A multi-cell pure niobium cavity inner surface niobium three-tin coating equipment

Abstract

The present invention discloses a device for coating the inner surface of a multi-cell pure niobium cavity with a niobium-tin film. The device comprises: an external vacuum system for providing temperature and vacuum conditions for the niobium-tin film, comprising an external vacuum chamber of a vacuum furnace and an external chamber vacuum system for providing a vacuum environment within the external vacuum chamber; an internal vacuum system for providing a clean growth environment for the niobium-tin film, comprising a pure niobium chamber of the vacuum furnace and an internal chamber vacuum system for providing a vacuum environment within the pure niobium chamber; a pure niobium chamber disposed within the external vacuum chamber for accommodating a multi-cell niobium chamber and a tin source evaporation chamber, the tin source evaporation chamber being fixed at both ends of the multi-cell niobium chamber and serving as a container for the tin source; a niobium chamber conveying device for conveying the multi-cell niobium chamber into the internal vacuum chamber; a heating power supply system for providing heat for the niobium-tin film deposition process; and an electrical automatic control system for controlling the niobium-tin film deposition process, collecting various parameters of the deposition process, and providing analytical feedback. The present invention facilitates and uniforms film deposition.

Description

Technical Field

[0001] The invention relates to a niobium-tin film coating device for the inner surface of a multi-cell pure niobium cavity. Background Art

[0002] A superconducting cavity is a microwave resonant cavity used in accelerators to accelerate charged particles. Currently, superconducting cavities are primarily made of niobium. Compared to room-temperature cavities, their advantages include high acceleration gradients, low cavity losses, and large beam apertures. Consequently, superconducting cavities are widely used in major accelerators worldwide to accelerate various charged particles.

[0003] There are two main indicators to measure the performance of superconducting cavities: acceleration gradient E acc and surface resistance R S . R S Proportional to the power consumption of the cavity, R S The smaller the resistance, the lower the power consumption of the superconducting cavity (thus saving on cryogenic construction and operating costs). Therefore, since the birth of superconducting cavities, researchers have adopted various methods to reduce the surface resistance of superconducting cavities, such as high-pressure pure water washing, low-temperature baking, clean room assembly, etc.

[0004] With the advancement of superconducting radio frequency technology, the surface resistance of pure niobium superconducting cavities has approached the limits of traditional BCS superconductivity theory and is difficult to reduce further. Therefore, it is necessary to develop new superconducting materials to further reduce the surface resistance of superconducting cavities, thereby reducing the power consumption of superconducting cavities. Among them, niobium-tin is the most promising new radio frequency superconducting material.

[0005] Compared with pure niobium, the advantages of niobium-tin are: (1) the radio frequency critical magnetic field can theoretically reach 450mT, while niobium is only 240mT; (2) the superconducting critical temperature of niobium-tin is 18.3K, while niobium is 9.2K; (3) the surface resistance R S The temperature decreases much faster than that of niobium. Therefore, the Q value of a niobium-tin superconducting cavity at 4.2K can reach the level of a pure niobium superconducting cavity at 2K. Furthermore, a niobium-tin superconducting cavity has the potential to operate at an acceleration gradient twice that of a pure niobium superconducting cavity, significantly reducing the operating and construction costs of large-scale superconducting accelerators. However, niobium-tin is brittle and has poor thermal conductivity, making it impractical to use as a bulk material. Instead, a high-quality niobium-tin thin film can only be grown on the inner surface of a substrate cavity. Currently, the best method for developing niobium-tin thin-film superconducting cavities is to grow a 1-3μm thick, high-quality niobium-tin thin film on the inner surface of a pure niobium substrate cavity using tin vapor diffusion. However, multi-cell pure niobium cavities are large and complex in structure; therefore, a comprehensive design of the coating equipment, including heating, vacuum, tin temperature control, and transport systems, is urgently required to grow uniformly distributed, high-quality niobium-tin thin films on the inner surface of a multi-cell pure niobium substrate cavity. Summary of the Invention

[0006] The purpose of the present invention is to provide a multi-cell pure niobium cavity inner surface niobium three-tin coating equipment.

[0007] The present invention provides a multi-cell pure niobium cavity inner surface niobium three-tin coating device, comprising:

[0008] An external vacuum system, used to provide temperature and vacuum conditions for the niobium-tin film plating, comprising an external vacuum chamber of the vacuum furnace and an external chamber vacuum system for providing a vacuum environment within the external vacuum chamber;

[0009] An inner vacuum system, for providing a clean growth environment for the niobium-tin film, comprises a pure niobium chamber of a vacuum furnace and an inner chamber vacuum system for providing a vacuum environment within the pure niobium chamber. The pure niobium chamber is disposed within an outer vacuum chamber and is used to house a multi-cell niobium chamber and a tin source evaporation chamber. The tin source evaporation chamber is fixed at both ends of the multi-cell niobium chamber and is configured as a container for holding the tin source.

[0010] A niobium cavity conveying device, used for conveying the multi-cell niobium cavity into the inner vacuum cavity;

[0011] Heating power supply system, used to provide heat for the evaporation process of niobium-tin thin film;

[0012] The electrical automatic control system is used to control the preparation process of the niobium-tin film and collect various parameters of the preparation process and provide analysis and feedback.

[0013] In the above-mentioned multi-cell pure niobium cavity inner surface niobium-tin film coating equipment, the external vacuum system includes:

[0014] An outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; an outer heat shield arranged inside the double-layer jacketed water-cooled shell and configured together with the double-layer jacketed water-cooled shell to form a heat-insulating shielding layer; a heater arranged in the space between the outer heat shield and the pure niobium chamber and configured into three independent heating zones for heating the side walls of the inner vacuum system corresponding to the niobium chamber to be coated; a temperature measuring thermocouple arranged in each independent heating zone and configured to control the temperature in each heating zone and to provide an over-temperature alarm; an ... a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the outer vacuum chamber The gauge is arranged on the inner surface of the outer vacuum chamber shell and is configured to measure and detect the vacuum pressure and inflation pressure of the outer vacuum chamber; the inner vacuum pure niobium chamber support is located on the inner wall of the outer vacuum chamber and contacts the outer wall of the pure niobium chamber to support the pure niobium chamber. It is arranged in the direction vertically downward of the axis of the pure niobium chamber and can bear the weight of the niobium chamber and the workpiece at high temperature while preventing the deformation of the inner vacuum pure niobium chamber; the outer chamber vacuum system consists of a three-stage exhaust system consisting of two diffusion pumps, two Roots pumps, and two mechanical pumps, and is configured to pump air from atmospheric pressure to 10 -4Pa has good pumping capacity.

[0015] In the present invention, the inner vacuum pure niobium cavity support is arranged in the direction vertically downward of the axis of the pure niobium cavity, that is, below the niobium-tin coating equipment on the inner surface of the multi-cell pure niobium cavity after it is built and placed in the site, and the operator faces it during normal operation.

[0016] In the above-mentioned multi-cell pure niobium cavity inner surface niobium three-tin coating equipment, in the inner vacuum system, the cavity axis of the multi-cell niobium cavity is parallel to the axis direction of the vacuum furnace;

[0017] The internal vacuum system comprises:

[0018] The pure niobium chamber is placed in the uniform temperature zone (the uniform temperature zone refers to the area with temperature uniformity within ±5 degrees) surrounded by the three independent heating zones of the outer vacuum chamber, and is configured together with the furnace door of the outer vacuum chamber to form an independent inner vacuum chamber for placing the multi-cell niobium chamber; the inner vacuum gauge is arranged on the furnace door of the pure niobium chamber and is configured to measure and detect the vacuum pressure and inflation pressure of the pure niobium chamber; the inner heat insulation screen is placed at the entrance and exit of the pure niobium chamber and is configured as the thermal insulation layer of the pure niobium chamber; the tin source evaporation chamber is fixed to the flanges at both ends of the pure niobium chamber using pure tungsten screws and pure tungsten nuts, and is configured to be a container for holding the tin source; the tin source heating element surrounds the tin source evaporation chamber and is configured to have a separate temperature control function; the inner chamber vacuum system adopts an oil-free pump group, a three-stage evacuation system consisting of two molecular pumps, one molecular pump and one dry pump, and is configured to pump from atmospheric pressure to 10 -6 Pa has good pumping capacity.

[0019] In the above-mentioned multi-cell pure niobium cavity inner surface niobium three-tin coating equipment, the niobium cavity conveying device includes: a niobium cavity conveying device, which is used to place the multi-cell niobium cavity and the inner heat insulation shield and convey them into the pure niobium chamber. It is configured to meet the needs of disassembling and assembling the niobium cylinder and conveying the niobium cavity, and can specifically bear a load of 500kg.

[0020] In the above-mentioned multi-cell pure niobium cavity inner surface niobium three-tin coating equipment, the heating power supply system includes: an external vacuum cavity heating system, located in the space between the external heat insulation shield and the pure niobium chamber, including multiple heating belts to form the three independent heating zones; a tin source heating system, located around the tin source evaporation chamber, configured to heat the tin source; a voltage-regulating power supply, configured with a secondary current transformer and a voltage measuring device; and an electric control cabinet, configured to display and control the heating power supply system.

[0021] In the above-mentioned multi-cell pure niobium cavity inner surface niobium tin coating equipment, the electrical automatic control system includes: an industrial computer monitoring and management module, configured to collect various parameters of the niobium tin film coating process and analyze and provide feedback; a process control module mainly based on a programmable controller, configured to be able to control various parameters of the niobium tin film coating process; and a multi-loop intelligent temperature controller furnace temperature control module, configured to be able to independently control the temperature and vacuum degree of the outer vacuum chamber and the tin source evaporation chamber.

[0022] In the above-mentioned multi-cell pure niobium cavity inner surface niobium three-tin coating equipment, the outer heat insulation shield is made of high-temperature resistant alloy, is cylindrical, and is provided with sufficient evacuation channels;

[0023] The pure niobium chamber is made of metallic niobium;

[0024] The heat shield inside the inner vacuum chamber is made of pure niobium, and the workpieces inside the chamber are all made of high-purity tungsten.

[0025] The tin source heating element is made of high-purity tungsten wire.

[0026] In the above-mentioned multi-cell pure niobium cavity inner surface niobium tin coating equipment, in the outer cavity vacuum system, a cryogenic cold trap is provided between the diffusion pump and the vacuum pipe connected to the outer vacuum cavity;

[0027] In the inner cavity vacuum system, a water-cooled cold trap is provided at the junction of the pure niobium chamber and the outer vacuum cavity furnace door.

[0028] In the above-mentioned multi-cell pure niobium cavity inner surface niobium three-tin coating equipment, the outer vacuum cavity is provided with a vacuum detection device for detecting the vacuum parameters of the outer vacuum cavity;

[0029] The inner vacuum cavity is provided with a vacuum detection device for detecting the vacuum parameters of the inner vacuum cavity.

[0030] In the above-mentioned multi-cell pure niobium cavity inner surface niobium three-tin coating equipment, each of the tin source heating elements has an independent temperature control system and heating power supply system, and its secondary power supply is equipped with a measuring device that can be displayed on the electric control cabinet.

[0031] The present invention has the following advantages:

[0032] 1. In view of the characteristics of the multi-cell cavity being large in volume and heavy in weight, the present invention provides a special conveying device for the multi-cell cavity.

[0033] 2. Tin source evaporation chambers, tin source heating elements and crucibles are designed at both ends of the niobium cavity. These can meet the requirements of evaporation on the inner surface of the multi-cell niobium cavity due to the long length of the multi-cell pure niobium cavity and ensure the uniformity of the coating.

[0034] 3. In order to accurately monitor and control the coating parameters, temperature and pressure monitoring equipment are designed on the inner and outer vacuum furnace bodies to monitor the furnace body vacuum temperature parameters and coating temperature and pressure parameters during the coating process.

[0035] 4. The present invention can uniformly plate a layer of pure and evenly distributed niobium-tin thin film on the inner surface of a multi-cell pure niobium cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the overall structure of a multi-cell pure niobium cavity inner surface niobium-tin coating device according to the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of the external vacuum system of the present invention;

[0038] Figure 3 This is a schematic diagram of the external vacuum system structure of the present invention;

[0039] Figure 4 Schematic diagram of the vacuum system structure of the present invention;

[0040] Figure 5 This is a schematic diagram of the vacuum system structure in the present invention;

[0041] Figure 6 This is a schematic diagram of the structure of the niobium cavity delivery device of the present invention.

[0042] The marks in the figure are as follows:

[0043] 1. External vacuum cover seal; 2. External vacuum cover; 3. Double-jacketed water-cooled shell; 4. External heat shield; 5. External vacuum pump assembly; 6. Heater; 7. Control cabinet; 8. External vacuum gauge; 9. Internal vacuum pure niobium chamber support; 10. Internal vacuum chamber cover; 11. Internal vacuum gauge; 12. Pure niobium chamber; 13. Internal chamber vacuum system (also known as internal vacuum pump assembly); 14. Internal heat shield; 15. Tin source crucible; 16. Pure niobium lifting fixture; 17. Tin source heating element; 18. External vacuum chamber; 19. Break valve; 20. Backfill valve; 21. Pneumatic baffle valve; 22. Cold trap; 23. Diffusion pump; 24. Roots pump; 25. Mechanical pump; 26. Cryogenic unit; 27. Gate valve; 28. Molecular pump; 29. ​​Dry pump; 30. Niobium chamber transfer device; 31. Multi-cell pure niobium chamber. DETAILED DESCRIPTION

[0044] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0045] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0046] To facilitate understanding of the present technical solution by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings in the embodiments. The contents of the embodiments are not intended to limit the present invention. All other embodiments obtained by those skilled in the art without creative work based on the present invention shall fall within the scope of protection of the present invention.

[0047] like Figure 1 The figure shows the overall structure of a multi-cell pure niobium cavity surface niobium-tin coating apparatus provided by the present invention. The apparatus's vacuum system is a dual vacuum system consisting of an external vacuum system and an internal vacuum system. The external vacuum system, used to provide temperature and vacuum conditions for the niobium-tin film coating, includes the outer vacuum chamber of the vacuum furnace and an outer chamber vacuum system for maintaining a vacuum environment within the outer vacuum chamber.

[0048] The inner vacuum system, used to provide a clean growth environment for the niobium-tin thin film, includes a pure niobium chamber 12 in the vacuum furnace and an inner chamber vacuum system (also known as an inner vacuum pump assembly) 13 for providing a vacuum environment within the pure niobium chamber. The pure niobium chamber is disposed within the outer vacuum chamber and is used to house a multi-cell niobium chamber 31 and a tin source evaporation chamber. The tin source evaporation chamber is fixed at both ends of the multi-cell niobium chamber 31 and is configured as a container for the tin source.

[0049] In view of the characteristics of the multi-cell cavity being large in volume and heavy in weight, a niobium cavity conveying device 30 is provided to convey the multi-cell niobium cavity 31 into the inner vacuum cavity;

[0050] Heating power supply system, used to provide heat for the evaporation process of niobium-tin thin film;

[0051] In order to accurately monitor and control the coating parameters, an electrical automatic control system is set up to control the preparation process of the niobium-tin film and collect various parameters of the preparation process for analysis and feedback.

[0052] The following will explain in detail from six aspects: external vacuum chamber, external chamber vacuum system, internal vacuum chamber, internal chamber vacuum system, niobium chamber conveying device, and electrical automatic control system.

[0053] (1) External vacuum system

[0054] The structure of the external vacuum system is as follows Figure 2As shown, the rated operating temperature of the external vacuum system is 1400°C, and the maximum allowable heating temperature is 1500°C. It includes: an external vacuum chamber 18 (including an external vacuum cover seal 1 and an external vacuum cover 2); a double-layer jacketed water-cooled shell 3, wrapped around the outside of the external vacuum chamber; an external heat insulation screen 4, arranged inside the double-layer jacketed water-cooled shell 3, and together with the double-layer jacketed water-cooled shell 3, configured as a heat insulation shielding layer; a heater 6, arranged in the space between the external heat insulation screen 4 and the pure niobium chamber 12, configured into three independent heating zones, used to heat the side walls of the internal vacuum system corresponding to the niobium cavity to be coated; temperature measuring thermocouples, arranged in each independent heating zone, configured to control the temperature in each heating zone and issue an over-temperature alarm; an external vacuum chamber 18; a heat insulation screen 4, arranged inside the double-layer jacketed water-cooled shell 3, and configured together with the double-layer jacketed water-cooled shell 3, configured as a heat insulation shielding layer; a heat insulation screen 6, arranged in the space between the external heat insulation screen 4 and the pure niobium chamber 12, configured into three independent heating zones, used to heat the side walls of the internal vacuum system corresponding to the niobium cavity to be coated; a temperature measuring thermocouple, arranged in each independent heating zone, configured to control the temperature in each heating zone and issue an over-temperature alarm; Gauge 8 is arranged on the inner surface of the outer vacuum chamber shell and is configured to measure and detect the vacuum pressure and inflation pressure of the outer vacuum chamber; the inner vacuum pure niobium chamber support 9 is located on the inner wall of the outer vacuum chamber and contacts the outer wall of the pure niobium chamber 12 to support the pure niobium chamber 12. It is arranged in the direction perpendicular to the axis of the pure niobium chamber 12 and can bear the weight of the niobium chamber and the workpiece at high temperatures while preventing the deformation of the inner vacuum pure niobium chamber; the outer chamber vacuum system (also known as the outer vacuum pump group 5) consists of two diffusion pumps 23, two Roots pumps 24, and two mechanical pumps 25 to form a three-stage exhaust system, which is configured to pump air from atmospheric pressure to 10 -4 Pa has good pumping capacity.

[0055] The heat shield is made of a high-temperature resistant alloy in a cylindrical shape and is equipped with sufficient evacuation channels. The heat shield used in this embodiment is composed of a combination of stainless steel and molybdenum-rhenium alloy. The heating element of heater 6 is composed of a high-temperature resistant alloy in a cylindrical shape. In this embodiment, molybdenum-lanthanum alloy is used as the heating element. Due to the large heating space and the temperature uniformity requirement of this equipment of ±3°C, the heating zones of the internal and external vacuum systems in this embodiment are designed as multiple independent heating zones. A separate temperature control system and heating power supply system are designed for each zone, and its secondary power supply is equipped with a measuring device that can be displayed on the electrical control cabinet 7. The inner vacuum pure niobium cavity support 9 is made of a high-temperature resistant alloy with a special-shaped grid structure with good support. In this embodiment, molybdenum-lanthanum alloy is used. A vacuum detection device is provided on each external vacuum cavity to detect the vacuum parameters of the external vacuum cavity.

[0056] (2) External cavity vacuum system

[0057] The schematic diagram of the external vacuum system structure is as follows: Figure 3 As shown, it is required to change from atmospheric pressure to 10 -4 Pa has good pumping capacity; the vacuum degree requirement during operation is <2×10 -3 Pa, the ultimate vacuum requirement is <1×10 -4Pa, and the pressure rise rate is required to be ≤0.1 Pa / h. In this embodiment, a three-stage exhaust system is employed, consisting of two diffusion pumps 23, two Roots pumps 24, and two mechanical pumps 25. One mechanical pump 25 serves as a maintenance pump for the two diffusion pumps 23. The corresponding detection system for the diffusion pumps 23 ensures normal operation. Reliable leak detection devices are installed at each stage.

[0058] In order to prevent the outer vacuum chamber from being contaminated and to maintain the vacuum limit of the vacuum system, a cryogenic cold trap 22 is set between the diffusion pump 23 and the high vacuum pneumatic damper valve 21. To avoid misoperation, the system is designed with a complete safety interlock.

[0059] (3) Internal vacuum system

[0060] Internal vacuum system structure Figure 4 As shown, it includes: a pure niobium chamber, which is required to remain stable and non-deformed under high temperature and high vacuum conditions, and is placed in the uniform temperature zone (the uniform temperature zone refers to the area with temperature uniformity within ±5 degrees) surrounded by three independent heating zones of the outer vacuum chamber. Together with the furnace door of the outer vacuum chamber (i.e., the outer vacuum cover 2), it is configured to form an independent inner vacuum chamber for accommodating the multi-cell niobium chamber. The inner vacuum chamber and its internal components are required to be stable at high temperatures and not contaminate the workpiece; an inner vacuum gauge 11, arranged on the furnace door of the pure niobium chamber 12 (i.e., the inner vacuum chamber cover 10), and is configured to measure and detect the vacuum pressure and inflation pressure of the pure niobium chamber 12; an inner heat shield 14, placed in the pure niobium chamber The entrance and exit are configured as a pure niobium chamber insulation layer; the tin source evaporation chamber (specifically, a tin source crucible 15, which is set at both ends of the niobium chamber to ensure the uniformity of the coating due to the long length of the multi-cell pure niobium chamber) is fixed to the flanges at both ends of the pure niobium chamber using pure tungsten screws and pure tungsten nuts, and is configured as a container for holding the tin source; the tin source heating element 17 surrounds the tin source evaporation chamber and is configured to have a separate temperature control function; the inner cavity vacuum system (also known as the inner vacuum pump group) 13 adopts an oil-free pump group, a three-stage evacuation system consisting of two molecular pumps 28, one molecular pump 28 and a dry pump 29, and is configured from atmospheric pressure to 10 -6 Pa has good pumping capacity.

[0061] In this embodiment, the pure niobium chamber is made of pure niobium. This chamber is connected to the outer vacuum chamber door to form an independent inner vacuum chamber. The heat shield 14 within the inner vacuum chamber is made of pure niobium, and the workpieces within the chamber are all made of high-purity tungsten. The multi-cell pure niobium chamber 31 is supported and hoisted within the inner vacuum chamber using a pure niobium / tungsten pure niobium hoisting fixture 16. Two tin evaporation sources are fixed to the ends of the niobium chamber using flanges. Tin source heating elements 17, made of high-purity tungsten filament, are located around the tin source evaporation chamber and have independent temperature control. Each heating element has its own independent temperature control system and heating power supply system, and its secondary power supply is equipped with a measurement device that can be displayed on the control cabinet 7. Each inner vacuum chamber is equipped with a vacuum detection device to monitor the vacuum parameters of the inner vacuum chamber.

[0062] (4) Inner cavity vacuum system

[0063] The structural principle of the internal vacuum system is as follows Figure 5 As shown, it is required to change from atmospheric pressure to 10 -6 Pa have good pumping ability and keep the vacuum chamber clean; the vacuum degree requirement during operation is <3×10 -4 Pa, the ultimate vacuum requirement is <5×10 -6 Pa, and the pressure rise rate is required to be ≤0.1 Pa / h. In this embodiment, a three-stage exhaust system consisting of two molecular pumps 28, one molecular pump 28, and one dry pump 29 is used to meet the exhaust requirements. An oil-free pump group is used to avoid contamination of the vacuum chamber. Each stage is equipped with a reliable leak detection device.

[0064] To prevent tin vapor from entering the molecular pump and damaging it, a water-cooled cold trap 22 is provided at the junction of the pure niobium chamber 12 and the outer vacuum chamber furnace door (i.e., the outer vacuum cover 2) (denoted as the molecular pump inlet, where the inlet refers to the interface where the gas inside the pure niobium chamber enters the molecular pump during pumping).

[0065] (5) Niobium cavity delivery device

[0066] The structure of the niobium cavity delivery device 30 is as follows: Figure 6 As shown, it is installed on the front door and is required to accommodate the transport requirements for the assembly and disassembly of the niobium cylinder and the multi-cell pure niobium chamber 31, with a maximum load capacity of 500 kg. In this embodiment, a main cart and auxiliary cart are combined. The multi-cell pure niobium chamber 31, tin source crucible 15, tin source, and thermocouple are placed on the auxiliary cart, which is then placed on the main cart. The main cart is responsible for transporting the auxiliary cart and the workpieces on it to a designated location near the vacuum furnace. The auxiliary cart then transports the workpieces to a designated location inside the vacuum furnace, completing the installation of the niobium chamber, heating equipment, and temperature measurement equipment.

[0067] (6) Electrical automatic control system

[0068] The electrical automatic control system consists of an industrial computer monitoring system, a programmable controller-based process control system, and a multi-loop intelligent temperature controller for furnace temperature control. It measures and controls various process parameters during the coating process to achieve uniform Nb3Sn thin films. It monitors, tracks, analyzes, processes, and stores field data, tracking and displaying multiple temperature curves in the form of dynamic graphs. It also features fault diagnosis and comprehensive safety interlocks.

[0069] The electrical control system features temperature control, PID auto-tuning, and the ability to set and store multiple process curves. The temperature and vacuum level in different zones can be controlled independently, with a vacuum delay protection function during heating pauses. Digital composite vacuum gauges are also installed on both the inner and outer vacuum chambers.

[0070] When using the multi-cell pure niobium cavity inner surface niobium three-tin coating equipment of the present invention to coat the film, the specific operation is as follows:

[0071] First, a multi-cell pure niobium cavity is assembled with accessories such as a tin source crucible and a tin source on a niobium cavity conveyor and transported to the interior of the inner vacuum cavity. After each vacuum cavity is sealed, heating and evacuation are started. After ensuring there are no leaks, heating, insulation, and cooling steps are performed according to the set coating program. After the coating is completed, the workpiece is removed.

Claims

1. A multi-cell pure niobium cavity inner surface niobium three-tin coating equipment, characterized by: include: An external vacuum system, used to provide temperature and vacuum conditions for the niobium-tin film plating, comprising an external vacuum chamber of the vacuum furnace and an external chamber vacuum system for providing a vacuum environment within the external vacuum chamber; An inner vacuum system, for providing a clean growth environment for the niobium-tin film, comprises a pure niobium chamber of a vacuum furnace and an inner chamber vacuum system for providing a vacuum environment within the pure niobium chamber. The pure niobium chamber is disposed within an outer vacuum chamber and is used to house a multi-cell niobium chamber and a tin source evaporation chamber. The tin source evaporation chamber is fixed at both ends of the multi-cell niobium chamber and is configured as a container for holding the tin source. A niobium cavity conveying device, comprising a main trolley and an auxiliary trolley, for conveying the multi-cell niobium cavity into the inner vacuum chamber; Heating power supply system, used to provide heat for the evaporation process of niobium-tin thin film; Electrical automatic control system, used to control the preparation process of niobium-tin-plated thin films and collect various parameters of the preparation process and provide analysis and feedback; The external vacuum system includes: an external vacuum chamber; a double-layer jacketed water-cooled shell wrapped around the outside of the external vacuum chamber; an external heat shield disposed inside the double-layer jacketed water-cooled shell and configured together with the double-layer jacketed water-cooled shell to form a heat-insulating shielding layer; a heater disposed in the space between the external heat shield and the pure niobium chamber and configured into three independent heating zones for heating the side walls of the internal vacuum system corresponding to the pure niobium chamber to be coated; a temperature measuring thermocouple disposed in each independent heating zone and configured to heat each of the three independent heating zones. The temperature in the heating zone is controlled and an over-temperature alarm is issued; an external vacuum gauge is arranged on the inner surface of the outer vacuum chamber shell and is configured to measure and detect the vacuum pressure and inflation pressure of the outer vacuum chamber; an inner vacuum pure niobium chamber support is located on the inner wall of the outer vacuum chamber and contacts the outer wall of the pure niobium chamber to support the pure niobium chamber and is arranged in the direction perpendicular to the axis of the pure niobium chamber downward; the outer chamber vacuum system consists of a three-stage exhaust system consisting of two diffusion pumps, two Roots pumps, and two mechanical pumps, and is configured to pump air from atmospheric pressure to 10 -4 Pa has the ability to pump air; In the inner vacuum system, the cavity axis of the multi-cell niobium cavity is parallel to the axis direction of the vacuum furnace; the inner vacuum system includes: the pure niobium chamber, which is placed in the uniform temperature zone surrounded by the three independent heating zones of the outer vacuum chamber, and is configured together with the furnace door of the outer vacuum chamber to form an independent inner vacuum chamber for accommodating the multi-cell niobium cavity; an inner vacuum gauge, arranged on the furnace door of the pure niobium chamber, and configured to measure and detect the vacuum pressure and inflation pressure of the pure niobium chamber; an inner heat insulation screen, placed at the entrance and exit of the pure niobium chamber, and configured to be a thermal insulation layer of the pure niobium chamber; a tin source evaporation chamber, which is fixed to the flanges at both ends of the pure niobium chamber using pure tungsten screws and pure tungsten nuts, and is configured to be a container for holding the tin source; a tin source heating element, which surrounds the tin source evaporation chamber and is configured to have a separate temperature control function; the inner cavity vacuum system adopts an oil-free pump group, a three-stage evacuation system consisting of two molecular pumps, one molecular pump and one dry pump, and is configured to pump from atmospheric pressure to 10 -6 Pa has the ability to pump air.

2. The multi-cell pure niobium cavity inner surface niobium three-tin coating equipment according to claim 1 is characterized in that: The niobium cavity conveying device includes: a niobium cavity conveying device for placing the multi-cell niobium cavity and the inner heat shield and conveying them into the pure niobium cavity, and is configured to meet the requirements of disassembling and assembling the niobium cylinder and conveying the niobium cavity.

3. The multi-cell pure niobium cavity inner surface niobium-tin coating equipment according to claim 1 or 2, characterized in that: The heating power supply system includes: an external vacuum chamber heating system, located in the space between the external heat shield and the pure niobium chamber, comprising multiple heating belts to form the three independent heating zones; a tin source heating system, located around the tin source evaporation chamber, configured to heat the tin source; a voltage-regulating power supply, configured with a secondary current transformer and a voltage measuring device; and an electric control cabinet, configured to display and control the heating power supply system.

4. The multi-cell pure niobium cavity inner surface niobium three-tin coating equipment according to claim 3 is characterized in that: The electrical automatic control system includes: an industrial computer monitoring and management module, configured to collect various parameters of the niobium-tin thin film plating process and perform analysis and feedback; a process control module mainly based on a programmable controller, configured to control various parameters of the niobium-tin thin film plating process; and a multi-loop intelligent temperature controller furnace temperature control module, configured to independently control the temperature and vacuum degree of the outer vacuum chamber and the tin source evaporation chamber.

5. The multi-cell pure niobium cavity inner surface niobium-tin coating equipment according to claim 1, characterized in that: The outer heat insulation screen is made of high temperature resistant alloy, is cylindrical, and is provided with an evacuation channel; The inner vacuum pure niobium cavity support is made of molybdenum-lanthanum alloy and has a special-shaped grid structure; The pure niobium chamber is made of metallic niobium; The heat shield inside the inner vacuum chamber is made of pure niobium, and the workpieces inside the chamber are all made of high-purity tungsten. The tin source heating element is made of high-purity tungsten wire.

6. The multi-cell pure niobium cavity inner surface niobium-tin coating equipment according to claim 1, characterized in that: In the outer cavity vacuum system, a cryogenic cold trap is provided between the diffusion pump and the vacuum pipe connected to the outer vacuum cavity; In the inner cavity vacuum system, a water-cooled cold trap is provided at the junction of the pure niobium chamber and the outer vacuum cavity furnace door.

7. The multi-cell pure niobium cavity inner surface niobium-tin coating equipment according to claim 1, characterized in that: The outer vacuum cavity is provided with a vacuum detection device for detecting the vacuum parameters of the outer vacuum cavity; The inner vacuum cavity is provided with a vacuum detection device for detecting the vacuum parameters of the inner vacuum cavity.

8. The multi-cell pure niobium cavity inner surface niobium-tin coating equipment according to claim 1, characterized in that: Each of the tin source heating elements has an independent temperature control system and heating power supply system, and its secondary power supply is provided with a measuring device which can be displayed on the electric control cabinet.

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