a cold connection element 103. The corresponding connection can preferably be a screw connection. This means that the second stage 110 of the refrigeration machine 109 is detachably screwed into the cold connection element 103. Any other mechanical connection which is detachable and at the same time ensures a good thermal contact between the second stage 110 of the refrigeration machine 109 and the cold connection element 103 is likewise suitable for the exemplary embodiment illustrated in FIG. 1. In this case, the connection elements 101 and 103 may be one part of the parts 102 to be cooled of a device or of the heat sink 104. Furthermore, they may be integrated in the corresponding components, or may be permanently and firmly connected to them.
The refrigeration machine 109 is partially located in a separate maintenance area 113 which can be evacuated. This maintenance area 113 is separated from the rest of the area, which can be evacuated, of the cryostat 108. The cold connection element 103 is highly thermally conductively and preferably also mechanically connected to a heat pipe 105. On the opposite side, the heat pipe 105 is connected to a warm connection element 101. This connection is likewise designed to be highly thermally conductive and can preferably also be a mechanical connection. The warm connection element 101 is in turn connected in a highly thermally conductive manner to the parts 102 to be cooled of a device. A fluid 106 which can circulate in the heat pipe 105 on the basis of a thermosiphon effect is located within the heat pipe 105. However, the heat pipe 105 is itself composed of a poorly thermally conductive material.
If the heat pipe 105 is completely filled with the fluid, then this can assume a higher density in the upper, cold area of the heat pipe 105, by virtue of the temperature, than in the lower, warmer area of the heat pipe 105. A circulation based on the so-called thermosiphon effect can occur in the heat pipe 105 as a result of the density differences of the fluid 106, and results in heat being transported from the parts 102 to be cooled of the device to the heat sink 104.
Furthermore, the heat pipe 105 may be only partially filled with a fluid 106. In this case, the fluid 106 can circulate in two different phases, for example liquid-gaseous. Gaseous fluid is accordingly liquefied in that part of the heat pipe 105 which is in thermal contact with the cold connection piece 103. Condensed fluid 106 moves, driven by the force of gravity, into that part of the heat pipe 105 which is illustrated further below in FIG. 1 and is in thermal contact with the warm connection piece 101. In this part of the heat pipe 105, the fluid 106 emits the cooling power to the warm connection piece 101 (and therefore also to the parts to be cooled of the device 102), in response to which gaseous fluid 106 once again rises into the upper part of the heat pipe. In this case, the cold connection piece 103 acts as a condenser, and the warm connection piece as an evaporator. This makes it possible to ensure a good thermal connection between the refrigeration machine 109, to be precise its second stage 110, and the parts 102 to be cooled of a device.
During operation of a refrigeration installation 100, it may be necessary to have to replace a refrigeration machine 109, for example for maintenance tasks or because of a defect. Before the refrigeration machine 109 is removed from the refrigeration installation 100, the fluid 106 which is located within the heat pipe 105 is pumped out via a pipeline 107 which leads to the exterior. In many cases, it is sufficient to pump the majority of the fluid 106 out of the heat pipe 105; however, it can also be completely removed from the heat pipe 105. Since the fluid 106 is removed from the heat pipe 105, the thermal conductivity of the heat pipe 105 is considerably reduced. In consequence, thermal conduction takes place between the cold connection element 103 and the warm connection element 101 only by virtue of solid-body thermal conduction via the material of the heat pipe 105. If the heat pipe 105 is produced from a poorly thermally conductive material such as stainless steel, the thermal conduction between the connection elements 101, 103 can be reduced to a minimum. In addition to stainless steel, various plastics, ceramics or other materials that are suitable for low temperatures may also be used as materials for the heat pipe 105. A further measure to minimize the thermal conduction is to manufacture the heat pipe 105 with particularly thin walls and/or with small geometric dimensions.
Once the fluid 106 has been pumped out of the heat pipe 105 via the pipeline 107, the maintenance area 113 can be ventilated. The environmental air flowing into the maintenance area 113 starts to warm up the cold connection element 103 as well as the previously cold parts of the refrigeration machine 109. The maintenance area 113 can likewise be flooded with a specific purging gas, such as dried air, nitrogen or helium. Once the maintenance area 113 has been ventilated, the refrigeration machine 109 can be removed from the refrigeration installation 100. The previously very cold connection element 103 is thermally decoupled from the other parts which are still very cold, in particular the warm connection element 101 and the parts 102 to be cooled of a device, and will therefore heat up quickly to a temperature close to room temperature. Since the cold connection element 103 warms up, as described above, this largely avoids ice formation resulting from condensing gas, preferably such as environmental air. A good thermal and mechanical contact is therefore ensured between the second stage 110 of the refrigeration machine 109 and the cold connection element 103 when the refrigeration machine 109 is reinserted.
Superconducting magnet windings are particularly suitable for radiation installations such as those used in particle therapy, for example for cancer treatment. Superconducting magnet windings such as these are preferably mounted in a so-called gantry, which can rotate about a fixed axis.
FIG. 2 shows a further exemplary embodiment of the refrigeration installation which is in general annotated 100, with the entire refrigeration installation 100 including the parts 102 to be cooled being arranged such that they can rotate about an axis A. According to the embodiment of the refrigeration installation 100 illustrated in FIG. 2, the parts 102 to be cooled are located in a cryostat 108, which additionally has a heat shield 112. The refrigeration machine 109 is preferably designed to be rotationally symmetrical with respect to a further axis B. The refrigeration machine 109 is accommodated in a maintenance area 113 which can be evacuated separately from the cryostat 108. The first stage 111 of the refrigeration machine 109 is connected to the heat shield 112, and the second stage 104 of the refrigeration machine 109 is connected to the cold connection element 103. The heat pipe 105 is located with a first part 202 thermally connected, and preferably mechanically connected as well, to the cold connection element 103. A further part 201 of the heat pipe 105 is in thermal contact, and preferably in mechanical contact as well, with the warm connection element 101. The first part 202 of the heat pipe 105 has a smaller cross section than the second part 201 of the heat pipe 105. The part 203 of the heat pipe 105 which connects the first part 202 and the second part 201 of the heat pipe 105 is designed such that condensed fluid 106 can pass without any impediment through this part 203, by the force of gravity, from the first area 202 into the second area 201. The overall heat pipe 105 can preferably be in the form of a truncated cone which is closed at both ends. A heat pipe 105 such as this can also be connected to the refrigeration machine 109 such that the axis of symmetry of the truncated cone coincides with the axis B.
A pipeline 107 is connected to the heat pipe 105 in the area of this axis B. The fluid 106 can be pumped out of the heat pipe 105 through this pipeline. The pipeline 107 is shaped such that any fluid 106 which enters the pipeline 107 from the heat pipe 105 cannot pass without impediment to the outer part of the pipeline 107, which is connected to the cryostat 108. For this purpose, the pipeline 107 has a part 204 which is bent in the direction of the axis A. A refinement of the pipe 107 such as this, even if the entire refrigeration installation 100 were to rotate about the axis A, will make it possible to prevent fluid 106 from making continuous contact with the outer part of the pipeline 107 through the pipeline 107.
As described in conjunction with FIG. 1, the fluid 106 can be pumped out of the heat pipe 105 through the pipeline 107. This results in thermal isolation between the parts 102 to be cooled of a device and the heat sink 104. In order to additionally allow the refrigeration machine 109 to be replaced, for example for maintenance purposes, in the case of a refrigeration installation 100 such as this which can rotate about an axis A, the working area 113 is ventilated after the fluid 106 has been pumped out. In the situation in which the heat shield 112 is rigidly connected to the cryostat 108, the parts of the working area 113 which are arranged between the mounting flange of the first stage 111 of the refrigeration machine with the heat shield 112 and the condenser 103, can be designed to be flexible. A flexible configuration such as this can be achieved, for example, with the aid of a bellows. In order to allow isolation between the second stage 110 of the refrigeration machine 109 and the condenser 103, the condenser 103 can be movable along the axis B, by virtue of a flexible configuration of the heat pipe 105. The heat pipe 105 may likewise have a bellows for this purpose.
FIG. 3 shows a further exemplary embodiment of a refrigeration installation, which is annotated 100 in general. The refrigeration installation 100 illustrated in FIG. 3 has had an additional cooling system added to it, in comparison to that which is illustrated in FIG. 2. A coolant area 301 is in thermal contact, and preferably mechanical contact as well, with the cold connection element 103. This coolant area 301 can be filled through a supply line 302 from a geodetically higher point. The same coolant, or a similar coolant, as that which is also used for the heat pipe 105 can be used as the coolant. By way of example, helium, neon or else nitrogen can be used. A pipeline system 303 is connected to the coolant area 301 and is connected over a large area to the parts 102 to be cooled of a device. This allows additional cooling power to be supplied to the parts 102 to be cooled of a device. This makes it possible to considerably shorten the cooling-down times, for example for a superconducting magnet. Any coolant which may be vaporized in the pipeline system 303 can escape from the pipeline system 303 via an off-gas line 304. This avoids any overpressure in the pipeline system 303.
The additional cooling device can be used, for example, such that the parts 102 to be cooled of a device are first of all initially cooled with nitrogen, which costs little and is widely available, before the parts 102 to be cooled are cooled to even lower temperatures with the aid of the refrigeration machine 109. In order to use the additional cooling device, it is technically necessary to stop the possible rotation about the axis A of the refrigeration installation 100, or at least to slow the movement down, such that a coolant circuit which is based on a thermosiphon effect can occur, driven by the force of gravity, in the pipeline system 303.

Claims

1.-15. (canceled)

16. A refrigeration installation, comprising:

a warm connection element which is thermally connected to a part to be cooled;

a heat sink;

a cold connection element which is thermally connected to the heat sink;

a heat pipe made of a material of poor thermal conductivity, said heat pipe having a first end connected to the warm connection element and a second end mechanically detachably connected to the cold connection element, said heat pipe having an interior which is at least partially filled with a fluid which circulates on the basis of a thermosiphon effect, and

a pipeline having a first end connected to the interior of the heat pipe, said pipeline being constructed such that at least a part of the pipeline is geodetically higher than a fluid level in the interior of the heat pipe, wherein the fluid is pumped out via the pipeline for thermal isolation of the warm and cold connection elements.

17. The refrigeration installation of claim 16, further comprising a cryostat which accommodates the part to be cooled and is evacuatable, said pipeline having a second end located outside the cryostat.

18. The refrigeration installation of claim 17, further comprising a heat shield which is arranged within the cryostat, and a multistage refrigeration machine having a first stage, which is mechanically detachably connected to the heat shield, and a second stage, which forms the heat sink.

19. The refrigeration installation of claim 18, wherein the refrigeration machine has at least one part which is replaceably fitted in a maintenance area which is separated from the cryostat and evacuatable.

20. The refrigeration installation of claim 16, wherein the fluid is a two-phase mixture.

21. The refrigeration installation of claim 16, constructed for rotation about a rotation axis in substantial parallel relationship to an axis of symmetry of the heat pipe, wherein the heat pipe has a first area which is connected to the warm connection element, a second area which is connected to the cold connection element, and a connecting part which connects the first and second areas to one another, said first area defined by a cross section which is greater than a cross section of the second area, said connecting part being constructed such that coolant which has condensed in the second area is able to flow unimpeded under the influence of force of gravity into the first area.

22. The refrigeration installation of claim 21, wherein the pipeline has a second end, said first and second ends of the pipeline being connected to the heat pipe and an outside of the cryostat, respectively, in close proximity to the axis of symmetry of the heat pipe, said pipeline having between the first and second ends an intermediate area in closer proximity the rotation axis.

23. The refrigeration installation of claim 22, wherein the intermediate area has a V-shaped bend extending in a direction of the rotation axis.

24. The refrigeration installation of claim 21, wherein the heat pipe is configured essentially in the form of a truncated cone.

25. The refrigeration installation of claim 17, further comprising a cooling system which comprises:

a coolant area connected to the cold connection element,

a supply line fluidly communicating with the coolant area for supply of a second coolant to the coolant area from a geodetically higher point outside the cryostat,

a pipeline system thermally which is connected over a large area to the part to be cooled and in which the second coolant is able to circulate based on a thermosiphon effect, and

an off-gas line for discharge of second coolant in gaseous state from the pipeline system.

26. The refrigeration installation of claim 16, wherein the warm and cold connection elements are each made of highly thermally conductive material.

27. The refrigeration installation of claim 16, wherein the warm and cold connection elements are each made of copper.

28. The refrigeration installation of claim 16, wherein the heat pipe is made of a material having a thermal conductivity which is lower than a thermal conductivity of copper.

29. The refrigeration installation of claim 16, wherein the heat pipe is made of a material having a thermal conductivity which is lower than a thermal conductivity of stainless steel.

30. The refrigeration installation of claim 16, wherein the part to be cooled is a superconducting part.

31. The refrigeration installation of claim 16, wherein the part to be cooled is a component of a gantry device for beam therapy.

32. The refrigeration installation of claim 31, wherein the part to be cooled is a magnet for deflection of a particle beam.

33. The refrigeration installation of claim 31, wherein the part to be cooled is a superconducting magnet for deflection of a particle beam.