A high pressure vessel experimental device for neutron scattering

Abstract

The present invention discloses a high-pressure container experimental device for neutron scattering, comprising: a cylinder, a sealing unit, a locking unit, a heating unit, a neutron absorption layer and a four-knife diaphragm. A window for neutron incidence and scattering is arranged on the side wall of the cylinder, a cavity for placing a sample tube is arranged in the cylinder, the sealing unit is used to seal the sample tube in the cavity, the locking unit is used to lock the sample tube in the cylinder, the neutron absorption layer is arranged on the outside of the heating unit, and the four-knife diaphragm is arranged on the side of the neutron absorption layer. In the above scheme provided by the present application, the setting on the locking device can ensure the loading and constant maintenance of the loading force; the setting of the window ensures the unimpeded passage of neutron incidence and scattering, and improves the neutron transmittance; the setting of the heating unit ensures that the sample reaches the required high temperature environment; the setting of the four-knife diaphragm and the neutron absorption layer respectively reduces the neutron beam spot and absorbs stray neutrons, and reduces the background of the sample diffraction spectrum.

Description

Technical Field

[0001] The invention relates to the fields of neutron scattering and high pressure science and technology, and in particular to a high pressure container experimental device for neutron scattering. Background Art

[0002] Neutrons interact with the nuclei of matter and have strong penetrating power. They can penetrate the thick walls of high-pressure containers, so it is convenient to load a high-pressure sample environment in neutron scattering experiments. High-pressure environment is very important for material research. It can shorten the distance between atoms in the material, affect the overlap of electron clouds, change the valence of elements, etc., causing huge changes in the structure and physical properties of the material. Some changes in the material are reversible. After the pressure is released, the material will return to the state before the experiment, and the characteristics of the material under pressure cannot be obtained. In-situ high-pressure neutron scattering can characterize the structure and physical properties of the material when high pressure is loaded. Therefore, conducting in-situ high-pressure neutron scattering research is of great significance to disciplines such as materials science, geophysical science, condensed matter physics, chemistry, energy and environment.

[0003] At present, in-situ high-pressure neutron scattering experiments mostly use metal high-pressure containers, which are made of high-strength alloy materials. Most of the high-strength alloy components contain cobalt, are magnetic, have small sample volumes, and have extremely low neutron transmittance (<10%). The above shortcomings of alloy materials have a significant impact on the personal safety of experimenters, the accuracy of experimental results, experimental efficiency, and background. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a high-pressure container experimental device for neutron scattering.

[0005] The present invention provides a high-pressure container experimental device for neutron scattering, comprising: a cylinder, a sealing unit, a locking unit, a heating unit, a neutron absorption layer and a four-knife diaphragm, wherein a window for neutron incidence and scattering is arranged on the side wall of the cylinder, a cavity for placing a sample tube is arranged in the cylinder, and the position of the cavity corresponds to the position of the window, the sealing unit is used to seal the sample tube in the cavity, the locking unit is used to lock the sample tube in the cylinder, the heating unit is arranged on the outer side wall of the cylinder, and is used to heat the sample in the sample tube, the neutron absorption layer is arranged on the outer side of the heating unit, and is used to absorb stray neutrons, and the four-knife diaphragm is arranged on the side of the neutron absorption layer.

[0006] In one of the embodiments, a ceramic cavity is disposed in the cylinder, the sample tube is disposed in the ceramic cavity, a wedge ring surrounds the ceramic cavity, and the ceramic cavity and the wedge ring are interference fit.

[0007] In one embodiment, the locking unit includes a lower locking nut, a lower piston, a locking ring and an upper piston, the lower locking nut is arranged at the lower end of the cylinder, the lower piston is arranged between the lower locking nut and the ceramic cavity, the locking ring is arranged at the upper end of the cylinder, and the upper piston is arranged between the locking ring and the ceramic cavity.

[0008] In one embodiment, the locking unit further includes a lower gasket, an upper gasket and an upper locking nut, the lower gasket is arranged between the lower piston and the lower locking nut, the upper locking nut is arranged at the open end of the cylinder, and the upper gasket is arranged between the upper locking nut and the upper piston.

[0009] In one of the embodiments, a force rod is further included, and the force rod is arranged on the upper locking nut.

[0010] In one embodiment, the sealing unit includes a lower sealing ring, an upper sealing ring and a sample tube cap, the lower sealing ring is arranged between the lower piston and the sample tube, the sample tube cap is arranged between the upper piston and the sample tube, and the upper sealing ring is arranged between the sample tube cap and the sample tube.

[0011] In one of the embodiments, the heating unit comprises a heating blanket, and the heating blanket is arranged on the outer side wall of the cylinder.

[0012] In one of the embodiments, the heating blanket comprises a heating resistance wire, a thermometer and a thermal insulation layer from inside to outside, and the heating resistance wire is in close contact with the outer wall of the cylinder.

[0013] In one of the embodiments, the four-blade aperture includes a plurality of neutron absorption devices, and the neutron absorption devices are arranged outside the heating blanket.

[0014] According to the high-pressure container experimental device for neutron scattering provided by the above embodiment, the locking nut and the pressure rod provided on the locking device can ensure the loading and maintaining of the loading force constant; the setting of the window ensures the unimpeded passage of neutron incidence and scattering, improves the neutron transmittance, reduces the interference of the neutron diffraction peak on the sample signal and reduces the background of the neutron diffraction spectrum, and the setting of the heating unit ensures that the sample reaches the required high temperature environment. The setting of the four-knife aperture and the neutron absorption layer respectively reduces the neutron beam spot and absorbs stray neutrons, reducing the background of the sample diffraction spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A cross-sectional view of a high-pressure container experimental device for neutron scattering provided by an embodiment of the present invention;

[0016] Figure 2 for Figure 1 A partial enlarged schematic diagram of

[0017] Figure 3 for Figure 1 Schematic diagram of the overall structure. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0019] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious 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 are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0020] The serial numbers of the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0021] like Figure 1-3 As shown, in one embodiment of the present invention, a high-pressure container experimental device for neutron scattering is provided, including: a cylinder 15, a sealing unit, a locking unit, a heating unit, a neutron absorption layer 17 and a four-knife aperture 18. A window 1501 for neutron incidence and scattering is arranged on the side wall of the cylinder 15, a cavity for placing a sample tube 6 is arranged in the cylinder 15, and the position of the cavity corresponds to the position of the window 1501. The sealing unit is used to seal the sample tube 6 in the cavity, and the locking unit is used to lock the sample tube 6 in the cylinder 15. The heating unit is arranged on the outer wall of the cylinder 15 for heating the sample in the sample tube 6. The neutron absorption layer 17 is arranged on the outer side of the heating unit for absorbing stray neutrons. The four-knife aperture 18 is arranged on the side of the neutron absorption layer 17.

[0022] Specifically, a ceramic cavity 4 is disposed in the cylinder 15 , and the sample tube 6 is disposed in the ceramic cavity 4 . The ceramic cavity 4 is surrounded by a wedge ring 3 , and the ceramic cavity 4 and the wedge ring 3 are interference fit.

[0023] Furthermore, the ceramic cavity 4 is made of high-purity, high-density, and high-strength alumina ceramic, and the material parameters are as follows: purity 99.8%, density 3.96 g / cm 3 , compressive strength 4000MPa, bending strength 630MPa, Vickers hardness HV1 is 2000; the performance of the ceramic material determines the pressure limit of the sample, and a pressure limit of 2GPa can be achieved. The ceramic cavity 4 is interference fit with the wedge ring 3, and the assembly pressure is 30 tons. After assembly, the bottom surface of the wedge ring 3 is ensured to be two millimeters away from the bottom surface of the ceramic cavity 4, and the bottom surface of the ceramic cavity 4 is in a concave state. In order to reduce the friction during assembly, molybdenum disulfide or lead foil is applied to the contact surface between the ceramic cavity 4 and the wedge ring 3; and the height of the wedge ring 3 is less than the height of the ceramic cavity 4, and the wedge ring 3 is provided with an opening to provide a 360-degree space for neutron incidence and scattering. The strength of the material of the wedge ring 3 should be close to that of the ceramic material. The alloy steel with a hardness of 54HRC is used in this application, and the ceramic material in the ceramic cavity 4 is one of aluminum oxide, zirconium oxide, and zirconium oxide-yttrium oxide.

[0024] The sealing unit is used to seal the sample and the pressure medium, and also to ensure the constant pressure limit of the sample high pressure environment. When assembling, put the lower sealing ring 7, sample tube 6, upper sealing ring 8 and sample tube cap 9 in sequence; the sample tube cap 9 needs to be embedded in the sample tube 6; the upper sealing ring 8 contacts the conical surface of the sample tube cap 9, and is located between the sample tube 6 and the sample tube cap 9; the lower sealing ring 7 contacts the conical surface of the bottom of the sample tube 6, and the sample volume of the sample tube 6 is greater than 500mm 3 , which is much larger than other high-pressure vessels with the same pressure limit, greatly improving the efficiency of neutron scattering experiments and reducing the background of neutron scattering experimental data. The material of the sample tube 6 and the sample tube cap 9 is one of aluminum, lead and polytetrafluoroethylene; the upper sealing ring 8 and the lower sealing ring 7 are annealed beryllium copper alloy or oxygen-free copper material.

[0025] The locking unit is used to fix the sample loading force, including an upper locking nut 13, a lower locking nut 1, a locking ring 10, an upper pad 12, a lower pad 2, an upper piston 11, a lower piston 5 and a force rod 14. The force rod 14 is pressurized by a tablet press (not shown in the figure), and the loading force is transmitted to the sample through the upper pad 12, the upper piston 11 and the sample tube cap 9 in turn. The cylinder 15 and the upper locking nut 13, the lower locking nut 1 and the locking ring 10 are all connected by a serrated thread. The serrated thread connection has two advantages: one is the unidirectional transmission of pressure, which ensures the constant loading force and prevents the reduction of the loading force caused by the loosening of the thread; the second is that the serrated thread has good coaxiality, which ensures the uniformity of the loading force.

[0026] The locking ring 10 is located between the upper locking nut 13 and the ceramic cavity 4 , and applies pressure to the ceramic cavity 4 , thereby fixing the ceramic cavity 4 .

[0027] The cylinder 15 is provided with openings in both the neutron incident and exit directions, and a neutron scattering window is provided in the direction perpendicular to the incident neutron channel. The hollow neutron scattering window is a major feature of the present application. Compared with other high-pressure vessels, this design can avoid the influence of the parasitic diffraction peak of the high-pressure vessel on the sample signal while ensuring the pressure limit, which is an advantage that other high-pressure vessels cannot match. The cylinder is processed using high-strength beryllium copper material, and the high-strength material can effectively reduce the mass of the components. The finite element method is used to simulate and analyze the stress conditions of the cylinder during operation, and the use of materials is reduced as much as possible while ensuring safety, thereby reducing the mass of the high-pressure container, making the high-pressure container portable, and reducing energy consumption during heating. Therefore, through finite element optimization analysis, the safety factor of the cylinder of this high-pressure container is 2, which is sufficient to ensure the safe operation of the high-pressure container.

[0028] The heating blanket is used to heat the high-pressure container, thereby achieving indirect heating of the sample. This heating method is indirect heating. The heating blanket includes a heating resistor, a thermometer and an insulation layer; the heating wire is placed in the inner layer of the heating blanket and is in close contact with the outer wall of the locking device, which can achieve good heat conduction; the cylinder of the high-pressure container is made of beryllium copper alloy, which has excellent thermal conductivity and achieves heat transfer to the sample. The insulation layer is placed on the outer layer of the heating blanket to prevent the heat loss of the high-pressure container; the thermometer is placed between the heating resistor and the insulation layer. The electrical plug connected to the heating blanket can better realize the heating, precise temperature control and temperature measurement of the high-pressure container, and ultimately achieve a temperature index of 150 degrees Celsius.

[0029] The four-knife diaphragm is used to control the incident neutron beam spot. By adjusting the size of the diaphragm, the beam spot size required for the experiment can be achieved, and other neutrons can be effectively absorbed to prevent neutrons outside the sample range from irradiating other materials and causing contamination of the sample signal. This four-knife diaphragm can effectively reduce the background of the sample neutron scattering experimental data. The four-knife diaphragm includes four neutron absorption devices, and the movement of the four neutron absorption devices can be controlled by a motor or manually to achieve the size of the controlled neutron range; the material of the neutron absorption device is one of boron carbide, boron nitride, boron, boron-containing polyethylene, cadmium, gadolinium, gadolinium oxide, etc.

[0030] The neutron absorption layer is used to absorb stray neutrons, thereby reducing the background of neutron scattering experimental data. The neutron absorption layer is placed on the outermost layer of the high-pressure container to achieve full coverage of other areas except the neutron incident, exit and scattering windows. The neutron absorption layer is a material that can be well formed, and can be one of cadmium, gadolinium, boron-containing polyethylene, gadolinium oxide coating, etc.

[0031] The specific working process of a high-pressure container experimental device for neutron scattering provided in this embodiment is as follows:

[0032] First, assemble the ceramic cavity: embed the ceramic cavity into the conical holes of the two wedge rings, and the three are coaxial to ensure that the contact surface fits tightly; place it in the tablet press and pressurize it for interference fit, with a loading force of 30 tons, so that the ceramic cavity produces prestress, so that it can withstand greater pressure; after assembly, the bottom surface of the wedge ring is processed flat, the bottom surface of the wedge ring is 2 mm away from the bottom surface of the ceramic cavity, and the ceramic cavity is concave. Secondly, put the assembled ceramic cavity into the cylinder, put the lower pad into the groove of the lower locking nut, and install the lower locking nut at the bottom of the cylinder; from the top of the cylinder, put the lower piston, lower sealing ring, sample tube (including sample and pressure transmission medium), upper sealing ring, sample tube cap, upper piston, upper pad in turn, and the upper piston is embedded in the groove on the bottom surface of the upper pad. Again, screw the locking ring into the cylinder until the locking ring presses the ceramic cavity; install the locking nut, insert the force rod into the center hole of the upper locking nut, and the bottom surface contacts the upper surface of the upper pad. Finally, the heating blanket and neutron absorption layer are wrapped on the outer wall of the high-pressure vessel, and a four-knife aperture is installed at the neutron entrance. This completes the assembly of the entire high-pressure vessel.

[0033] Place the assembled high-pressure container in the tablet press for pressurization, gradually increase the loading force, tighten the upper locking nut before each increase in loading force until the target pressure is loaded; after pressurization, connect the heating blanket plug to the power supply to load the temperature to the target temperature; adjust the four-knife diaphragm to limit the neutron incident spot size. Transfer the high-pressure container to the neutron scattering spectrometer to carry out in-situ high-pressure neutron scattering experimental tests of the samples.

[0034] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A high-pressure container experimental device for neutron scattering, characterized in that: include: A cylinder, a sealing unit, a locking unit, a heating unit, a neutron absorption layer and a four-knife diaphragm, wherein a window for neutron incidence and scattering is arranged on the side wall of the cylinder, a cavity for placing a sample tube is arranged in the cylinder, and the position of the cavity corresponds to the position of the window, the sealing unit is used to seal the sample tube in the cavity, and the locking unit is used to lock the sample tube in the cylinder, the heating unit is arranged on the outer side wall of the cylinder, and is used to heat the sample in the sample tube, the neutron absorption layer is arranged on the outer side of the heating unit, and is used to absorb stray neutrons, the four-knife diaphragm is arranged on the side of the neutron absorption layer, a ceramic cavity is arranged in the cylinder, the sample tube is arranged in the ceramic cavity, the ceramic cavity is surrounded by a wedge ring, and the ceramic cavity and the wedge ring are interference fit, The upper and lower parts of the ceramic cavity are respectively embedded in the conical holes of the wedge-shaped ring, the three are coaxial, and the contact surfaces are tightly fitted. The locking unit includes a lower locking nut, a locking ring, and an upper locking nut. The lower locking nut is located on the lower side of the wedge-shaped ring at the lower part of the ceramic cavity, the locking ring is located on the upper side of the wedge-shaped ring at the upper part of the ceramic cavity, and the locking ring is located between the upper locking nut and the ceramic cavity, exerting pressure on the ceramic cavity to fix the ceramic cavity.

2. The high-pressure container experimental device for neutron scattering according to claim 1, characterized in that: The locking unit includes a lower piston and an upper piston, the lower locking nut is arranged at the lower end of the cylinder, the lower piston is arranged between the lower locking nut and the ceramic cavity, the locking ring is arranged at the upper end of the cylinder, and the upper piston is arranged between the locking ring and the ceramic cavity.

3. The high-pressure container experimental device for neutron scattering according to claim 2, characterized in that: The locking unit further comprises a lower pad, an upper pad and an upper locking nut, wherein the lower pad is arranged between the lower piston and the lower locking nut, the upper locking nut is arranged at the open end of the cylinder, and the upper pad is arranged between the upper locking nut and the upper piston.

4. The high-pressure container experimental device for neutron scattering according to claim 3, characterized in that: It also includes a force rod, which is arranged on the upper locking nut.

5. The high-pressure container experimental device for neutron scattering according to claim 2, characterized in that: The sealing unit comprises a lower sealing ring, an upper sealing ring and a sample tube cap, wherein the lower sealing ring is arranged between the lower piston and the sample tube, the sample tube cap is arranged between the upper piston and the sample tube, and the upper sealing ring is arranged between the sample tube cap and the sample tube.

6. The high-pressure container experimental device for neutron scattering according to claim 1, characterized in that: The heating unit includes a heating blanket, and the heating blanket is arranged on the outer side wall of the cylinder.

7. The high-pressure container experimental device for neutron scattering according to claim 6, characterized in that: The heating blanket comprises a heating resistance wire, a thermometer and a heat preservation layer in sequence from the inside to the outside, and the heating resistance wire is in close contact with the outer side wall of the cylinder.

8. The high-pressure container experimental device for neutron scattering according to claim 6, characterized in that: The four-blade aperture includes a plurality of neutron absorption devices, and the neutron absorption devices are arranged outside the heating blanket.

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