GB2294362A

GB2294362A - Cryogenic device for optoelectronic and/or electronic equipment

Info

Publication number: GB2294362A
Application number: GB9521266A
Authority: GB
Inventors: Serge Reale
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 1994-10-18
Filing date: 1995-10-17
Publication date: 1996-04-24
Anticipated expiration: 2015-10-17
Also published as: FR2725779A1; FR2725779B1; GB9521266D0; DE19538664A1; GB2294362B

Description

1 2294362 Cryogenic device for optoelectronic and/or electronic eguipment

and equipment comprising such a device The present invention relates to the f ield of cryogenics and, in particular, to cryogenic devices used for cooling components which are sensitive to temperature and more precisely to infrared (IR) radiation and pertaining to electronic and/or optoelectronic (optronic) equipment.

It is well known that certain electronic and/or optoelectronic components can only work properly provided they are kept at a low temperature. In the sense used in the present invention, "low temperature" means temperatures below or equal to approximately 210 K, preferably approximately 180 K and even more preferably in the range 50 K to 150 K. These sensitive components may be amplifiers of a particular type or infrared detectors used in infrared optoelectronics.

Cryogenic devices conventionally Include a double-envelope cryostatwhich is evacuated or filled with a neutral gas in order to provide thermal insulation. The sensitive components are placed at the bottom of the internal envelope of this cryostat, and this end of the internal envelope constitutes the cold zone cooled by cryogenic means in the strict sense.

Cryogenic machines are based on thermodynamic cycles which may be, for example, of the Stirling, Vuillemier, pulsed-tube, Gifford MacMahon or Brayton type. In the majority of cases these cryogenic machines have two heat sources: a cold, source and a hot source (with the exception of Vuillemier-type machines, which have a supplementary heat source). These means thus work by pumping heat to a cold source, where the sensitive components for cooling are located. This cold source, the temperature of which is TF1 gives up a quantity of heat QF to the cryogenic means (QF, TF). The latter transfer heat to a hot source at a temperature of Tc, the quantity of 2 heat of which is denoted by Qc. To do so, cryogenic machines use a refrigerating fluid which undergoes a cycle of thermodynamic transformations (compression/expansion with or without change of state), calling for an input of mechanical 5 power and therefore, in conclusion, of electrical energy W..

The thermodynamic systems which characterise closed-circuit cryogenic means can be defined using the following equation:

QC WE + QF For the purposes of the present invention, the ratio:

QF/WE = VQC - QF shall be called coefficient of performance (COP).

(1) In the case of an ideal machine functioning according to the Carnot cycle, the COP is defined as follows:

QF/WE = TF/Tc - TF (2) Given that the cryogenic applications more particularly relevant to the invention (e.g. IR optoelectronics) involve low cryogenic temperatures below or equal to approximately 210 K, preferably approximately 180 K and, even more preferably, between 50 K and 150 K, or even below approximately 100 K, and that, moreover, the COPs concerned are between 1% and 20%, preferably between 2% and 10%, it can be deduced from (1) that QF is negligible compared with W. and therefore that Q. is substantially equal to W..

Moreover, equation (2) shows that, for a given quantity of heat QF to be extracted at a given temperature TFi WE increases. It also follows that Qc/Ws will also increase.

It should also be noted that Tc rises with the ambient temperature.

3 The higher Tc and therefore WE are, the greater will be the mechanical and thermal stresses imposed on the cryogenic means. The direct result of this Is a reduction of the service life of these means, caused on the one hand by premature mechanical wear of their constituent elements, such as the bearings or friction parts, and, on the other hand, to the phenomenon of degassing of the lubricants or organic materials contained in these cryogenic means. Degassing consists of a change to a gaseous state of certain constituents of the materials, of lubricant or plastic type, which then solidify in the cold parts of the machine when the temperature falls. The solidified particles thus produced are likely to cause blockages. clogging, seizing or other impairment in the moving mechanical parts in the cryogenic machines and refrigerating fluid circuits.

It is known, moreover, that the cryogenic machines In question are characterised by a maximum operating temperatureTc, beyond which they are saturated with regard to cryogenic performance and the supply of greater cryogenic power.

Conventionally, these limits are reached at a maximum operating temperature Tc between 700C and 900C, depending on the nature of the cryogenic means involved. At such temperatures, considerable self-heating is observed, which is a contributor to the phenomena of wear and degassing referred to above.

This problem of a high temperature Tc affecting the operation of known closed circuit cryogenic machines is aggravated by the temperature prevailing at the surface (housing) of heat exchange with the outside. This exchange surface temperature, which depends on WE, Qc and the heat transfer conditions, is always substantially higher than Tc (a few degrees to a few tens of degrees). This only accentuates the wear and limitation of performance referred to above.

4 We are therefore forced to observe that known cryogenic devices used to cool components which are sensitive to temperature, especially to infrared radiation, pertaining to electronic and/or optoelectronic equipment, are not entirely satisfactory under certain service conditions, because of their limited cryogenic performance, and in the case of devices with cryogenic machines, of their tendency to premature wear and their limited reliability.

In the light of this observation, one of the objects of the invention is to provide a cryogenic device which counters these shortcomings and which to this end exhibits:

higher cryogenic power; small space requirement; and great reliability.

Another object of the invention is to provide a cryogenic device suitable for service in a very hot environment.

Another object of the invention is to provide a cryogenic device which is endowed with autonomy, particularly in energy terms (when a device incorporating a cryogenic machine is involved), it being necessary to consider this autonomy in the light of the constraints of compatibility with the equipment in which this device is intended to be incorporated.

Another object of the present invention is to provide electronic and/or optoelectronic equipment, such as that of the type incorporating infrared detectors, equipped with the improved cryogenic device referred to above.

These objects and others are achieved by the present invention, which relates to a cryogenic device intended for use, in particular, for cooling components which are sensitive to temperature, especially to infrared radiation, and pertaining to electronic and/or optoelectronic equipment, comprising closed-circuit main cryogenic means capable of producing temperatures below or equal to approximately 210 K and having at least one hot zone (Qj, Trj), and incorporating electronic supplementary cooling means exhibiting, on the one hand, at least one cold area (FF) and, on the other hand, at least one hot area (FC), the cold area of the supplementary means being thermally connected to the hot zone of the main means.

The coupling according to the invention of the main cryogenic means to the electronic-type supplementary cooling means provides an advantageous and unexpected solution to the technical problems referred to above and not resolved In the prior art.

The electronic supplementary cooling means enable the main cryogenic means to be moved out of their critical operating zone in respect of the phenomena of wear and reduced cryogenic performance at extreme service temperatures: ambient temperature between 5011C and 1200C, for example. Quite apart from these critical operating zones, the electronic cooling means enable the phenomena of degassing, wear and lack of reliability to be attenuated, and cryogenic performance to be improved, for a wide ambient temperature range, e.g. from -WC to 120'C.

Intrinsically, such electronic cooling means have the attraction of being robust, reliable and compact, and having a reasonable cost price.

The present invention also provides electronic and/or optoelectronic equipment (possibly autonomous), incorporating at least one cryogenic device according to the invention.

The present invention will be more easily understood and its other characteristics will be apparent from the following 6 description, by reference to the appended drawings, which show, by way of non-exhaustive examples, several embodiments of the invention, wherein:-

Figure I is a symbolic and diagrammatic representation of electronic and/or optoelectronic equipment comprising sensitive components and incorporating a cryogenic device according to the invention; Figure 2 is a partial simplified representation, in side view, of an embodiment of the electronic supplementary cooling means; Figure 3 is a diagrammatic representation of a f irst embodiment of a cryogenic device according to the invention, of the compact Stirling type, and of its interface with part of the other constituent elements, with which the device forms electronic and/or optoelectronic equipment with sensitive components; Figure 4 represents a second embodiment of a cryogenic device according to the invention, of the exploded or "split" Stirling type, and of its interface with part of the other constituent elements, with which the device forms electronic and/or optoelectronic equipment with sensitive components; Figure 5 is a diagrammatic representation, in side view and partial section, of a first variant of the second embodiment in Figure 4; Figure 6 is a fraction of Figure 4 showing, in side view, part of the cryogenic device according to a second variant of the second embodiment; Figure 7 is a fraction of Figure 4 showing, in side view, part of the cryogenic device according to a third 7 variant of the second embodiment; Figure 8 is a fraction of Figure 5 showing, in side view, part of the cryogenic device according to a fourth variant of the second embodiment; Figure 9 is a fraction of Figure 5 showing, in side view, part of the cryogenic device according to a fifth variant of the second embodiment; and Figure 10 is a diagrammatic representation, in side view and partial section, of a sixth variant of the second embodiment of Figure 4.

Figure 1 shows, In a schematic manner:

electronic and/or optoelectronic equipment 1 comprising components 2 sensitive in particular to IR radiation; a cryogenic device 3 according to the invention, comprising main cryogenic means 31 and supplementary cooling means 32; and other constituent elements of the equipment 1 with 25 which the device 3 interacts and which is symbolised by the diagram block 4 in the drawing.

This equipment 1 may, for example, be infrared optoelectronic equipment incorporating infrared detectors 2 sensitive to infrared radiation proper and to parasitic infrared radiation. These detectors 2, which require cryogenic cooling in order to be efficient, may be fitted especially in IR optoelectronic equipment such as automatic guidance missile systems, thermal cameras, aerial reconnaissance analysers, early warning and tracking systems, deviation measuring equipment or transmission systems, some of which equipment may, if appropriate, be portable and autonomous.

8 The means 3, and 32 are supplied with energy, preferably electrical, with powers of WE, and WE2 respectively. For a piece of equipment 1 of autonomous configuration, the source of electrical energy such as a battery or alternator (not shown In the drawing) may for example be located in the portion 4 of the equipment 1.

The detectors or sensitive components 2 are located in the cold source (quantity of heat QF and temperature TF)# into which the cryogenic device 3, the subject-matter of the invention, is intended to pump heat.

More precisely, this pumping is performed by the main cryogenic means 31 capable of producing temperatures below or equal to approximately 210 K for example, preferably approximately 180 K and, even more preferably, in a range from 50 K to 150 K. For the purposes of the present invention, achieving such temperatures should be understood as being for a "primary" cold source located in a double envelope cryostat, thermally insulated by evacuating it or by filling it with a neutral gas, or in a simpler cryostat, thermally insulated with an insulating material, of the K16gecel type, for example. The thermal load of the cryostat may be equal to a few tens of mW to a few Watts at the temperature TF of the "primary" cold source. The ambient temperature required to evaluate this thermal performance is advantageously between -400C and 1201t. Finally the electrical consumption involved may be from a few Watts to a few hundred Watts.

The main cryogenic means 31 are also characterised:

either by a coefficient of performance COP of between 1% and 20%, preferably between 2% and 10%, when dealing with cryogenic means of the closed-circuit type; or by a gas-expansion enthalpy difference greater than 9 or equal to 10 J.g", preferably between 10 and 70 J.9'1 Moreover, the main cryogenic means 31 incorporate at least one cold zone corresponding to the "primary" cold source (QF, TF) # and at least one hot zone with a given quantity of heat Qc, and a given temperature Tcl.

Depending on the type and characteristics of the machines, there may be several cold stages and therefore several cold sources (QF1, TF1) F MF2, TP2) F MF3, TF3)... and, in the case of Vulllemier-cycle machines, there will be two hot sources Mcl, Tcl) and (QC3, TC3) The electronic supplementary cooling means of the cryogenic device 3 according to the invention are of the thermoelectric Peltier-ef f ect type and/or thermomagnetic Ettinghausen-ef f ect type. Nevertheless, according to a preferred embodiment of the invention, the supplementary cooling means 32 are Peltier- effect thermoelements.

1 According to one arrangement of the invention, the supplementary cooling means 32 exhibit at least one cold area and at least one hot area (Qc2, T, 2), the cold area being thermally connected to the hot area of the main means 31, in a direct manner by physical contact, or indirectly via the remainder 4 of the equipment 1.

When supplied with electrical energy with a power of WE2f these thermoelectric means 3, are able in particular to cool the main means 3, by pumping heat to a f irst hot source (QcI, T.1), which can be likened to an intermediate cold source, and by transferring it to a second hot source characterised by the quantity of heat Qc2 and the temperature T.2.

As indicated diagrammatically in Figure 1 by the double broken-line arrows a, b and c, the intermediate cold source Qcj delivering heat to the means 3. may be located at any point of the main means 3, and of the rest 4 of the equipment 1, provided obviously that it remains distinct from the "primary" cold source (QF, Tr). There are thus as many implementation alternatives as there are points a, b, c.. . n capable of forming an intermediate cold source (Qcl, Tcl). It should be noted that the case where the intermediate cold source (Qcl, Tcl) is located at any point c of the rest 4 of the equipment corresponds to indirect cooling of the main means 3,. In this case, the heat produced by the main means 31 passes through the equipment 1 and is finally absorbed by the cold area of the supplementary means 32. For example, this indirect heattransfer between the main means 3, and the supplementary means 32 may be undertaken by heat-transfer elements pertaining to the equipment 1 and, more precisely, to the rest 4 of the latter. These heat-transfer elements may be, for example, one or more thermally conducting mechanical parts supporting the cryogenic device (machine) 3 (e.g. fixing brackets) and/or one or more copper braids and/or one or more heat conduits.

Advantageously, the thermoelectric supplementary cooling means 32 are compatible with intermediate cold sources, the temperature Tc, of which is above or equal to temperature TF of the "primary" cold source of the main means 3, and is, more particularly, between +1000C and -600C, preferably between +80T and O1C.

In an advantageous manner, the supplementary cooling means 32 consist of Peltier-effect thermoelements comprising:

at least one thermocouple semiconductor element and element, incorporating an n-type a p-type semiconductor and, preferably, several such thermocouples in series in electrical terms and in parallel in thermal terms, so as to produce at least one Peltier- effect module.

The Peltier-ef f ect module is preferably single-layer or multilayer and has at least one cold face FF and at least one hot face FC.

As shown in Figure 2, the thermoelement module is produced by a bonding process. It is advantageously of a parallelepiped shape and is formed by several alternating n-type and p-type bars. Each bar is separated from its neighbours by a calibrated bonded seal 5. Each n-type bar is electrically connected to each of the two adjacent p-type bars by a conducting bridge 6, so as to form thermocouples. Several lines of bars can be assembled together so as to form a plate, one face of which will be the cold face (FF) and the other the hot face (FC), depending on the direction of current flow through the Peltier module concerned. Such a module 3, is a virtual static heat pump capable of taking calories from the intermediate cold source (Q.,, T.1) and returning them to the second hot source (Qc2, Tc2): QC2 " QC1 + WE2) Naturally, the invention is not limited to the illustrated case where the supplementary cooling means 3. are constituted by a single Peltier-effect module, but also covers the variants in which several such modules are provided at dif f erent points of the equipment I and/or of the main cooling means 31.

Such Peltier-effect thermoelectric coolers have the advantage of being compact and easily miniaturised. They are also only slightly subject to wear, since they are not subjected to mechanical and dynamic stresses.

According to a variant, the Peltier modules can also be produced by an aerated process.

According to a variant of the invention, the cold zone(Qr, TF) has at least two stages (QF.1, TF1) and (QF2, TF1) with TF1 less than or equal to TF2, and the supplementary cooling means 3.

12 are thermally connected to the stage (QF2, TF2) via their cold areas, preferably via the cold face (FF) of a Peltier-effect module. In this staged variant, the temperature TFI can be, for example, between 20 K and 50 K, while the temperature TF2 may, for example, be in the range 100 K to 200 K.

According to the invention, the hot area of the supplementary cooling means 32, preferably a hot face (FC) of a Peltiereffect module, is thermally connected to the equipment 1, in such a way as to be able to evacuate the heat which the supplementary means 3. are capable of pumping to the mains means 3,.

This thermal evacuation link is advantageously implemented:

via at least one portion 4 of the equipment 1 comprising the component(s) 2 to be cooled, the link being executed either directly by physical contact or indirectly by any appropriate means of heat transfer, e.g. by means of at least one suitable heat conduit and/or at least one copper braid and/or one or more thermally conducting mechanical parts supporting the device 3, and/or by means of at least one device 15 for direct heat exchange with the internal atmosphere of the equipment 1, which device may be, for example, of radiator type.

It is possible to envisage a different method of evacuation of the heat likely to be accumulated by the supplementary means 32 This different method does not involve the equipment 1, but at least one cooling element independent of the latter and thermally connected to the hot area of the supplementary means 32.

Figures 3 to 6 and 10 illustrate the method of evacuation of heat by direct physical contact between the means 32 and at 13 least one portion of the equipment 1, 4. Figure 7 Illustrates the method of evacuation by using at least one device for direct heat exchange with the internal atmosphere of the equipment 1, and Figures 8 and 9 the method of evacuation using at least one cooling element which is external to and independent of the equipment 1.

Advantageously, the thermally conducting links between these constituent elements 31, 4 and 15 of the equipment 1 are implemented using at least one of the following techniques:

high-pressure screw fixing, preferably using a contact grease at the interface; bonding with a thermally conducting adhesive; soldering.

It is desirable for these thermally conducting links to be executed in such a way that there is a high contact pressure.

Thus, any fixing technique which is appropriate and known in itself (apart from those mentioned above) may be considered for producing the equipment 1 according to the invention.

In order to improve the performance of the cryogenic device 3, it is possible to insulate it thermally, apart of course from at least the heat exchange zones. This thermal insulation may be executed using any known and appropriate means. This could be, for example, insulating materials with a basis of moulded cellular expanded plastics (for example, KAgecelO, polystyrene, etc.) or even fibrous materials, of the glass-wool or rockwool type. When such an insulating envelope is fitted, one must obviously be careful not to obstruct a portion of the housing of the device which has openings, such as, for example, the inspection windows associated with the infrared detectors 2. It is preferable for this envelope to be easily fitted and dismantled, with a view 14 to maintenance operations. This variant with insulation may be provided for all equipment and devices according to the invention. This enables heat losses and energy requirements to be limited. Without it being restrictive, only the first embodiment of the equipment 1 of the invention, as exemplified in the present exposition, comprises a cryogenic device provided with such insulation.

According to one aspect of the invention, the main cryogenic means 31 operate according to one of the following thermodynamic cycles: Stirling, Vuillemier, pulsed-tube, Gifford MacMahon, Brayton.

With regard to the working of the device according to the invention, it should be noted that the supplementary cooling means 32 may or may not be operated simultaneously with the main cryogenic means 31. In particular, the supplementary cooling means 32 may be brought into operation before the main means 31. In this case, prior cooling is employed, using the supplementary means 32. This enables the cooling down time of the main means 31 to be reduced and their heating up to be retarded. This results in Improved cryogenic performance and endurance for the device according to the invention. This particular operational case is more specifically appropriate to cyclical use of the device.

Figures 3 to 10 make reference to cryogenic devices of the Stirling type and, more precisely, of the compact or integral Stirling type for Figure 3 and the exploded or "split" Stirling type for Figures 4 to 10.

Figure 3 shows a cryogenic device 3, together with its interface with a piece of electronic and/or optoelectronic equipment (e.g. thermal camera) via a portion 4 of a constituent element of said equipment 1.

This device 3 incorporates main cryogenic means 31 and is electronic supplementary cooling means 32.

The main means 31 consist of a compact Stirling machine 311 and a cryostat 3,21 at the heart of which there is a cold f inger 7 of the micro-machine 31,, as well as components 2 which are sensitive to temperature, in particular to IR proper and to parasitic IR, when IR detectors are involved. The cryostat 312 is a double-walled hermetic enclosure 8, in which a sealed thermally insulating vacuum is produced, the vacuum being, for example, below or equal to 10-3 mbar.

The end of the cold f inger 7 of this cryostat 312thus constitutes the cold source (QF, TF) The double Insulating wall 8 of the cryostat 3,2 has a window 9 arranged opposite the sensitive components formed by the infrared detector. The cold finger 7 forms part of the probe 10, which is itself connected to a pressure oscillator 11, the combination of 7, and 11 constituting the compact Stirling micro-machine 311.

The supplementary cooling means 32 are presented in the form of parallelepiped plates and are of the type shown In Figure 2 (thermoelements constructed by a bonding method).

In the equipment 1, the supplementary cooling means 32, preferably the Peltier module(s) 32, are inserted between at least one portion of the main cryogenic means 31, in the case in point the pressure oscillator 11 at at least one portion 4 of the equipment 1. In this way, the cold area of the supplementary cooling -means 32, namely preferably the cold face (FF) of a Peltier module, is thermally connected to at least one portion of the hot area (Qcl, Tcl) of the main cryogenic means 3,. In addition, the hot area of the supplementary means 3211 preferably the hot face (FC) of a Peltier module, is in thermal contact with at least one portion 4 of the equipment 1. The thermally conducting connections between these three elements are executed by bonding and/or screwing.

16 When in operation, this device 3 permits the transfer of heat from the "primary" cold source(QF, TF) to the intermediate cold source (Q,,, Tcl) located in the module 32, as f ar as the hot source (Qc2, Tc2) of the portion 4.

Advantageously, this device 3 carries an insulating envelope 12 which completely covers it, apart from the window 9 and the interface with the portion 4 of the equipment 1.

Figure 4 shows a device 3 and its interface with a portion 4 of a piece of infrared electronic and/or optoelectronic equipment 1. This device differs from that in Figure 3 in that the main cryogenic means 3, are constituted by a Stirling machine 31, of an exploded or "split" configuration. In Figure 4, the elements held in common with Figure 3 are denoted by the same references. Thus the "split" Stirling machine incorporates a pressure oscillator 11 constituting a first subassembly, connected by a conduit 13 to the second subassembly formed by the probe 10, the finger 7 of which is covered by the cryostat 3,2. The Peltier module 32 is interposed between the pressure oscillator 11 and the portion 4 of the equipment 1.

Figure 5 shows a device 3 and its interface with the portions 4 and 41 of a piece of IR electronic and/or optoelectronic equipment. Unlike the embodiment in Figure 4, the supplementary cooling Peltier module 32 is in this case located between the probe head 10 and the portion 4 of the equipment 1. Here again, we are dealing with a Stirling machine device 31 of exploded or "split" type, the elements of which are denoted by the same references as those in the embodiment in Figure 4.

Figure 6 shows a second variant of the machine of the exploded or "split" type 311, in which the Peltier module 32 is integral with a portion 4 of the equipment 1 via its hot face, while its cold face is attached to the external face of the double wall 8 of the cryostat 312.

17 The links 4/32/312 are obviously thermally conducting. This variant with a cryostat cooled by the Peltier module is given, by way of example, f or a Stirling machine, but it is of course clear that it can be applied to other types and configurations of cryogenic machines.

The attachment of the Peltier cooler 32 to the cryostat 312 permits a reduction of the maximum and minimum cryogenic power required for the cryogenic device 3, while maintaining said cryostat below the ambient temperature, and thereby reducing the heat losses of the latter.

Figure 7 represents only a fraction of the main cryogenic means 3, formed by a "split" Stirling machine 311. This fraction includes the probe 10 with its cold finger 7, covered by the cryostat 312, and the free end of which is adjacent to the IR detectors or sensitive components 2.According to this 20 variant, at least part of the hot area of the supplementary cooling means 32, in the case in point the Peltier module, is attached by thermally conducting connections, on the one hand to the probe head 10 via its cold face (FF) and, on the other, to at least, in this case, one device 15 f or direct heat 25 exchange with the ambient atmosphere, via its hot face (FC). The ambient atmosphere is, in fact, the inside of the equipment 1. This device 15 may in fact be likened to a radiator, the major exchange surface of which permits a good evacuation of the heat pumped by the means 32, by natural 30 convection and/or by forced convection with a ventilation circuit.

This third variation imparts freedom of movement to the probelcryostat assembly. In other words the sensitive components 2 can move with the radiator-type device 15. One can advantageously profit from this characteristic, e.g. in portable and autonomous contained IR optoelectronic equipment.

18 is The f ourth variant, shown in Figure 8, represents the case where the pressure oscillator 11 of a "split" cryogenic machine is integral with a Peltier module 321 which is itself connected to a radiator 151 acting as a direct heat exchange device, permitting evacuation of the heat pumped by the Peltier supplementary means 32, Depending on whether the pressure oscillator 11 is arranged inside or outside, preferably outside, equipment 11, the device 151 has heat exchanges with the internal and/or external atmosphere of the equipment. The device 151 behaves like a radiator, which is capable of cooling by natural convection and/or forced convection using any appropriate means, such as a fan.

Figure 9 illustrates a fifth variant, where the pressure oscillator 11 is thermally connected to a Peltier module 32. Evacuation of the calories likely to be absorbed by this module 3. is undertaken by a cooling element 1511, the latter being independent of and external to the equipment 1. This element 15" consists of a supporting plate cooled by a circuit of cooling fluid, for example cold water. According to an alternative arrangement, this circuit may be replaced in particular by a heat conduit.

In the variant in Figure 10, the Peltier module 32 is arranged so that it can pump heat to the conduit 13 connecting the pressure oscillator 11 to the probe 10, in order to transmit it to the portion 4 of the equipment 1. The module 32 is in thermally conducting contact with the conduit 13 via a metal plate 14.

It goes without saying that the examples of variants shown in Figures 4 to 10 can be combined with each other by a person skilled in the art, capable of determining and executing the embodiment most appropriate to the application concerned.

19 It should be clear after reading the above that the equipment according to the invention can be cooled by natural convection in the ambient air and/or, if required, by a supplementary external cooling system, such as, for example, a water cooling 5 system (marine applications) or a suitable heat conduit.

Claims

CLAIMS is A cryogenic device Intended for use, in particular, for cooling

components which are sensitive to temperature, of an item of equipment, said device comprising closedcircuit main cryogenic means capable of producing temperatures below or equal to approximately 210 K and having at least one hot zone, and incorporating electronic supplementary cooling means exhibiting, on the one hand, at least one cold area and, on the other hand, at least one hot area, the cold area of the supplementary cooling means being thermally connected to the hot zone of the main cryogenic means.
A device according to Claim 1, wherein the electronic supplementary cooling means are of Peltier-effect thermoelectric type and/or Ettinghausen-effect thermomagnetic type.
3.

A device according to one of Claims 1 and 2, wherein the hot area of the supplementary cooling means is thermally connected to the equipment, in such a way as to enable the heat to be evacuated via at least one portion of the equipment incorporating the component(s) to be cooled, the connection being made either directly by physical contact or indirectly, and/or via at least one device for direct heat exchange with the internal atmosphere of the equipment.
A device according to one of Claims 1 to 3, comprising at least one cooling element, which is independent of the equipment and thermally connected to the hot area of the supplementary cooling means, and which permits evacuation of the heat likely to have been accumulated by the latter.
9 is 21 A device according to one of Claims 1 to 4, wherein the cold zone consists of at least two stages and with respective temperatures T.1, T.2, and the supplementary cooling means are thermally connected to one stage via their cold area, by the cold face of a Peltier-effect module.
6. A device according to one of Claims 1 to 5, wherein the main cryogenic means operate according to one of the following thermodynamic cycles: Stirling, Vuillemier, pulsed-tube, Gifford, MacMahon, Brayton.
Equipment incorporating a temperature-sensitive component to be cooled, and being provided with a device according to any one of Claims 1 to 6.
8. Equipment according to Claim 7, wherein the supplementary cooling means are inserted between at least one portion of the main cryogenic means and at least one portion of the equipment, in such a way that, on the one hand, the cold area of the supplementary cooling means is thermally connected to at least one portion of the hot zone of the main cryogenic means and/or the rest of the equipment and that, on the other hand, the hot area of the supplementary means is in thermal contact with at least one portion of the equipment.
9. Equipment according to one of Claims 7 and 8, wherein the cryogenic device according to any one of Claims 1 to 6 is thermally insulated, apart from at least the area of heat exchange between the hot area of the supplementary cooling means and the rest of the equipment and/or ambient atmosphere.
10. Equipment according to one of Claims 7 to 9, comprising an element of a compressor unit of the optoelectronic p 22 equipment, thermal cameras, aerial reconnaissance analysers, early warning and tracking systems, deviation measuring equipment or transmission systems.
11. A cryogenic device substantially as herein described with reference to any one of the Figures of the accompanying drawings.
12. Equipment incorporating a temperature-sensitive component to be cooled and provided with a cryogenic device substantially as herein described with reference to any one of the Figures of the accompanying drawings.