Calorimeter with stabilized temperature

Abstract

Calorimeter comprising at least one measurement sensor (4) intended to receive at least one sample, the calorimeter comprising at least two temperature regulation stages (1, 2) of decreasing sizes nested within one another, each stage comprising a support (10, 20) and temperature regulation means, the at least one sensor (4) being associated with the smallest stage whose temperature regulation means make it possible to obtain temperature values necessary for obtaining measurements by the at least one sensor (4).

Description

STABILIZED TEMPERATURE CALORIMETER Technical field of the invention

[0001] The present invention relates to the field of differential scanning calorimetry, and, more particularly, to a temperature-stabilized calorimeter. Technological background

[0002] In general, a calorimeter is a measuring instrument designed to measure quantities of heat exchanged, for example, during a chemical reaction or a transformation of matter.

[0003] Differential scanning calorimetry is a technique for measuring the differences in heat exchange between a sample to be analyzed and a reference.

[0004] We know, for example, of the Ultimate DSC® calorimeter marketed by the company Calneos®, the structure of which is detailed in application FR3012880. This calorimeter includes at least one sensor intended to receive at least one sample, the structure and operation of this sensor being detailed, for example, in application FR2977034.

[0005] This calorimeter comprises three temperature control stages of decreasing size nested one inside the other in a "Russian doll" configuration, with the smallest stage associated with at least one sensor. In particular, this calorimeter includes a temperature control system incorporating dual-stage Peltier element cooling for a range of -40 to 160 degrees Celsius, advantageous for measurements on proteins that have relatively low crystallization temperatures due to supercooling, on the order of -20 degrees Celsius.

[0006] In general, commercially available calorimeters that allow low temperatures below -80 degrees Celsius include liquid nitrogen cooling methods with a tank or sweep that require high consumption of liquid nitrogen, thus presenting many disadvantages such as the cost of liquid nitrogen, the inherent safety of its use, and the management of liquid nitrogen in terms of supply and storage.

[0007] A calorimeter constructed with a cryorefrigerator is known from the document Luo Ji-Peng et al. Design and construction of a refrigerator-cooled adiabatic calorimeter for heat capacity measurement in liquid helium temperature region, review of scientific instruments, vol. 95, no. 3, 2024. This calorimeter, however, does not allow the integration of a sensor similar to that detailed in application FR2977034, the operation of which is particularly advantageous.

[0008] The present invention aims to overcome the aforementioned drawbacks by providing a temperature-stabilized calorimeter that is efficient, safe, and economical.

[0009] To this end, the present invention relates to a calorimeter comprising at least one measuring sensor intended to receive at least one sample, the calorimeter comprising at least two temperature control stages of decreasing sizes and nested one inside the other, each stage comprising a support and temperature control means, the at least one sensor being associated with the smaller stage whose temperature control means make it possible to obtain temperature values ​​necessary for obtaining measurements by the at least one sensor, in which: - a first stage comprises a screen forming a first enclosure with the support of this first stage, the first stage being intended to be placed in the external environment of the calorimeter from which it is thermally decoupled,and the temperature control means for this first stage, allowing the interior of the first enclosure to be isolated from temperature variations in the external environment, and a second stage is placed inside the first enclosure.

[0010] According to the invention, the temperature control means for the second stage include a cryo-cooler, said cryo-cooler comprising a cylindrical cold end called a cryogenic finger, the cold portion of which is thermally coupled to the second stage support via at least one thermal conductance filter. Furthermore, the temperature control means for the second stage include at least one heating element thermally coupled to the second stage support.

[0011] Thus, this calorimeter does not require a cold block such as a liquid nitrogen cooling system.

[0012] In this way, this calorimeter is economical, safe, and simple to use; a simple 230V-16A electrical outlet is sufficient to reach cryogenic temperatures.

[0013] Furthermore, this calorimeter is compatible with a sensor of the type detailed in application FR2977034.

[0014] Furthermore, this calorimeter is more efficient because the temperature of the cryogenic finger can be controlled more sensitively over a range of 0 to -200 degrees Celsius, unlike liquid nitrogen bath calorimeters whose temperature is fixed at -196 degrees Celsius and which require high-power heating to counteract significant heat loss. The cryogenic finger of the cryo-refrigerator according to the invention allows for the regulation of heat loss and thus limits the required heating power, resulting in greater temperature stability and homogeneity within the third chamber, and therefore more stable measurements.

[0015] According to an advantageous feature of the invention, the cryorefrigerator is of the Stirling type.

[0016] Thus, the compact profile of the cryorefrigerator makes it possible to minimize that of the opening passing through the support of the first stage, and thus limit thermal leaks at the level of this opening.

[0017] According to another advantageous feature of the invention, the calorimeter comprises a third stage placed inside a second enclosure defined by the second stage, the support of the third stage being thermally coupled to the support of the second stage via thermal conductances, the temperature control means of the third stage comprising at least one heating element thermally coupled to the support of the third stage.

[0018] In this way, the thermal conductances ensure very strong insulation of the third floor against external thermal disturbances.

[0019] According to another advantageous feature of the invention, the cryorefrigerator is mechanically connected to the first stage support in such a way that the cryogenic finger extends at least partially through the first stage support.

[0020] According to another advantageous feature of the invention, the cryogenic finger is mechanically connected to the first stage support via a fixing flange, the fixing flange comprising vacuum sealing means for sealing the first enclosure against vacuum at the level of the cryogenic finger.

[0021] According to another advantageous feature of the invention, the hot part of the cryogenic finger is thermally coupled to a liquid cooling circuit via the flange, the liquid cooling circuit being arranged at the level of the first stage support as close as possible to the flange.

[0022] According to another advantageous feature of the invention, at least one heating element of the temperature control means of the smallest stage consumes a heating power of between 1 and 5 watts.

[0023] According to another advantageous feature of the invention, the outer wall of the first enclosure is anodized in black.

[0024] According to another advantageous feature of the invention, the second enclosure is surrounded by at least one anti-radiation layer interposed inside the first enclosure between the first enclosure and the second enclosure.

[0025] Thus, thermal leaks between the first enclosure and the second enclosure are minimized.

[0026] According to another advantageous feature of the invention, the second enclosure is surrounded by two anti-radiation layers. Brief description of the figures

[0027] is an elevational view of a calorimeter according to an embodiment of the invention.

[0028] is an elevational view of a calorimeter according to another embodiment of the invention.

[0029] With reference to Figures 1 and 2, a calorimeter is described comprising at least one differential calorimetric sensor 4 for receiving at least one sample. The calorimeter includes at least two nested temperature control stages of decreasing size, each stage comprising a support and temperature control means. The at least one sensor 4 is associated with the smallest of the at least one temperature control stages whose temperature control means enable the sensor 4 to obtain the temperature values ​​necessary for measurements.

[0030] The invention is not limited to this application.

[0031] The smaller stage could include several differential measurement sensors, a sensor with at least two thermometers, or a non-differential sensor with a single thermometer.

[0032] We now describe, with reference to the, a calorimeter according to an embodiment of the invention, the calorimeter comprising two temperature regulation stages 1, 2 of decreasing sizes and nested one inside the other.

[0033] The first floor 1 includes a support 10 and a screen 11.

[0034] It therefore defines a first enclosure, in which the other temperature regulation stages are arranged.

[0035] This first stage 1 is in contact with the external environment of the calorimeter. Its primary function is therefore to isolate the interior 22 of the second enclosure, described below, from temperature variations in this environment.

[0036] In practice, the screen 11 is made of a material with very good thermal conductivity. Its temperature is regulated via the support 10 to which it is thermally coupled. The outer surface of the screen 11 is covered with thermal insulation to ensure thermal decoupling between the first floor 1 and the external environment.

[0037] Furthermore, the first enclosure, defined by the support 10 and the screen 11, is airtight. It can therefore be connected to a pumping device to establish a secondary vacuum inside 12 of the first enclosure, i.e., a primary pressure of around 100 to 1000 pascals, or a secondary pressure between And pascals.

[0038] Placing the first chamber under vacuum eliminates thermal bonds by conduction and convection between the different stages within the first chamber, defined by the first stage 1, and also between the first stage 1 and the others. The only parasitic thermal coupling is then thermal radiation, which the calorimeter according to the invention eliminates.

[0039] For this purpose, when the screen 11 is made of aluminium, magnesium, or titanium, the outer wall of the screen 11 can advantageously be anodized in black, thus minimizing thermal radiation from the first vacuum enclosure defined by the first stage 1 to the different stages inside the first enclosure defined by the first stage 1.

[0040] The support 10 consists of a metal plate exhibiting good thermal conductivity and good thermal diffusivity.

[0041] This metal can notably be aluminium.

[0042] Temperature control means are associated with support 10. These control means advantageously consist of a fluid circulation bath, in particular water, associated with a thermometer.

[0043] Devices of this type are designed to regulate temperature to within a few tens of millikelvins.

[0044] The calorimeter according to the invention comprises a second temperature regulation stage 2, placed inside 12 of the first enclosure.

[0045] In the embodiment illustrated in the figure, the second control stage 2 includes a support 20 and a screen 21 which define a second enclosure, the second stage 2 also including temperature control means associated with the support 20 of the second stage 2.

[0046] In the embodiment illustrated in Figure 1, the second stage 2 is nested inside the first stage 1, the second stage 2 thus being the smallest stage of the calorimeter. Inside the second chamber 22 is placed at least one differential calorimetric measuring sensor 4, for example of the type described in document FR2977034, the at least one sensor 4 being associated with this smaller stage whose temperature control means allow obtaining the temperature values ​​necessary for obtaining measurements by the at least one sensor 4.

[0047] Screen 21 could be omitted.

[0048] The support 20 of the second stage of regulation 2 consists of a plate of a material which is a very good conductor of heat.

[0049] It can notably be made of copper, like screen 21.

[0050] The calorimeter according to the invention further comprises a cryocooler 5 (translated from the Anglo-Saxon term "cryocooler").

[0051] According to the invention and in a known manner, a cryo-refrigerator comprises a compressor and a plunger in a concentric cylinder bore called a "cryogenic finger." A gas circulates within the compressor, generally in a closed loop, to absorb heat from the interior of the cryo-refrigerator and transfer it to the external environment. This gas may be hydrogen, helium, or another gas or mixture of gases.

[0052] The cryorefrigerator 5 can advantageously be of the Stirling type, Gifford McMahon type, Joule-Thomson type, pulsed gas tube type, or magnetic demagnetization type.

[0053] According to a preferred embodiment of the invention, the cryorefrigerator 5 is a Stirling type cryorefrigerator, the Stirling type cryorefrigerator 5 being for example a CryoTel® cryorefrigerator.

[0054] In general, a Stirling-type cryo-refrigerator uses the Stirling cycle to convert electricity into heat from a cold end of the cryogenic finger to a heat ejection outlet. The electricity is converted via a linear motor into piston motion, which, through the system's dynamics, causes the plunger to move; this constitutes a Stirling cycle between the piston and the plunger.

[0055] The cryorefrigerator 5 can be of rotary or linear type.

[0056] The cryogenic finger of the cryo-refrigerator 5 advantageously extends through the support 10 of the first regulating stage 1, in other words, through the bottom of the first chamber. When the cryo-refrigerator 5 is of the Stirling type, its compact profile minimizes the size of the opening passing through the support 10 of the first stage 1, thus limiting heat loss at this opening.

[0057] The cold end of the cryogenic finger is coupled to the support 20 of the second control stage 2 via a thermal conductance filter 23 adapted to the temperature range. This stabilizes heat loss to the cryogenic finger and regulates the temperature of the second stage 2 while minimizing electrical power consumption (stability of only 0.1 degrees Celsius compared to a target closer to millidegrees Celsius). Heating elements are installed on the support 20 of stage 2 and serve as temperature control means for this second stage 2.

[0058] The heating elements are connected to a thermometer.

[0059] They define a time constant between 100 and 1000 seconds.

[0060] Heating elements can be, but are not limited to, one or more miniature heating cartridges, and are designed to regulate the temperature from a few millikelvins to a few tens of millikelvins.

[0061] The cryogenic finger is mechanically connected to the support 10 of the first stage 1 via a fixing flange 6.

[0062] The support 20 is fixed to the cold end of the cryogenic finger by screws, thus allowing the second enclosure to be mechanically joined to the cryorefrigerator 5. The second enclosure is advantageously supported by the cryogenic finger of the cryorefrigerator 5, thus limiting thermal leaks by conduction to the outside of the second enclosure.

[0063] The hot part of the cryogenic finger is thermally coupled to a liquid cooling circuit 7 located at the support 10 of the first stage 1 as close as possible to the flange 6, the liquid cooling circuit 7 thus allowing the interior 12 of the first enclosure and the cryogenic finger to be maintained at a stable temperature.

[0064] The flange 6 is adapted to mechanically retain the cryogenic finger passing through the support 10 of the first stage 1, in other words the bottom of the first enclosure, and includes vacuum sealing means 6a, 6b, such as O-rings or lip seals, the vacuum sealing means 6a, 6b enabling the first enclosure to be sealed against vacuum at the level of the cryogenic finger.

[0065] The second enclosure can advantageously be surrounded by at least one anti-radiation layer 8, preferably two anti-radiation layers 8, to minimize thermal radiation from the first enclosure defined by the first control stage 1 to the various smaller stages nested inside the at least one anti-radiation layer 8. Each anti-radiation layer is treated, for example by electropolishing, to reduce thermal leakage by radiation.

[0066] When the second enclosure is surrounded by at least one radiation shielding layer 8, the cryorefrigerator 5 is mechanically connected to the support 10 of the first stage 1 in such a way that the cryogenic finger extends at least partly through the at least one radiation shielding layer 8.

[0067] When the second enclosure is surrounded by at least one anti-radiation layer 8, the support 10 of the first stage 1 is mechanically connected to at least one anti-radiation layer 8, for example by insulating rods 12a, thus allowing the second stage 2 to be thermally decoupled from the first stage 1.

[0068] According to a preferred embodiment of the invention illustrated in the figure, the calorimeter further comprises a third regulating stage 3, which is placed inside 22 of the second enclosure defined by the second regulating stage 2, the third stage 3 being here the smaller stage.

[0069] This third stage 3 comprises a support 30 and a screen 31 which define a third enclosure. Inside 32 of this third enclosure is placed at least one differential calorimetric measurement sensor 4, for example of the type described in document FR2977034.

[0070] The support 30 and the screen 31 are made of a material that is a very good conductor of heat, namely copper.

[0071] Screen 31 could be omitted.

[0072] This third stage 3 is temperature-regulated by at least one heating element (not shown in the diagram). This heating element(s), consuming between 1 and 5 watts of heating power, establish the temperature levels necessary for the proper functioning of sensor 4.

[0073] Thus, these methods can create a temperature ramp or establish an isothermal mode.

[0074] The third stage 3 is regulated to a temperature close to the second stage 2 in order to create around the sensor 4 a homogeneous and thermally stable environment with very little thermal leakage, thus allowing the finest possible thermal stability at the level of the sensor 4.

[0075] Thanks to the combination of the cryorefrigerator 5 thermally coupled to the support 20 of the second stage 2 with at least one heating element of the third stage 3 thermally coupled to the support 30 of the third stage 3, the temperature of the support 30 can be below 0 degrees Celsius, in particular between -230 and 50 degrees Celsius, in particular between -175 and 30 degrees Celsius.

[0076] This allows for a wider temperature range to set the starting temperature of the temperature ramp that will be applied at the third stage 3.

[0077] Furthermore, this third stage 3 is thermally coupled to the second stage 2 via thermal conductances 33.

[0078] These thermal conductances 33 are appropriately chosen to define a time constant ranging from 10 seconds to several hundred seconds. In practice, this time constant is chosen to be relatively high, for example on the order of 100 seconds.

[0079] Thus, these thermal conductances 33 make it possible to create very effective thermal insulation between the second floor 2 and the third floor 3, the last floor 3 being able to be regulated between 0.1 and 0.01 millikelvins.

[0080] In practice, this allows a thermal gradient to be created between the second and third stage, typically on the order of 1 degree Celsius, thanks to specific heating means provided at the support level 30. They are designed to provide a power P such that P = (K)×(ΔT), where K is the value of the thermal conductances 33, and ΔT is the temperature gradient.

[0081] The combination of these three temperature regulation stages makes it possible to obtain temperature stability on the order of a few tenths to a few hundredths of a microkelvin inside the third enclosure containing the differential calorimetric measurement sensor 4.

[0082] This result is due in particular to the presence of thermal conductances 33 between the second stage 2 and the third stage 3, these thermal conductances 33 ensuring very strong insulation of the third stage 3 against external thermal disturbances.

[0083] The present invention should not be considered as limited to the embodiment described and illustrated, but on the contrary covers all variants thereof.

Claims

Calorimeter comprising at least one measuring sensor (4) intended to receive at least one sample, the calorimeter comprising at least two temperature control stages (1, 2) of decreasing sizes and nested one inside the other, each stage (1, 2) comprising a support (10, 20) and temperature control means, the at least one sensor (4) being associated with the smaller stage whose temperature control means make it possible to obtain temperature values ​​necessary for obtaining measurements by the at least one sensor (4), in which: - a first stage (1) comprising a screen (11) forming a first enclosure with the support (10) of this first stage (1), the first stage (1) being intended to be placed in the external environment of the calorimeter from which it is thermally decoupled,and the temperature control means of this first stage (1) allowing the interior (12) of the first enclosure to be isolated from temperature variations in the external environment, and a second stage (2) placed inside the first enclosure, characterized in that the temperature control means of the second stage (2) comprise a cryo-refrigerator (5), said cryo-refrigerator (5) comprising a cylindrical cold end called a cryogenic finger, the cold part of which (51) is thermally coupled to the support (20) of the second stage (2) via at least one thermal conductance filter (23), and in that the temperature control means of the second stage (2) comprise at least one heating element thermally coupled to the support (20) of the second stage (2). Calorimeter according to claim 1, characterized in that cryorefrigerator (5) is of the Stirling type. Calorimeter according to claim 1 or according to claim 2, characterized in that the calorimeter comprises a third stage (3) placed inside a second enclosure defined by the second stage (2) and at least its support (20), the support (30) of the third stage (3) being thermally coupled to the support (20) of the second stage (2) via thermal conductances (33), the temperature control means of the third stage (3) comprising at least one heating element thermally coupled to the support (30) of the third stage (3). Calorimeter according to any one of claims 1 to 3, characterized in that the cryorefrigerator (5) is mechanically connected to the support (10) of the first stage (1) such that the cryogenic finger extends at least partially through the support (10) of the first stage (1). Calorimeter according to claim 4, characterized in that the cryogenic finger is mechanically connected to the support (10) of the first stage (1) via a fixing flange (6), the fixing flange (6) comprising vacuum sealing means (6a, 6b) allowing the first chamber to be sealed against vacuum at the level of the cryogenic finger. Calorimeter according to claim 5, characterized in that the hot part (52) of the cryogenic finger is thermally coupled to a liquid cooling circuit (7) via the flange (6), the liquid cooling circuit (7) being disposed at the support (10) of the first stage (1) as close as possible to the flange (6). Calorimeter according to any one of claims 1 to 6, characterized in that at least one heating element of the temperature control means of the smallest stage consumes a heating power of between 1 and 5 watts. Calorimeter according to any one of claims 1 to 7, characterized in that the outer wall of the first chamber is anodized black. Calorimeter according to claim 3 or according to any one of claims 4 to 8 taken in combination with claim 3, characterized in that the second enclosure is surrounded by at least one anti-radiation layer (8) interposed inside the first enclosure between the first enclosure and the second enclosure. Calorimeter according to claim 9, characterized in that the second enclosure is surrounded by two anti-radiation layers.

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