Variable temperature thermostat for neutron scattering

Abstract

The application discloses a variable-temperature thermostat for neutron scattering, which comprises a sample rod assembly, a sample tube assembly and a sample tube wall heater. The variable-temperature thermostat for neutron scattering optimizes a heat transfer structure, controls the temperature of a sample tube wall and a sample seat through two paths, and realizes that a sample is in a uniform temperature zone in a range of 4-300K of the thermostat, so that the accuracy of the sample temperature is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material analysis, in particular to a variable-temperature thermostat for neutron scattering. BACKGROUND

[0002] Neutrons are not charged, have magnetic moments, have strong penetration, can distinguish light elements, isotopes and near elements, and, like X-rays, are powerful means for humans to explore the microscopic structure of matter. Neutron scattering can not only study the crystal structure of matter, but also give information on the magnetic structure of matter; not only can it explore the static microscopic structure of matter, but also can observe the dynamic change process of matter; not only can it complete in-situ experimental measurement under special sample environment, but also can strictly verify physical assumptions and establish new theoretical models. At present, neutron scattering has been widely used in condensed matter physics, chemistry, nanomaterials, proteins and biology, industrial non-destructive deep flaw detection and many other fields, and has become an important tool for scientific research, new materials and new process research and development. Typical application examples include phase change processes of battery materials during charging and discharging in lithium-ion batteries, magnetic interaction and magnetic fluctuations in high-temperature superconductors, protein hydration and catalysis, etc.

[0003] Sample environment equipment is an important auxiliary equipment of a neutron scattering spectrometer, and a variable-temperature thermostat of 4-300K is the most commonly used sample environment equipment for neutron scattering experiments. Due to the strong penetration of neutrons, it is easy to penetrate the thermostat window that maintains the sample temperature, so that the sample can be measured at different temperatures, and accurate sample temperature is crucial to the experiment. Due to the particularity of neutron scattering, a thermometer cannot be placed at the sample, otherwise the thermometer will be irradiated by neutrons, causing the thermometer to be damaged, and the signal of the material of the thermometer will be mixed into the signal spectrum of the sample, affecting the accuracy of the sample information analysis. The design of the neutron scattering variable-temperature thermostat must be considered from the aspects of heat transfer and structure to ensure that the sample is in a uniform temperature zone, that is, the temperature measuring point and the sample are in a temperature uniform region, and the temperature of the measuring point can reflect the true temperature of the sample. SUMMARY

[0004] The variable-temperature thermostat for neutron scattering provided in the present application has the temperature measuring point and the sample in a temperature uniform region, and the temperature of the measuring point can reflect the true temperature of the sample.

[0005] According to a first aspect, in an embodiment, a variable-temperature thermostat for neutron scattering is provided, comprising:

[0006] A sample tube assembly, the sample tube assembly comprising a sample tube, the sample tube being provided with a neutron beam window, the neutron beam window being used for the neutron beam to enter or exit;

[0007] A sample rod assembly comprises a sample rod, one end of the sample rod is provided with a sample seat for installing a sample and controlling a sample temperature, the sample rod extends into the sample tube to deliver the sample to the neutron beam window position;

[0008] Further, a sample tube wall heater is installed on the tube wall of the sample tube.

[0009] According to the above-mentioned variable temperature thermostat for neutron scattering, since the sample tube wall heater is installed on the tube wall of the sample tube, the sample tube wall heater can heat the temperature of the tube wall of the sample tube near the neutron beam window position to the same temperature as that of the sample seat, at this time, the fluid around the sample is at the same temperature, the sample is in static thermal equilibrium, and strong thermal convection of cold and hot fluids does not occur, thereby avoiding the generation of temperature gradient, the sample seat, the sample and the sample tube cavity within a certain range around the sample are in a uniform temperature area, and the sample temperature can be reflected by the temperature at the sample seat, so that the temperature measuring point of the variable temperature thermostat for neutron scattering and the sample are in an area with uniform temperature, and the temperature of the measuring point can reflect the real temperature of the sample. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 A schematic view of the finite element simulation results of the temperature of the sample seat and the sample of the variable temperature thermostat for neutron scattering in the prior art when the temperature is controlled at 55K;

[0011] Figure 2 A schematic view of the structure of the variable temperature thermostat for neutron scattering in an embodiment;

[0012] Figure 3 A schematic view of the internal structure of the variable temperature thermostat for neutron scattering in an embodiment;

[0013] Figure 4 A schematic view of the structure of the variable temperature thermostat for neutron scattering (without the vacuum cylinder and the heat shield cylinder) in an embodiment;

[0014] Figure 5 A schematic view of the structure of the variable temperature thermostat for neutron scattering in an embodiment; Figure 4 A schematic view from another angle;

[0015] Figure 6 A schematic view of the structure of the sample tube of the variable temperature thermostat for neutron scattering in an embodiment;

[0016] Figure 7 A schematic view of the structure of the first cylinder of the variable temperature thermostat for neutron scattering in an embodiment;

[0017] Figure 8 A schematic view of the structure of the second cylinder of the variable temperature thermostat for neutron scattering in an embodiment;

[0018] Figure 9Fig. 1 is a schematic view of a heat shield flange structure of a variable-temperature thermostat for neutron scattering in an embodiment;

[0019] Figure 10 Fig. 2 is a schematic view of a sample rod adapter of a variable-temperature thermostat for neutron scattering in an embodiment;

[0020] Figure 11 Fig. 3 is a schematic view of a sample rod assembly of a variable-temperature thermostat for neutron scattering in an embodiment;

[0021] Figure 12 Fig. 4 is a sample seat and sample temperature over time line graph of a variable-temperature thermostat for neutron scattering in an embodiment.

[0022] Fig. 1 is a schematic view of a heat shield flange structure of a variable-temperature thermostat for neutron scattering in an embodiment; DETAILED DESCRIPTION

[0023] The application will be further described below in conjunction with the drawings. Like reference numerals in different embodiments designate similar elements. In the following embodiments, many details are described in order to provide a more thorough understanding of the application. However, it will be apparent to one skilled in the art that some features, which are not necessary for an understanding of the application, can be omitted, or can be substituted with other features, materials, or methods. In some cases, some operations related to the application are not shown or described in the specification in order to avoid obscuring the core of the application with too much detail, and it is not necessary to describe these operations in detail for one skilled in the art to understand the application based on the description in the specification and general knowledge in the art.

[0024] In addition, features described in the specification, operations or characteristics can be combined in any appropriate manner in various embodiments. Meanwhile, the steps or actions in the method description can also be sequentially changed or adjusted in a manner that can be apparent to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment, and do not mean that the sequence is necessary, unless otherwise stated that a certain sequence must be followed.

[0025] The serial numbers of components in the text, such as "first", "second", etc., are only used to distinguish the described objects, and do not have any sequence or technical meaning. The "connection" and "coupling" in the present application include direct and indirect connection (coupling) unless otherwise specified.

[0026] Neutron scattering experiments require sample analysis at different temperatures, so accurate sample temperature is crucial to the experiment. However, due to the particularity of neutron scattering, a thermometer cannot be placed at the sample 102, otherwise the spectrometer detector will collect the signal of the thermometer material, affecting the experimental results. In the experiment, the sample temperature is generally reflected by the thermometer on the sample holder 10. When the sample holder 10 turns on the heater 101, the sample 102 is affected by the heater 101 and the surrounding cold helium gas. Because the heater 101 is set at the upper end of the sample 102, there may be a temperature gradient from top to bottom of the sample 102, and the thermal simulation analysis also verifies the existence of the temperature gradient, Figure 1 The temperature finite element simulation results of the sample holder 10 and the sample 102 of the existing variable temperature thermostat sample holder 10 for neutron scattering when the temperature of the sample holder 10 is controlled at 55K are shown in the figure. According to the finite element analysis results in Figure 1 According to the finite element analysis results in

[0027]

[0028] As can be seen from the above table, the temperature of the sample 102 cannot be accurately reflected by the thermometer at the sample holder 10 of the existing variable temperature thermostat for neutron scattering, which may have an adverse effect on the experimental results.

[0029] The main reasons for the temperature difference between the sample seat 10 and the sample 102 are: 1. The heater 101 is installed on the upper end of the sample 102. When the heater 101 is heated and controlled, the helium gas on the upper end of the sample 102 rises due to heating, and the temperature of the wall of the sample tube is low. The cold helium gas near the wall of the sample tube descends, resulting in that the temperature is high near the sample seat 10 and the temperature is low far from the sample seat 10; 2. The thermal conductivity of the sample 102 is poor, and the heat cannot be uniformly conducted to each part of the sample 102.

[0030] From the above, it can be seen that the main reason for the temperature gradient is the strong thermal convection of the cold and hot fluids around the sample 102, and the power of the thermal convection comes from the temperature difference of the surrounding fluids. Specifically, the temperature of the sample seat 10 is inconsistent with the temperature of the wall of the sample tube. In summary, when the temperature of the sample seat 10 is set to be consistent with the temperature of the wall of the sample tube, the fluids around the sample 102 are at the same temperature, the sample 102 is in static thermal equilibrium, the sample seat 10, the sample 102 and the surrounding area are in a uniform temperature area, the temperature of the sample 102 is uniform, and the temperature of the sample 102 can also be reflected by the temperature of the sample seat 10.

[0031] Therefore, in the embodiment of the present application, the variable temperature thermostat 100 for neutron scattering includes a sample rod assembly 1, a sample tube assembly 2 and a sample tube wall heater. The sample tube assembly 2 includes a sample tube 21, and the sample tube 21 is provided with a neutron beam window 211 for the neutron beam to enter and exit. The sample rod assembly 1 includes a sample rod 11, and one end of the sample rod 11 is provided with a sample seat 10 for installing a sample 102 and controlling the temperature of the sample 102. The sample rod 11 extends into the sample tube 21 to send the sample 102 to the position of the neutron beam window 211. The sample tube wall heater is installed on the wall of the sample tube 21, and the sample tube wall heater is used to control the temperature of the wall of the sample tube 21. Since the sample tube wall heater is installed on the wall of the sample tube 21, the sample tube wall heater can control the temperature of the wall of the sample tube 21 near the position of the neutron beam window 211 to be the same as the temperature of the sample seat 10. At this time, the fluids around the sample 102 are at the same temperature, the sample 102 is in static thermal equilibrium, and the strong thermal convection of the cold and hot fluids does not occur, thereby avoiding the generation of the temperature gradient. The sample seat 10, the sample 102 and the surrounding area are in a uniform temperature area, and the temperature of the sample 102 can be reflected by the temperature of the sample seat 10. The temperature measuring point of the variable temperature thermostat 100 for neutron scattering and the sample 102 are in a uniform temperature area, and the temperature of the measuring point can reflect the real temperature of the sample 102.

[0032] The present application will be described below through specific embodiments.

[0033] Embodiment one:

[0034] As Figures 2 to 12As shown, an embodiment of the present application provides a variable temperature thermostat for neutron scattering 100, which comprises a sample rod assembly 1, a sample tube assembly 2 and a sample tube wall heater. The sample tube assembly 2 comprises a sample tube 21, which is provided with a neutron beam window 211 for the neutron beam to enter or exit, and is filled with high-purity helium gas to achieve temperature conduction from the sample tube wall to the sample. The sample rod assembly 1 comprises a sample rod 11, which is provided at one end with a sample holder 10 for mounting a sample 102 and controlling the temperature of the sample 102, and extends into the sample tube 21 to deliver the sample 102 to the position of the neutron beam window 211. The neutron beam enters via the neutron beam window 211, irradiates on the sample 102, and then exits via the neutron beam window 211 on the opposite side to obtain the diffraction spectrum of the sample 102. Those skilled in the art can understand that certain types of samples 102 (such as flowing samples 102) may not be suitable for being directly mounted on the sample holder 10. In this case, in order to ensure the normal progress of the experiment, a sample box can be used to hold the sample 102, and the sample box is mounted on the sample holder 10. The sample box is made of the same material as the neutron beam window 211, and the neutron beam can enter / exit the sample box to ensure the normal progress of the neutron scattering experiment. The sample tube wall heater is installed on the wall of the sample tube 21, and is used to control the temperature of the wall of the sample tube 21. Those skilled in the art can understand that the length of the sample tube 21 is generally large. If the sample tube wall heater controls the temperature of the entire wall of the sample tube 21, the cost may be high, and in general, it is only necessary to control the temperature of the wall of the sample tube 21 near the neutron beam window 211 to be consistent with the temperature of the sample holder 10 to avoid heat convection of the helium gas near the sample holder 10 and the sample 102. Therefore, generally, the sample tube wall heater only needs to be installed near the neutron beam window 211 to control the temperature of the wall of the sample tube 21 near the neutron beam window 211.

[0035] Since the sample tube wall heater is installed on the wall of the sample tube 21, the sample tube wall heater can heat the temperature of the wall of the sample tube 21 near the neutron beam window 211 to be the same as the temperature of the sample holder 10. At this time, the fluid around the sample 102 is at the same temperature, the sample 102 is in static thermal equilibrium, and there is no strong heat convection of cold and hot fluids, thereby avoiding the generation of temperature gradient. The sample holder 10, the sample 102 and the surrounding area are in a uniform temperature region, and the temperature of the sample 102 can be reflected by the temperature at the sample holder 10. Therefore, the temperature measuring point of the variable temperature thermostat for neutron scattering 100 and the sample 102 are in a region with uniform temperature, and the temperature of the measuring point can reflect the true temperature of the sample 102.

[0036] The sample tube 21 is used to provide an experimental environment for the neutron scattering experiment. The sample rod 11 extends into the sample tube 21 to deliver the sample 102 to the position of the neutron beam window 211 of the sample tube 21, so that the neutron beam can smoothly hit the sample 102 to complete the experiment. In order to ensure that the temperature at the sample seat 10 can accurately reflect the temperature of the sample 102, it is necessary to avoid strong thermal convection of helium gas near the sample seat 10 and the sample 102 in the sample tube 21, which can cause the temperature at the sample seat 10 to be inconsistent with the temperature of the sample 102. In order to achieve this effect, the temperature at the sample seat 10 should be consistent with the temperature of the wall of the sample tube 21 near the neutron beam window 211. In the embodiment, the sample tube wall heater is installed near the neutron beam window 211 to control the temperature of the wall of the sample tube 21 near the neutron beam window 211. In the embodiment, the sample tube wall heater includes a tube wall heater and a tube wall thermometer. The tube wall heater and the tube wall thermometer are electrically connected to an external temperature controller. After the electrical signal of the tube wall thermometer is input to the external temperature controller, the external temperature controller displays the corresponding temperature. At the same time, the external temperature controller outputs appropriate current to the tube wall heater through the pid algorithm to adjust the power of the tube wall heater, so that the temperature of the tube wall at the control point is finally consistent with the set temperature.

[0037] Specifically, in an embodiment, the sample tube 21 comprises a first tube body 201, a second tube body 202 and a third tube body 203 arranged in sequence, the sample tube wall heater is installed on the second tube body 202, and the neutron beam window 211 is arranged on the third tube body 203. In this embodiment, the material of the first tube body 201 is stainless steel, the material of the second tube body 202 is oxygen-free copper, and the material of the third tube body 203 is aluminum material with high neutron transmission rate, which reduces the influence of the tube material on the experimental results of neutron scattering. The second tube body 202 is connected with the first tube body 201 by brazing, and the connection end of the second tube body 202 and the third tube body 203 is provided with a flange structure, which facilitates the disassembly and assembly of the third tube body 203, and the second tube body 202 and the third tube body 203 are connected by an indium wire sealing screw, which ensures the uniform temperature of the second tube body 202 and the third tube body 203. Those skilled in the art can understand that, in some embodiments, according to actual experimental requirements and conditions, the first tube body 201 and the second tube body 202 can also be an integrated structure of the same material. In this embodiment, the second tube body 202 made of oxygen-free copper is used to make the temperature of the tube wall more uniform and avoid strong thermal convection of the gas in the tube. In this embodiment, the axial length of the third tube body 203 is relatively short, and the sample tube wall heater can control the temperature of the helium gas near the tube wall of the second tube body 202 by controlling the tube wall temperature of the second tube body 202, so that the temperature of the helium gas in this part is the same as that of the helium gas near the sample seat 10 and the sample 102, thereby avoiding strong thermal convection and ensuring that the sample seat 10 and the sample 102 are in a uniform temperature region. The reason for selecting to install the sample tube wall heater on the second tube body 202 instead of directly on the third tube body 203 is to avoid the influence of the material of the sample tube wall heater on the results of the neutron scattering experiment.

[0038] Before the neutron scattering experiment is performed, the temperature in the sample tube 21 often needs to be lowered to a lower state to provide an environment for the neutron scattering experiment, and then the sample 102 is heated by the sample seat 10 and the sample tube wall heater to reach the target temperature for the experiment. Therefore, the variable temperature thermostat 100 for neutron scattering in this embodiment further comprises a cooling assembly 3.

[0039] Specifically, in an embodiment, the cooling assembly 3 comprises a first heat conduction member 31, a second heat conduction member 32 and a refrigerator 33. One end of the first heat conduction member 31 is connected with the refrigerator 33, and the other end of the first heat conduction member 31 is connected with the first tube body 201. The other end of the second heat conduction member 32 is connected with the refrigerator 33, and the other end of the second heat conduction member 32 is connected with the second tube body 202. The first heat conduction member 31 is used for heat conduction to the first tube body 201 to pre-cool the whole sample tube 21. The second heat conduction member 32 is used for heat conduction to the second tube body 202 to cool the area of the neutron beam window 211 to meet the experimental conditions.

[0040] One focus of the present application is to ensure that the temperature of the helium gas near the region of the neutron beam window 211 is uniform to avoid strong thermal convection of the helium gas, and therefore, the cooling of the region of the neutron beam window 211 should also be uniform, i.e., the heat conduction of the second heat conducting member 32 to the second tube body 202 should be uniform.

[0041] In an embodiment, the second heat conduction member 32 comprises a heat conduction assembly 321 and a connecting member 322, one end of the heat conduction assembly 321 is connected with the refrigerator 33, the other end of the heat conduction assembly 321 is connected with the connecting member 322, and the connecting member 322 is sleeved on the second pipe body 202. In this way, the second heat conduction member 32 can conduct heat to the second pipe body 202, so that the pipe walls of the second pipe body 202 and the third pipe body 203 are uniformly cooled, and the temperature of the helium gas near the pipe wall in the area of the neutron beam window 211 is uniform, so that convection does not occur in the subsequent heating process due to uneven temperature distribution, and the sample holder 10 and the sample 102 are in a uniform temperature region. In this embodiment, the heat conduction assembly 321 comprises a heat conduction plate 3211 and a heat conduction copper wire 3212, one end of the heat conduction plate 3211 is connected with the refrigerator 33, the other end of the heat conduction plate 3211 is connected with the heat conduction copper wire 3212, one end of the heat conduction copper wire 3212 is connected with the heat conduction plate 3211, the other end of the heat conduction copper wire 3212 is connected with the connecting member 322, and the connecting member 322 encircles the second pipe body 202. The second heat conduction member 32 transmits the cold energy on the refrigerator 33 to the connecting member 322 through the heat conduction plate 3211 and the heat conduction copper wire 3212, and the connecting member 322 tightly encircles the second pipe body 202 to conduct heat to the second pipe body 202, so that the pipe walls of the second pipe body 202 and the third pipe body 203 are uniformly cooled, and the temperature of the helium gas near the pipe wall in the area of the neutron beam window 211 is uniform. Those skilled in the art can understand that the reason for using the heat conduction plate 3211 and the heat conduction copper wire 3212 to conduct heat to the connecting member in this embodiment is to save installation space, because the second pipe body 202 in this embodiment has a large height difference with the refrigerator 33, if the heat conduction plate 3211 is directly connected with the connecting member 322, the heat conduction plate 3211 will occupy a large amount of installation space, and because of the installation angle, it may cause inconvenience in installation, therefore, in this embodiment, the heat conduction plate 3211 and the heat conduction copper wire 3212 are used to cooperatively conduct heat to the connecting member 322, in order to ensure that the connecting member 322 is uniformly heated in the circumferential direction, the end of the heat conduction plate 3211 close to the sample tube 21 is arranged around the sample tube 21, accordingly, the heat conduction copper wire 3212 is also arranged around the sample tube 21, in order to ensure the heat conduction efficiency, the material of the connecting member 322 is oxygen-free copper, the material of the heat conduction copper wire 3212 is high-3R-value copper, the contact surface between the connecting member 322 and the second pipe body 202 is padded with indium sheets to enhance heat conduction, and the heat conduction plate 3211 and the heat conduction copper wire 3212 are not connected with the sample tube 21, that is, there is a gap between the heat conduction plate 3211 and the heat conduction copper wire 3212 and the sample tube 21, so as to avoid the loss of cold energy. In this embodiment, the connecting member 322 arranged around the second pipe body 202 is fixed by pressing the second pipe body 202 through the screws on the connecting member 322, the connecting member 322 can be a complete circular arc, after being sleeved on one end of the second pipe body 202, it is slid to the target installation position, or it can be two half-circular arc components, which are combined to complete the installation at the target installation position.

[0042] The cooling assembly 3 comprises a first heat conduction member 31, a second heat conduction member 32 and a refrigerator 33. The first heat conduction member 31 is used for heat conduction to the first tube body 201 to pre-cool the sample tube 21. The second heat conduction member 32 is used for heat conduction to the second tube body 202 to cool the area of the neutron beam window 211 to provide an environment for the experiment. Therefore, the heat conduction temperature of the first heat conduction member 31 is different from the heat conduction temperature of the second heat conduction member 32 in most cases. Therefore, in this embodiment, the refrigerator 33 comprises two-stage cold heads (a first-stage cold head 331 and a second-stage cold head 332). The lowest temperature of the first-stage cold head 331 is higher than the lowest temperature of the second-stage cold head 332. The first heat conduction member 31 is connected to the first-stage cold head 331. The second heat conduction member 32 is connected to the second-stage cold head 332 to conduct heat at different temperatures to the first tube body 201 and the second tube body 202, respectively. In this embodiment, the temperature of the first-stage cold head 331 is 40 K. The temperature of the second-stage cold head 332 is 4 K.

[0043] The sample rod 11 extends into the sample tube 21 to deliver the sample 102 to the neutron beam window 211 for neutron scattering experiment. To ensure the normal progress of the experiment, the sample rod 11 needs to accurately deliver the sample 102 to the position of the neutron beam window. In this embodiment, the sample rod assembly 1 further comprises heat insulation sheets 12 and a sample rod flange 13.

[0044] Specifically, in an embodiment, the sample seat 10 is arranged at one end of the sample rod 11. The sample seat 10 is used for mounting the sample 102 and controlling the temperature of the sample 102. The sample seat 10 is internally provided with a heater 101 and a thermometer. The heater 101 is used for controlling the temperature of the sample 102. The thermometer is used for measuring the temperature at the sample seat 10, which can reflect the temperature of the sample 102. The sample rod flange 13 is arranged at the other end of the sample rod 11. The sample rod flange 13 is used for fixing the sample rod 11 to keep the position of the sample 102 unchanged during the experiment. A plurality of heat insulation sheets 12 are arranged at intervals on the sample rod 11. The edge size of the heat insulation sheet 12 is slightly smaller than the inner wall size of the sample tube 21. The heat insulation sheet 12 can reduce the heat radiation of other areas of the sample tube 21 to the area of the neutron beam window 211. At the same time, because the edge size of the heat insulation sheet 12 is slightly smaller than the inner wall size of the sample tube 21, the heat insulation sheet 12 also plays a limiting role, so that the sample rod 11 cannot be inclined at a large angle, and the sample 102 is kept in the central area of the neutron beam window 211. In this embodiment, the sample tube 21 is in the shape of a cylindrical cylinder. Correspondingly, the heat insulation sheet 12 is in the shape of a round sheet. The diameter of the heat insulation sheet 12 is slightly smaller than the diameter of the inner wall of the sample tube 21. In this embodiment, the material of the sample rod 11 is stainless steel. The material of the sample seat 10 is oxygen-free copper, so as to conduct the temperature of the heater 101 to the sample 102 as much as possible. The sample rod flange 13 is further provided with a sample rod electrical connector 131. The sample rod electrical connector 131 is used for leading out the lead wires of the heater 101 and the thermometer.

[0045] The sample rod flange 13 is used to fix the sample rod 11, so as to ensure that the sample 102 is always at the center of the neutron beam window 211 during the experiment, that is, the sample rod flange 13 needs to ensure that the relative position of the sample rod 11 and the sample tube 21 is unchanged, therefore, in the embodiment, the sample tube assembly 2 further comprises a sample tube flange 22 and a sample rod adapter 23, the sample tube flange 22 is arranged at the opening of the sample tube 21, one end of the sample rod adapter 23 is connected with the sample tube flange 22, and the other end of the sample rod adapter 23 is connected with the sample rod flange 22, so that the relative position of the sample rod 11 and the sample tube 21 is fixed.

[0046] Specifically, in an embodiment, the sample rod adapter 23 is provided with a gas release valve 231, an air nozzle 232 and a pressure gauge 233. The gas release valve 231 is used to prevent overpressure in the sample tube 21, and when the pressure in the sample tube 21 exceeds a preset threshold, the gas release valve 231 releases gas, and when the pressure in the sample tube 21 is less than the preset threshold, the gas release valve 231 remains in a sealed state, and in the embodiment, the preset threshold is 40 KPa. The air nozzle 232 is used to inflate or deflate the sample tube 21. The pressure gauge 233 is used to measure the pressure in the sample tube 21. In order to ensure the airtightness of the sample tube 21, O-shaped sealing rubber rings are arranged at the connection between the sample rod adapter 23 and the sample tube flange 22 and at the connection between the sample rod adapter 23 and the sample rod flange 13; the sample rod 11 is inserted into the sample rod flange 13, and the connection between the two is achieved by pressing the O-shaped sealing rubber ring through the taper structure to realize the sealing of the sample rod 11 and the sample rod flange 13, and the relative position of the sample rod 11 and the sample rod flange 13 is adjustable. By adjusting the relative position of the sample rod 11 and the sample rod flange 13, the position of the sample 102 can be finely adjusted to meet different experimental requirements.

[0047] In order to obtain a better neutron scattering experimental environment, the variable-temperature thermostat 100 for neutron scattering in the embodiment further comprises a vacuum assembly, which is used to maintain the vacuum of the cavity of the variable-temperature thermostat 100 for neutron scattering, avoid rapid heat exchange between the sample tube 21 and the outside world, and maintain a stable experimental environment.

[0048] Specifically, in an embodiment, the vacuum assembly includes a vacuum cylinder having a vacuum cavity 40 into which the sample tube 21 extends, a neutron beam window 211 located within the vacuum cavity 40, and a vacuum beam window 401 provided on the vacuum cylinder corresponding to the neutron beam window 211 for the neutron beam to enter / exit. The vacuum cavity 40 is in a vacuum environment to avoid rapid heat exchange between the components of the variable-temperature thermostat 100 for neutron scattering and the outside world, thereby maintaining a stable experimental environment. Therefore, the cold head of the refrigerator 33, the first heat-conducting member 31, the second heat-conducting member 32, the second tube body 202, the third tube body 203, and most of the first tube body 201 should be provided in the vacuum cavity 40. Meanwhile, the vacuum cylinder accommodating the cold head of the refrigerator 33 and part of the sample tube 21 requires a large diameter, the vacuum cylinder accommodating the third tube body 203 requires a small diameter, and the material of the vacuum cylinder cannot interfere with the experimental results. Therefore, in the present embodiment, the vacuum cylinder includes a first vacuum cylinder 41 for accommodating the cold head of the refrigerator 33 and part of the sample tube 21, and a second vacuum cylinder 42 for accommodating the third tube body 203. The first vacuum cylinder 41 and the second vacuum cylinder 42 are in communication, and the sample tube 21 extends through the first vacuum cylinder 41 into the second vacuum cylinder 42. In the present embodiment, to reduce the number of parts of the product and facilitate installation, the sealing cover of the first vacuum cylinder 41 is a thermostat main flange 50, the refrigerator 33 is connected to the thermostat main flange 50 through a refrigerator flange 333, and the cold head of the refrigerator 33 extends into the first vacuum cylinder 41 through the refrigerator flange 333 and the thermostat main flange 50. The refrigerator flange 333 and the thermostat main flange 50 each correspondingly have a sample tube mounting port and a vacuum port. The sample tube mounting port is for the sample tube 21 to pass through, and the vacuum port is for vacuumizing. The refrigerator flange 333 also has an electrical connector socket for electrical connection of components, leading wires of components, input / output of electrical signals of components, and maintaining the sealing of the vacuum cavity 40. In the present embodiment, the material of the thermostat main flange 50 is stainless steel, one side of the thermostat main flange 50 is connected to the refrigerator flange 333, the other side is connected to the first vacuum cylinder 51, and the thermostat main flange 50 is also used to support the variable-temperature thermostat 100 for neutron scattering in the present embodiment on a flange of a spectrometer scattering chamber to perform neutron scattering experiments. The material of the first vacuum cylinder 41 is stainless steel, one end of the first vacuum cylinder 41 is connected to the thermostat main flange 50 and the refrigerator flange 333, the other end is connected to the second vacuum cylinder 42, and O-rings are provided at the above connections to maintain the sealing effect. The material of the second vacuum cylinder 42 is pure aluminum, the second vacuum cylinder has a vacuum beam window 401 located opposite the neutron beam window 211, and the vacuum beam window 401 is used for the neutron beam to enter / exit.

[0049] The neutron scattering experiment often needs to be carried out in a lower temperature environment, and the sample 102 area needs to be able to be lowered to the target temperature, and other components with higher temperature will produce heat radiation to the sample 102 area, which can cause the temperature of the sample 102 area to be unable to be lowered to the low temperature required by the experiment, therefore, the variable temperature thermostat 100 for neutron scattering in the embodiment further includes a heat shield assembly. The heat shield assembly is used to reduce the heat radiation of other components outside the heat shield to the components inside the heat shield.

[0050] Specifically, in an embodiment, the heat shield assembly is arranged in the vacuum cavity 40, and the heat shield assembly comprises a heat shield cylinder having a heat shield cavity 60, the sample tube 21 extends into the heat shield cavity 60, the neutron beam window 211 is located in the heat shield cavity 60, and the heat shield cylinder is provided with a heat shield beam window corresponding to the neutron beam window 211, and the heat shield beam window is used for the incident / emission of the neutron beam. The heat shield assembly reduces the heat radiation from other components outside the heat shield cavity 60 to the components in the heat shield cavity 60. Considering the low-temperature area required by the variable-temperature thermostat 100 for neutron scattering in the embodiment, the second heat conduction member 32, the second-stage cold head 332, the second tube body 202, the third tube body 203, and part of the first tube body 201 should be arranged in the heat shield cavity 60. For the same reason as the above-mentioned vacuum cylinder, in the embodiment, the heat shield cylinder comprises a first heat shield cylinder 61 and a second heat shield cylinder 62, the first heat shield cylinder 61 is used for accommodating the second-stage cold head 332 and part of the sample tube 21, and the second heat shield cylinder 62 is used for accommodating the third tube body 203. The first heat shield cylinder 61 and the second heat shield cylinder 62 are communicated, and the sample tube 21 extends through the first heat shield cylinder 61 into the second heat shield cylinder 62. In the embodiment, in order to reduce the number of product connections and facilitate installation, the sealing cover of the first heat shield cylinder 61 is a heat shield flange 63, the heat shield flange 63 also serves as a heat transfer plate of the first heat conduction member 31, the heat shield flange 63 is connected with the first-stage cold head 331 of the refrigerator 33, the heat shield flange 63 is provided with a heat conduction copper member 311, the structure of the heat conduction copper member 311 is similar to that of the connecting member 322, the material of the heat conduction copper member 311 is also oxygen-free copper, the heat conduction copper member 311 surrounds the first tube body 201, and the heat shield flange 63 and the heat conduction copper member 311 jointly constitute the first heat conduction member 31. In this way, the installation space can be saved, the number of product parts is reduced, the installation is simple, and the cost is low. The material of the heat shield flange 63 is oxygen-free copper, one end of the heat shield flange 63 is connected with the first heat shield cylinder 61, the other end is connected with an oxygen-free copper member 3221, the heat shield flange 63 is also provided with a signal line hole, a through hole for communication between the inside and outside of the heat shield, and a through hole for the sample tube 21 to pass through; the material of the first heat shield cylinder 61 is oxygen-free copper, one end of the first heat shield cylinder 61 is connected with the heat shield flange 63, and the other end is connected with the second heat shield cylinder 62. The above connections are all threaded connections, and the connection surfaces of the connections are also coated with heat-conducting grease or filled with indium sheets to enhance the heat conduction effect of the heat shield; the material of the second heat shield cylinder 62 is pure aluminum, the second heat shield cylinder 62 is provided with a heat shield beam window, the heat shield beam window is arranged opposite to the neutron beam window 211, and the heat shield beam window is used for the incident / emission of the neutron beam.

[0051] The neutron beam window 211, vacuum beam window 401, and thermal shield beam window are the windows for neutron beam inflow / outflow. Although neutrons easily penetrate the beam window, different materials produce beam windows with varying diffraction peak intensities. The choice of beam window material is also related to the research field of various spectrometers. For example, small-angle spectrometers typically use sapphire or quartz windows; diffraction spectrometers typically use vanadium, vanadium-nickel alloys, or titanium-zirconium alloys; and inelastic spectrometers use aluminum windows. Different window materials have different thermal conductivity, and the design of the thermostat must also consider the influence of the window material. Currently, most variable-temperature thermostats used for neutron scattering use aluminum windows. Aluminum windows have high diffraction peaks, requiring further data processing. If the sample signal is weak, data processing can easily filter out sample information. Therefore, in this embodiment, the materials of the neutron beam window 211, the vacuum beam window 401, and the heat shield beam window are titanium-zirconium alloy foil or vanadium-nickel alloy foil. The beam window alloy foil is bonded to each cylinder with epoxy resin. The epoxy resin has good adhesion and sealing properties at a temperature of 4-403K, ensuring the sealing of each cylinder.

[0052] In this embodiment, thermometers are provided at the heat-conducting plate 321, the sample holder 10, and the second tube 202, and the thermometers at each location are used to measure the temperature at each location.

[0053] like Figure 12 As shown, this embodiment presents the measured results of the temperature of sample holder 10 and sample 102 under dual-path temperature control by the variable-temperature thermostat 100 for neutron scattering and the sample tube wall heater. From the line graph of the temperature of sample holder 10 and sample 102 changing with time, it can be seen that the temperature measured at sample holder 10 and sample 102 is almost the same, with no large error. The temperature of sample 102 can be reflected by the temperature of sample holder 10.

[0054] In one specific embodiment, the variable temperature thermostat 100 for neutron scattering includes a refrigerator 33, a refrigerator flange 333, a thermostat main flange 50, a vacuum assembly, a heat shield assembly, a sample rod assembly 1, a sample tube assembly 2, a first heat-conducting element 31, a second heat-conducting element 32, several thermometers, several electrical connectors / plugs, and several valves.

[0055] The 100-type constant temperature variable heater for neutron scattering requires installation before use. The installation process is as follows:

[0056] First, the thermostat main flange 50 is placed on the trolley to facilitate product installation and movement after completion; the refrigerator 33, sample tube 21, valve for vacuumizing and electrical connector are installed to the corresponding positions on the refrigerator flange 333; the sample rod adapter 23 is connected with the sample tube flange 22; the heat shield flange 63 is connected to the first-stage cold head 331 and the sample tube 21, and the oxygen-free copper piece 3221 is installed on the heat shield flange 63 to embrace the first tube body 201 and the heat shield flange 63 to form the first heat conduction piece 31; the second heat conduction piece 32 is connected to the second-stage cold head 332 and the second tube body 202; the heat shield flange 63, the first heat shield cylinder 61 and the second heat shield cylinder 62 are connected in sequence; the first vacuum cylinder 41 is installed on the thermostat main flange 50, and the first vacuum cylinder 41 is connected with the refrigerator flange 333; the second vacuum cylinder 42 is connected to the first vacuum cylinder 41; the sample rod 11 is inserted into the sample tube 21 and connected with the sample rod flange 13 and the sample rod adapter 23; finally, the neutron scattering variable-temperature thermostat 100 is installed on the flange of the scattering spectrometer room through the thermostat main flange 50. The heat conduction plate 331, the sample holder 10 and the second tube body 202 are all provided with thermometers for measuring the wall temperatures of the second-stage cold head 332, the sample holder 10 and the second tube body 202 respectively. The sample holder 10 is provided with a heater 101, and the second tube body 202 is provided with a sample tube wall heater, which cooperates with the corresponding temperature meter to realize temperature control of the corresponding position.

[0057] After the neutron scattering variable-temperature thermostat 100 is assembled, the cooling test can be carried out. First, the vacuum cavity 40 is vacuumized from the vacuumizing port on the refrigerator flange 333 to the order of 10^-4 Pa and maintained at the constant opening of the molecular pump; then the sample tube 21 is vacuumized to the order of 10^-4 Pa from the gas nozzle 232 on the sample rod adapter 23, and then high-purity helium is filled into the gas nozzle 232 to 40 KPa. The neutron scattering variable-temperature thermostat 100 is connected with the auxiliary equipment including the compressor, the temperature controller and the cold water machine, and the cold water machine, the compressor and the temperature controller are sequentially turned on, and the equipment is cooled. The lowest temperature of the neutron scattering variable-temperature thermostat 100 in the embodiment can reach 4K, and the temperature control at any point from 4K to 300K can be realized by using the temperature controller. When the temperature is controlled (taking 50K as an example), the temperature of the second tube body 202 is set to 50K, and then the temperature of the sample holder 10 is set to 50K, and when the temperatures of the two are both stable at 50K, the temperature of the sample 102 is also 50K. The temperature control stability and accuracy of the neutron scattering variable-temperature thermostat 100 in the application within 4K to 300K are within 0.5K.

[0058] According to the variable-temperature thermostat for neutron scattering in the above embodiment, the heat transfer structure is optimized, the sample tube wall and the sample seat temperature are controlled in two ways, the sample is kept in a uniform temperature zone in the range of 4-300K of the thermostat, and the accuracy of the sample temperature is ensured. Meanwhile, a suitable beam window material is used, the variable-temperature thermostat is suitable for various diffraction spectrometers, and there is no diffraction peak, so that the data analysis of the spectrometer is facilitated.

[0059] The above application of specific examples is used to illustrate the present application, which is only used to help understand the present application, and does not limit the present application. For those skilled in the art to which the present application belongs, according to the idea of the present application, a number of simple deductions, deformations or substitutions can be made.

Claims

1. A variable-temperature thermostat for neutron scattering, characterized in that, include: A sample tube assembly, the sample tube assembly including a sample tube, the sample tube being provided with a neutron beam window, the neutron beam window being used for the injection and emission of a neutron beam; A sample rod assembly includes a sample rod, one end of which is provided with a sample holder for mounting a sample and controlling the sample temperature. The sample rod extends into the sample tube to deliver the sample to the neutron beam window position. And a sample tube wall heater, which is installed on the wall of the sample tube and is used to control the temperature of the sample tube wall at the neutron beam window position to be the same as the temperature of the sample holder. The sample tube includes a first tube body, a second tube body, and a third tube body arranged in sequence; the sample tube wall heater is mounted on the second tube body; and the neutron beam window is disposed on the third tube body. The variable-temperature thermostat for neutron scattering further includes a cooling component; the cooling component includes a first heat-conducting element, a second heat-conducting element, and a refrigerator. One end of the first heat-conducting component is connected to the refrigerator, and the other end of the first heat-conducting component is connected to the first tube body; one end of the second heat-conducting component is connected to the refrigerator, and the other end of the second heat-conducting component is connected to the second tube body.

2. The variable-temperature thermostat for neutron scattering as described in claim 1, characterized in that, The second heat-conducting component includes a heat-conducting assembly and a connector. One end of the heat-conducting assembly is connected to the refrigerator, and the other end of the heat-conducting assembly is connected to the connector. The connector is sleeved on the second tube body.

3. The variable-temperature thermostat for neutron scattering as described in claim 2, characterized in that, The heat-conducting component includes a heat-conducting plate and a heat-conducting copper wire. One end of the heat-conducting plate is connected to the refrigerator, and the other end of the heat-conducting plate is connected to the heat-conducting copper wire. One end of the heat-conducting copper wire is connected to the heat-conducting plate, and the other end of the heat-conducting copper wire is connected to the connector.

4. The variable-temperature thermostat for neutron scattering as described in claim 1, characterized in that, The refrigeration unit includes a primary cold head and a secondary cold head, with the first heat-conducting component connected to the primary cold head and the second heat-conducting component connected to the secondary cold head.

5. The variable-temperature thermostat for neutron scattering as described in claim 1, characterized in that, The sample rod assembly further includes: a heat insulation sheet and a sample rod flange; a sample holder is located at one end of the sample rod, and a heater and a thermometer are provided inside the sample holder, which is used to install the sample and control the sample temperature; the sample rod flange is located at the other end of the sample rod, and the sample rod flange is used to fix the sample rod; a plurality of heat insulation sheets are spaced apart on the sample rod, and the edge size of the heat insulation sheet is slightly smaller than the inner wall size of the sample tube.

6. The variable-temperature thermostat for neutron scattering as described in claim 1, characterized in that, Also includes: Vacuum components; The vacuum assembly includes a vacuum chamber, the sample tube extends into the vacuum chamber, the neutron beam window is located inside the vacuum chamber, and the vacuum assembly includes a vacuum beam window corresponding to the neutron beam window.

7. The variable-temperature thermostat for neutron scattering as described in claim 6, characterized in that, Also includes: Hot screen components; The thermal shield assembly is disposed within the vacuum cavity. The thermal shield assembly includes a thermal shield cavity, the sample tube extends into the thermal shield cavity, the neutron beam window is located within the thermal shield cavity, and the thermal shield assembly includes a thermal shield beam window corresponding to the neutron beam window.

8. The variable-temperature thermostat for neutron scattering as described in claim 7, characterized in that, The materials of the neutron beam window, the vacuum beam window, and the thermal shield beam window are titanium zirconium foil or vanadium nickel foil.

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