EP1063482A1 - Refrigeration device - Google Patents

Abstract

The electrical connections (62) run at least partially in thermal contact with the first pulse tube (20) and/or partially in thermal contact with the first regenerator (40).

Description

Technical field

The invention relates to a cooling device according to claim 1 and 3.

Such cooling device have due to their use one or more pulse tube coolers a wide one Area of application and are used especially for cooling objects used by electrical or mechanical Lines are connected. A cooling device according to the invention is therefore suitable, for example, for cooling High temperature superconductor devices, such as SQUIDs, for cooling semiconductor components, such as infrared detectors or high speed circuitry for a very fast data processing, or also for cooling sensors, based on a low temperature effect.

State of the art

From Info-Phys-Tech No. 6, 1996, from VDI Technology Center, Physical technologies, is a cooling device known in the form of a pulse tube cooler, the pulse tube cooler has (see Figure 1): a pulse tube 20, on one end of which is a cold heat exchanger 24 or cold head 24, on which heat is absorbed by an object 82 to be cooled is provided (here at a temperature of about 77K) is, and at the other end a warm heat exchanger (not shown), on the heat to the outside (here at a temperature of about 300K) is provided is a regenerator 40, which acts as an intermediate heat store serves, and a pressure oscillator (not shown), which is used to generate periodic pressure changes, the pulse tube at the end where the cold heat exchanger 24 is provided, via respective lines via the Regenerator 40 is connected to the pressure oscillator, so that a periodic shift of a working gas between the pulse tube and the pressure oscillator is made possible.

Should an object, such as a magnet 82, be cooled are, it is known, the object to the cold head 24 of the pulse tube 20, which is arranged in a cooling container can be to couple thermally and with electrical cables 62 to connect. As a disadvantage of this conventional Cooling arrangement turns out, however, that the Thermal load on the cold head 24 is considerable in this cooling arrangement is. On the one hand, this is because the electrical Lines with the outside of the cooling container or with devices 60 (connection device 60) whose temperature is above the temperature of the cold head 24, in (thermal) contact and on the other hand that the Current through the electrical lines 62 that at the above mentioned magnet 82 can assume values from 20 to 120 A, Generates heat. This can cause the cold head 24 heat sink to be provided is no longer the desired one low temperature reached or temperature fluctuations occur. Such a device for cooling a magnet is from C. Wang et al .: Cryogen Free Operation of a Niobium-Tin Magnet Using a Two-Stage Pulse Tube Cooler ", in Proceedings of the conference "Applied Superconductivity" 1998 known in Palm Desert, where instead of a one-tier Pulse tube cooler system uses a two-stage becomes.

From G. Thummes et al.: "Small scale ⁴ He liquefaction using a two-stage 4K pulse tube cooler", in Cryogenics 1998 Volume 00, Number 0, a device for liquefying ⁴ He housed in a cryostat is known two-stage pulse tube cooler system connected in series. In this case, a gas line for cooling or liquefying a gas is led from the outside of the cryostat into the inside, where it is wound around the cold head of the second pulse tube, which provides a higher temperature than the first pulse tube, around the regenerator of the first pulse tube Cold head of the first pulse tube wound and finally connected to a container containing the gas to be liquefied, which is arranged on the cold head of the first pulse tube. Furthermore, a sensor runs from the outside of the cryostat directly to the liquefaction container, as a result of which a certain additional heat load is applied to the container due to the large temperature gradient.

Presentation of the invention

It is now an object of the present invention Cooling device with a pulse tube cooler for cooling to further develop an object such that the heat load on the pulse tube cold head by electrical or mechanical Connection devices to the object to be cooled is caused, is minimized.

This task is performed by a cooling device according to the Features of claim 1 or 3 solved. Advantageous configurations are the subject of the subclaims.

According to a first aspect, the cooling device according to the invention comprises a first pulse tube cooler with a first pulse tube, which has a warm head with a first temperature T _A1 and a cold head with a second temperature T _E lower than the first temperature, and a first regenerator which has a warm end section and 'has a cold end portion connected to the cold head of the first pulse tube; an object to be cooled, which is thermally coupled to the cold head of the first pulse tube cooler; and a connecting device, in particular in the form of superconducting or high-temperature superconducting and / or normal-conducting electrical leads, for electrically connecting the object to be cooled to a region, such as a connecting device, which has a higher temperature T _V than the second temperature T _E. According to the invention, the connecting device runs at least partially in thermal contact with the first pulse tube and / or partially in thermal contact with the first regenerator in order to cause the connecting device to be precooled.

According to a second aspect, the cooling device according to the invention comprises a first pulse tube cooler with a first pulse tube, which has a warm head with a first temperature T _A1 and a cold head with a second temperature T _{E which is} lower than the first temperature, and a first regenerator which has a warm end section and a cold end portion connected to the cold head of the first pulse tube; an object to be cooled, which is thermally coupled to the cold head of the first pulse tube cooler; and a connecting device, for example in the form of rods, wires, threads made of metal or plastic, for mechanically connecting the object to be cooled to a region, such as a connecting device, which has a higher temperature T _V than the second temperature T _E. The mechanical connection includes that the object to be cooled is held or supported on the area or the connecting device via the connecting device or that the object to be cooled is mechanically acted on via the connecting device. According to the invention, the connecting device runs at least partially in thermal contact with the first pulse tube and / or partially in thermal contact with the first regenerator in order to cause the connecting device to be precooled.

According to an advantageous embodiment of the connecting device can this in the form of a two-part holding device be trained. A first part or holding part consists preferably of a poorly heat-conducting Material, such as plastic, is used for the real thing Holding the object to be cooled on the connection device. A second part or contact part is preferably made made of a highly conductive material, such as metal, and serves to bring the holding device into thermal contact with a pulse tube or regenerator, and thus for Pre-cooling of the entire holding device.

According to a further advantageous embodiment of the connecting device, it can be designed in the form of a shaft which, for example, starts from a motor at a temperature level, for example from T _A1 or T _A2 , and then leads to the object to be cooled. Instead of the shaft, however, wires or threads can also be used to act mechanically on the object to be cooled.

In the following, advantageous configurations are both of the first as well as the second aspect explained:

According to an advantageous embodiment, the Connection device at least partially in thermal Contact along the first pulse tube from the warm head to Cold head and / or partially in thermal contact along of the first regenerator from the warm end section to the cold one End section. This measure causes the Connection device before contact with the cooling object or cold head of the first pulse tube the thermal contact at least partially along the first Pulse tube from warm head to cold head and / or thermal Contact at least partially along the first regenerator from the warm end section to the cold end section is pre-cooled. Because of the heat or temperature gradient between the hot head and cold head of the (first) Pulse tube thus becomes the temperature of one or more Place with the pulse tube or regenerator in thermal Contact connecting device at different Temperature levels "caught" or adjusted.

The connecting device can, for example, by means of Clamps or the like or by gluing the connecting device with the pulse tube or regenerator in thermal Be brought in contact. It is also conceivable that Connection device around the pulse tube or the regenerator to wrap.

A second pulse tube cooler can be used to effectively counteract the heat load on the first pulse tube cold head or to improve the cooling capacity of the first pulse tube cold head connected to the object to be cooled, and thus also to lower the cooling temperature. This has having a second pulse tube, which is a hot head with a third temperature T _A2, and a cold head with respect to the third temperature T _A2 deeper fourth temperature T _Z, the first between the temperature T _A1 and the second temperature T _E, and a second regenerator which has a warm end section and a cold end section which is connected to the second pulse tube cold head. The fourth temperature T _Z provided by the second pulse tube cooler serves to precool the first pulse tube cooler. Instead of the second pulse tube cooler, a plurality of pulse tube coolers can also be used for pre-cooling the first pulse tube cooler. The entirety of the pulse tube coolers is advantageously arranged such that a predetermined temperature T _E , ie temperature at the first pulse tube cold head, is reached in several successive cooling stages, to which the object to be cooled is to be cooled.

To further minimize the thermal load on the first pulse tube cold head, the fourth temperature T _{Z of} the cold head of the second pulse tube cooler can be set such that it is lower than the temperature T _{V of} the area or of the connecting device, the connecting device for its pre-cooling being at least partially in thermal contact is guided along the second pulse tube in the direction from the warm head to the cold head and / or at least partially in thermal contact along the second regenerator in the direction from the warm end section to the cold end section.

That to be cooled by the cooling device according to the invention Object has, for example, one on a superconducting one or normal conductive material based magnet or a sensor for detecting particles, radiation or Fields. Such sensors can be sensors with a Operating temperature in the range of about 30 to 100 K, such as for example silicon detectors (Si (Li) detectors), germanium detectors (HPGe detectors) or on high-temperature superconductors based SQUIDs ("Superconducting Quantum Interference Device ", superconducting quantum interference devices) his. The object to be cooled can also also sensors based on a low temperature effect, have, these sensors due to their operating temperature less than 20 K, usually even less than 4K, of a low-temperature cooling device (e.g. a demagnetization stage), the one with the cold head of the first pulse tube is cooled to the appropriate operating temperature become. Such sensors are advantageous a two-stage or three-stage pulse tube cooling system used.

i) Temperaturerhöhung nach Energiedeposition (Kalorimeter) in einem Absorber (Dielektrikum, Metall, Supraleiter, usw.).

ii) Erzeugung von Phononen (Gitterschwingungen in einem Absorbermaterial) durch die Energiedeposition. Je tiefer die Ausgangstemperatur, desto weniger Gitterschwingungen sind vorhanden.

iii) Erzeugung von Quasiteilchen (Aufbrechen von Cooperpaaren) in einem Supraleiter. Supraleitung ist ein Tieftemperatureffekt. Je tiefer die Übergangstemperatur zur Supraleitung, desto mehr dieser Quasiteilchen werden durch die Energiedeposition erzeugt. Je mehr Quasiteilchen erzeugt werden, desto genauer kann die Energie bestimmt werden.

iv) Änderung der Spinausrichtung bzw. Magnetisierung in einem auf tiefe Temperaturen abgekühlten Spinsystem bestehend aus paramagnetischen Ionen aufgrund einer Energiedeposition.

The sensors used in the detector device, based on a low-temperature effect, or also cryodetectors or cryogenic detectors, are sensors which measure energy deposited by radiation or particle absorption by means of an effect which only or in particular occurs at low temperatures. These temperatures are provided by a heat sink which is thermally coupled to the detector device, which has a respective sensor based on a low-temperature effect. These effects can be:

i) Temperature increase after energy deposition (calorimeter) in an absorber (dielectric, metal, superconductor, etc.).

ii) Generation of phonons (lattice vibrations in an absorber material) by energy deposition. The lower the initial temperature, the less grid vibrations are present.

iii) Generation of quasiparticles (breaking up of Cooper pairs) in a superconductor. Superconductivity is a low-temperature effect. The lower the transition temperature to superconductivity, the more of these quasiparticles are generated by the energy deposition. The more quasiparticles are generated, the more precisely the energy can be determined.

iv) Change of the spin orientation or magnetization in a spin system cooled to low temperatures, consisting of paramagnetic ions due to an energy deposition.

a) Supraleitende Phasenübergangsthermometer, wie beispielsweise als Sensor in einem Mikrokalorimeter: Diese bestehen im wesentlichen aus einem Absorber, einem Phasenübergangsthermometer (supraleitende Schicht, beispielsweise aus Wolfram, Iridium, Aluminium oder Tantal) und einer Kühleinrichtung bzw. einer Kopplung an eine Wärmesenke. Im Temperaturübergangsbereich zwischen seiner supraleitenden und normalleitenden Phase ändert das Thermometer seinen elektrischen Widerstand sehr stark in Abhängigkeit von der Temperatur, d.h. auch nach Absorption von Gitterschwingungen und Quasiteilchen.

b) Supraleitende Tunneldioden: Sie bestehen aus zwei überlappenden dünnen supraleitenden Filmen (SIS: Supraleiter-Isolator-Supraleiter, wobei die Filme nicht notwendigerweise aus dem gleichen Supraleiter auf beiden Seiten bestehen müssen) oder einem supraleitenden und einem normalleitenden Film (NIS: Normalleiter-Isolator-Supraleiter), wobei die jeweiligen Filme durch eine dünne elektrisch isolierende Barriere getrennt sind. Die Barriere ist so dünn, daß sie quantenmechanisches Tunneln von Elektronen, bzw. Quasiteilchen von der einen Elektrode zur anderen erlaubt. Wird die NIS-Diode oder SIS-Diode unterhalb der Sprungtemperatur der jeweiligen Supraleiter betrieben, und ist die angelegte Spannung kleiner als die der supraleitenden Energielücke entsprechenden Spannung (NIS) bzw. kleiner als zweimal diese Spannung (SIS), so steigt der über die Barriere fließende Strom, wenn in der Tunneldiode Energie deponiert wird. Die Deposition der Energie kann durch Temperaturerhöhung, Absorption von Gitterschwingungen oder Quasiteilchen oder direkt durch Absorption von Strahlung oder Teilchen geschehen.

c) Thermistor, wie NTD-Thermometer (NTD: "Neutron Transmutation Doping", d.h. mittels Neutronen hochdotierter Halbleiter). Diese Thermometer können zum Messen von Temperaturschwankungen verwendet werden, da bei ihnen, wie bei allen Halbleitern, der Widerstand mit sinkender Temperatur zunimmt. Um zu vermeiden, daß bei sehr tiefen Temperaturen die Widerstände so hoch anwachsen, daß sie nicht mehr mit genügender Genauigkeit gemessen werden können, werden die verwendeten Halbleiter hochdotiert, wodurch ihr Widerstand abgesenkt wird.

d) Magnetische Bolometer. Diese Sensoren, die eine schwache thermische Kopplung an ein Kältebad bzw. eine Wärmesenke mit einer Temperatur vorzugsweise im Millikelvinbereich haben, umfassen eine schwache Konzentration von paramagnetischen Ionen in einem magnetischen Feld. Als derartige Ionen werden vorteilhafterweise Ionen von seltenen Erden, wie beispielsweise von Erbium (Er³⁺), verwendet. Wenn ein kleiner Energiebetrag, beispielsweise durch elektromagnetische Strahlung, in einem derartigen Sensor deponiert wird, verursacht der Temperaturanstieg eine Änderung der Magnetisierung des von den paramagnetischen Ionen gebildeten Paramagneten, die beispielsweise unter Verwendung einer Spule, die an einen Eingang eines SQUIDs angeschlossen ist, gemessen werden kann. Vorteilhafterweise ist an das magnetische Bolometer ein Absorber thermisch gekoppelt.

There are various ways of measuring the temperature increase, the lattice vibrations, the quasiparticles (generally the excitations) or the change in the magnetization, with the general rule that the excitations are generated in an absorber and are detected in a sensor. Sensor and absorber can be identical. Possible sensors are:

a) Superconducting phase transition thermometer, such as a sensor in a microcalorimeter: These essentially consist of an absorber, a phase transition thermometer (superconducting layer, e.g. made of tungsten, iridium, aluminum or tantalum) and a cooling device or a coupling to a heat sink. In the temperature transition area between its superconducting and normal conducting phase, the thermometer changes its electrical resistance very strongly depending on the temperature, ie also after absorption of lattice vibrations and quasiparticles.

b) Superconducting tunnel diodes: They consist of two overlapping thin superconducting films ( SIS : superconductor-insulator-superconductor, whereby the films do not necessarily have to consist of the same superconductor on both sides) or a superconducting and a normal-conducting film ( NIS : normal-conductor-insulator Superconductor), the respective films being separated by a thin electrically insulating barrier. The barrier is so thin that it allows quantum mechanical tunneling of electrons or quasiparticles from one electrode to the other. If the NIS diode or SIS diode is operated below the step temperature of the respective superconductor, and the applied voltage is less than the voltage (NIS) corresponding to the superconducting energy gap or less than twice this voltage (SIS), this rises above the barrier flowing electricity when energy is deposited in the tunnel diode. The deposition of the energy can take place through an increase in temperature, absorption of lattice vibrations or quasiparticles or directly through absorption of radiation or particles.

c) Thermistor, such as NTD thermometer ( NTD : "Neutron Transmutation Doping", ie semiconductors highly doped with neutrons). These thermometers can be used to measure temperature fluctuations because, like all semiconductors, the resistance increases with decreasing temperature. In order to avoid that the resistors grow so high at very low temperatures that they can no longer be measured with sufficient accuracy, the semiconductors used are heavily doped, as a result of which their resistance is reduced.

d) Magnetic bolometers. These sensors, which have a weak thermal coupling to a cold bath or a heat sink with a temperature preferably in the millikelvin range, comprise a weak concentration of paramagnetic ions in a magnetic field. As such ions, rare earth ions such as erbium (Er ³⁺ ) are advantageously used. If a small amount of energy is deposited in such a sensor, for example by electromagnetic radiation, the temperature rise causes a change in the magnetization of the paramagnet formed by the paramagnetic ions, which is measured, for example, using a coil connected to an input of a SQUID can. An absorber is advantageously thermally coupled to the magnetic bolometer.

It is also conceivable to use low-temperature superconductors to use based SQUIDs as sensors.

The object to be cooled can also be a variety of Have sensors. This is advantageous, for example, if two different types of sensors are used, their Energy resolution in different energy areas is different.

Brief description of the drawing

Further details, features and advantages of the invention result from the following description more preferred Embodiments based on the drawing.

Figur 1 eine schematische Darstellung einer Kühlvorrichtung unter Verwendung eines Pulsröhrenkühlers im Stand der Technik;

Figur 2 eine schematische Darstellung einer erfindungsgemäßen Kühlvorrichtung gemäß einer ersten Ausführungsform;

Figur 3 eine schematische Darstellung einer erfindungsgemäßen Kühlvorrichtung gemäß einer zweiten Ausführungsform;

Figur 4 eine schematische Darstellung einer erfindungsgemäßen Kühlvorrichtung gemäß einer dritten Ausführungsform;

Figur 5 eine schematische Darstellung einer erfindungsgemäßen Kühlvorrichtung gemäß einer vierten Ausführungsform;

Figur 6 eine schematische Darstellung einer erfindungsgemäßen Kühlvorrichtung gemäß einer fünften Ausführungsform;

Figur 7 eine schematische Darstellung einer erfindungsgemäßen Kühlvorrichtung gemäß einer sechsten Ausführungsform;

Figur 8 eine schematische Darstellung einer erfindungsgemäßen Kühlvorrichtung gemäß einer siebten Ausführungsform;

Figur 9 eine schematische Darstellung eines Pulsröhrenkühlers gemäß einer ersten Ausgestaltung;

Figur 10 eine schematische Darstellung eines Pulsröhrenkühlers gemäß einer zweiten Ausgestaltung;

Figur 11 eine schematische Darstellung eines Pulsröhrenkühlers gemäß einer dritten Ausgestaltung;

Figur 12 eine schematische Darstellung eines Pulsröhrenkühlers gemäß der dritten Ausgestaltung in einer konkreteren Darstellung als in Figur 11; und

Figur 13 eine schematische Darstellung eines zweistufigen Pulsröhrenkühlersystems mit den wichtigstem Komponenten.

Show it:

Figure 1 is a schematic representation of a cooling device using a pulse tube cooler in the prior art;

Figure 2 is a schematic representation of a cooling device according to the invention according to a first embodiment;

Figure 3 is a schematic representation of a cooling device according to the invention according to a second embodiment;

Figure 4 is a schematic representation of a cooling device according to the invention according to a third embodiment;

Figure 5 is a schematic representation of a cooling device according to the invention according to a fourth embodiment;

Figure 6 is a schematic representation of a cooling device according to the invention according to a fifth embodiment;

Figure 7 is a schematic representation of a cooling device according to the invention according to a sixth embodiment;

Figure 8 is a schematic representation of a cooling device according to the invention according to a seventh embodiment;

Figure 9 is a schematic representation of a pulse tube cooler according to a first embodiment;

Figure 10 is a schematic representation of a pulse tube cooler according to a second embodiment;

Figure 11 is a schematic representation of a pulse tube cooler according to a third embodiment;

Figure 12 is a schematic representation of a pulse tube cooler according to the third embodiment in a more concrete representation than in Figure 11; and

Figure 13 is a schematic representation of a two-stage pulse tube cooler system with the most important components.

Preferred embodiments

The following is the cooling device according to the present Invention described.

First embodiment

Reference is first made to FIG. 2, the one schematic representation of a first embodiment of a shows cooling device according to the invention. Here, like in the following figures, the same parts with the same reference numerals designated.

The cooling device according to the invention of this embodiment, as well as the following embodiments, partially to improve cooling performance in one Arranged cooling container or a cryostat (not shown), where the temperature levels shown in the figures Represent areas that are advantageous surrounded by heat or radiation shields for thermal insulation are.

Viewed from top to bottom, a connection device 60 is located on a cover of the cryostat, which represents the 300 K temperature level (or the temperatures T _A1 , T _V mentioned in the introduction) due to the thermal contact with the exterior of the cryostat or cooling area for electrical supply lines 62, as well as a warm head (not shown) of a first pulse tube 20 and a warm end section 44 of an associated first regenerator 40. At the lower end of the pulse tube, a cold head 24 is provided, is received at the heat from an object to be cooled, in this case of a magnet 82, at a temperature of about 77K (or T _E). Furthermore, the cold head 24 of the first pulse tube 20 is connected via a line 42 to a cold end section 46 of the regenerator 40. Further components which are important for the operation of a pulse tube cooler and which are not necessary to illustrate the invention are illustrated below in the general description of the functional principle of a pulse tube cooler.

It should be noted that the specified temperature levels serve only for illustration and according to the prevailing Operating state or depending on the ambient temperature can have other values.

According to the invention, the electrical supply lines run 62, which is a connecting device between the Exterior of the cooling area in thermal contact Connection device 60 or the cryostat cover and the Magnet 82 forms, partially or over a predetermined Distance in thermal contact along the pulse tube 20 in Direction from the hot head (not shown) to the cold head 24. As a result, the electrical leads 62 are already in front the contact with the magnet 82 or cold head 24 of the first Pulse tube 20 pre-cooled, resulting in a lower heat load leads to the cold head 24.

In this as well as in the following embodiments can the electrical leads 62 made of superconducting (Superconducting here means both high temperature and low temperature superconducting) and / or normal conducting wires exist, which are advantageously electrically isolated are. The thermal contact of the leads 62 with the Pulse tube 20 (or the second pulse tube 30, see FIG. 5) or as in the second embodiment with the regenerator 40 can by gluing the leads 62 to the pulse tube 20 or the regenerator 40 or by winding the supply lines 62 around these components 20.40. It is further possible with the supply lines over a certain distance Clamps or the like on components 20, 40 (or to attach the second pulse tube 30).

Second embodiment

Reference is now made to FIG. 3, which is a schematic Representation of a second embodiment of the invention Cooling device shows.

As in the first embodiment, the second Embodiment the connection device 60 for electrical Supply lines 62, and the hot head (not shown) of first pulse tube 20 and the warm end portion 44 of the associated first regenerator 40 in thermal contact with the 300 K temperature level. At the lower end of the pulse tube 20, the cold head 24 is again provided, at which a cooling temperature provided on the magnet 82 of about 77K becomes. Furthermore, the cold head 24 of the first pulse tube 20 via line 42 with a cold end portion 46 of the Regenerator 40 connected.

In contrast to the first embodiment run here the electrical leads 62 partially or via a certain distance in thermal contact along the regenerator 40 toward the warm end portion 44 the cold end section 46, which is connected via line 42 to the Cold head 24 is connected. Because of the exchange a working gas between the regenerator 40 and the Pulse tube 20 (the general principle of operation of the pulse tube cooler is explained in more detail below) is the regenerator 40 also in thermal contact with the pulse tube 20 and like this has a temperature gradient from the warm end portion 44 to the cold end section 46. Thus the temperature of the in one or more places with the Regenerator in thermal contact electrical Supply lines 62 at different temperature levels "intercepted" or adjusted (for the purpose of pre-cooling), before they reach the magnet 82, which in turn leads to a leads to a lower heat load on the cold head 24.

Third embodiment

Reference is now made to FIG. 4, which is a schematic Representation of a third embodiment of the invention Cooling device shows, the characteristic of this Embodiment is the two-stage pulse tube cooler system.

Similar to the first two embodiments, in the third embodiment there is a connection device 60 for electrical leads 62, a warm head (not shown) of a first pulse tube 20, a warm head (not shown) of a second pulse tube 30, and a warm end section 54 of a second regenerator 50 in thermal contact with the 300 K temperature level (T _A1 , T _A2 , T _V ), for example a cryostat cover. In this illustration, the two regenerators 40 and 50 are connected to one another, so that the upper regenerator 50 is used as a warm regenerator section 50 or for coupling to the 300K temperature level from the regenerator 40. However, an arrangement with two separate regenerators is conceivable. At the lower end of the first pulse tube 20, a cold head 24 is provided, is provided at the cooling temperature at an object to be cooled, here on a magnet 82, of about 4K (T _E). At the lower end of the second pulse tube 30, a cold head 34 is provided, at which a cooling temperature of approximately 77K (T _Z ) is provided for precooling the first pulse tube 20. More specifically, the temperature of 77K is provided to a cooling area containing the cold head 24 of the first pulse tube and the magnet 82, which in the case of using a cryostat is surrounded by a heat shield for thermal insulation. Furthermore, the cold head 24 of the first pulse tube 20 is connected to a cold end section 46 of the regenerator 40 via a line 42 and the cold head 34 of the second pulse tube 30 is connected to a cold end section 56 of the second regenerator 50 via a line 52.

In the third embodiment, electrical leads meet 62, which is a connecting device between the in thermal contact with the exterior of the cooling area standing connection device 60 or cryostat cover and the magnet 82 forms, initially on one on the 77K temperature level thermal interception device 64, at which the temperature of the supply lines 62 to 77K "intercepted" or (for the purpose of pre-cooling) adjusted becomes. From there, the supply lines 62 partially run or over a predetermined distance in thermal contact along the pulse tube 20 towards the hot head (not to the cold head 24. As in the first embodiment the electrical supply lines 62 even before contact with the magnet 82 or cold head 24 of the first pulse tube 20 pre-cooled, resulting in a lower Thermal load on the cold head 24 leads.

Fourth embodiment

Reference is now made to FIG. 5, which is a schematic Representation of a fourth embodiment of the invention Cooling device shows.

As in the third embodiment, the fourth Embodiment a connection device 60 for electrical Supply lines 62, a warm head (not shown) a first pulse tube 20, a warm head (not shown) a second pulse tube 30, and a warm end section 54 of a second regenerator 50 in thermal contact with the 300 K temperature level, for example of a cryostat cover. At the lower end of the first pulse tube 20 is again a cold head 24 is provided at which a cooling temperature on an object to be cooled, here on a magnet 82, of about 4K is provided. At the bottom of the second A cold head 34 is provided on the pulse tube 30 Cooling temperature of about 77K for pre-cooling the first one Pulse tube 20 is provided. Furthermore, the cold head 24 of the first pulse tube 20 via a line 42 with a cold end portion 46 of the regenerator 40 and is the Cold head 34 of the second pulse tube 30 via a line 52 with a cold end portion 56 of the second regenerator 50 connected.

In the fourth embodiment, the electrical Supply lines 62 partially or over a predetermined distance in thermal contact along the second pulse tube 30 performed where the temperature of the leads 62 already on the Temperature of the second pulse tube 30 (for the purpose of pre-cooling) is adjusted. The supply lines run from there 62 partially or over a predetermined distance in thermal contact along the pulse tube 20 in the direction from the hot head (not shown) to the cold head 24. As in the first embodiment, the electrical Leads 62 even before contact with the magnet 82 or Cold head 24 of the first pulse tube 20 pre-cooled, resulting in a leads to a lower heat load on the cold head 24.

Fifth embodiment

Reference is now made to FIG. 6, which is a schematic Representation of a fifth embodiment of an inventive Cooling device shows. Here, as in the following Figures, same parts with the same reference numerals designated.

Viewed from top to bottom, a connection device 60 is located on a cover of the cryostat, which represents the 300 K temperature level (or the temperatures T _A1 , T _V mentioned in the introduction) due to the thermal contact with the exterior of the cryostat or cooling area for a vertical holding device 62 or supporting device 62 for holding or supporting an object 82 to be cooled, as well as a warm head (not shown) of a first pulse tube 20 and a warm end section 44 of an associated first regenerator 40. Between the vertical holding arrangement 62 and the first pulse tube 20, a vertical holding arrangement 63 is provided, which establishes thermal contact between the components 62 and 20. At the lower end of the pulse tube, a cold head 24 is provided, is received at the heat from an object to be cooled, in this case of a magnet 82, at a temperature of about 77K (or T _E). Furthermore, the cold head 24 of the first pulse tube 20 is connected via a line 42 to a cold end section 46 of the regenerator 40. Further components which are important for the operation of a pulse tube cooler and which are not necessary to illustrate the invention are illustrated below in the general description of the functional principle of a pulse tube cooler.

It should be noted again that the temperature levels given serve only for illustration and accordingly the prevailing operating state or depending on the ambient temperature may have different values.

To reduce the thermal load on the cold head 24 is in this embodiment, the holding device 62, 63 two parts, namely the actual holding part 62 and the Contact part 63 for making a thermal contact formed between the holding part 62 and the pulse tube 20. For heat insulation of the object to be cooled 82 from the 300K temperature level, the holding part 62 is advantageously from a poorly heat-conducting material, such as for example plastics, in particular glass fibers or Kevlar threads. For a stable bracket from heavy to cooling objects can also be rod-shaped or tubular Holding parts, especially made of poorly heat-conducting materials be used. For thermal coupling to the Pulse tube 20, however, is advantageous for the contact part 63 a thermally highly conductive material, such as metal, to be used in the form of wires, rods, pipes, etc. Because of this holding arrangement, the holding device 62,63 pre-cooled before contact with magnet 82, resulting in a lower thermal load on the cold head 24 leads.

The thermal contact of the holding or contact parts 62 and 63 with each other or with the pulse tube 20 or as in the seventh embodiment with the regenerator 40 can by gluing the holding or contact parts 62 and 63 together with each other or by sticking to the pulse tube 20 or the regenerator 40, or by winding the contact parts 63 around components 20, 40 or 62. It is further possible to use clamps or the like for fastening.

Sixth embodiment

Reference is now made to FIG. 7, which is a schematic Representation of a sixth embodiment of the invention Cooling device shows, the characteristic of this Embodiment again the two-stage pulse tube cooler system is.

Similar to the fifth embodiment, in the sixth embodiment, a warm head (not shown) of a first pulse tube 20, a warm head (not shown) of a second pulse tube 30, and a warm end section 54 of a second regenerator 50 are in thermal contact with the 300 K temperature level (T _A1 , T _A2 , T _V ), for example a cryostat cover. In this illustration, the two regenerators 40 and 50 are connected to one another, so that the upper regenerator 50 is used as a warm regenerator section 50 or for coupling to the 300K temperature level from the regenerator 40. However, an arrangement with two separate regenerators is conceivable. At the lower end of the first pulse tube 20, a cold head 24 is provided, is provided at the cooling temperature at an object to be cooled, here on a magnet 82, of about 4K (T _E). At the lower end of the second pulse tube 30, a cold head 34 is provided, at which a cooling temperature of approximately 77K (T _Z ) is provided for precooling the first pulse tube 20. More specifically, the temperature of 77K is provided to a cooling area containing the cold head 24 of the first pulse tube and the magnet 82, which in the case of using a cryostat is surrounded by a heat shield for thermal insulation. Furthermore, the cold head 24 of the first pulse tube 20 is connected to a cold end section 46 of the regenerator 40 via a line 42 and the cold head 34 of the second pulse tube 30 is connected to a cold end section 56 of the second regenerator 50 via a line 52.

A holding device is used to hold or support the magnet 82 62,63 provided, the holding part 62 (vertical) the magnet 82 via a connection device 60 on the cold head 34 or on a 77K heat shield of a cryostat holds. To establish a thermal contact between the holding part 62 and the lower part of the pulse tube 20 and thus for precooling the entire holding device 62, 63 contact parts 63 (horizontal) are provided. The materials of the individual holding or contact parts are corresponding to choose the fifth embodiment. Thus by the thermal contact with the pulse tube 20, the temperature "Intercepted" by 77K of the holding device 62.63 or at low temperatures in the area of the cold head temperature adjusted, resulting in a reduction in thermal load leads to the cold head.

Seventh embodiment

Reference is now made to FIG. 8, which is a schematic Representation of a seventh embodiment of the invention Cooling device shows.

The two-stage pulse tube cooler system essentially has the same structure as that of the sixth embodiment on. The difference in this embodiment however, consists of holding or supporting the magnet 82.

A holding device is used to hold or support the magnet 82 62,63 provided, the holding part 62 (vertical) the magnet 82 via a connection device 60 on the cold head 34 or on a 77K heat shield of a cryostat holds. In contrast to the sixth embodiment, here a thermal contact between the holding part 62 and the Regenerator 40 for pre-cooling the entire holding device 62,63 provided by contact parts 63 (horizontal). The Materials of the individual holding or contact parts are to choose according to the fifth embodiment. Consequently is due to thermal contact with the regenerator 40 the temperature of 77K of the holding device 62.63 "intercepted" or at low temperatures in the range of Cold head temperature adjusted, resulting in a decrease the heat load leads to the cold head.

Pulse tube cooler

The following is the general structure and mode of operation one in the cooling device according to the invention described pulse tube cooler to be used. It shows Figure 9 is a schematic representation of a pulse tube cooler according to a first embodiment. Here, like in the following figures, are again the same parts with the the same reference numerals.

The cooling effect in the pulse tube cooler is based on the periodic Pressure change and displacement ("pulsation") of a Working gas in a thin-walled cylinder with heat exchangers at both ends, the so-called pulse tube 20. The Pulse tube 20 is connected to pressure oscillator 10 via a regenerator 40 connected. The regenerator 40 serves as an intermediate heat store, which flows in from the pressure oscillator 10 Gas cools before entering pulse tube 20 and then the escaping gas back to room temperature warmed up. For this purpose it is advantageously with a Material filled with high heat capacity, which is a good one Heat exchange with the flowing gas at the same time low Has flow resistance. At temperatures above 30 K one uses stacks of fine-meshed stainless steel or bronze sieves as regenerator filling. For deeper ones Temperatures are set due to the high heat capacity Lead shot and more recently magnetic materials, e.g. Er-Ni alloys, a. To generate the pressure oscillation becomes a compressor as shown in FIG 10 in combination with a downstream rotary valve 15 used that periodically the high and low pressure side of the compressor connects to the cooler. Alternatively the pressure oscillation can be done directly via the Piston movement of a valveless compressor are generated.

In the first embodiment of the pulse tube cooler the pulse tube at the warm end 22 closed. The cooling process runs qualitatively as follows: in the compression phase the gas pre-cooled in the regenerator 40 flows into the pulse tube 20 a. By increasing the pressure, the gas is in the pulse tube 20 warmed and at the same time to the warm heat exchanger 22 or warm head 22 moved where part of the heat of compression is dissipated to the environment. Through the subsequent expansion, the gas is cooled in the Pulse tube 20. The gas leaving pulse tube 20 is colder than when entering and can therefore heat from the cold Heat exchanger 24 or cold head 24 and the one to be cooled Object or another cooling device. A more detailed analysis of the process in this embodiment shows that for the heat transfer from cold 24 to warm 22 Heat exchange between gas and pipe wall required is ("surface heat pumps"). Because the thermal contact however only in a thin layer of gas on the pipe wall this cooling process has not yet been optimized.

Figure 10 now shows a schematic representation of a Pulse tube cooler 20 according to a second embodiment. This results in a significant increase in effectiveness by connecting a ballast volume 70 over a flow resistance (needle valve) 26 on the warm heat exchanger 22. On the one hand, more gas flows through the warm one Heat exchanger 22, which then give off heat of compression there can. On the other hand, the gas in the pulse tube does 20 work when moving gas into the ballast volume 70, whereby a significantly higher cooling effect is achieved.

Figure 11 shows a schematic representation of a Pulse tube cooler according to a third embodiment, at which further increases the effectiveness of the cooler lets by the proportion of gas flow that leads to pressure change is necessary in the warm part of the pulse tube 20, by a second inlet at the warm end. Because of this Gas flow no longer passes the regenerator 40, the Losses in regenerator 40 reduced. It also turns out at a second inlet (with a valve 28) one for the Cooling more favorable chronological sequence of pressure and flow variation on.

Figure 12 shows a schematic overall structure of a Pulse tube cooler according to the third embodiment in one more concrete representation than in FIG. 11 a commercial helium compressor 10 motor-driven rotary valve 15, which for controlling the Helium gas flow is used.

For mechanical decoupling and for reducing Electromagnetic interference can be the real cooler and the rotary valve via a flexible plastic line 12 connected to each other.

Figure 13 shows a schematic representation of a two-stage pulse tube cooler system with the most important Components, such as for the third or fourth embodiment of the cooling device according to the invention is usable. To generate pressure oscillations a compressor 10 is coupled to a rotary valve 15. A line 12 connects the rotary valve 15 with the Pulse tube cooler system. This has a regenerator 40 of the first stage and a regenerator 50 of the second stage , with a flow aligner ("flow straightener ") 55 is arranged. It is also conceivable to use a to choose another regenerator arrangement, for example two separate regenerators can be used. Further the pulse tube cooler system has a first pulse tube 20 a warm heat exchanger 22 and a cold heat exchanger or cold head 24 and a second pulse tube 30 with a warm heat exchanger 32 and a cold heat exchanger or cold head 34. The respective warm heat exchangers 22 and 32 are via throttle valves, for example in the Form of needle valves 26 and 36, with a common Ballast container or ballast volume 70 connected. It is further conceivable that instead of the common ballast volume two separate ballast volumes can be used. Moreover are on the respective warm heat exchangers 22 and 32 valves 38 and 28 are provided for a second inlet. The cold head 24 of the second pulse tube 30 cools one area surrounded by a heat or radiation shield 92 up to a maximum of about 50 K, while on the cold head 24 of the first pulse tube 20 has a temperature of approximately 2.2 up to 4.2 K is provided (see also C. Wang et al.:"A two-stage pulse tube cooler operating below 4 K ", Cryogenics 1997, Volume 37, No. 3).

The cooling device according to the invention, the pulse tube cooler has due to the lack of moving Parts with very little vibration and therefore particularly good for suitable for cooling sensitive sensors such as SQUIDs.

A cooling device is disclosed which comprises the following components: a first pulse tube cooler with a first pulse tube 20, which has a warm head with a first temperature T _A1 and a cold head 24 with a second temperature T _{E which is} lower than the first temperature, and a first regenerator 40 having a warm end portion 44 and a cold end portion 46 connected to the cold head of the first pulse tube; an object to be cooled 82 that is thermally coupled to the cold head of the first pulse tube cooler; and a connecting device 62 for mechanically or electrically connecting the object to be cooled to a region 60 which has a temperature T _V that is higher than the second temperature T _E. The region 60, which generally designates an area or a device with a temperature higher than T _E , can be formed by a connection device 60 for the connecting device or be in thermal contact with it. The connection device can furthermore have a mechanical fastening means, such as an adhesive or a screw connection, or also an electrical connection. According to the invention, the connecting device runs at least partially in thermal contact along the first pulse tube from the warm head to the cold head and / or partially in thermal contact along the first regenerator from the warm end section to the cold end section. As a result, the connecting device is pre-cooled even before contact with the object or cold head of the first pulse tube 20 to be cooled, which leads to a lower thermal load on the cold head 24.

Reference list

10th

compressor

12th

Line away from the compressor

15

Rotary valve

20th

Pulse tube, first pulse tube

22

warm heat exchanger from 20

24th

cold heat exchanger, cold head of 20

26

Flow resistance, needle valve to 70

28

Second inlet valve

30th

second pulse tube

32

warm heat exchanger from 30

34

cold heat exchanger, cold head of 30

36

Flow resistance, needle valve to 70

38

Second inlet valve

40

Regenerator, first stage regenerator

42

Line from 46 to 24

44

warm end section of 40

46

cold end section of 40

50

Second stage regenerator

52

Leading from 56 to 34

54

warm end section of 50

55

Flow aligners between 40 and 50

56

cold end section of 50

60

Connection facility, area

62

Connecting device (electrical, mechanical), Holding part

63

Contact part

64

thermal interception device

70

Ballast volume

82

Magnet, object to be cooled

Claims (17)

Cooling device comprising: a first pulse tube cooler with a first pulse tube (20), which has a warm head with a first temperature (T _A1 ) and a cold head (24) with a second temperature (T _E ) lower than the first temperature, and a first regenerator (40) which has a warm end section (44) and a cold end section (46) which is connected to the cold head (24) of the first pulse tube (20); an object (82) to be cooled, which is thermally coupled to the cold head (24) of the first pulse tube (20); and a connecting device (62) for electrically connecting the object (82) to be cooled to a region (60) which has a higher temperature (T _V ) than the second temperature (T _E ), characterized in that that the connecting device (62) runs at least partially in thermal contact with the first pulse tube (20) and / or partially in thermal contact with the first regenerator (40). Cooling device according to claim 1, characterized in that the connecting device (62) superconducting and / or has normally conducting electrical feed lines. Cooling device comprising: a first pulse tube cooler with a first pulse tube (20), which has a warm head with a first temperature (T _A1 ) and a cold head (24) with a second temperature (T _E ) lower than the first temperature, and a first regenerator (40) which has a warm end section (44) and a cold end section (46) which is connected to the cold head (24) of the first pulse tube (20); an object (82) to be cooled, which is thermally coupled to the cold head (24) of the first pulse tube (20); and a connecting device (62, 63) for mechanically acting on and / or for holding the object to be cooled with a first end which is connected to the object to be cooled and a second end which is connected to a Region (60) which has a higher temperature (T _V ) than the second temperature (T _E ) is connected, wherein the connecting device (62, 63) runs at least partially in thermal contact with the first pulse tube (20) and / or partially in thermal contact with the first regenerator (40). Cooling device according to claim 3, characterized in that the connecting device (62,63) for holding the object to be cooled (82) has a two-part structure, which is a holding part (62) for holding the object to be cooled (82) on a connection device (60) which is connected to the area (60) is in thermal contact, and a contact part (63) for making thermal contact between the first Pulse tube (20) and / or the first regenerator (40) having. Cooling device according to claim 4, characterized in that the holding part (62) from a poorly heat-conducting Material and the contact part (63) from a good heat-conducting Material exists. Cooling device according to one of claims 1 to 5, characterized characterized in that the connecting device (62, 63) at least partially along the first pulse tube (20) from the hot head to the cold head (24) and / or partially along of the first regenerator (40) from the warm end section (44) to the cold end section (46). Cooling device according to one of claims 1 to 6, characterized by a second pulse tube cooler with a second pulse tube (30) which a warm head with a third temperature (T _A2 ) and a cold head (34) with a lower with respect to the third temperature (T _A2 ) fourth temperature (T _Z ), which lies between the first temperature (T _A1 ) and the second temperature (T _E ), and a second regenerator (50), which has a warm end section (54) and a cold end section (56) , which is connected to the cold head (34) of the second pulse tube (30), the fourth temperature (T _Z ) for precooling the first pulse tube cooler being provided on the second pulse tube cooler. Cooling device according to claim 7, characterized in that the first regenerator (20) the second regenerator (30) used as its warm end section. Cooling device according to claim 7 or 8, characterized in that the temperature (T _V ) of the region (60) is higher than the fourth temperature (T _Z ), the connecting device (62, 63) at least partially along the second pulse tube (30) from the warm head to the cold head (34) and / or at least partially along the second regenerator (50) from the warm end section (54) to the cold end section (56). Cooling device according to one of claims 1 to 9, characterized characterized in that the object to be cooled (82) has a Magnet has. Cooling device according to one of claims 1 to 10, characterized characterized in that the object to be cooled (82) has a Sensor for the detection of particles, radiation or fields having. Cooling device according to claim 11, characterized in that the sensor is a high temperature superconductor SQUID or is a low temperature superconductor SQUID. Cooling device according to claim 11, characterized in that the sensor is based on a low temperature effect Sensor is connected to a cryogenic cooler is thermally coupled and cooled by it becomes. Cooling device according to claim 13, characterized in that the cryogenic cooling device has a demagnetization stage having. Cooling device according to claim 13 or 14, characterized in that that the sensor is a phase transition thermometer, a superconducting tunnel diode, a thermistor or has a magnetic bolometer. Cooling device according to one of claims 11 to 15, characterized in that the object to be cooled (82) is a Has a variety of sensors. Cooling device according to one of claims 1 to 16, characterized characterized in that the connecting device (62,63) by gluing, wrapping or using clamps on the first (20) or second (30) pulse tube and / or on the first (40) or second (50) regenerator in thermal contact brought.

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