MX2009013548A - Cryogenic temperature controller by thermal conduction. - Google Patents

Abstract

The present invention refers to a controller or system for cooling and heating, at different speeds, a group of different samples in a simultaneous manner, from room temperature to cryogenic temperature and vice versa. The system comprises several chambers useful as sample carriers for supporting a disc including a temperature meter and a cap of compacted material. The chambers are closed at the upper portion and opened at the lower portion thereof. Said lower portion of the chambers comprises an orifice located at the lateral surface.

Description

DRIVER OF CRYOGENIC TEMPERATURES BY THERMAL CONDUCTION FIELD OF THE INVENTION The present invention consists of an apparatus for the cooling of samples of various nature at cryogenic temperatures with applications to the solid state, in those situations where low temperatures are required, for example for studies in various fields of study in biology, chemistry and physics as in the studies of electrical superconductivity in human and veterinary medicine, and in a great variety of scientific and / or educational experiments.

BACKGROUND OF THE INVENTION In some research experiments in the area of physics, for example in studies of high temperature transition superconductors (HTCS), it is required that the reasons for temperature changes of the samples can be adequately controlled, in order to measure and know their physical properties more explicitly. The problem is accentuated if the temperatures at which the experiments are done are extreme.

Coolers for cryogenic temperatures are generally sophisticated in their design, manufacture and operation, and consist of equally sophisticated elements or with certain limitations, such as the following: The temperature controllers, in the temperature range of 20 ° C to -196 ° C are electronically controlled heaters, coupled with materials that can withstand these temperatures. Systems composed of these materials must not undergo considerable structural changes, which alter or interfere negatively with the purpose of the measure.

Nowadays, commercial liquefiers, which are specialized systems of large volume, can be obtained. The systems require compressors, with which it is possible to liquify large quantities of some gases, such as nitrogen, oxygen and helium. They are used to cool other systems and achieve temperatures below -272 ° C. In the market there is a second group of systems with which the temperature can be lowered to -269 ° C, they are a little lighter, they compress and expand helium gas in different stages of a closed cycle.

A third group of systems is built in the research and teaching laboratories themselves, these devices are cooled with cryogenic liquids and use sophisticated electronic devices to control the temperature of the sample. Generally, these teams only handle a single sample.

In all the aforementioned equipment, a variety of experimental techniques can be implemented to characterize certain materials at low temperatures. The systems require unions, connections and special welding, electronic controls, and measurement and evacuation systems. The simplest arrangements change the temperature of the sample when using the thermal conduction of some gases and metals, but its construction is complicated due to the tools that are required to build them.

The apparatus object of the present invention is a much simpler alternative, easy to use, easy to control parameters, suitable to simueously obtain several samples or specimens same or different, at different temperatures, for use in a variety of tests or experiments This is described in detail in the figures and description presented later.

The apparatus object of the present invention allows, among other uses, the cooling of several samples simueously for use in the field of electronic microscopy, as well as the freezing of biological material for educational and scientific purposes. In the semiconductor industry, such devices are used for depositing metals in high vacuum. In the field of assisted reproduction, it is used to freeze fertilized eggs and sperm, as well as embryos. In the field of fermentation technology, is used to freeze biological material, preserving its long-term viability. In the field of physics, it finds use in the area of spectroscopy, where the movement of atoms must be reduced to a minimum, to investigate the temperature-dependent phases. In the industrial field it is used in the storage of pharmaceutical products, tapes and computer disks, to minimize thermal damage during handling, shipping and storage. It is also used in the testing of circuits or superconducting devices. Another industrial use is in the freezing of reagents for use in the analysis of biological material. Next, we refer to a series of patents related to the invention: The patent US 3195620 refers to a system for the maintenance of pre-selected temperatures that operates below the minus 100 ° Celsius (° C). However, this invention is extremely complex, requiring different components such as vacuum pumps, heaters, blade agitators, which increases the complexity of operation.

The patent US 4232453 refers to an apparatus for lyophilization of biological material, requires sophisticated components that hinder its simple daily operation.

Patent US 4459823 discloses an apparatus for the evaporation and manufacture of thin films in substrates cooled to cryogenic temperatures, but requires the addition of evacuation and measurement equipment.

The patent US 4480682 discloses an apparatus for the lyophilization of biological material only, for its use in the field of the solid state it is necessary to make substantial modifications, as well as use evacuation and measurement equipment.

Patent US 4485641 discloses a sophisticated apparatus for the freezing of biological material, requires a gas to regulate the temperature and contains an attachment with an electric motor to maintain the viability of said biological material. For different uses it is necessary to make modifications to the equipment, which complicates its use.

The patent US 4566283 discloses an apparatus for freezing at very low temperatures, with applications in the fields of spectroscopy, especially in the diffraction of X-rays and neutrons, as well as in the investigation of electrical properties of materials. Use a double-walled container with a vacuum between them. This container must be manufactured expressly, which increases the complexity of its possible use.

Patent US 4757692 discloses an apparatus for the freezing and maintenance at very low temperatures, of biological material of the type used in assisted fertilization, requires the use of complexity components.

Patent US 5052183 discloses a sophisticated cryo camera for testing electronic components and circuits.

Patent US 5241828 discloses a thermoelectric effect cooler that operates through the Peltier effect, for use at extremely low temperatures. This apparatus can be used to change the temperature in solid state samples by means of a directed current (SeebeO effect), but it is not possible to change the temperature of the samples to the temperatures operated by the invention proposed herein.

US 5275016 discloses an apparatus for cooling liquid reagents in biological samples only.

The patent US 5346570 discloses a DEWAR type container, for use in cryogenic environments.

Patent US 5644922 discloses a system for characterizing high temperature transition superconductors (HTCS), the invention does not require electronic controls or complicated systems to change the temperature of the samples, however it requires a specialized mechanical workshop, sophisticated welding and of gas containers for nitrogen or helium.

Patent JP 2125199, proposes a device that was created to save and reduce the consumption of liquid nitrogen by maintaining the samples at a fixed temperature of liquid nitrogen, does not contain a temperature control of the sample between ambient and liquid nitrogen temperatures.

Patent JP 2125199, requires: a Dewar container or container that is extremely expensive, compared to the liquid nitrogen container proposed in the present invention; a pressure container container of nitrogen gas gas. and a valve to regulate the internal pressure, where the sample is, with the atmospheric pressure. Comparatively, the present invention does not require an internal pressure regulator or seals, since it is a system open to the atmosphere and regulates itself. The document JP 2125199 is required to place the electronic temperature measurement and control lines in the system, requires connectors for vacuum or special adhesives, this involves performing specialized machinery work, creating electronic devices and increasing cost, which is not necessary in the present invention.

Patent JP 1090027 does not contain a temperature control of the sample between ambient and liquid nitrogen temperatures. This invention was created for 'transport a sample in vacuum and at a temperature close to liquid nitrogen. Initially the system has to be evacuated to extract all gases that can liquefy and eventually solidify at liquid nitrogen temperatures, since these substances can contaminate the samples. 5 Although the vacuum system does not require it in transport, it does require a pre-vacuum so that it can work. Being a completely hermetic system, it is required that the containers are sealed, glued or welded. Placing electronic temperature measurement and control lines in the system requires vacuum connectors or special adhesives, this involves performing specialized machinery work, creating electronic devices and increasing costs. In the portions that adapt to the system require a machining and a special seal for vacuum.

Patent JP 57073649, 1982. This invention was created to cool a sample at a temperature close to liquid nitrogen. It does not contain a temperature control of the sample between the ambient temperatures and liquid nitrogen, requiring the following: an infrastructure of tools to manufacture the support and the container that contains and support the block. This fabrication will require metal machining as well as special solders or glues. In addition, a Dewar container or container is required, which is extremely expensive compared to the liquid nitrogen container proposed in the present invention.

BRIEF DESCRIPTION OF THE FIGURES 25 Figure 1: Graph of electrical resistance as a function of the temperature of a superconducting ceramic material of type YiBa2Cu3Ox.

Figure 2: Graph of electrical resistance as a function of temperature, for a sample of graphite. 30 Figure 3: Graph of electrical resistance as a function of temperature for a copper wire.

Figure 4: Side cut of the system.

Figure 5: Top plane of the system.

Figure 6: Temperature in various cooling conditions with the system. Figure 7: Temperature under various heating conditions with the system.

DETAILED DESCRIPTION OF THE INVENTION > The invention object of the present application consists of a controller of cryogenic temperatures by thermal conduction, which changes the temperature of the samples, in the temperature range from 20 ° C to -196 ° C. 10 It is understood for the purposes of the present invention that a controller consists of the system for cooling and controlling at cryogenic temperatures, several samples simultaneously that can also reach different temperatures with each other in equal times. fifteen The controller consists of a set of cameras of different shapes, preferably cylindrical concentric with respect to its longitudinal axis, placed in vertical position (Figure 4 (la), (Ib), (le)). The upper base of each chamber is covered. The lower ones are open and their edges 20 have a hole (2). The chambers are placed inside a container preferably of glass (3), although other plastic, ceramic, metallic materials or a combination thereof may be used. This vessel stores liquid nitrogen or other cryogenic liquid that "boils" below room temperature (22 ° C). The holes (2) face each other 25 alternately in opposite position, to sufficiently decrease heat transfer by particle exchange. In the chambers, heat exchange occurs between the samples to be treated and the thermal bath of liquid nitrogen or any other liquid of the aforementioned characteristics. On each of the upper covers, except the outer one (4), a disc of material is placed 30 conductor, preferably copper (5a), (5b) and (5c) which is used as sample holder. The discs of conductive material are stuck on the covers, with grease of very good thermal conductivity. Additionally it is attached to the driver disk, a temperature indicator. The container (3) is covered with a lid of thermal insulating material (6). See figures 3 and 4.

Figures 4 and 5 illustrate the assembled system in which the position of the chambers (la), (Ib), (le) and (4), the sample holders (5a), (5b), (5c) are indicated. and the lid (6). The chambers are immobilized between them through the mechanical pressure exerted by the placement of six blocks of insulating material that act as fasteners (7), as shown in figure 5.

The system is operated by pouring and filling the container (3) with cryogenic liquid through the hole in the lid (6). Due to the difference in temperature between the sample holder and the cryogenic bath, the liquid evaporates violently, generating strong turbulence and high pressure inside the chambers. This liquid vapor is discharged into the air through the opening of the chambers. The outer chamber (4) prevents the parts (5a), (5b) and (5c) from coming into direct contact with the cryogenic liquid. As a consequence of the high pressure, the liquid level reaches the hole (2) of all the chambers. The temperature change in (5a), (5b) and (5c) is produced by its heat exchange with the outside of the container (3). The system has its thermal energy sink in the same cryogenic liquid and its source of heat is the environment, outside the container of cryogenic liquid.

Figure 6 shows the temperature change of (5a), (5b) and (5c) with respect to the time during the cooling process. The curve "ac" is the result of directly cooling one of the discs (5a) without cameras. By placing one, two and three more cameras, the curves "be", "ce" and "de" are obtained that are more extended. The following table, obtained from graph 6, gives us the times to cool to (5a), (5b) and (5c) from room temperature to a temperature of 200 ° K (-73.16 ° C) and 123.16 ° K (- 150 ° C) with different number of cameras. The times to reach 2 temperatures are exemplified in table I.

Table I Figure 7 shows the results of the heating of the samples. In this experiment the data was taken when the system started to heat up when the cryogenic liquid in the container (3) had run out. The curves "bh", "ch" and "dh" were obtained with cameras (4), (la), (Ib) and (le). The curve "ah" was obtained without placing any camera, the conductive disk (5a) presented moisture and ice on its surface, this can modify the data and damage the possible samples to be characterized.

Consequently, it can be affirmed that the results presented in the curves of figures 6 and 7, confirm the effectiveness of the system, which is achieved thanks to the assembly of the cameras, the size and shape of the cameras, the materials and the arrangement of the samples.

The change of state of the system when pouring the cryogenic liquid, generates an overpressure and dislodges the air from the chambers avoiding the formation of humidity inside and ice on the sample holders. Subsequently, the system increases its temperature when heated by thermal inertia until it reaches room temperature.

The system can incorporate a greater number of cameras that cover the samples, to modify its temperature more slowly. The assembly of the system is simple, economical and effective.

EXAMPLES Example 1.

The electrical resistance was measured as a function of the temperature of a superconducting ceramic sample of YiBa2Cu30x. The temperature control system is presented in figure 1. The sample and a temperature indicator were placed on the disc (5a), which is stuck on the upper base of the chamber (la) with a capacity of 5 ml. The data acquisition lines are routed through the holes (2) of the cameras. The chamber (la) is held with the chamber (Ib) by means of agglomerated polyurethane blocks (7), see figure 5. When the other samples were integrated into the system of figure 4, liquid nitrogen was poured into the container (3) until the chamber (4) was covered. The system was closed with part (6). The measurement curve in the experiment is shown in figure 1, where the graph of the electrical resistance as a function of temperature reproduces the behavior of a ceramic material superconductor type YiBa2Cu3Ox. When the temperature decreases, the behavior of the resistance is of the metallic type until before sharpening its fall, to then reach its transition temperature. Then the sample becomes a superconductor.

Example 2 The electrical resistance was measured as a function of the temperature of a graphite sample. The temperature control system already described is presented in figure 4. The sample and a temperature indicator were placed on the disc (5b), which is stuck on the upper base of the chamber (Ib) with a capacity of 50 ml. . The data acquisition lines are routed through the holes (2) of the cameras. The chamber (I b) is fastened with the chamber (le) by blocks of agglomerated polyurethane (7), see figure 5. When the other samples were integrated into the system of figure 4, liquid nitrogen was poured into the container (3) until covering the camera (4). The system was closed with the part (6) of polyurethane of radio 47.5 millimeters, thickness of 10 millimeters and a perforation of five millimeters of diameter. The measurement curve in the experiment is shown in Figure 2, where the graph of electrical resistance as a function of temperature reproduces the behavior of graphite.

Example 3 The electrical resistance was measured as a function of the temperature of a copper wire sample. The temperature control system used, already described, is presented in Figure 4. The sample and a temperature indicator were placed on the disc (5c), which is stuck on the upper base of the chamber (le) with the capacity of 50 mi. The data acquisition lines are routed through the holes (2) of the cameras. The chamber (le) is held with the chamber (4) by blocks of agglomerated polyurethane (7), see figure 5. When the other samples were integrated into the system of figure 4, liquid nitrogen was poured into the container (3) until cover the camera (4). The system was closed with part (6) of polyurethane. The measurement curve in the experiment is shown in Figure 3, where the graph of the electrical resistance as a function of temperature reproduces the behavior of the copper wire.

Claims (10)

1. A controller or system for cooling and controlling at cryogenic temperatures, one or more than one sample or specimen, simultaneously by thermal conduction in the temperature range from 20 ° C to -196 ° C, characterized in that: a) the system is assembled with at least two chambers that function as heat exchangers, b) the samples are cooled at different speeds reaching different final temperatures depending on the chamber in which they are located, and the arrangement of the same. c) the chambers are closed in the upper face and open in the lower face, the chambers have a hole in the side face next to the lower face, d) the chambers are placed with the lower face down, inside a container in which the cryogenic liquid will be emptied, e) each of the chambers also form the sample holders, by placing a disk of a diathermic material that in turn has a temperature meter f) the container where the cryogenic liquid is emptied and where the cameras are positioned, is covered with a lid; the cameras are immobilized to each other by fasteners. g) the system is assembled so that the pressures and temperatures of the chambers are controlled depending on their dimensions, their arrangement and the materials of each of the parts
2. The controller of cryogenic temperatures by thermal conduction, in accordance with clauses 1, characterized in that the arrangement of the materials allows the exchange of heat between the sample holders, the inside and outside of the cryogenic liquid container, through the chambers, the lid and the cryogenic liquid in liquid and gaseous state.
3. 3. The cryogenic temperature controller by thermal conduction, in accordance with clause 1 or 2, characterized in that the cryogenic liquid gas and the walls of the chambers allow the exchange of heat, the cryogenic liquid of the system being its cryogenic liquid, and its source of heat, the environment outside the container of the liquid.
4. 4. The controller of cryogenic temperatures by thermal conduction, according to clause 3, characterized in that the gas of the cryogenic liquid does not allow ice to form on the sample carriers or on the samples they contain.
5. 5. The controller of cryogenic temperatures by thermal conduction, in accordance with clause 1 to 4, further characterized because, as required, by assembly according to its volumetric capacity, shape and type of materials of the covers and chambers attached to the system , that cover the sample holders, it is possible to effect the changes of temperature, cooling or heating, in controlled times.
6. 6. The controller of cryogenic temperatures by thermal conduction, in accordance with clause 1 to 5, wherein the chambers are made of material and of the suitable form to achieve an expected temperature profile of the samples.
7. 7. The cryogenic temperature controller by thermal conduction, according to clause 1 to 6, wherein the chambers are of material that is selected from the group consisting of: polyurethane, cork, wood, ceramic, plastic, tempered glass, or combinations of the same depending on the profile of desired temperatures for each of the samples.
8. 8. The cryogenic temperature controller by thermal conduction, according to clause 1 to 7 wherein the chambers have various shapes that are selected from the group consisting of: cylinders, prisms, tunnels, hemispherical, or combinations thereof depending on the profile of desired temperatures for each of the samples.
9. 9. The controller of cryogenic temperatures by thermal conduction, in accordance with clause 1, wherein the material of the lid is insulating material that resists changes in temperature.
10. 10. The cryogenic temperature controller by thermal conduction, in accordance with clause 9 wherein the lid material is selected from the group consisting of polyurethane, cork, wood, ceramic, glass, plastic or a combination thereof. 1 1. The controller of cryogenic temperatures by thermal conduction, in accordance with clauses 1 to 10 wherein the fasteners of the system are insulating material at temperature changes that are selected from the group consisting of: polyurethane, cork, wood, ceramic, plastic or a combination thereof.