EP0188976A1 - Dilution cryostat - Google Patents

Dilution cryostat Download PDF

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Publication number
EP0188976A1
EP0188976A1 EP19850420228 EP85420228A EP0188976A1 EP 0188976 A1 EP0188976 A1 EP 0188976A1 EP 19850420228 EP19850420228 EP 19850420228 EP 85420228 A EP85420228 A EP 85420228A EP 0188976 A1 EP0188976 A1 EP 0188976A1
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EP
European Patent Office
Prior art keywords
dilution
circuit
pumping
evaporator
chamber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP19850420228
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German (de)
French (fr)
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EP0188976B1 (en
Inventor
Alain Daniel Benoit
Serge Pujol
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Centre National de la Recherche Scientifique CNRS
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Centre National de la Recherche Scientifique CNRS
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Publication of EP0188976A1 publication Critical patent/EP0188976A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C3/00—Vessels not under pressure
    • F17C3/02—Vessels not under pressure with provision for thermal insulation
    • F17C3/08—Vessels not under pressure with provision for thermal insulation by vacuum spaces, e.g. Dewar flask
    • F17C3/085—Cryostats
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/12—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using 3He-4He dilution
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2270/00—Applications
    • F17C2270/05—Applications for industrial use
    • F17C2270/0518—Semiconductors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D2400/00—General features of, or devices for refrigerators, cold rooms, ice-boxes, or for cooling or freezing apparatus not covered by any other subclass
    • F25D2400/28—Quick cooling

Definitions

  • the invention relates to dilution cryostats, that is to say devices or installations making it possible to reach very low temperatures, of the order of 1 ° Kelvin.
  • the invention relates to apparatuses of the above type which can be used for laboratory research purposes, or even for industrial purposes, for example for the analysis of the physical properties of various materials or, more particularly, of materials. superconductors.
  • the invention relates, more specifically, to devices or installations making it possible to reach very low temperatures, below 1 ° Kelvin.
  • Dilution cryostats can be classified into two categories.
  • the first relates to devices or installations in which the sample to be analyzed is fixed on the cold point.
  • this cold point is constituted by a wall of the dilution chamber which is arranged in a sealed enclosure.
  • the operating principle of these cryostats consists of introducing helium in the gaseous phase into the sealed enclosure in order to perform precooling prior to the subsequent operating mode in dilution.
  • the second category relates to dilution devices comprising, in order to remedy the above drawbacks, a sample changer placed in relation to the cold point.
  • a sample changer placed in relation to the cold point.
  • the object of the invention is to remedy the above drawbacks by proposing a new dilution cryostat designed to allow rapid commissioning, from the sole components of said device or installation, as well as access quick to change the sample.
  • the single figure is a schematic view illustrating the structure of the dilution cryostat according to the invention.
  • the dilution cryostat comprises a suspension frame 1 to which is suspended a first precooling stage 2 under which is fixed a second precooling stage 3 associated with a suspended dilution unit 4.
  • the frame 1 mainly comprises a plate 5 under which a sealed enclosure 6 is fitted, by means of a removable seal 7.
  • the assembly makes it possible to isolate the internal volume which can be evacuated using the pump 8 and the valve 9.
  • the first precooling stage 2 comprises an exchange plate 10 made of a metal having very good thermal conductivity characteristics and, for example, of copper.
  • the plate 10 is suspended from the plate 5 by the pumping tubes described below and having a low thermal conductivity.
  • the plate 10 is extended downwards by a removable enclosure 11 with a closed bottom.
  • This enclosure constructed of a conductive material, such as copper or aluminum, is not waterproof and only serves as a barrier to thermal radiation.
  • the first precooling stage 2 comprises an evaporator 16 carried by the exchange plate 10.
  • the evaporator 16 is connected to an evacuation pipe 17 controlled by a valve 18.
  • the evaporator 16 is also connected to its inlet , via a line 19, to a reservoir 20 of a cryogenic liquid, such as liquid nitrogen.
  • the reservoir 20 is enclosed in a sealed compartment 21.
  • the reservoir 20 is placed under load relative to the evaporator 16.
  • the pipe 17 is responsible for discharging, in the open air, the vaporized nitrogen.
  • the precooling plate 10 also supports an exchanger-condenser 22 with two independent circuits, the function of which appears in the following.
  • the second precooling stage 3 comprises an exchange plate 23 which is suspended from the plate 10 by the pumping and circulation tubes described below and having a low thermal conductivity.
  • the plate 23 is made of a metal which is a very good conductor of heat and, for example, of copper.
  • the plate 23 is extended downwards by a removable enclosure 24, with a closed bottom. This enclosure, constructed of a conductive material, such as copper or aluminum, is not waterproof and only serves as a barrier to thermal radiation.
  • the plate 23 supports an evaporator 29 comprising a discharge line 30 passing through the plate 10 and the plate 5 and comprising, outside the latter, a valve 31 placed upstream of an extraction pump 32.
  • the evaporator 29 is connected, by a pipe 33 including a valve 34, to a tank 35 containing a cryogenic product, such as liquid helium.
  • the tank 35 is enclosed in the sealed compartment 21.
  • a screen 36 connected to the liquid nitrogen tank 20, protects it from thermal radiation.
  • the pipes 17, 19 and 33 pass through the plate 5 by a thermal insulation sheath 21a formed by the compartment 21.
  • the plate 23 also supports an exchanger-condenser 37 with two independent internal circuits, the function of which appears in the following.
  • the dilution unit 4 comprises, according to the invention, a main evaporator-distiller 40, suspended from the plate 23 by a main pumping circuit 41 rising vertically and passing through the plates 10 and 5 successively.
  • the main evaporator-distiller 40 is connected at its base by a pipe 43 to a dilution chamber 44 constituting the cold point of the dilution unit 4.
  • the dilution chamber 44 is shaped so that its bottom represents a fixing support of a sample 45 to be analyzed.
  • the main pumping circuit 41 comprises a pump 46, the outlet of which is connected, by a valve 47, to a main discharge circuit 48 constituted by a small section pipe passing through the exchanger-condensers 22 and 37.
  • the circuit 48 comprises, beyond the exchanger-condenser 37, an expansion restrictor 49 beyond which it passes through an exchanger 50 placed in relation to the main evaporator-distiller 40.
  • the circuit 48 At the outlet of the exchanger 50, the circuit 48 comprises a second expansion restrictor 51 beyond which it passes through an exchanger 52 concentrically surrounding the tube 43. The circuit 48 then opens into the upper part of the dilution chamber 44.
  • the dilution cryostat further comprises a bypass pumping circuit 53 comprising an evaporator-distiller 54 suspended from the plate 23 by a column 55 also passing through the plates 10 and 5.
  • the column 55 is controlled by a valve 57 at the -from which it is connected to the main circuit 41.
  • the evaporator 54 is connected, by a pipe 56, to the dilution chamber 44.
  • the dilution cryostat further comprises a branched discharge circuit 58 also connected to the outlet of the pump 46 by a valve 59.
  • the circuit 58 passes through the exchanger-condenser 22, then the exchanger-condenser 37 beyond which it is connected to column 55 in the part of the latter located above the plate 23 of the second precooling stage 3.
  • a reserve 42 containing the quantities of 3 He and 4 He necessary for operation and mixed in gaseous form.
  • a valve 100 allows the reserve to be emptied using the pump 46, a valve 101 allowing the 3 He, 4 He mixture to return to the reserve at the end of use.
  • the structure described above has the advantage of allowing easy installation and removal of the sample 45. In fact, for all these operations, it suffices to establish the normal pressure in the enclosure 6 by the valve 9, then successively dismantle the speakers 6, 11 and 24.
  • the structure of the cryostat is also chosen so that the effective commissioning of the device can take place quickly.
  • the structure of the device is chosen so that the pre-cooling phase is carried out more simply and more quickly than according to the prior art.
  • a pumping and vacuuming phase can occur simultaneously with a precooling which is ensured in the following manner.
  • the valve 18 is open, so that the liquid nitrogen passes by gravity through the evaporator 16, in order to ensure the cooling of the plate 10. Simultaneously, the valves 31 and 34 are open and the pump 32 is turned on. running, so as to create a circulation of helium in the evaporator 29 responsible for cooling the exchange plate 23.
  • the valve 57 is then closed, as is the valve 47, while the valve 59 is, on the contrary, open.
  • the pump 46 is started, so as to discharge the cryogenic mixture extracted from the reserve 42 into the derivative discharge circuit 58.
  • the cryogenic mixture in the gas phase is cooled by passing through the exchanger-condenser 22, then from the exchanger-condenser 27, before being introduced into column 55 where it arrives at low temperature.
  • the cold mixture then borrows the pipe 56, passes through the dilution chamber 44 and rises through the main pumping circuit 41, before being recycled by the pump 46.
  • This circulation has the effect of cooling the dilution unit by internal circulation, while the dilution cryostats, of the known type, provide a pre-cooling phase by external circulation of a cryogenic product in the vapor phase, such as helium.
  • valves 47 and 57 are open, while the valve 59 is closed.
  • the pump 46 then delivers cryogenic mixture into the main circuit 48. After having cooled in the exchanger 22, the mixture condenses in the exchanger-condenser 37, before expanding through the restrictors 49 and 51. The liquid thus obtained accumulates in the lower parts of the apparatus until completely filling the mixing chamber 44, then the tube 56, as well as the exchanger 52, finally, partially, the evaporators 40 and 54 where the levels s 'balance.
  • the reserve 42 begins the distillation of the mixture in the two evaporators.
  • the 4 He fraction remains at the bottom of the cryostat and the 3 He fraction is pumped by the pump 46.
  • the pure 3 He fraction thus obtained is then discharged by the valve 47, cooled in the exchanger 22, condensed in the exchanger 37, expanded in 49, further cooled in 50, expanded in 51 and, finally, cooled by the exchanger 52, before diluting in the fraction 4 He contained in the dilution chamber 44 thereby cooling the sample.
  • the 3 He fraction rises to the two evaporators by diffusing into the 4 He fraction, cooling the exchanger 52 in passing and preventing any heat from descending along the tubes 56 and 43.
  • the structure of the dilution cryostat according to the invention makes it possible, using the same cryogenic mixture, to ensure precooling by circulation of the mixture in the gas phase inside the constituent elements of the dilution unit 4, then d '' maintain operation in dilution mode by circulating the same mixture in the liquid phase, switching from one operating mode to another being effected by the control of valves 47, 59 and 57. It thus becomes possible to put into service quickly such an apparatus and thus fully benefit from the advantages of rapid change of samples due to the structure of the removable concentric envelopes 6, 11 and 24. It also becomes possible to apply to the sample 45 all the desired temperature ranges, since this depends only on the circulation mode and not on the temperature of the cryogenic liquid reserves 20 and 35.

Abstract

Le cryostat à dilution comprend: - un circuit de pompage dérivé (53) comportant un évaporateur (54) et une vanne (57) placés entre la chambre de dilution (44) et la pompe de circulation (46) faisant partie du circuit principal de pompage et refoulement, - et un circuit de refoulement dérivé (58) contrôlé au-delà de la pompe par une vanne d'admission (59), passant par les premier et second étages (2, 3) et aboutissant dans le circuit de pompage dérivé (53) en aval de l'èvaporateur par rapport à la chambre de diluton. Application à l'analyse de matériaux supra-conducteurs.The dilution cryostat comprises: - a derived pumping circuit (53) comprising an evaporator (54) and a valve (57) placed between the dilution chamber (44) and the circulation pump (46) forming part of the main circuit of pumping and discharge, - and a branched discharge circuit (58) controlled beyond the pump by an intake valve (59), passing through the first and second stages (2, 3) and ending in the pumping circuit derivative (53) downstream of the evaporator with respect to the diluton chamber. Application to the analysis of superconductive materials.

Description

L'invention est relative aux cryostats à dilution, c'est-à-dire aux appareils ou installations permettant d'atteindre des températures très basses, de l'ordre de 1° Kelvin.The invention relates to dilution cryostats, that is to say devices or installations making it possible to reach very low temperatures, of the order of 1 ° Kelvin.

L'invention concerne les appareils du type ci-dessus pouvant être utilisés à des fins de recherche en laboratoire, ou, encore, à des fins industrielles, par exemple pour l'analyse des propriétés physiques de matériaux divers ou, plus particulièrement, de matériaux supra-conducteurs.The invention relates to apparatuses of the above type which can be used for laboratory research purposes, or even for industrial purposes, for example for the analysis of the physical properties of various materials or, more particularly, of materials. superconductors.

L'invention vise, plus spécialement, les appareils ou installations permettant d'atteindre de très basses températures, inférieures à 1° Kelvin.The invention relates, more specifically, to devices or installations making it possible to reach very low temperatures, below 1 ° Kelvin.

Les cryostats à dilution peuvent être classés en deux catégories.Dilution cryostats can be classified into two categories.

La première concerne les appareils ou installations dans lesquels l'échantillon devant être analysé est fixé sur le point froid. En règle générale, ce point froid est constitué par une paroi de la chambre de dilution qui est disposée dans une enceinte étanche. Le principe de fonctionnement de ces cryostats consiste à introduire de l'hélium en phase gazeuse dans l'enceinte étanche afin de réaliser un prérefroidissement préalable au mode de fonctionnement ultérieur en dilution.The first relates to devices or installations in which the sample to be analyzed is fixed on the cold point. As a rule, this cold point is constituted by a wall of the dilution chamber which is arranged in a sealed enclosure. The operating principle of these cryostats consists of introducing helium in the gaseous phase into the sealed enclosure in order to perform precooling prior to the subsequent operating mode in dilution.

La mise en service d'un appareil du type ci-dessus est longue, étant donné que pour chaque échantillon il convient d'ouvrir l'enceinte, d'adapter l'échantillon, de refermer l'enceinte, d'introduire dans cette dernière de l'hélium gazeux afin d'assurer le prérefroidissement de la chambre de dilution jusqu'à environ 4° Kelvin puis, ensuite, de pomper totalement ce gaz avant d'engager le fonctionnement en mode dilution du mélange cryogénique.The commissioning of an apparatus of the above type is long, since for each sample it is necessary to open the enclosure, to adapt the sample, to close the enclosure, to introduce into it helium gas in order to ensure the precooling of the dilution chamber to around 4 ° Kelvin and then, to completely pump this gas before initiating operation in dilution mode of the cryogenic mixture.

Les manipulations longues, voire délicates, devant être conduites pour permettre le montage ou le démontage d'un échantillon à traiter, ainsi que la durée préalable de mise en service, s'opposent à une application industrielle d'un tel type d'appareil.Long, even delicate, manipulations must be pipes to allow the assembly or disassembly of a sample to be treated, as well as the prior duration of commissioning, oppose an industrial application of such a type of device.

La seconde catégorie concerne des appareils à dilution comportant, dans le but de remédier aux inconvénients ci-dessus, un changeur d'échantillons placé en relation avec le point froid. L'existence d'un changeur d'échantillon, s'il permet de faciliter le changement, ne résoud pas le problème du prérefroidissement assuré par le gaz d'échange en phase gazeuse dans l'enceinte entourant la chambre de dilution.The second category relates to dilution devices comprising, in order to remedy the above drawbacks, a sample changer placed in relation to the cold point. The existence of a sample changer, if it facilitates the change, does not solve the problem of the precooling provided by the exchange gas in the gas phase in the enclosure surrounding the dilution chamber.

L'objet de l'invention est de remédier aux inconvénients ci-dessus en proposant un nouveau cryostat à dilution conçu pour permettre une mise en service rapide, à partir des seuls éléments constitutifs dudit appareil ou de l'installation, ainsi qu'un accès rapide pour le changement de l'échantillon.The object of the invention is to remedy the above drawbacks by proposing a new dilution cryostat designed to allow rapid commissioning, from the sole components of said device or installation, as well as access quick to change the sample.

Pour atteindre les buts ci-dessus, l'objet de l'invention se caractérise en ce qu'il comprend :

  • - un circuit de pompage dérivé comportant un évaporateur et une vanne placés entre la chambre de dilution et la pompe de circulation faisant partie du circuit principal de pompage et refoulement,
  • - et un circuit de refoulement dérivé contrôlé au-delà de la pompe par une vanne d'admission, passant par les premier et second étages et aboutissant dans le circuit de pompage dérivé en aval de l'évaporateur par rapport à la chambre de dilution.
To achieve the above aims, the object of the invention is characterized in that it comprises:
  • - a derivative pumping circuit comprising an evaporator and a valve placed between the dilution chamber and the circulation pump forming part of the main pumping and delivery circuit,
  • - And a derivative discharge circuit controlled beyond the pump by an intake valve, passing through the first and second stages and ending in the derivative pumping circuit downstream of the evaporator relative to the dilution chamber.

Diverses autres caractéristiques ressortent de la description faite ci-dessous en référence au dessin annexé qui montre, à titre d'exemple non limitatif, une forme de réalisation de l'objet de l'invention.Various other characteristics will emerge from the description given below with reference to the appended drawing which shows, by way of nonlimiting example, an embodiment of the subject of the invention.

La figure unique est une vue schématique illustrant la structure du cryostat à dilution selon l'invention.The single figure is a schematic view illustrating the structure of the dilution cryostat according to the invention.

Le cryostat à dilution selon l'invention comprend une ossature de suspension 1 à laquelle est suspendu un premier étage de prérefroidissement 2 sous lequel est fixé un second étage de prérefroidissement 3 associé à une unité de dilution suspendue 4.The dilution cryostat according to the invention comprises a suspension frame 1 to which is suspended a first precooling stage 2 under which is fixed a second precooling stage 3 associated with a suspended dilution unit 4.

L'ossature 1 comprend, principalement, une platine 5 sous laquelle s'adapte une enceinte étanche 6, par l'intermédiaire d'un joint démontable 7.The frame 1 mainly comprises a plate 5 under which a sealed enclosure 6 is fitted, by means of a removable seal 7.

L'ensemble permet d'isoler le volume interne que l'on peut mettre sous vide à l'aide de la pompe 8 et la vanne 9.The assembly makes it possible to isolate the internal volume which can be evacuated using the pump 8 and the valve 9.

Le premier étage de prérefroidissement 2 comprend une platine d'échange 10 réalisée en un métal présentant de très bonnes caractéristiques de conductibilité thermique et, par exemple, en cuivre. La platine 10 est suspendue à la platine 5 par les tubes de pompage décrits ci-après et présentant une faible conductivité thermique.The first precooling stage 2 comprises an exchange plate 10 made of a metal having very good thermal conductivity characteristics and, for example, of copper. The plate 10 is suspended from the plate 5 by the pumping tubes described below and having a low thermal conductivity.

La platine 10 est prolongée vers le bas par une enceinte démontable 11 à fond fermé. Cette enceinte, construite en un matériau conducteur, tel que cuivre ou aluminium, n'est pas étanche et sert uniquement de barrière aux radiations thermiques.The plate 10 is extended downwards by a removable enclosure 11 with a closed bottom. This enclosure, constructed of a conductive material, such as copper or aluminum, is not waterproof and only serves as a barrier to thermal radiation.

Le premier étage de prérefroidissement 2 comporte un évaporateur 16 porté par la platine d'échange 10. L'évaporateur 16 est relié à une conduite d'évacuation 17 contrôlée par une vanne 18. L'évaporateur 16 est raccordé, également, à son entrée, par une canalisation 19, à un réservoir 20 d'un liquide cryogénique, tel que de l'azote liquide. Le réservoir 20 est enfermé dans un compartiment 21 étanche. Le réservoir 20 est placé en charge par rapport à l'évaporateur 16. La canalisation 17 est chargée d'évacuer, à l'air libre, l'azote vaporisé.The first precooling stage 2 comprises an evaporator 16 carried by the exchange plate 10. The evaporator 16 is connected to an evacuation pipe 17 controlled by a valve 18. The evaporator 16 is also connected to its inlet , via a line 19, to a reservoir 20 of a cryogenic liquid, such as liquid nitrogen. The reservoir 20 is enclosed in a sealed compartment 21. The reservoir 20 is placed under load relative to the evaporator 16. The pipe 17 is responsible for discharging, in the open air, the vaporized nitrogen.

La platine de prérefroidissement 10 supporte, par ailleurs, un échangeur-condenseur 22 à deux circuits indépendants, dont la fonction apparait dans ce qui suit.The precooling plate 10 also supports an exchanger-condenser 22 with two independent circuits, the function of which appears in the following.

Le second étage de prérefroidissement 3 comprend une platine d'échange 23 qui est suspendue à la platine 10 par les tubes de pompage et de circulation décrits ci-après et présentant une faible conductivité thermique. La platine 23 est réalisée en un métal très bon conducteur de la chaleur et, par exemple, en cuivre. La platine 23 est prolongée vers le bas par une enceinte démontable 24, à fond fermé. Cette enceinte, construite en un matériau conducteur, tel que cuivre ou aluminium, n'est pas étanche et sert uniquement de barrière aux radiations thermiques.The second precooling stage 3 comprises an exchange plate 23 which is suspended from the plate 10 by the pumping and circulation tubes described below and having a low thermal conductivity. The plate 23 is made of a metal which is a very good conductor of heat and, for example, of copper. The plate 23 is extended downwards by a removable enclosure 24, with a closed bottom. This enclosure, constructed of a conductive material, such as copper or aluminum, is not waterproof and only serves as a barrier to thermal radiation.

La platine 23 supporte un évaporateur 29 comprenant une canalisation de refoulement 30 traversant la platine 10 et la platine 5 et comportant, à l'extérieur de cette dernière, une vanne 31 placée en amont d'une pompe d'extraction 32. L'évaporateur 29 est raccordé, par une canalisation 33 incluant une vanne 34, à un réservoir 35 contenant un produit cryogénique, tel que de l'hélium liquide. Le réservoir 35 est enfermé dans le compartiment étanche 21. Un écran 36, relié au réservoir d'azote liquide 20, le protège des radiations thermiques.The plate 23 supports an evaporator 29 comprising a discharge line 30 passing through the plate 10 and the plate 5 and comprising, outside the latter, a valve 31 placed upstream of an extraction pump 32. The evaporator 29 is connected, by a pipe 33 including a valve 34, to a tank 35 containing a cryogenic product, such as liquid helium. The tank 35 is enclosed in the sealed compartment 21. A screen 36, connected to the liquid nitrogen tank 20, protects it from thermal radiation.

Les canalisations 17, 19 et 33 traversent la platine 5 par une gaine d'isolation thermique 21a formée par le compartiment 21.The pipes 17, 19 and 33 pass through the plate 5 by a thermal insulation sheath 21a formed by the compartment 21.

La platine 23 supporte, également, un échangeur-condenseur 37 à deux circuits internes indépendants, dont la fonction apparait dans ce qui suit.The plate 23 also supports an exchanger-condenser 37 with two independent internal circuits, the function of which appears in the following.

L'unité de dilution 4 comprend, selon l'invention, un évaporateur-distillateur 40 principal, suspendu à la platine 23 par un circuit de pompage principal 41 s'élevant verticalement et traversant les platines 10 et 5 successivement. L'évaporateur-distillateur principal 40 est raccordé à sa base par une canalisation 43 à une chambre de dilution 44 constituant le point froid de l'unité de dilution 4. La chambre de dilution 44 est conformée pour que son fond représente un support de fixation d'un échantillon 45 à analyser.The dilution unit 4 comprises, according to the invention, a main evaporator-distiller 40, suspended from the plate 23 by a main pumping circuit 41 rising vertically and passing through the plates 10 and 5 successively. The main evaporator-distiller 40 is connected at its base by a pipe 43 to a dilution chamber 44 constituting the cold point of the dilution unit 4. The dilution chamber 44 is shaped so that its bottom represents a fixing support of a sample 45 to be analyzed.

Le circuit de pompage principal 41 comporte une pompe 46 dont la sortie est raccordée, par une vanne 47, à un circuit principal de refoulement 48 constitué par une canalisation de faible section traversant les échangeurs-condenseurs 22 et 37. Le circuit 48 comporte, au-delà de l'échangeur-condenseur 37, un restricteur de détente 49 au-delà duquel il traverse un échangeur 50 placé en relation avec l'évaporateur-distillateur principal 40. A la sortie de l'échangeur 50, le circuit 48 comprend un deuxième restricteur de détente 51 au-delà duquel il traverse un échangeur 52 entourant concentriquement le tube 43. Le circuit 48 débouche, ensuite, dans la partie haute de la chambre de dilution 44.The main pumping circuit 41 comprises a pump 46, the outlet of which is connected, by a valve 47, to a main discharge circuit 48 constituted by a small section pipe passing through the exchanger-condensers 22 and 37. The circuit 48 comprises, beyond the exchanger-condenser 37, an expansion restrictor 49 beyond which it passes through an exchanger 50 placed in relation to the main evaporator-distiller 40. At the outlet of the exchanger 50, the circuit 48 comprises a second expansion restrictor 51 beyond which it passes through an exchanger 52 concentrically surrounding the tube 43. The circuit 48 then opens into the upper part of the dilution chamber 44.

Le cryostat à dilution comprend, par ailleurs, un circuit de pompage dérivé 53 comportant un évaporateur-distillateur 54 suspendu à la platine 23 par une colonne 55 traversant, également, les platines 10 et 5. La colonne 55 est contrôlée par une vanne 57 au-delà de laquelle elle est raccordée au circuit principal 41. L'évaporateur 54 est relié, par une canalisation 56, à la chambre de dilution 44.The dilution cryostat further comprises a bypass pumping circuit 53 comprising an evaporator-distiller 54 suspended from the plate 23 by a column 55 also passing through the plates 10 and 5. The column 55 is controlled by a valve 57 at the -from which it is connected to the main circuit 41. The evaporator 54 is connected, by a pipe 56, to the dilution chamber 44.

Le cryostat à dilution comprend, encore, un circuit de refoulement dérivé 58 également raccordé à la sortie de la pompe 46 par une vanne 59. Le circuit 58 traverse l'échangeur-condenseur 22, puis l'échangeur-condenseur 37 au-delà duquel il est raccordé à la colonne 55 dans la partie de cette dernière située au-dessus de la platine 23 du second étage de prérefroidissement 3.The dilution cryostat further comprises a branched discharge circuit 58 also connected to the outlet of the pump 46 by a valve 59. The circuit 58 passes through the exchanger-condenser 22, then the exchanger-condenser 37 beyond which it is connected to column 55 in the part of the latter located above the plate 23 of the second precooling stage 3.

A l'extérieur du cryostat se trouve une réserve 42 contenant les quantités de 3 He et 4 He nécessaires au fonctionnement et mélangées sous forme gazeuse. Une vanne 100 permet de vider la réserve à l'aide de la pompe 46, une soupape 101 permettant le retour du mélange 3 He, 4 He dans la réserve en fin d'utilisation.Outside the cryostat is a reserve 42 containing the quantities of 3 He and 4 He necessary for operation and mixed in gaseous form. A valve 100 allows the reserve to be emptied using the pump 46, a valve 101 allowing the 3 He, 4 He mixture to return to the reserve at the end of use.

La structure décrite ci-dessus présente l'avantage de permettre une mise en place et un retrait faciles de l'échantillon 45. En effet, pour toutes ces opérations, il suffit d'établir la pression normale dans l'enceinte 6 par la vanne 9, puis de démonter successivement les enceintes 6, 11 et 24.The structure described above has the advantage of allowing easy installation and removal of the sample 45. In fact, for all these operations, it suffices to establish the normal pressure in the enclosure 6 by the valve 9, then successively dismantle the speakers 6, 11 and 24.

Pour que cet avantage d'accessibilité soit effectivement pratique, la structure du cryostat est aussi choisie pour que la mise en service effective de l'appareil puisse intervenir rapidement. En d'autres termes, la structure de l'appareil est choisie pour que la phase de prérefroidissement préalable s'effectue plus simplement et plus rapidement que selon la technique antérieure.For this accessibility advantage to be effectively practical, the structure of the cryostat is also chosen so that the effective commissioning of the device can take place quickly. In other words, the structure of the device is chosen so that the pre-cooling phase is carried out more simply and more quickly than according to the prior art.

En effet, selon l'invention, après adaptation d'un échantillon 45 et montage des différentes enveloppes 24, 11 et 6, une phase de pompage et de mise sous vide peut intervenir simultanément à un prérefroidissement qui est assuré de la façon suivante.In fact, according to the invention, after adapting a sample 45 and mounting the various envelopes 24, 11 and 6, a pumping and vacuuming phase can occur simultaneously with a precooling which is ensured in the following manner.

La vanne 18 est ouverte, de manière que l'azote liquide transite par gravité dans l'évaporateur 16, en vue d'assurer le refroidissement de la platine 10. Simultanément, les vannes 31 et 34 sont ouvertes et la pompe 32 est mise en marche, de manière à créer une circulation d'hélium dans l'évaporateur 29 chargé de refroidir la platine d'échange 23.The valve 18 is open, so that the liquid nitrogen passes by gravity through the evaporator 16, in order to ensure the cooling of the plate 10. Simultaneously, the valves 31 and 34 are open and the pump 32 is turned on. running, so as to create a circulation of helium in the evaporator 29 responsible for cooling the exchange plate 23.

La vanne 57 est ensuite fermée, de même que la vanne 47, alors que la vanne 59 est, au contraire, ouverte. La pompe 46 est mise en marche, de manière à refouler du mélange cryogénique extrait de la réserve 42 dans le circuit de refoulement dérivé 58. Le mélange cryogénique sous phase gazeuse se refroidit par traversée de l'échangeur-condenseur 22, puis de l'échangeur-condenseur 27, avant d'être introduit dans la colonne 55 où il arrive à basse température. Le mélange froid emprunte alors la canalisation 56, traverse la chambre de dilution 44 et remonte par le circuit de pompage principal 41, avant d'être recyclé par la pompe 46.The valve 57 is then closed, as is the valve 47, while the valve 59 is, on the contrary, open. The pump 46 is started, so as to discharge the cryogenic mixture extracted from the reserve 42 into the derivative discharge circuit 58. The cryogenic mixture in the gas phase is cooled by passing through the exchanger-condenser 22, then from the exchanger-condenser 27, before being introduced into column 55 where it arrives at low temperature. The cold mixture then borrows the pipe 56, passes through the dilution chamber 44 and rises through the main pumping circuit 41, before being recycled by the pump 46.

Cette circulation a pour effet de refroidir l'unité de dilution par circulation interne, alors que les cryostats à dilution, du type connu, assurent une phase de prérefroidissement par circulation externe d'un produit cryogénique en phase vapeur, tel que l'hélium.This circulation has the effect of cooling the dilution unit by internal circulation, while the dilution cryostats, of the known type, provide a pre-cooling phase by external circulation of a cryogenic product in the vapor phase, such as helium.

Lorsque la température la plus basse est atteinte par la phase de circulation décrite ci-dessus, par exemple aux environs de 4° Kelvin, les vannes 47 et 57 sont ouvertes, alors que la vanne 59 est fermée.When the lowest temperature is reached by the circulation phase described above, for example around 4 ° Kelvin, the valves 47 and 57 are open, while the valve 59 is closed.

La pompe 46 refoule alors du mélange cryogénique dans le circuit principal 48. Après s'être refroidi dans l'échangeur 22, le mélange se condense dans l'échangeur-condenseur 37, avant de se détendre à travers les restricteurs 49 et 51. Le liquide ainsi obtenu s'accumule dans les parties basses de l'appareil jusqu'à remplir complètement la chambre de mélange 44, puis le tube 56, ainsi que l'échangeur 52, enfin, partiellement, les évaporateurs 40 et 54 où les niveaux s'équilibrent.The pump 46 then delivers cryogenic mixture into the main circuit 48. After having cooled in the exchanger 22, the mixture condenses in the exchanger-condenser 37, before expanding through the restrictors 49 and 51. The liquid thus obtained accumulates in the lower parts of the apparatus until completely filling the mixing chamber 44, then the tube 56, as well as the exchanger 52, finally, partially, the evaporators 40 and 54 where the levels s 'balance.

A ce moment, la réserve 42 étant vide, commence la distillation du mélange dans les deux évaporateurs. La fraction 4 He reste au fond du cryostat et la fraction 3 He est pompée par la pompe 46. La fraction 3 He pure ainsi obtenue est refoulée alors par la vanne 47, refroidie dans l'échangeur 22, condensée dans l'échangeur 37, détendue en 49, refroidie encore en 50, détendue en 51 et, pour finir, refroidie par l'échangeur 52, avant de se diluer dans la fraction 4 He contenue dans la chambre de dilution 44 en refroidissant ainsi l'échantillon. La fraction 3 He remonte vers les deux évaporateurs en diffusant dans la fraction 4 He, refroidissant au passage l'échangeur 52 et empêchant toute chaleur de descendre le long des tubes 56 et 43.At this time, the reserve 42 being empty, begins the distillation of the mixture in the two evaporators. The 4 He fraction remains at the bottom of the cryostat and the 3 He fraction is pumped by the pump 46. The pure 3 He fraction thus obtained is then discharged by the valve 47, cooled in the exchanger 22, condensed in the exchanger 37, expanded in 49, further cooled in 50, expanded in 51 and, finally, cooled by the exchanger 52, before diluting in the fraction 4 He contained in the dilution chamber 44 thereby cooling the sample. The 3 He fraction rises to the two evaporators by diffusing into the 4 He fraction, cooling the exchanger 52 in passing and preventing any heat from descending along the tubes 56 and 43.

Ainsi, la structure du cryostat à dilution selon l'invention permet, en utilisant le même mélange cryogénique, d'assurer un prérefroidissement par circulation du mélange en phase gazeuse à l'intérieur des éléments constitutifs de l'unité de dilution 4, puis d'entretenir le fonctionnement en mode dilution par circulation du même mélange en phase liquide, le passage d'un mode de fonctionnement à l'autre s'effectuant par la commande des vannes 47, 59 et 57. Il devient ainsi possible de mettre en service rapidement un tel appareil et de bénéficier ainsi pleinement des avantages de changement rapide d'échantillons dus à la structure des enveloppes concentriques démontables 6, 11 et 24. Il devient aussi possible d'appliquer à l'échantillon 45 toutes les gammes de températures souhaitées, étant donné que celle-ci dépend uniquement du mode de circulation et non de la température des réserves de liquide cryogénique 20 et 35.Thus, the structure of the dilution cryostat according to the invention makes it possible, using the same cryogenic mixture, to ensure precooling by circulation of the mixture in the gas phase inside the constituent elements of the dilution unit 4, then d '' maintain operation in dilution mode by circulating the same mixture in the liquid phase, switching from one operating mode to another being effected by the control of valves 47, 59 and 57. It thus becomes possible to put into service quickly such an apparatus and thus fully benefit from the advantages of rapid change of samples due to the structure of the removable concentric envelopes 6, 11 and 24. It also becomes possible to apply to the sample 45 all the desired temperature ranges, since this depends only on the circulation mode and not on the temperature of the cryogenic liquid reserves 20 and 35.

Etant donné que les phases de prérefroidissement et de refroidissement interviennent par circulation interne, il devient possible de procéder rapidement au changement de l'échantillon 45. Il suffit, en effet, de rétablir la pression et la température ambiante à l'intérieur de l'enveloppe 24 pour permettre un démontage des enceintes. A cette fin, il suffit de provoquer la vaporisation de la phase liquide du mélange cryogénique occupant les évaporateurs 40 et 54 et la chambre de dilution 44. Dans ce but, ces trois éléments constitutifs sont associés à des résistances électriques 60.Since the pre-cooling and cooling phases occur through internal circulation, it becomes possible to quickly change the sample 45. It suffices, in fact, to restore the pressure and the ambient temperature inside the envelope 24 to allow disassembly of the speakers. To this end, it suffices to cause the vaporization of the liquid phase of the cryogenic mixture occupying the evaporators 40 and 54 and the dilution chamber 44. For this purpose, these three constituent elements are associated with electrical resistors 60.

Il convient de noter, également, que les réserves de liquide cryogénique, nécessaires au prérefroidissement par l'intermédiaire des platines 10 et 23, sont totalement indépendantes des enveloppes 6, 11 et 24 et de l'unité de dilution 44 qui peut donc ainsi être rapidement réchauffée à température ambiante lors dela phase de changement d'un échantillon 45.It should also be noted that the reserves of cryogenic liquid, necessary for precooling via the plates 10 and 23, are completely independent of the envelopes 6, 11 and 24 and of the dilution unit 44 which can therefore be rapidly warmed up to room temperature during the sample change phase 45.

L'invention n'est pas limitée à l'exemple décrit et représenté, car diverses modifications peuvent y être apportées sans sortir de son cadre.The invention is not limited to the example described and shown, since various modifications can be made thereto without departing from its scope.

Claims (7)

1 - Cryostat à dilution, du type comprenant au moins un étage de prérefroidissement (2, 3), associé à au moins une réserve de liquide cryogénique indépendante, un réservoir de mélange cryogénique de refroidissement (42), une chambre (44) de dilution dudit mélange et un circuit de refoulement (48) et de pompage (41) comprenant, entre la réserve et la chambre, une pompe (46), un évaporateur (40) placé sur le circuit de pompage et des condenseurs (22, 37) placés sur le circuit de refoulement,
caractérisé en ce qu'il comprend : - un circuit de pompage dérivé (53) comportant un évaporateur (54) et une vanne (57) placés entre la chambre de dilution (44) et la pompe de circulation (46) faisant partie du circuit principal de pompage et refoulement, - et un circuit de refoulement dérivé (58) contrôlé au-delà de la pompe par une vanne d'admission (59), passant par les premier et second étages (2, 3) et aboutissant dans le circuit de pompage dérivé (53) en aval de l'évaporateur par rapport à la chambre de dilution. 1 - Dilution cryostat, of the type comprising at least one precooling stage (2, 3), associated with at least one independent cryogenic liquid reserve, a cryogenic cooling reservoir (42), a dilution chamber (44) of said mixture and a discharge (48) and pumping (41) circuit comprising, between the reserve and the chamber, a pump (46), an evaporator (40) placed on the pumping circuit and condensers (22, 37) placed on the discharge circuit,
characterized in that it comprises: - a derived pumping circuit (53) comprising an evaporator (54) and a valve (57) placed between the dilution chamber (44) and the circulation pump (46) forming part of the main pumping and delivery circuit, - And a branched discharge circuit (58) controlled beyond the pump by an inlet valve (59), passing through the first and second stages (2, 3) and ending in the branched pumping circuit (53) downstream of the evaporator relative to the dilution chamber. 2 - Cryostat à dilution selon la revendication 1, caractérisé en ce que l'évaporateur (54) du circuit de pompage dérivé (53) est placé entre la chambre de dilution (44) et le second étage de prérefroidissement (3).2 - Dilution cryostat according to claim 1, characterized in that the evaporator (54) of the derived pumping circuit (53) is placed between the dilution chamber (44) and the second precooling stage (3). 3 - Cryostat à dilution selon la revendication 1 ou 2, caractérisé en ce que l'évaporateur (54) du circuit de pompage dérivé (53) est placé sensiblement dans le même plan que l'évaporateur (40) du circuit de pompage principal (41) et constitue avec ce dernier et la chambre de dilution (44) une unité de dilution (4) enfermée dans une enveloppe étanche (6).3 - Dilution cryostat according to claim 1 or 2, characterized in that the evaporator (54) of the derived pumping circuit (53) is placed substantially in the same plane as the evaporator (40) of the main pumping circuit ( 41) and constitutes with the latter and the dilution chamber (44) a dilution unit (4) enclosed in a sealed envelope (6). 4 - Cryostat à dilution selon la revendication 3, caractérisé en ce que l'unité de dilution (4) est incluse à une enveloppe (24) suspendue au second étage de prérefroidissement (3) qui est disposé en-dessous d'un premier étage (2) auquel est suspendue une enveloppe intermédiaire (11) entourant l'enveloppe (24) de l'unité de dilution et elle-même entourée par une enveloppe extérieure (6) suspendue à une ossature de support (1), lesdites enveloppes étant en relation avec une unité de pompage et de mise sous vide (8, 9).4 - Dilution cryostat according to claim 3, characterized in that the dilution unit (4) is included in an envelope (24) suspended from the second precooling stage (3) which is arranged below a first stage (2) to which is suspended a intermediate casing (11) surrounding the casing (24) of the dilution unit and itself surrounded by an outer casing (6) suspended from a support frame (1), said casings being in relation to a pumping unit and vacuum (8, 9). 5 - Cryostat à dilution selon la revendication 4, caractérisé en ce que les circuits de pompage et de refoulement principaux et dérivés traversent les premier et second étages de prérefroidissement.5 - Dilution cryostat according to claim 4, characterized in that the main and derived pumping and discharge circuits pass through the first and second pre-cooling stages. 6 - Cryostat à dilution selon la revendication 4, caractérisé en ce que les enveloppes (6, 11, 24) sont concentriques et adaptées aux étages (2, 3) et à l'ossature (1).6 - Dilution cryostat according to claim 4, characterized in that the envelopes (6, 11, 24) are concentric and adapted to the stages (2, 3) and to the framework (1). 7 - Cryostat à dilution selon la revendication 4, caractérisé en ce que les moyens de refroidissement (20, 21 et 35, 36) des premier et second étages sont portés par l'ossature de support.7 - Dilution cryostat according to claim 4, characterized in that the cooling means (20, 21 and 35, 36) of the first and second stages are carried by the support frame.
EP19850420228 1984-12-17 1985-12-16 Dilution cryostat Expired EP0188976B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8419488 1984-12-17
FR8419488A FR2574914B1 (en) 1984-12-17 1984-12-17 DILUTION CRYOSTAT

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EP0188976A1 true EP0188976A1 (en) 1986-07-30
EP0188976B1 EP0188976B1 (en) 1989-03-08

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JP (1) JPH0621755B2 (en)
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Also Published As

Publication number Publication date
FR2574914B1 (en) 1987-03-06
EP0188976B1 (en) 1989-03-08
DE3568628D1 (en) 1989-04-13
US4672823A (en) 1987-06-16
FR2574914A1 (en) 1986-06-20
JPH0621755B2 (en) 1994-03-23
JPS61191845A (en) 1986-08-26

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