Superconducting cavity niobium-plated three-tin film vacuum evaporation furnace

Abstract

The invention discloses a superconducting cavity niobium-plated three-tin film vacuum evaporation furnace. Wherein the outer vacuum system is communicated with the furnace body and provides a vacuum environment for the hearth; the inner vacuum system is communicated with the superconducting cavity coating chamber, and the inner vacuum system provides a vacuum environment for Ni3Sn coating; a gas interface is arranged between the furnace body and the superconducting cavity coating chamber; the furnace body power regulator is divided into a front furnace door heating area, a rear furnace door heating area, a coating area left heating area and a coating area right heating area of the furnace body for heating and temperature control; in a coating area in the superconducting cavity coating chamber, superconducting cavity thermocouples are installed on six dimensions of the front side, the rear side, the upper side and the lower side through superconducting cavity supports respectively, and the superconducting cavity thermocouples and tin source thermocouples are connected with a temperature control monitoring system. And the temperature control monitoring system and the furnace body power regulator form a coating chamber temperature control system to control and balance the temperature in the superconducting cavity coating chamber. And the temperature deviation of the uniform temperature zone is less than or equal to + / -3 DEG C, so that the equipment meets the requirements of industrial operation stability and reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of plating materials with metal materials, and in particular relates to a vacuum evaporation furnace for plating niobium-tin thin films in a superconducting cavity. Background Art

[0002] Particle accelerators are vacuum experimental devices that use electromagnetic fields to accelerate charged particles. Their application areas include advanced light sources, particle colliders, industrial accelerators, and medical accelerators. Particle accelerators not only provide important research methods in the fields of materials science, nuclear science, medicine, and chemistry, but also play a unique role in various national economic fields such as isotope production, radiation medicine, and industrial irradiation. Radio frequency superconducting technology is an advanced technology of modern particle accelerators. It couples external radio frequency power through antennas or waveguides to excite electromagnetic fields in metal superconductor cavities. Charged particles enter the electromagnetic field at a suitable phase and interact with it, which increases the energy of the particles. Compared with room temperature accelerators, radio frequency superconducting accelerators use superconductors as acceleration cavity materials, which can reduce the radio frequency loss and operating costs of the acceleration cavity and improve energy utilization. Superconducting cavity materials generally use pure niobium. In large superconducting accelerators, superconducting cavities are cooled by immersion in liquid helium to maintain the temperature of the superconducting cavity stable. In order to provide sufficient liquid helium, a complete set of complex and expensive liquid helium cryogenic systems are required for superconducting modules. The cryogenic system is large in size, expensive, and requires long-term investment for maintenance. This leads to significant limitations on the application of superconducting accelerators in other fields.

[0003] As a key component of radio frequency superconducting accelerators, radio frequency superconducting cavities have the advantages of high quality factor, continuous wave operation capability, large beam aperture, etc., and are widely used in high-current particle accelerators. With the development of niobium (Nb) material smelting technology, the improvement of superconducting cavity processing level, and the research of post-processing processes such as nitrogen doping and baking, the performance of traditional pure niobium cavities has approached its material limit. Compared with Nb, niobium tin (Nb3Sn) material has a high superconducting transition temperature, high overheat magnetic field, and low surface resistance. The overheat magnetic field of Nb3Sn at a lower temperature is 420mT, which is far higher than the 240mT of pure Nb, which means that under the same cavity conditions, the Nb3Sn cavity can theoretically withstand a higher peak magnetic field and can provide a higher acceleration gradient. Taking the 1.3GHz TESLA cavity as an example, the theoretical acceleration gradient of Nb3Sn is nearly 100MV / m (pure Nb cavity is 57MV / m), so the Nb3Sn superconducting cavity has good development potential.

[0004] Nb3Sn thin film superconducting cavity has the ability to operate at a high quality factor at 4.2K, which can realize the application of liquid helium-free conduction cooling thermostat. The tin vapor diffusion method is currently the most effective method for preparing Nb3Sn thin film cavity.

[0005] In the prior art, for example, a multi-cell pure niobium cavity inner surface niobium three-tin coating device with Chinese publication number CN116752090A discloses a device including an external vacuum system, an internal vacuum system, a pure niobium chamber, a niobium chamber conveying device and a heating electrical control system; the pure niobium chamber is arranged in the external vacuum chamber, which is used to place the multi-cell niobium chamber and the tin source evaporation chamber, and the tin source evaporation chamber is fixed at both ends of the multi-cell niobium chamber, which is used as a container for holding the tin source. Summary of the invention

[0006] In view of the problems existing in the background technology, the present invention provides a superconducting cavity niobium-tin thin film vacuum evaporation furnace, the technical scheme includes: a furnace body, an external vacuum system, a superconducting cavity coating chamber, an internal vacuum system and a furnace body power regulator, wherein the external vacuum system is connected with the furnace body, and the external vacuum system provides a vacuum environment for the furnace chamber; the internal vacuum system is connected with the superconducting cavity coating chamber, and the internal vacuum system provides a vacuum environment for the niobium-tin coating; a gas interface is provided between the furnace body and the superconducting cavity coating chamber;

[0007] The furnace body includes a columnar shell, a front furnace door, a rear furnace door and a support base. The shell is fixed on the ground through the support base. The front furnace door and the rear furnace door are respectively sealed and installed at both ends of the shell. The main body of the superconducting cavity coating chamber is installed in the furnace body. One end of the feeding furnace door of the superconducting cavity coating chamber passes through the front furnace door.

[0008] The superconducting cavity coating room includes: a niobium tube, a support rail, a superconducting cavity support, a tin source crucible, a tin source thermocouple, a feed furnace door, a tin source heater, a niobium superconducting cavity, a circulating water system, a compressed air system, a temperature control monitoring system and a stainless steel water jacket; the support rail is fixed to the bottom of the inner side of the niobium tube by welding, the superconducting cavity support is installed on the support rail by sliding connection, and the niobium superconducting cavity is fixed above the superconducting cavity support; the tin source crucible is fixedly installed at both ends of the niobium superconducting cavity, the tin source heater is wound around the outside of the tin source crucible, and the tin source thermocouple used to measure the tin source temperature is inserted from the end face of the tin source crucible;

[0009] The end face of the niobium cylinder is welded with a niobium-titanium sealing flange, and the niobium-titanium sealing flange and the flange of the stainless steel water jacket are sealed with a metal sealing ring; the stainless steel water jacket is a stainless steel double-layer jacket structure, the jacket layer is connected to the circulating water system, and a niobium heat insulation screen is also provided between the niobium cylinder and the metal sealing ring; the stainless steel water jacket is equipped with a feed furnace door;

[0010] The furnace power regulator is divided into four areas for heating and temperature control, namely the front furnace door heating zone, the rear furnace door heating zone, the left heating zone of the coating zone and the right heating zone of the coating zone. The four heating zones heat the niobium tube, and then radiate heat to the niobium superconducting cavity through the niobium tube. In the coating area inside the superconducting cavity coating room, superconducting cavity thermocouples are installed in six dimensions on the front, back, upper and lower sides through superconducting cavity brackets. The superconducting cavity thermocouples and tin source thermocouples are connected to the temperature control monitoring system.

[0011] The superconducting cavity coating chamber is located within the uniform temperature zone of the furnace body; the temperature control monitoring system and the furnace body power regulator form a coating chamber temperature control system, and the coating chamber temperature control system controls the temperature deviation of the uniform temperature zone to ≤±3°C.

[0012] An additional superconducting cavity thermocouple is installed in the space between the front tin source crucible and the niobium heat shield; the temperature control monitoring system and the furnace power regulator control the temperature difference between the niobium superconducting cavity and the furnace body to be 50-100°C; the tin source temperature is 0-200°C higher than the niobium superconducting cavity temperature.

[0013] The tin source heater and the tin source crucible are separated by 99 porcelain, and the tin source heater is softly connected to the water jacket electrode.

[0014] The end surface of the tin source crucible is provided with a doping gas pipe, which is in contact with various gas sources; the material of the doping gas pipe is high-purity niobium or high-purity tungsten, which is used to introduce inert gas and / or doping gas into the superconducting cavity.

[0015] The tin source crucible is a cylindrical hollow structure, and an upper cover for placing the tin source is provided on the top of the tin source crucible; the material of the tin source crucible is high-purity tungsten or high-purity niobium, and the two tin source crucibles are located on both sides of the superconducting cavity, and are heated and temperature-controlled respectively.

[0016] The material of the niobium cylinder is high-purity niobium; the niobium cylinder heat insulation screen is 12 layers of high-purity niobium foil; the feed furnace door is made of stainless steel.

[0017] The superconducting cavity bracket includes: a bottom plate support, a cavity V-shaped bracket and a superconducting cavity thermocouple bracket; the bottom plate support is placed on the niobium tube guide rail, the V-shaped bracket is stably placed in the middle position of the bottom plate support, the beam tube and dumbbell reinforcement ribs of the cavity are supported in the openings of the corresponding V-shaped brackets to ensure that the niobium superconducting cavity is horizontal and centrally arranged; the superconducting cavity thermocouple bracket welded to the bottom plate support is arranged on both sides of the niobium superconducting cavity along the length direction, and the superconducting cavity thermocouple is fixed on the superconducting cavity thermocouple bracket.

[0018] It also includes: a compressed air system with a gas supply pressure of 0.6-0.8MPa. The compressed air system includes: a furnace door cylinder, a charging valve and a venting valve;

[0019] The furnace door cylinder uses compressed air to drive the front and rear doors of the evaporation furnace to open / close;

[0020] The charging valve is driven by compressed air to inject the doping gas into the niobium cylinder;

[0021] Venting: compressed air drives the vacuum breaking / closing of the niobium cylinder and furnace body.

[0022] The shell is made of 304 stainless steel and has a double-layer jacketed horizontal structure. The front furnace door and the rear furnace door are hinged to the shell and fixed with bolts. The support seat is made of carbon steel. The shell, the front furnace door and the rear furnace door are all equipped with heat insulation screens. The heat insulation screen in the shell is a cylindrical structure, and the heat insulation screen in the front furnace door and the rear furnace door is a disc structure, both of which are fully reflective screens. The fully reflective screen has a total of 7 layers, of which the inner 3 layers are high-temperature molybdenum and the outer 4 layers are stainless steel. A workpiece car is installed on the ground outside the front furnace door.

[0023] The inner vacuum system is connected to the niobium cylinder by a stainless steel water jacket, and is equipped with a residual gas analyzer; the circulating water system includes: a water inlet system and a drainage system, and the water inlet temperature is ≤32℃.

[0024] The beneficial effects of the present invention are:

[0025] 1. The tin source of the superconducting cavity has the function of independent temperature control. The high temperature zone of the pure niobium chamber is located within the uniform temperature zone of the furnace, so that the Sn vapor at high temperature is deposited on the inner surface of the niobium cavity to react in situ to form a high-quality Nb3Sn film in a high vacuum diffusion coating device. The tin source is located on the flange side of the beam tube on both sides of the superconducting cavity in the pure niobium chamber. An independent heater is set around the tin source to form a temperature difference of 0-200℃ between the tin source and the superconducting cavity coating temperature zone, which meets the niobium-tin coating process.

[0026] 2. The furnace power regulator is divided into four zones, which independently heat and control the temperature of the front furnace door zone, the rear furnace door zone, the left coating zone, and the right coating zone; the temperature control monitoring system and the furnace power regulator form a coating room internal control system to control and balance the temperature in the superconducting cavity coating room. It has the characteristics of high temperature, high vacuum, good temperature uniformity, and advanced temperature control system. The temperature deviation in the uniform temperature zone is ≤±3℃, which enables the equipment to meet the requirements of industrial operation stability and reliability, and further facilitates operation and equipment maintenance; it can complete the niobium-tin coating of superconducting cavities such as 650MHz 1-cell, 650MHz 3-cell1, 650MHz 5-cell, and 1.3GHz 9cell.

[0027] 3. The vacuum evaporation furnace adopts a double vacuum structure to ensure the cleanliness of the vacuum environment in the coating area; the niobium tube and heat shield are made of high-purity niobium (RRR40), and the superconducting cavity support and heater are made of high-purity tungsten, which can reduce the precipitation of high-temperature impurities in the coating chamber and affect the coating quality.

[0028] 4. A ring heater is used outside the tin source crucible, separated by 99 porcelain, so that the tin source can be heated and controlled separately. Compared with the patent for heating the tin source inside the superconducting cavity, the niobium tin of the present invention will not be deposited on the heater, causing the heater to short-circuit.

[0029] 5. A doping gas pipe interface is added to the tin source, which can introduce inert gas into the superconducting cavity, improve the uniformity of the tin vapor in the superconducting cavity, and improve the uniformity of the coating; by introducing doping gas, doping process research can be carried out.

[0030] 6. The superconducting cavity adopts a bracket support structure. According to the height and diameter of the beam tube and the cell reinforcement ribs, the height of the support frame is adjusted to achieve multiple horizontal supports for the entire cavity. Compared with the superconducting cavity suspension system, the present invention can reduce the influence of high temperature coating on the coaxiality and field flatness of the cavity; niobium and tin are relatively brittle, and adjusting the coaxiality and field flatness after superconducting cavity coating will cause the coating to crack. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The diagram is a top view of an embodiment of a vacuum evaporation furnace for coating niobium-tin thin films in a superconducting cavity according to the present invention.

[0032] Figure 2 It is a side view schematic diagram of an embodiment of the present invention.

[0033] Figure 3 It is a schematic diagram of the elevation structure of the superconducting cavity coating chamber in an embodiment of the present invention.

[0034] Among them, 100-furnace body, 110-external vacuum system, 200-superconducting cavity coating chamber, 210-internal vacuum system, 101-shell, 102-front furnace door, 103-rear furnace door, 104-support seat, 201-niobium cylinder, 202-support rail, 203-superconducting cavity support, 204-tin source crucible, 205-tin source thermocouple, 206-doping gas pipe, 207-feed furnace door, 208-tin source heater, 209-niobium superconducting cavity, 220-circulating water system, 240-stainless steel water jacket, 241-niobium heat insulation screen, 242-metal sealing ring, 300-workpiece car, 400-furnace body power regulator. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0036] like Figure 1 and Figure 2 The embodiment of the present invention shown in the figure comprises: a furnace body 100, an external vacuum system 110, a superconducting cavity coating chamber 200, an internal vacuum system 210, a furnace body power regulator 400, a compressed air system (not shown in the figure) and a workpiece vehicle 300, wherein the external vacuum system 110 is connected with the furnace body 100, and the external vacuum system 110 provides a vacuum environment for the furnace; the internal vacuum system 210 is connected with the superconducting cavity coating chamber 200, and the internal vacuum system 210 provides a vacuum environment for niobium-tin coating; a gas interface for cooling or doping is provided between the furnace body 100 and the superconducting cavity coating chamber 200;

[0037] The furnace body 100 includes a columnar shell 101, a front furnace door 102, a rear furnace door 103 and a support base 104. The shell 101 is fixed to the ground through the support base 104. The front furnace door 102 and the rear furnace door 103 are sealed and installed at both ends of the shell 101 respectively. The main body of the superconducting cavity coating chamber 200 is installed in the furnace body 100. One end of the feeding furnace door 207 of the superconducting cavity coating chamber 200 passes through the front furnace door 102. A workpiece vehicle 300 is installed on the ground outside the front furnace door 102.

[0038] The furnace power regulator 400 is divided into four heating and temperature control zones: the front furnace door heating zone, the rear furnace door heating zone, the coating zone (left) heating zone, and the coating zone (right) heating zone. The four heating zones heat the niobium tube 201, and then heat the niobium superconducting cavity 209 through the niobium tube 201. In this embodiment, the heater is made of high-temperature molybdenum, the working temperature of the furnace heating zone is 1300°C, and the maximum allowable heating temperature is 1500°C;

[0039] The compressed air system includes: furnace door cylinder, charging valve and venting valve; compressed air drives the furnace door cylinder to open / close the front furnace door 102 and the rear furnace door 103 of the evaporation furnace; compressed air drives the reversing valve to open / close the charging valve to inject doping gas into the niobium cylinder; compressed air drives the reversing valve to break / close the vacuum of the niobium cylinder and the furnace body. The compressed air distribution system equipped with oil mist, water filter, pressure gauge and distributor has the function of insufficient air pressure alarm, and the air supply pressure is 0.6-0.8MPa.

[0040] In this embodiment, the housing 101 is made of 304 stainless steel and is a double-layer jacket horizontal structure. The housing is equipped with water-cooled electrodes, vacuum gauges, and an air inlet valve.

[0041] In this embodiment, the front furnace door 102 and the rear furnace door 103 are installed with the shell 101 by hinge connection and are locked and fixed with bolts for easy maintenance; except for the furnace door, the other connection joints and flanges are all sealed with metal.

[0042] In this embodiment, the support base 104 is made of carbon steel and has a load-bearing capacity of about 30 tons;

[0043] In this embodiment, heat insulation screens are provided in the shell 101, the front furnace door 102 and the rear furnace door 103. The heat insulation screen in the shell 101 is a cylindrical structure, and the heat insulation screens in the front furnace door 102 and the rear furnace door 103 are disc structures. All of them adopt full reflection screens with a total of 7 layers (3 layers on the inner side are high-temperature molybdenum, and 4 layers on the outer side are stainless steel).

[0044] In this embodiment, the workpiece cart 300 uses a multifunctional workpiece cart that can meet the needs of entering and exiting the coated superconducting cavity and disassembling the superconducting cavity chamber. The workpiece cart has a maximum load capacity of 500kg and is equipped with guide wheels, lifting and limiting devices, etc.

[0045] The external vacuum system 110 and the internal vacuum system 210 are isolated from each other. In this embodiment, the external vacuum system 110 uses three DN250 molecular pumps (pumping speed 2000L / S) and one WXG-16A vortex dry pump to form a two-stage oil-free pumping part, and the ultimate vacuum is 1×10 -5 The internal vacuum system 210 uses a DN250 molecular pump (pumping speed 2000L / S) and a WXG-16A vortex dry pump to form a two-stage oil-free pumping part, with a limit vacuum of 1×10 -6 The inner vacuum system 210 is equipped with a cold trap to prevent tin vapor from entering the molecular pump; the inner vacuum system 210 is equipped with a residual gas analyzer (RGA) to monitor the coating environment.

[0046] like Figure 3 The superconducting cavity coating chamber 200 shown in the figure includes: a niobium cylinder 201, a support rail 202, a superconducting cavity support 203, a tin source crucible 204, a tin source thermocouple 205, a doping gas pipe 206, a feed furnace door 207, a tin source heater 208, a niobium superconducting cavity 209, a circulating water system 220, a compressed air system, a temperature control monitoring system and a stainless steel water jacket 240; the support rail 202 is fixed to the bottom of the inner side of the niobium cylinder 201 by welding, and the superconducting cavity support 203 is installed on the support rail 202 by sliding connection The niobium superconducting cavity 209 is fixed above the superconducting cavity bracket 203; the tin source crucible 204 is fixedly installed at both ends of the niobium superconducting cavity 209, the tin source heater 208 is wound around the outside of the tin source crucible 204, the tin source heater 208 and the tin source crucible 204 are separated by 99 porcelain, and the tin source heater is softly connected to the water jacket electrode; the tin source thermocouple 205 and the doping gas pipe 206 are both inserted from the end face of the tin source crucible 204, the tin source thermocouple 205 is used to measure the tin source temperature, and the doping gas pipe 206 is connected to a variety of gas sources.

[0047] A niobium-titanium sealing flange is welded on the end face of the niobium cylinder 201, and a metal sealing ring 242 is used to seal the niobium-titanium sealing flange and the flange of the stainless steel water jacket 240; the stainless steel water jacket 240 is a stainless steel double-layer jacket structure, and the jacket layer is connected to the circulating water system 220 so as to be cooled by the cooling circulating water, and a niobium heat insulation screen 241 is also provided between the niobium cylinder 201 and the metal sealing ring 242; the outer end of the stainless steel water jacket 240 is connected with a feed furnace door 207 via a hinge.

[0048] In the coating area in the superconducting cavity coating chamber 200 (the open space between the superconducting cavity coating chamber 200 and the 3cell niobium superconducting cavity 209), superconducting cavity thermocouples are installed in six dimensions on the front, back, top and bottom sides to monitor the temperature difference in six directions. The thermocouples are installed on the superconducting cavity bracket 203. The superconducting cavity thermocouples and the tin source thermocouples 205 together constitute a temperature control monitoring system; the niobium superconducting cavity 209 is mainly heated by the four heating zones of the furnace body. Since the coating cavity is long and there is heat loss in the front and rear furnace doors; in order to ensure the temperature difference in the coating area In order to ensure the uniformity of temperature, the furnace power regulator is divided into four zones, which independently heat and control the temperature of the front furnace door zone, the rear furnace door zone, the left coating zone and the right coating zone; the coating zone is equipped with multiple temperature measuring points to return the temperature to the temperature control monitoring system to monitor the temperature of the superconducting cavity coating zone; the superconducting cavity coating zone is located within the range of the furnace uniform temperature zone; the temperature control monitoring system and the furnace power regulator form a coating room temperature control system, and the coating room temperature control system controls the temperature deviation of the uniform temperature zone to ≤±3℃, and the size of the uniform temperature zone is not less than φ800×2200(L).

[0049] The temperature in the superconducting cavity coating chamber 200 is controlled to ensure the uniformity of the temperature of the niobium superconducting cavity 209; after heating to the coating temperature according to the coating temperature curve, the tin source heater is started, and the tin source temperature is 0-200°C higher than the superconducting cavity temperature. The specific temperature difference is determined according to the cavity type test; before the coating is completed, the tin source heater is stopped first, and then the temperature is lowered according to the process curve to room temperature to take out the superconducting cavity.

[0050] In this embodiment, 7 superconducting cavity thermocouples are evenly installed, 6 of which are installed in the open space in 6 dimensions on the front, back, top and bottom sides of the superconducting cavity coating chamber 200, and an additional one is installed in the space between the tin source crucible 204 and the niobium heat insulation shield 241 on the front side. Due to the presence of cooling circulating water in the jacket layer, additional temperature control is required in this area.

[0051] The tin source crucible is a cylindrical hollow structure, and an upper cover for placing the tin source is provided on the top of the tin source crucible; the material of the tin source crucible is high-purity tungsten or high-purity niobium (RRR40), and the tin source crucible 204 is fixedly installed on both ends of the niobium superconducting cavity 209 in the following manner: the crucible flange and the superconducting cavity beam tube flange are connected with tungsten bolts; in this embodiment, two tin source crucibles are located on both sides of the superconducting cavity as superconducting cavity tin sources, and are independently heated and temperature-controlled. The heater is made of high-purity tungsten and is equipped with no less than 9 sets of WRe5 / 26 type thermocouples; the temperature difference between the tin source area and the coating area is adjustable from 0 to 200°C, and the working temperature of the tin source area is 1400°C.

[0052] In this embodiment, the niobium tube is installed in the housing 101 through a molybdenum support rod (not shown in the figure), and the molybdenum support rod can support the superconducting cavity coating chamber, the superconducting cavity bracket and the superconducting cavity.

[0053] In this embodiment, the material of the niobium tube 201 is high-purity niobium (RRR40); the niobium tube heat shield is high-purity niobium foil (RRR40), with a total of 12 layers, and the size of the niobium tube is The main function is to insulate and heat-preserve so that the niobium superconducting cavity 209 is isolated from the furnace body by vacuum, which can ensure that the coating atmosphere is not polluted and provide a clean environment for coating.

[0054] In this embodiment, the superconducting cavity support 203 includes: a bottom plate support, a cavity V-shaped support and a superconducting cavity thermocouple support. The bottom plate support is placed on the niobium tube guide rail, the V-shaped support is stably placed in the middle of the bottom plate support, the beam tube and dumbbell reinforcement ribs of the cavity are supported in the opening of the corresponding V-shaped support, ensuring that the niobium superconducting cavity 209 is horizontal and centered; the superconducting cavity thermocouple support welded to the bottom plate support is arranged on both sides of the niobium superconducting cavity 209 along the length direction, and multiple superconducting cavity thermocouples are fixed on the superconducting cavity thermocouple support to measure the temperature at different positions of the superconducting cavity.

[0055] In this embodiment, the material of the doping gas tube 206 is high-purity niobium or high-purity tungsten, and an inert gas or a doping gas can be introduced into the superconducting cavity; the introduction of inert gas can improve the fluidity of the tin source vapor and improve the uniformity of the coating. The introduction of doping gas can be used to dope the coating.

[0056] The main function of the stainless steel water jacket 240 is to connect the niobium tube to the furnace body and isolate the temperature for control. The internal vacuum system 210 is passed into the niobium tube 201 by the stainless steel water jacket 240. In this embodiment, the stainless steel water jacket 240 is installed with tin source heater electrodes, thermocouple conversion joints, etc. The circulating water system 220 includes: water inlet system and drainage system, which are respectively for the furnace body, front and rear furnace doors, electrodes, vacuum pumps, molecular pumps and cold sinks, etc., equipped with flow meters, thermometers and water pressure monitoring devices, and have automatic alarm functions. Cooling water flow ≥30m 3 / h, water quality PH7.0-8.0, pressure 0.3-0.4MPa, inlet water temperature ≤32℃.

[0057] In this embodiment, the feed furnace door 207 is made of stainless steel and is sealed by a hand wheel to tighten the rubber seal.

Claims

1. A vacuum evaporation furnace for coating niobium-tin thin films in superconducting cavities, characterized in that: include: A furnace body (100), an external vacuum system (110), a superconducting cavity coating chamber (200), an internal vacuum system (210) and a furnace body power regulator (400), wherein the external vacuum system (110) is in communication with the furnace body (100), and the external vacuum system (110) provides a vacuum environment for the furnace chamber; the internal vacuum system (210) is in communication with the superconducting cavity coating chamber (200), and the internal vacuum system (210) provides a vacuum environment for niobium-tin coating; and a gas interface is provided between the furnace body (100) and the superconducting cavity coating chamber (200); The furnace body (100) comprises a columnar shell (101), a front furnace door (102), a rear furnace door (103) and a support seat (104); the shell (101) is fixed on the ground through the support seat (104); the front furnace door (102) and the rear furnace door (103) are respectively sealed and installed at two ends of the shell (101); the main body of the superconducting cavity coating chamber (200) is installed in the furnace body (100); one end of the feeding furnace door (207) of the superconducting cavity coating chamber (200) passes through the front furnace door (102); The superconducting cavity coating chamber (200) comprises: a niobium cylinder (201), a support rail (202), a superconducting cavity support (203), a tin source crucible (204), a tin source thermocouple (205), a feed furnace door (207), a tin source heater (208), a niobium superconducting cavity (209), a circulating water system (220), a compressed air system, a temperature control monitoring system and a stainless steel water jacket (240); the support rail (202) is fixed to the niobium cylinder (201) by welding. 01), a superconducting cavity support (203) is installed on the support rail (202) through a sliding connection, and a niobium superconducting cavity (209) is fixed above the superconducting cavity support (203); a tin source crucible (204) is fixedly installed at both ends of the niobium superconducting cavity (209), a tin source heater (208) is wound around the outside of the tin source crucible (204), and a tin source thermocouple (205) for measuring the temperature of the tin source is inserted from the end surface of the tin source crucible (204); A niobium-titanium sealing flange is welded to the end face of the niobium cylinder (201), and a metal sealing ring (242) is used to seal the niobium-titanium sealing flange and the flange of the stainless steel water jacket (240); the stainless steel water jacket (240) is a stainless steel double-layer jacket structure, and the jacket layer is connected to the circulating water system (220); a niobium heat insulation screen (241) is also provided between the niobium cylinder (201) and the metal sealing ring (242); the stainless steel water jacket (240) is provided with a feed furnace door (207); The furnace power regulator (400) is divided into four areas for heating and temperature control, namely, a front furnace door heating area, a rear furnace door heating area, a left coating area heating area, and a right coating area heating area. The four heating areas heat the niobium tube (201), and then radiate heat to the niobium superconducting cavity (209) through the niobium tube (201). In the coating area in the superconducting cavity coating chamber (200), superconducting cavity thermocouples are respectively installed in six dimensions, namely, front, back, top, and bottom, through a superconducting cavity bracket (203). The superconducting cavity thermocouples and the tin source thermocouples (205) are both connected to a temperature control monitoring system.

2. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to claim 1, characterized in that: The superconducting cavity coating chamber is located within the uniform temperature zone of the furnace body; the temperature control monitoring system and the furnace body power regulator form a coating chamber temperature control system, and the coating chamber temperature control system controls the temperature deviation of the uniform temperature zone to ≤±3°C.

3. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to claim 2, characterized in that: A superconducting cavity thermocouple is additionally installed in the space between the front tin source crucible (204) and the niobium heat shield (241), and the temperature control monitoring system and the furnace power regulator control the temperature difference between the niobium superconducting cavity (209) and the furnace (100) to be 50-100°C; the temperature of the tin source is 0-200°C higher than the temperature of the niobium superconducting cavity (209).

4. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to any one of claims 1 to 3, characterized in that: The tin source heater (208) and the tin source crucible (204) are separated by 99 porcelain, and the tin source heater is softly connected to the water jacket electrode.

5. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to any one of claims 1 to 3, characterized in that: The end surface of the tin source crucible (204) is provided with a doping gas pipe (206), which is in contact with a plurality of gas sources; the doping gas pipe (206) is made of high-purity niobium or high-purity tungsten and is used to introduce inert gas and / or doping gas into the superconducting cavity.

6. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to claim 5, characterized in that: The tin source crucible is a cylindrical hollow structure, and an upper cover for placing the tin source is provided on the top of the tin source crucible; the material of the tin source crucible is high-purity tungsten or high-purity niobium, and the two tin source crucibles are located on both sides of the superconducting cavity, and are heated and temperature-controlled respectively.

7. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to any one of claims 1 to 3, characterized in that: The material of the niobium cylinder (201) is high-purity niobium; the niobium cylinder heat shield is 12 layers of high-purity niobium foil; and the feed furnace door (207) is made of stainless steel.

8. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to claim 1, characterized in that: The superconducting cavity support (203) comprises: a bottom plate support, a cavity V-shaped support and a superconducting cavity thermocouple support; the bottom plate support is placed on the niobium tube guide rail, the V-shaped support is stably placed in the middle of the bottom plate support, the cavity beam tube and dumbbell reinforcement ribs are supported in the openings of the corresponding V-shaped support, ensuring that the niobium superconducting cavity (209) is horizontal and centrally arranged; the superconducting cavity thermocouple support welded to the bottom plate support is arranged on both sides of the niobium superconducting cavity (209) along the length direction, and the superconducting cavity thermocouple is fixed on the superconducting cavity thermocouple support.

9. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to claim 1, characterized in that: Also includes: Compressed air system, air supply pressure 0.6-0.8MPa, compressed air system includes: furnace door cylinder, charging valve and venting valve; A furnace door cylinder, which uses compressed air to drive the front furnace door (102) and the rear furnace door (103) of the evaporation furnace to open / close; The charging valve is driven by compressed air to inject the doping gas into the niobium cylinder; Venting: compressed air drives the vacuum breaking / closing of the niobium cylinder and furnace body.

10. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to claim 1, characterized in that: The shell (101) is a double-layer jacketed horizontal structure, and the material is 304 stainless steel; the front furnace door (102) and the rear furnace door (103) are both hingedly connected to the shell (101) and are locked and fixed with bolts; the support seat (104) is made of carbon steel; the shell (101), the front furnace door (102) and the rear furnace door (103) are all provided with heat insulation screens, the heat insulation screen in the shell (101) is a cylindrical structure, and the heat insulation screens in the front furnace door (102) and the rear furnace door (103) are disc structures, and all adopt full reflection screens; the full reflection screen has a total of 7 layers, of which the inner 3 layers are high-temperature molybdenum and the outer 4 layers are stainless steel; a workpiece vehicle (300) is installed on the ground outside the front furnace door (102).

11. A superconducting cavity niobium-tin thin film vacuum evaporation furnace according to claim 1, characterized in that: The inner vacuum system (210) is connected to the niobium cylinder (201) through the stainless steel water jacket (240), and the inner vacuum system (210) is equipped with a residual gas analyzer; The circulating water system (220) comprises: a water inlet system and a drainage system, and the inlet water temperature is ≤32°C.

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