Double helix piston pressurization device for magnetic measurement system helium-3 temperature region and method of use thereof

Abstract

The application provides a double helix piston pressurization device for a helium-3 temperature range of a magnetic measurement system and a use method thereof. The device comprises a piston assembly and a pressurization assembly. The piston assembly comprises a piston sleeve, two piston bases respectively screwed into two ends of the piston sleeve and having opposite screw directions, and two piston cylinders and a sample container coaxially arranged in the piston sleeve. The pressurization assembly comprises a pressurization sleeve, a torque snap ring arranged in the pressurization sleeve, and two pressurization bases respectively inserted from two ends of the pressurization sleeve. The pressurization bases are positioned through concave-convex matching, and a side wall of the pressurization sleeve is provided with a side wall hole for applying torque. When the pressurization sleeve is rotated, the piston sleeve drives the two piston bases to move towards each other and push the piston cylinders to compress the sample. The piston assembly has a diameter greater than or equal to 5.8 mm and less than 6 mm and a weight of 4-5 g, can be matched with an MPMS helium-3 refrigerator plug-in, and can realize accurate magnetic measurement under a hydrostatic pressure condition of 0-2 GPa in a temperature range of 0.3-1.8 K.

Description

Technical Field

[0001] This invention belongs to the field of cryogenic high-pressure magnetic testing technology. Specifically, this invention relates to a double-helix piston pressurization device and its method of use for the helium-3 temperature range (0.3 to 1.8 K) of a magnetic property measurement system (MPMS). Background Technology

[0002] High-pressure technology plays an increasingly important role in condensed matter science research because many novel physical phenomena in materials only manifest under high-pressure conditions. A classic example is the superconducting transition of hydrogen sulfide when pressurized to over 150 GPa, with a transition temperature reaching 203 K, approaching room-temperature superconductivity (Drozdov AP et al., Conventional superconductivity at 203 Kelvin at high pressures in the sulfurhydride system. Nature 525, 73 (2015)). The importance of high-pressure control is reflected in the following aspects: First, pressure is one of the fundamental thermodynamic parameters alongside temperature, directly controlling the state of matter. It is predicted that when the pressure reaches 100 GPa, matter will undergo an average of four to five phase transitions. Therefore, high pressure provides an extremely effective means to explore new states of matter, greatly expanding the scope of materials science research. Secondly, pressure can effectively shorten the distance between atoms, enhance orbital coupling, and promote electron transfer, thereby balancing the competing forces in strongly correlated electron systems. This is one of the key adjustment parameters for achieving the quantum critical point (Coleman P and Schofield A J., Quantum criticality. Nature 433, 226 (2005)). Furthermore, high-pressure technology helps clarify the key factors affecting physical properties, not only revising existing theories but also having a profound impact on practical material applications.

[0003] With advancements in high-pressure technology, researchers have combined high pressure with other measurement methods to develop a variety of integrated measurement approaches, such as high-pressure electrical transport technology, high-pressure Raman spectroscopy, high-pressure XRD, and high-pressure magnetic measurement technology. Many interesting phenomena in condensed matter physics, such as heavy fermion superconductivity, the giant magnetocalor effect, and magnetoresistive fault behavior, require magnetic measurements under ultra-low temperature and high-pressure conditions. Furthermore, these properties exhibit extremely high sensitivity to pressure and require highly uniform pressure. Therefore, achieving near-hydrostatic pressure control of samples at ultra-low temperatures has become a critical technical challenge in the field of high-pressure magnetic testing.

[0004] Currently, the mainstream high-voltage magnetic measurement methods mainly fall into the following categories:

[0005] 1. Diamond Anvil Cell (DAC) Device

[0006] Magnetic testing methods based on DAC as the core component include: embedding miniature mutual inductance coils on or around the diamond surface for magnetic testing; placing the diamond in a non-magnetic BeCu material Mcell Ultra and using the high-sensitivity SQUID of MPMS for magnetic testing; and distributing nitrogen-vacancy centers (NV centers) on the diamond surface and using an optical magnetic measurement device for magnetic testing (Jayaraman A, Diamond anvil cell and high-pressure physical investigations. Rev. Mod. Phys. 55, 65 (1983); Jian-Hong Dai et al., Optically Detected Magnetic Resonance of Diamond Nitrogen-Vacancy Centers under Megabar Pressures. Chin. Phys. Lett. 39 ,117601 (2022); Yinghao Zhu et al., Superconductivity in pressurized trilayer La4Ni3O 10-δ Single crystals. Nature 631, 531 (2024); Feiyu Li et al., Bulk superconductivity up to 96 K inpressurized nickelate single crystals. Nature 649, 871 (2025). The advantage of DAC technology lies in its ability to withstand pressures up to hundreds of GPa and to be placed in a dilution cryostat for cryogenic measurements, meeting the needs of most high-pressure research. However, the uniaxial pressure of diamond results in poor hydrostatic properties and prevents fine control within a small pressure range (less than 2 GPa).

[0007] 2. Six-sided cubic anvil cell (CAC) device

[0008] The CAC device can provide a pressure environment up to 15 GPa. Its internal sample space is relatively large, and the force is uniform in all directions. When pressurized, the sample is in a near-static hydrostatic state, which to some extent compensates for the shortcomings of DAC (Mori N, Takahashi Hand Takeshita N, Low-temperature and high-pressure apparatus developed at ISSP, University of Tokyo. High Pressure Research 24, 225 (2004)). However, due to its large size, it requires an ultra-large and expensive dilution refrigerator to achieve extremely low temperature testing, resulting in very low equipment adoption and limiting its widespread application.

[0009] 3. Piston-Cylinder Cell (PCC) Device

[0010] This device provides a good hydrostatic environment, has a relatively large sample space, and typically operates at a maximum pressure of around 2 GPa. It can be placed in a vibrating sample magnetometer (VSM) for high-pressure magnetic measurements (Walker IR, Rev. Sci. Instrum. 1999). In recent years, PCC devices based on non-magnetic BeCu materials have been widely used in the field of high-pressure magnetism due to their ease of operation and good compatibility with MPMS and PPMS VSM kits. They can achieve hydrostatic temperature variations within a pressure range of 0-2 GPa and above 1.8 K, playing a key role in the discovery of double-Dome superconductivity in the AV3Sb5 system. However, the size and structure of existing PCC devices limit their further miniaturization, making them incompatible with MPMS helium-3 refrigerator modules with an inner diameter of only 6 mm, thus preventing ultra-low temperature measurements below 1.8 K.

[0011] In summary, existing technologies are limited by factors such as pressure uniformity (DAC), equipment size and cost (CAC), or test temperature range (PCC). To date, there is still a lack of a testing device that can simultaneously meet the requirements of the helium-3 temperature range (0.3 to 1.8 K) and hydrostatic pressure (0 to 2 GPa), while being easy to operate and compatible with existing commercial magnetic measurement systems. Summary of the Invention

[0012] The present invention aims to solve the technical problems in existing high-pressure magnetic measurement technology that cannot simultaneously meet the requirements of ultra-low temperature testing in the helium-3 temperature range (0.3~1.8K), hydrostatic pressure conditions (0~2GPa), small size compatibility, and ease of operation.

[0013] The purpose of this invention is to provide a double-helix piston pressurization device for the helium-3 temperature range of a magnetic measurement system, which achieves both extremely low temperature and hydrostatic pressure. Furthermore, the piston assembly of this device has an overall diameter greater than or equal to 5.8 mm and less than 6 mm, and a weight of 4 g to 5 g, perfectly fitting the helium-3 refrigerator insert of the magnetic measurement system (MPMS) with an inner diameter of only 6 mm. This enables extremely low temperature magnetic measurements in the helium-3 temperature range of 0.3–1.8 K, solving the technical problems of poor pressure uniformity in the DAC and the inability of the PCC to enter the helium-3 temperature range in existing technologies.

[0014] The above-mentioned objective of the present invention is achieved through the following technical solution.

[0015] In a first aspect, the present invention provides a double-helix piston pressurizing device for a magnetic measurement system in the helium-3 temperature range, the device comprising a piston assembly and a pressurizing assembly, wherein:

[0016] The piston assembly includes a piston sleeve (2), two piston cylinders (3) coaxially disposed within the piston sleeve (2), a container for accommodating a sample located between the two piston cylinders (3), and two piston bases (1) screwed into the piston sleeve (2) from both ends respectively; wherein the piston bases (1) are connected to the piston sleeve (2) by a threaded connection, and the direction of their threaded connection is configured such that when the piston sleeve (2) rotates relative to the piston bases (1), the two piston bases (1) move towards each other, thereby pushing the two piston cylinders (3) to compress the sample within the container; and

[0017] The pressurizing assembly includes a pressurizing sleeve (8), a torque retaining ring (6) disposed within the pressurizing sleeve (8), and two pressurizing bases (7) inserted from both ends of the pressurizing sleeve (8); wherein the torque retaining ring (6) has an adjustable clamping structure for detachably clamping the piston assembly.

[0018] This invention achieves precise hydrostatic pressure application within the 0–2 GPa range by screwing two piston bases with oppositely screwed threads into both ends of a piston sleeve, and coaxially arranging the piston cylinder and sample container between them. When the pressure sleeve is rotated, the piston sleeve drives the two piston bases to move synchronously in opposite directions, pushing the piston cylinder to symmetrically compress the sample from both sides. Simultaneously, by separating the pressurization and measurement functions, after pressurization, only the piston assembly is transferred to the MPMS helium-3 refrigerator insert via a connector, achieving for the first time compatible magnetic measurements under hydrostatic pressure conditions in the 0.3–1.8 K cryogenic region. This invention, with its simple mechanical structure, balances pressure uniformity, miniaturization, and ease of operation, providing an effective solution for cryogenic high-pressure property research on heavy fermion superconductors, giant magnetic card materials, and other materials.

[0019] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system described in this invention, one end of the piston base (1) is provided with a groove (11), and the other end is provided with a support structure for abutting the piston cylinder (3), and the side wall of the piston base (1) is provided with an external thread (12); the piston sleeve (2) is provided with two sets of internal threads (21) with opposite directions, and the piston base (1) is screwed into both ends of the piston sleeve (2) through the external thread (12) and the internal thread (21).

[0020] Preferably, in the double-helix piston pressurizing device for the helium-3 temperature region of the magnetic measurement system described in this invention, the pressurizing base (7) is composed of a large cylindrical part and a small cylindrical part arranged coaxially. The small cylindrical part is used to insert into the end of the pressurizing sleeve (8). The end face of the small cylindrical part is provided with a protrusion (71). The protrusion (71) is adapted to the shape of the groove (11) of the piston base (1) to achieve angle positioning and center positioning.

[0021] Preferably, in the double-helix piston pressurizing device for the helium-3 temperature range of the magnetic measurement system described in this invention, the pressurizing sleeve (8) is a hollow cylindrical structure with an inner wall protrusion (81) inside for accommodating and securing the torque retaining ring (6); the two ends of the pressurizing sleeve (8) respectively rotatably accommodate the small cylindrical portions of the two pressurizing bases (7), and the side wall of the pressurizing sleeve (8) is provided with a side wall hole (82) for applying torque.

[0022] Preferably, in the double-helix piston pressurizing device for the helium-3 temperature region of the magnetic measurement system described in this invention, the piston base (1) has three grooves (11) that are evenly spaced at 120° along the circumference of the piston base (1); the pressurizing base (7) has three protrusions (71) on the end face of the small cylindrical part that are evenly spaced at 120° along the end face of the small cylindrical part, and the protrusions (71) and the grooves (11) are in a concave-convex interlocking positioning fit.

[0023] Preferably, in the double-helix piston pressurization device for the helium-3 temperature range of the magnetic measurement system described in this invention, the abutting structure of the piston base (1) is a cylindrical recess (13) for seamlessly accommodating the end of the piston cylinder (3) and fixing it in the center.

[0024] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system described in this invention, the container includes a Teflon tube (5) and two Teflon plugs (4), the Teflon tube (5) is located between two piston cylinders (3), and the two Teflon plugs (4) are respectively sealed at both ends of the Teflon tube (5).

[0025] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system of the present invention, the piston sleeve (2) has an inner tube wall (22) extending along its axis, the inner tube wall (22) being a smooth cylindrical surface for accommodating and radially constraining two piston cylinders (3) and a container for accommodating samples.

[0026] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system described in this invention, the torque retainer (6) has a cylindrical structure and a hollow inner cavity for accommodating the piston assembly; the outer peripheral surface of the torque retainer (6) is composed of two opposing planes and two opposing arc surfaces, the planes extend along the axial direction of the torque retainer (6), and the distance between the two planes is less than the distance between the two arc surfaces; a slit (63) is provided on the cylindrical wall of the torque retainer (6) along the axial direction, the slit (63) extends inward from the outer wall of one of the arc surfaces and penetrates into the hollow inner cavity, and the slit (63) extends radially to the interior of the opposite arc surface, but does not penetrate the outer wall of the other arc surface.

[0027] Preferably, in the double-helix piston pressurizing device for the helium-3 temperature region of the magnetic measurement system described in this invention, the inner wall protrusion (81) of the pressurizing sleeve (8) is two, respectively disposed on opposite sides of the inner wall of the pressurizing sleeve (8). The inner wall protrusion (81) extends along the axial direction of the pressurizing sleeve (8), and the side of the inner wall protrusion (81) facing the axis of the pressurizing sleeve (8) is a plane. The two planes of the torque retainer (6) respectively form face-to-face contact with the planes of the two inner wall protrusions (81), which is used to restrict the rotation of the torque retainer (6) relative to the pressurizing sleeve (8) in the circumferential direction.

[0028] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system described in this invention, the torque retainer (6) has at least two side wall screw holes (61) on its side wall. By screwing in the long screw (62), the width of the slit (63) can be reduced, thereby clamping and fixing the piston assembly.

[0029] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system described in this invention, the piston base (1), piston sleeve (2) and piston cylinder (3) are all made of non-magnetic beryllium copper alloy.

[0030] Preferably, in the double-helix piston pressurizing device for the helium-3 temperature range of the magnetic measurement system described in this invention, the torque retaining ring (6), the pressurizing base (7), and the pressurizing sleeve (8) are all made of non-magnetic stainless steel.

[0031] Preferably, in the double-helix piston pressurization device for the helium-3 temperature range of the magnetic measurement system described in this invention, the device further includes a connector (10), one end of which is provided with an internal thread (101) for detachably connecting with the external thread (12) of the piston base (1), and the other end of which is used to connect with the plastic tube of the helium-3 carbon fiber rod of the magnetic measurement system.

[0032] Preferably, in the double-helix piston pressurizing device for the helium-3 temperature region of the magnetic measurement system described in this invention, the device further includes an L-shaped wrench (9), the wrench (9) including a hand-held part and a working part; the working part is located at the tail end of the wrench (9), and the working part is provided with a protrusion (91), the shape of the protrusion (91) being adapted to the shape of the groove (11) of the piston base (1), for inserting into the groove (11) to apply torque when the piston base (1) is screwed.

[0033] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system described in this invention, the diameter of the piston assembly is greater than or equal to 5.8 mm and less than 6 mm.

[0034] Preferably, in the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system described in this invention, the weight of the piston assembly is 4 g to 5 g.

[0035] Secondly, the present invention provides a method of using the double-helix piston pressurization device for a magnetic measurement system in the helium-3 temperature range, comprising the following steps:

[0036] Step S1: Sample packaging step

[0037] The sample to be tested, the pressure gauge, and the pressure transmission medium are loaded into the container used to hold the sample.

[0038] Step S2: Piston assembly steps

[0039] The sealed container and two piston cylinders (3) are placed into the piston sleeve (2) in sequence, so that the container is located between the two piston cylinders (3). Then, the two piston bases (1) are screwed into the piston sleeve (2) from both ends, so that the abutting structure of the two piston bases (1) abuts against the ends of the two piston cylinders (3) respectively, thus completing the assembly of the piston assembly.

[0040] Step S3: Assembly of pressurized components

[0041] The assembled piston assembly is inserted into the torque retainer (6) and clamped and fixed. The torque retainer (6) holding the piston assembly is placed into the pressure sleeve (8) and secured with the inner wall protrusion (81). Then, the small cylindrical parts of the two pressure bases (7) are inserted from both ends of the pressure sleeve (8) so that the protrusion (71) of the pressure base (7) and the groove (11) of the piston base (1) form a concave-convex interlocking circumferential positioning.

[0042] Step S4: Pressurization Step

[0043] The assembled pressurizing assembly is placed under the hydraulic press. After the piston assembly is compressed a certain distance by applying pressure through the hydraulic press, the tool is inserted into the side wall hole (82) of the pressurizing sleeve (8) and rotated, so that the pressurizing sleeve (8) rotates relative to the pressurizing base (7), which drives the piston sleeve (2) to rotate. The two piston bases (1) are driven to move towards each other through two sets of internal threads (21) with opposite directions, thereby locking the current pressure. The hydraulic press is restarted to apply greater pressure and then rotated to lock again. The hydraulic press pressurization and manual rotation locking are alternated until the sample reaches the target pressure.

[0044] Step S5: Measurement connection steps

[0045] After pressurization, the piston assembly is removed from the pressurization assembly and connected to the helium-3 carbon fiber rod of the magnetic measurement system via connector (10). One end of the connector (10) is provided with an internal thread (101) for detachable connection with the external thread (12) of the piston base (1). The other end of the connector (10) is used to connect to the plastic tube of the helium-3 carbon fiber rod of the magnetic measurement system. The entire device is then placed into the magnetic measurement system for cryogenic magnetic measurement.

[0046] Preferably, in the method described in this invention, after the two piston bases (1) in step S2 are screwed into the piston sleeve (2), the lengths of the external threads (12) of the two piston bases (1) protruding from the piston sleeve (2) are equal.

[0047] Preferably, in the method described in this invention, the hydraulic press in step S4 is a commercial hydraulic press, and the tool is a steel bar.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) Achieving both extremely low temperature and hydrostatic pressure

[0050] This invention employs a double-helix reverse-thread structure, with two piston bases screwed in from both ends of the piston sleeve. As the piston sleeve rotates, the two piston bases move synchronously towards each other, pushing the two piston cylinders to symmetrically compress the sample container from both sides. This symmetrical pressurization method ensures uniform force on the sample in all directions during the pressurization process, achieving precise hydrostatic pressure conditions within the range of 0 to 2 GPa. Simultaneously, the piston assembly has an overall diameter greater than or equal to 5.8 mm and less than 6 mm, weighing 4 g to 5 g, perfectly fitting the helium-3 refrigerator insert of the magnetic measurement system (MPMS) with an inner diameter of only 6 mm. This allows for extremely low-temperature magnetic measurements in the helium-3 temperature range of 0.3 to 1.8 K, solving the technical problems of poor pressure uniformity in the DAC and the inability of the PCC to enter the helium-3 temperature range in existing technologies.

[0051] (2) Compact structure and strong compatibility

[0052] The piston assembly and pressurization assembly of this invention adopt a modular design. After pressurization, the piston assembly can be removed from the pressurization assembly and directly connected to the helium-3 carbon fiber rod of the MPMS system via a connector. The device is small in size and light in weight, fully meeting the stringent requirements of the MPMS helium-3 option for sample rod load (diameter less than 6 mm, weight not exceeding 5 g). It can be used directly without any modification to existing commercial magnetic measurement systems, and has good compatibility and versatility.

[0053] (3) Good pressure uniformity and high control precision

[0054] Unlike the traditional Piston method of uniaxial pressurization, this invention employs a double-ended symmetrical pressurization structure. Two piston bases move simultaneously towards each other, applying pressure to the sample evenly on both axial sides. The two sets of internal threads with opposite directions inside the piston sleeve have the same pitch, ensuring consistent feed rates to both piston bases. This prevents the geometric center of the sample from shifting during pressurization, achieving a stable hydrostatic environment. Calibration with a pressure gauge (such as 1.2K superconducting aluminum) allows for precise pressure control within the range of 0–2 GPa.

[0055] (4) Easy to operate and implement

[0056] This invention separates the pressurization and measurement functions. The pressurization component can be used with a commercial hydraulic press, and torque can be manually applied by inserting a steel rod into the side wall hole of the pressurization sleeve, making operation simple. After pressurization, the piston assembly can maintain pressure independently, eliminating the need for continuous external force. The pressure can then be transferred directly to the measurement system via a connector for low-temperature testing. The entire operation process requires no complex equipment, lowering the technical threshold for high-voltage magnetic testing.

[0057] (5) Material selection takes into account both non-magnetic properties and high strength

[0058] The piston base, piston sleeve, and piston cylinder are all made of non-magnetic beryllium copper alloy (BeCu), which meets the high sensitivity requirements of the MPMS system for magnetic measurements while also possessing sufficient hardness to withstand pressures up to 2 GPa. The torque circlip, pressure base, and pressure sleeve are made of non-magnetic stainless steel, ensuring that the pressure components do not deform or generate magnetic interference under the action of the hydraulic press. The entire device has no magnetic components, thus not affecting the measurement accuracy of the superconducting quantum interference device (SQUID).

[0059] (6) Simple structure and low cost

[0060] Compared to the six-sided cubic anvil (CAC) device, which requires an ultra-large dilution refrigerator and a complex hydraulic system, the device of this invention has a simple structure, fewer parts, and lower processing costs. It can achieve high-pressure magnetic measurement in the helium-3 temperature range without expensive auxiliary equipment, which is conducive to its widespread application in the field of high-pressure research.

[0061] In summary, this invention provides an ultra-miniature double-helix piston pressurization device specifically designed for the MPMS helium-3 temperature range, enabling precise magnetic testing under extremely low temperatures of 0.3–1.8 K and hydrostatic pressures of 0–2 GPa. This provides a convenient and reliable solution for fields such as heavy fermion superconductors and giant magnetic card materials that require physical property studies under extremely low temperature and high pressure conditions. Attached Figure Description

[0062] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0063] Figure 1 These are perspective and sectional views of a piston assembly according to a specific embodiment of the present invention;

[0064] Figure 2 This is a schematic diagram of the internal structure of a piston assembly according to a specific embodiment of the present invention;

[0065] Figure 3 This is an engineering drawing of a piston assembly according to a specific embodiment of the present invention;

[0066] Figure 4 These are perspective and cross-sectional views of a pressurization assembly according to a specific embodiment of the present invention;

[0067] Figure 5 This is a schematic diagram of the internal structure of a pressurization assembly according to a specific embodiment of the present invention;

[0068] Figure 6 This is an engineering drawing of a pressurization assembly according to a specific embodiment of the present invention;

[0069] Figure 7This is a perspective view of a wrench according to a specific embodiment of the present invention;

[0070] Figure 8 This is a perspective view of a connector according to a specific embodiment of the present invention;

[0071] Among them, 1-piston base, 11-groove, 12-external thread, 13-inner recess, 2-piston sleeve, 21-internal thread, 22-inner tube wall, 3-piston cylinder, 4-Teflon plug, 5-Teflon tube, 6-torque retaining ring, 61-side wall screw hole, 62-long screw, 63-slit, 7-pressure base, 71-protrusion, 8-pressure side wall, 81-inner wall protrusion, 82-side wall hole, 9-wrench, 91-wrench protrusion, 10-connector, 101-connector internal thread. Detailed Implementation

[0072] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0073] According to a specific embodiment of the present invention, a double-helix piston pressurization device is provided for the helium-3 temperature range of a magnetic measurement system. For example... Figures 1 to 8 As shown, the double-helix piston pressurization device for the helium-3 temperature region of the magnetic measurement system in this embodiment mainly includes two parts: a piston assembly and a pressurization assembly. The piston assembly is used to contain the sample and pressurize it, while the pressurization assembly is used to apply pressure to the piston assembly.

[0074] Specific structure of piston assembly

[0075] like Figure 1 , Figure 2 and Figure 3 As shown, the piston assembly includes two piston bases 1, a piston sleeve 2, two piston cylinders 3, two Teflon plugs 4, and a Teflon tube 5.

[0076] The piston sleeve 2 is a hollow cylinder with an inner tube wall 22 along its axial direction. This inner tube wall 22 is a smooth cylindrical surface used to accommodate and radially constrain the two piston cylinders 3, the Teflon tube 5, and the two Teflon plugs 4. The piston sleeve 2 also has two sets of internal threads 21 with opposite directions. These two sets of internal threads 21 are arranged at intervals along the axial direction of the piston sleeve 2 and are located at both ends of the piston sleeve 2.

[0077] The two piston bases 1 have identical structures, each with a groove 11 at one end and a cylindrical recess 13 at the other end, and external threads 12 on their sidewalls. The external threads 12 of the piston base 1 are adapted to the internal threads 21 of the piston sleeve 2. The two piston bases 1 are screwed into the piston sleeve 2 from both ends, achieving axial fixation through the threaded engagement. Since the two sets of internal threads 21 rotate in opposite directions, when the piston sleeve 2 rotates, the two piston bases 1 will move synchronously towards or away from each other.

[0078] The Teflon tube 5 is used to contain the sample to be tested, the pressure gauge, and the pressure transmitting medium. Two Teflon plugs 4 are respectively sealed at both ends of the Teflon tube 5 to form a sealed sample container. This sample container is coaxially disposed within the inner wall 22 of the piston sleeve 2 and located between the two piston cylinders 3. The two piston cylinders 3 are respectively disposed at both ends of the Teflon tube 5, with one end abutting against the Teflon plug 4 and the other end abutting against the cylindrical recess 13 of the piston base 1. The shape of the cylindrical recess 13 is adapted to the shape of the end of the piston cylinder 3, allowing for seamless accommodation and central fixation of the piston cylinder 3.

[0079] like Figure 1 and Figure 2 As shown, the piston base 1 has three grooves 11, which are distributed at 120° intervals along the circumference of the piston base 1, and are used to cooperate with the corresponding structure of the pressurizing component to achieve angular positioning and center positioning.

[0080] Specific structure of the pressurization component

[0081] like Figure 4 , Figure 5 and Figure 6 As shown, the pressurization assembly includes a torque retaining ring 6, two pressurization bases 7, and a pressurization sleeve 8.

[0082] Torque circlip 6 is used for detachably clamping the piston assembly. For example... Figure 4 and Figure 5 As shown, the torque retainer 6 has a cylindrical structure with a hollow inner cavity for accommodating the piston assembly. The outer circumferential surface of the torque retainer 6 is composed of two opposing planes and two opposing arc surfaces. These two planes extend axially along the torque retainer 6, and the distance between the two planes is less than the distance between the two arc surfaces, forming a "double-flat" structure. A slit 63 is axially formed on the cylindrical wall of the torque retainer 6. This slit 63 extends inward from the outer wall of one of the arc surfaces and penetrates into the hollow inner cavity, and extends radially into the interior of the opposite arc surface, but does not penetrate the outer wall of that other arc surface. Two sidewall screw holes 61 are provided on the sidewall of the torque retainer 6. By screwing in long screws 62, the width of the slit 63 can be reduced, thereby clamping and fixing the piston assembly.

[0083] The pressure base 7 is used to cooperate with the piston base 1 during the pressurization process to achieve angular positioning. For example... Figure 4 and Figure 5 As shown, each pressure base 7 consists of a large cylindrical part and a small cylindrical part arranged coaxially, forming a stepped shaft shape. The end face of the small cylindrical part has three protrusions 71, which are evenly distributed at 120° intervals along the end face of the small cylindrical part. The shape of the protrusions 71 matches the shape of the groove 11 of the piston base 1, forming a concave-convex interlocking positioning fit to achieve angular positioning and center positioning.

[0084] The pressure sleeve 8 is used to accommodate and support the pressure base 7 and the torque retaining ring 6. For example... Figure 4 , Figure 5 and Figure 6 As shown, the pressure sleeve 8 is a hollow cylindrical structure, with two small cylindrical portions of the pressure base 7 rotatably accommodating at each end. The pressure sleeve 8 has two inner wall protrusions 81, located on opposite sides of the inner wall and extending axially along the pressure sleeve 8. The side of the inner wall protrusion 81 facing the axis of the pressure sleeve 8 is a plane, which forms a face-to-face contact with the two planes of the torque retainer 6, thereby restricting the rotation of the torque retainer 6 relative to the pressure sleeve 8 in the circumferential direction. Side wall holes 82 are provided on the side walls of the pressure sleeve 8 for inserting tools (such as steel bars) to apply torque during pressurization.

[0085] Auxiliary components

[0086] like Figure 7 As shown, the wrench 9 is used to tighten the piston base 1 when assembling the piston assembly. The wrench 9 has a wrench protrusion 91 that matches the groove 11 of the piston base 1.

[0087] like Figure 8 As shown, connector 10 is used to connect the pressurized piston assembly to the helium-3 carbon fiber rod of the magnetic measurement system. One end of connector 10 is provided with an internal thread 101 for detachable connection with the external thread 12 of piston base 1; the other end of connector 10 is used to connect to the plastic tube of the helium-3 carbon fiber rod of the magnetic measurement system.

[0088] Material selection

[0089] To meet the requirements of non-magnetic properties and high strength, the piston base 1, piston sleeve 2, and piston cylinder 3 are all made of non-magnetic beryllium copper alloy (BeCu). This material satisfies the sensitivity requirement of the magnetic measurement system to non-magnetic properties while also possessing sufficient hardness to withstand pressures up to approximately 2 GPa. The torque circlip 6, pressure base 7, and pressure sleeve 8 are all made of non-magnetic stainless steel, possessing sufficient strength to withstand the rotational pressure applied by the hydraulic press.

[0090] How to use

[0091] The following is combined with Figures 1 to 8 The method of using the apparatus of this embodiment will be described in detail.

[0092] Step S1: Sample packaging

[0093] Install a Teflon plug 4 onto one end of the Teflon tube 5. Slide the assembly of the Teflon plug 4 and the Teflon tube 5 into the inner wall 22 of the piston sleeve 2, with its open end facing upwards, and push it in until the end of the Teflon tube 5 slightly extends beyond the inner wall 22 to facilitate sample loading. Using a syringe, load the sample to be tested, a pressure gauge (e.g., aluminum, whose superconducting transition temperature is approximately 1.2K), and the pressure transmitting medium (e.g., 7373 oil) into the Teflon tube 5. Then, seal the opening of the Teflon tube 5 with another Teflon plug 4 and wipe away any spilled oil and particles with lint-free paper.

[0094] Step S2: Assemble the piston assembly

[0095] Using a piston cylinder 3, carefully push the Teflon tube 5 containing the sample into the inner wall 22 of the piston sleeve 2, ensuring the Teflon tube 5 is fully inserted. Insert the other piston cylinder 3 from the opposite direction and adjust the positions of the two piston cylinders 3 so that the Teflon tube 5 is centered. Screw the two piston bases 1 into the piston sleeve 2 from both ends, and tighten them with a wrench 9 using the engagement of the external thread 12 and the internal thread 21, ensuring that the lengths of the external thread 12 protruding from the piston sleeve 2 of the two piston bases 1 are equal. At this point, the cylindrical recess 13 of the piston base 1 is tightly engaged with the end of the piston cylinder 3, completing the assembly of the piston assembly.

[0096] Step S3: Install the pressurization component

[0097] The assembled piston assembly is inserted into the torque retaining ring 6. By tightening the long screws 62 in the two side wall screw holes 61, the slit 63 is narrowed, thereby clamping and fixing the piston assembly. The torque retaining ring 6 holding the piston assembly is placed into the pressure sleeve 8, so that the two planes of the torque retaining ring 6 and the two inner wall protrusions 81 of the pressure sleeve 8 form a surface contact fit to achieve circumferential positioning. The two pressure bases 7 are inserted from both ends of the pressure sleeve 8, so that the small cylindrical part of the pressure base 7 enters the pressure sleeve 8. The pressure base 7 is rotated so that the three protrusions 71 on the end face of the small cylindrical part form a concave-convex fitting fit with the three grooves 11 of the piston base 1, achieving angular positioning and center positioning, thus completing the assembly of the pressure assembly.

[0098] Step S4: Pressurize the sample

[0099] The assembled pressurizing assembly is placed under a commercial hydraulic press. Initial pressure is applied using the press, causing the two pressurizing bases 7 to move towards each other, pushing the two piston bases 1 and two piston cylinders 3 to compress the sample inside the Teflon tube 5, compressing the piston assembly a certain distance. Then, a steel rod is inserted into the side wall hole 82 of the pressurizing sleeve 8, and the sleeve 8 is rotated, causing it to rotate relative to the pressurizing bases 7. This drives the torque retaining ring 6 and piston sleeve 2 to rotate synchronously. The piston sleeve 2, through its two sets of internal threads 21 with opposite directions, drives the two piston bases 1 to move further towards each other, thus locking the current pressure. The hydraulic press is then depressurized, and the pressure is checked to ensure it is maintained. If the target pressure is not reached, the hydraulic press is restarted to apply greater pressure, repeating the alternating operation of "hydraulic press pressurization – manual rotation locking" until the target pressure is reached. Finally, the piston assembly is manually locked to maintain pressure, completing the pressurization process.

[0100] Step S5: Low-temperature measurement connection

[0101] Remove the pressurized piston assembly from the pressurization assembly. Connect the piston assembly to the helium-3 carbon fiber rod of the magnetic measurement system via connector 10: securely connect the internal thread 101 of one end of connector 10 to the external thread 12 of one of the piston bases 1, and connect the other end of connector 10 to the plastic tube of the helium-3 carbon fiber rod. Place the entire device into the magnetic measurement system to perform magnetic measurements under extremely low temperature conditions (0.3 to 1.8 K).

[0102] The double-helix piston pressurization device of this embodiment has an overall diameter of less than 6mm and a weight of no more than 5g, making it perfectly compatible with the helium-3 insert of the magnetic measurement system. Through its double-helix symmetrical pressurization structure, precise hydrostatic pressure conditions can be achieved within the range of 0 to 2GPa. Furthermore, the entire device is made of non-magnetic materials, ensuring no impact on the measurement accuracy of the magnetic measurement system. This device is simple in structure and easy to operate, meeting the research needs of heavy fermion superconductors and giant magnetic card materials requiring magnetic measurements under extremely low temperature and high pressure conditions.

Claims

1. A double-helix piston pressurization device for a magnetic measurement system in the helium-3 temperature range, characterized in that, Includes piston assembly and pressurization assembly, wherein: The piston assembly includes a piston sleeve (2), two piston cylinders (3) coaxially disposed within the piston sleeve (2), a container for accommodating a sample located between the two piston cylinders (3), and two piston bases (1) screwed into the piston sleeve (2) from both ends respectively; wherein the piston bases (1) are connected to the piston sleeve (2) by a threaded connection, and the direction of their threaded connection is configured such that when the piston sleeve (2) rotates relative to the piston bases (1), the two piston bases (1) move towards each other, thereby pushing the two piston cylinders (3) to compress the sample within the container; and The pressurizing assembly includes a pressurizing sleeve (8), a torque retaining ring (6) disposed within the pressurizing sleeve (8), and two pressurizing bases (7) inserted from both ends of the pressurizing sleeve (8); wherein the torque retaining ring (6) has an adjustable clamping structure for detachably clamping the piston assembly.

2. The double-helix piston pressurization device for the helium-3 temperature region of a magnetic measurement system according to claim 1, characterized in that, The piston base (1) has a groove (11) at one end and a support structure for abutting the piston cylinder (3) at the other end. The side wall of the piston base (1) is provided with external threads. The piston sleeve (2) has two sets of internal threads with opposite directions inside. The piston base (1) is screwed into both ends of the piston sleeve (2) through the cooperation of the external threads and the internal threads. Preferably, the pressure base (7) is composed of a large cylindrical part and a small cylindrical part arranged coaxially. The small cylindrical part is used to insert into the end of the pressure sleeve (8). The end face of the small cylindrical part is provided with a protrusion (71). The protrusion (71) is adapted to the shape of the groove (11) of the piston base (1) to achieve angle positioning and center positioning. Preferably, the pressure sleeve (8) is a hollow cylindrical structure with an inner wall protrusion (81) inside for accommodating and securing the torque retaining ring (6); the two ends of the pressure sleeve (8) respectively rotatably accommodate the small cylindrical parts of the two pressure bases (7), and the side wall of the pressure sleeve (8) is provided with a side wall hole (82) for applying torque.

3. The double-helix piston pressurization device for the helium-3 temperature region of a magnetic measurement system according to claim 2, characterized in that, The piston base (1) has three grooves (11) that are evenly spaced at 120° along the circumference of the piston base (1); the pressure base (7) has three protrusions (71) on the end face of the small cylindrical part that are evenly spaced at 120° along the end face of the small cylindrical part, and the protrusions (71) and the grooves (11) are in a concave-convex interlocking positioning fit. Preferably, the piston base (1) has a cylindrical recess (13) as the abutting structure, which is used to seamlessly accommodate the end of the piston cylinder (3) and fix it in the center.

4. The double-helix piston pressurization device for the helium-3 temperature region of a magnetic measurement system according to claim 1, characterized in that, The container includes a Teflon tube (5) and two Teflon plugs (4). The Teflon tube (5) is located between two piston cylinders (3), and the two Teflon plugs (4) are respectively sealed at both ends of the Teflon tube (5).

5. The double-helix piston pressurization device for the helium-3 temperature region of a magnetic measurement system according to claim 1, characterized in that, The piston sleeve (2) has an inner tube wall (22) extending along its axis, the inner tube wall (22) being a smooth cylindrical surface, for accommodating and radially constraining two piston cylinders (3) and a container for accommodating samples.

6. The double-helix piston pressurization device for the helium-3 temperature region of a magnetic measurement system according to claim 2, characterized in that, The torque retainer (6) has a cylindrical structure and a hollow inner cavity for accommodating the piston assembly. The outer circumferential surface of the torque retainer (6) is composed of two opposing planes and two opposing arc surfaces. The planes extend along the axial direction of the torque retainer (6), and the distance between the two planes is less than the distance between the two arc surfaces. A slit (63) is provided on the cylindrical wall of the torque retainer (6) along the axial direction. The slit (63) extends inward from the outer wall of one of the arc surfaces and penetrates into the hollow inner cavity. The slit (63) extends radially to the interior of the opposite arc surface, but does not penetrate the outer wall of the other arc surface.

7. The double-helix piston pressurizing device for the helium-3 temperature region of a magnetic measurement system according to claim 6, characterized in that, The inner wall protrusions (81) of the pressure sleeve (8) are two, respectively located on opposite sides of the inner wall of the pressure sleeve (8). The inner wall protrusions (81) extend along the axial direction of the pressure sleeve (8), and the side of the inner wall protrusions (81) facing the axis of the pressure sleeve (8) is a plane. The two planes of the torque retainer (6) respectively form face-to-face contact with the planes of the two inner wall protrusions (81), which is used to restrict the rotation of the torque retainer (6) relative to the pressure sleeve (8) in the circumferential direction.

8. The double-helix piston pressurization device for the helium-3 temperature region of a magnetic measurement system according to claim 1, characterized in that, The torque retainer (6) has at least two sidewall screw holes (61) on its sidewall. By screwing in the long screw (62), the width of the slit (63) can be reduced, thereby clamping and fixing the piston assembly. Preferably, the piston base (1), piston sleeve (2) and piston cylinder (3) are all made of non-magnetic beryllium copper alloy. Preferably, the torque retaining ring (6), the pressure base (7), and the pressure sleeve (8) are all made of non-magnetic stainless steel.

9. The double-helix piston pressurizing device for the helium-3 temperature region of a magnetic measurement system according to claim 2, characterized in that, The device also includes a connector (10), one end of which is provided with an internal thread for detachably connecting with the external thread of the piston base (1), and the other end of which is used to connect with the plastic tube of the helium-3 carbon fiber rod of the magnetic measurement system. Preferably, the device further includes an L-shaped wrench (9), which includes a hand-held part and a working part; the working part is located at the tail end of the wrench (9), and the working part is provided with a protrusion (91), the shape of which is adapted to the shape of the groove (11) of the piston base (1), for inserting into the groove (11) to apply torque when the piston base (1) is screwed; Preferably, the diameter of the piston assembly is greater than or equal to 5.8 mm and less than 6 mm; Preferably, the piston assembly weighs 4 g to 5 g.

10. A method of using a double-helix piston pressurizing device for a magnetic measurement system in the helium-3 temperature range, characterized in that, The device is the device according to any one of claims 1 to 10, comprising the following steps: Step S1: Sample packaging step The sample to be tested, the pressure gauge, and the pressure transmission medium are loaded into the container used to hold the sample. Step S2: Piston assembly steps The sealed container and two piston cylinders (3) are placed into the piston sleeve (2) in sequence, so that the container is located between the two piston cylinders (3). Then, the two piston bases (1) are screwed into the piston sleeve (2) from both ends, so that the abutting structure of the two piston bases (1) abuts against the ends of the two piston cylinders (3) respectively, thus completing the assembly of the piston assembly. Step S3: Assembly of pressurized components The assembled piston assembly is inserted into the torque retainer (6) and clamped and fixed. The torque retainer (6) holding the piston assembly is placed into the pressure sleeve (8) and secured with the inner wall protrusion (81). Then, the small cylindrical parts of the two pressure bases (7) are inserted from both ends of the pressure sleeve (8) so that the protrusion (71) of the pressure base (7) and the groove (11) of the piston base (1) form a concave-convex interlocking circumferential positioning. Step S4: Pressurization Step The assembled pressurizing assembly is placed under the hydraulic press. After the piston assembly is compressed a certain distance by applying pressure through the hydraulic press, the tool is inserted into the side wall hole (82) of the pressurizing sleeve (8) and rotated, so that the pressurizing sleeve (8) rotates relative to the pressurizing base (7), which drives the piston sleeve (2) to rotate. The two piston bases (1) are driven to move towards each other through two sets of internal threads with opposite directions, thereby locking the current pressure. The hydraulic press is restarted to apply greater pressure and then rotated to lock again. The hydraulic press pressurization and manual rotation locking are alternated until the sample reaches the target pressure. Step S5: Measurement connection steps After pressurization, the piston assembly is removed from the pressurization assembly and connected to the helium-3 carbon fiber rod of the magnetic measurement system via connector (10). One end of the connector (10) is provided with an internal thread for detachable connection with the external thread of the piston base (1), and the other end of the connector (10) is used to connect to the plastic tube of the helium-3 carbon fiber rod of the magnetic measurement system. The entire device is then placed into the magnetic measurement system for cryogenic magnetic measurement.

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