CRYOSTAT WITH COMPOSITE PANEL STRUCTURE

Abstract: The cryostat has a structure (2) internally comprising a chamber (3) containing a liquid at low temperature and bounded by perimetral walls. Each wall comprises a plurality of panels (4, 5, 6, 13), a first most inner pair of panels (4, 5) being of metal and containing separator and spacer means (6) positioned between its panels, at least one panel of insulating material of low thermal conductivity being provided externally.

Description: CRYOSTAT WITH COMPOSITE PANEL STRUCTURE This invention relates to a cryostat in accordance with the introduction to the main claim. Known cryostats have a structure defining an inner chamber to contain a liquid (for example argon) at low temperature. This structure generally comprises two elements or shells usually of metal such as steel contained one in the other, between them there being provided an insulating material, such as a superinsulant or perlite. These known cryostats are very heavy, making their transportation difficult. They are also of relatively complex construction because of their structure. This is particularly the case if perlite is used as insulant, this being a kind of sand which is difficult to work and very dangerous if inhaled by the cryostat construction personnel. Moreover, because of the presence of such perlite, known cryostats in which it is used are also difficult and laborious to dismantle, this having to be done very carefully in a suitably equipped environment in which any dispersion of the insulant into the atmosphere is prevented. An object of this invention is to provide a cryostat which is improved compared with similar known cryostats. A particular object of the invention is to provide a cryostat of very low weight and therefore easily transportable. A further object is to provide a cryostat of the stated type which is of simple construction and can be assembled without risk to assembly personnel . A further object is to provide a cryostat of low constructional cost and easy dismantling. These and further objects which will be apparent to teh expert of the art are attained by a cryostat in accordance with the characterising part of the main claim. The invention will be more apparent from the accompanying drawing, which is provided by way of non-limiting example and on which: Figure 1 is a section through a cryostat of the invention; Figure 2 is a detail of a modification of the cryostat of Figure 1 ; and Figure 3 is a section through a further modification of the cryostat of Figure 1. With reference to said figures, the cryostat of the invention is indicated overall by 1 and comprises a structure 2 defining an inner chamber containing a liquid at low temperature, such as liquid argon. The structure 2 has walls comprising a plurality of panels connected together. More specifically, starting from the chamber 3, the structure 2 comprises, on each side, a pair of panels 4, 5 of light metal such as aluminium, separated from each other by an intermediate panel 6 also of light metal such as aluminium. The panel 6 has a cellular structure, for example of honeycomb type. The panels 4, 5 and 6 formed in this manner (and connected together mechanically for example by welding, bonding, bolts or a combination of these mechanical fixings) form a single body 8 of light weight, but of high mechanical strength. Preferably, within the body 8 (for example within the panel 6) there is provided a plurality of conduits 10 defining a cooling circuit in which gas such as liquid nitrogen is present. This circuit eliminates or at least considerably reduces heat passage from the outside of the structure 2 to the chamber 3. Advantageously, to reduce the temperature gradient between the chamber 3 and the outside of the structure 2, within the honeycomb structure of the panel 6 there is an atmosphere present containing a high percentage of helium (or totally of helium). In this case the cells (ie each honeycomb cavity) of the panel 6 are provided with apertures to enable said atmosphere (ie helium) to be fed into said panel (ie between the panels 4 and 6). On its outer part (with respect to the chamber 3) the body 10 is provided with an least one insulating member 12 (for example two in Figures 1 and 3). This latter comprises composite panels having a cellular structure 13, for example honeycomb. In other words these panels comprise solid panels (not indicated on the figures) between which the structure 13 is present. This latter is constructed of materials of low thermal conductivity such as glass fibre, resin, paper or the like, and preferably comprises cells (or honeycombs) of small cross-section to prevent natural convection within it. Advantageously, each insulating member 12 contains a nitrogen atmosphere within its interior to prevent moisture entering the cryostat. To prevent air entering between the most inner member 12 and the body 8 by natural convection, between them there is provided an insulating interspace 15 of known material resistant to low temperature such as glass wool, so as to prevent any free space existing between said member and body. A further thermal screen 16 complete with an insulating interspace such as the interspace 15 can be positioned (see Figure 2) between two adjacent insulating members 12. The screen 16 can be cooled by nitrogen vapour present in a plurality of conduits 17 embedded within the screen and originating from the cold-producing circuit of the body 10 (which defines the actual cryostat). A cryostat such as described is of low weight, and because of its multiple panel form is simple to assemble and dismantle. It can be constructed in a short time at a lower cost than known cryostats. A particular embodiment of the invention has been described. Others are however possible and are to be considered as falling within the present document.

Claims: Cl aims : 1. A cryostat having a structure (2) internally comprising a chamber (3) containing a liquid at low temperature and bounded by perimetral walls, characterised in that each wall comprises a plurality of panels (4, 5, 6, 13) . , a first most inner pair of panels (4, 5) being of metal and containing separator and spacer means (6) positioned between its panels, at least one member (12) of insulating material of low thermal conductivity being provided externally. 2. A cryostat as claimed in claim 1, characterised in that the first pair of panels comprises panels of light metal sι/ch as aluminium, the spacer means being at least one panel (6) of cellular structure. 3. A cryostat as claimed in claim 2, characterised in that the panel (6) of cellular structure is of honeycomb form. 4. A cryostat as claimed in claim 2, characterised in that the cellular structure (6) contains an atmosphere having at least a high percentage of helium, the cells being in mutual communication. 5. A cryostat as claimed in claim 2, characterised in that the panel (6) of cellular structure contains a cooling circuit comprising a plurality of conduits (10). 6. A cryostat as claimed in claim 5, characterised in that the cooling circuit contains nitrogen. 7. A cryostat as claimed in claim 1, characterised in that the first pair of panels (4, 5) and the spacer means (6) are fixed together to define a single-piece body. 8. A cryostat as claimed in claim 1, characterised in that the insulating member (12) has a composite panel structure. 9. A cryostat as claimed in claim 8, characterised in that the composite panel structure comprises a cellular structure (13). 10. A cryostat as claimed in claim 9, characterised in that the cellular structure (13) is of honeycomb type. 11. A cryostat as claimed in claim 8, characterised in that the insulating member (12) contains a nitrogen atmosphere. 12. A cryostat as claimed in claim 1, characterised in that between that panel (5) most outer from the chamber (3) containing the liquid at low temperature, and the insulating member (12), there is positioned a screen (15) of material resistant to low temperature and preferably highly conducting. 13. A cryostat as claimed in claim 12, characterised in that the screen (15) contains a cooling circuit defined by a plurality of conduitts (17) in which a refrigerant fluid is present. 14. A cryostat as claimed in claim 13, characterised in that the cooling circuit contains nitrogen vapour originating from the cryostat cold-producing circuit. 15. A cryostat as claimed in claim 1, characterised by comprising at least two insulating members (12) between which a thermal screen (16) is positioned. 16. A cryostat as claimed in claim 15, characterised in that the thermal screen (16) contains a cooling circuit comprising a plurality of conduits (17) in which a refrigerant fluid is present. 17. A cryostat as claimed in claim 16, characterised in that the refrigerant fluid contains nitrogen vapour originating from the cryostat cold-producing circuit.

Inventors: DISDIER JEAN-MARIE, PELLOUX-GERVAIS PIERRE, DISDIER, JEAN-MARIE, PELLOUX-GERVAIS, PIERRE
Applicants: AIR LIQUIDE, DISDIER JEAN MARIE, PELLOUX GERVAIS PIERRE, DISDIER, JEAN-MARIE, L'AIR LIQUIDE, SOCIETE ANONYME POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE, PELLOUX-GERVAIS, PIERRE
Application year: 1997
Main classification: F17C13
IPC codes: F17C3, F17C13