A heating device for the exhaust pipe of the liquid nitrogen circulation system of a molecular beam epitaxy device

Abstract

The present invention provides a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device, which relates to the technical field of molecular beam epitaxy growth. The device includes an exhaust pipe of the liquid nitrogen circulation system, a first heating zone, a first transition zone, a second heating zone, a second transition zone, a third heating zone, a silencer cover, and a liquid nitrogen storage container. The first heating zone wraps the exhaust pipe of the liquid nitrogen circulation system and is connected to the first transition zone. The first transition zone is connected to the second heating zone. The second heating zone is connected to the second transition zone. The second transition zone is connected to the third heating zone and the liquid nitrogen storage container. The third heating zone is connected to the silencer cover. Compared with the prior art, when the liquid nitrogen circulation system works, it solves the problems that the nozzle is prone to ice slag blockage, resulting in unsmooth liquid nitrogen circulation and a large increase in system vacuum fluctuations, which affect the growth of epitaxial materials. At the same time, it also avoids the safety hazard that the ejected low-temperature gaseous nitrogen forms a nitrogen / water mist group by absorbing water molecules in the atmosphere and obscuring the line of sight of pedestrians.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular beam epitaxy growth, and particularly relates to a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device. Background Art

[0002] The liquid nitrogen circulation system is an important component in a molecular beam epitaxy device and is widely used in the technical field of semiconductor epitaxial growth. On the one hand, in order to avoid the blockage of the exhaust pipe opening of the liquid nitrogen circulation system of the molecular beam epitaxy device due to the easy freezing of ice slag, which affects the circulation of liquid nitrogen in the molecular beam epitaxy device system, resulting in a large increase in the system vacuum fluctuation during the molecular beam epitaxy growth process and a significant reduction in the quality of the thin film material grown by epitaxy; on the other hand, the low-temperature gaseous nitrogen discharged from the exhaust port of the liquid nitrogen circulation system of the molecular beam epitaxy device has a lower temperature than the outside atmospheric temperature and is easy to absorb water molecules in the outside atmosphere, forming a local nitrogen and water mixed fog group, resulting in the generation of a blind spot of vision and affecting the safety of outdoor pedestrians. Facing these problems, a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device needs to be proposed to solve these problems. Summary of the Invention

[0003] The purpose of the present invention is to provide, in view of the above-mentioned deficiencies of the prior art, a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device to solve the problems that the exhaust pipe opening of the liquid nitrogen circulation system of the molecular beam epitaxy device is easily blocked by frozen ice slag, the circulation of liquid nitrogen in the molecular beam epitaxy device system is not smooth, resulting in a significant reduction in the quality of the thin film material grown by epitaxy due to the instability of the system vacuum during the molecular beam epitaxy growth process; at the same time, due to the low temperature of the low-temperature gaseous nitrogen sprayed to the outside, it is easy to absorb water molecules in the atmosphere, forming a local nitrogen and water mixed fog group, resulting in the generation of a blind spot of vision and affecting the safety of pedestrians.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] The present invention provides a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device, including an exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy device, a first heating zone, a first transition zone, a second heating zone, a second transition zone, a third heating zone, a silencer cover, a liquid nitrogen storage container, a controller, an exhaust pipe sleeve, a metal heating wire, a honeycomb heating tube group, a metal heating wire mesh group, a circuit integration box, a cable, a groove, a barrier strip, a cylindrical heating long tube, a heating patch;

[0006] The exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment is wrapped by the first heating zone. The first heating zone is provided with an exhaust pipe sleeve, a metal heating wire, a groove, and a barrier strip. The outer wall of the exhaust pipe sleeve is engraved with a groove, and a barrier strip is provided in the middle of the groove. Two metal heating wires are placed in the groove on the outer wall of the exhaust pipe sleeve and are separated by the barrier strip. The two metal heating wires are not entangled with each other and are evenly wound around the exhaust pipe sleeve. The exhaust pipe sleeve is tightly sleeved on the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. The exhaust pipe sleeve is made of ceramic material. The first heating zone is connected to the first transition zone, and the first transition zone is connected to the second heating zone. The second heating zone is provided with a honeycomb heating tube group, a cylindrical Heating long tubes, heating stickers, the honeycomb heating tube group is composed of multiple cylindrical heating long tubes, and the material of the cylindrical heating long tubes is ceramic material. The diameter of the cylindrical heating long tube is 1 / 5 smaller than the diameter of the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. The honeycomb heating tube group is wrapped by the heating sticker. The second heating zone is connected to the second transition zone, and the second transition zone is connected to the third heating zone, the liquid nitrogen storage container, and the line integration box. A metal heating wire mesh group is provided in the third heating zone, and the line integration box is provided with heating wire groups of the first heating zone, the second heating zone, and the third heating zone. The line integration box is connected to the controller through a cable, and the third heating zone is connected to the silencer.

[0007] The present invention provides an exhaust pipe heating device for a liquid nitrogen circulation system of a molecular beam epitaxy device. A first temperature measuring thermocouple is provided in a first transition zone. The first temperature measuring thermocouple is placed facing the exhaust pipe opening of the liquid nitrogen circulation system of the molecular beam epitaxy device. A communication line of the first temperature measuring thermocouple is connected to a line integration box.

[0008] The present invention provides an exhaust pipe heating device for a liquid nitrogen circulation system of a molecular beam epitaxy device. A second temperature measuring thermocouple is provided in a second transition zone. The second temperature measuring thermocouple is arranged directly below the second heating zone. The communication line of the second temperature measuring thermocouple is connected to a line integration box.

[0009] The present invention provides an exhaust pipe heating device for a liquid nitrogen circulation system of a molecular beam epitaxy device. A metal heating wire mesh group and a third temperature measuring thermocouple are provided in a third heating zone. The metal heating wire mesh group is composed of a first metal heating wire mesh and a second metal heating wire mesh with two different apertures. The aperture of the first metal heating wire mesh is larger, measuring 1 cm×1 cm, and is placed in front of the second metal heating wire mesh. The aperture of the second metal heating wire mesh is smaller, measuring 0.5 cm×0.5 cm. The first metal heating wire mesh and the second metal heating wire mesh are 4-6 cm apart. The third temperature measuring thermocouple is placed directly behind the second metal heating wire mesh. The communication line of the third temperature measuring thermocouple is connected to a line integration box.

[0010] The present invention provides a heating device for the exhaust pipe of the liquid nitrogen circulation system of a molecular beam epitaxy device. The diameter of the air inlet of the silencer cover is twice as large as that of the air outlet. Sound-absorbing cotton is arranged inside the silencer cover and is closely attached to the inner wall of the silencer cover.

[0011] The present invention provides a heating device for the exhaust pipe of the liquid nitrogen circulation system of a molecular beam epitaxy device. A metal heating plate and a liquid nitrogen level gauge are arranged inside the liquid nitrogen storage container. The metal heating plate is placed at the bottom of the liquid nitrogen storage container, and the control line of the metal heating plate is connected into the circuit integration box. The liquid nitrogen level gauge is installed above the metal heating plate, and the height from the metal heating plate is 0.2 - 0.3 cm.

[0012] The present invention provides a heating device for the exhaust pipe of the liquid nitrogen circulation system of a molecular beam epitaxy device. Heat-insulating clothes are arranged on the outer surfaces of the first heating zone, the first transition zone, the second heating zone, the second transition zone, the third heating zone, the silencer cover, and the liquid nitrogen storage container. The heat-insulating clothes wrap the first heating zone, the first transition zone, the second heating zone, the second transition zone, the third heating zone, the silencer cover, and the liquid nitrogen storage container, and the heat-insulating clothes are made of aluminum foil, flame-retardant cotton, heat-insulating cotton, and waterproof cloth.

[0013] The beneficial effects of the present invention include:

[0014] The present invention provides a heating device for the exhaust pipe of the liquid nitrogen circulation system of a molecular beam epitaxy device. For the exhaust pipe nozzle of the liquid nitrogen circulation system of the molecular beam epitaxy device, it is easy to be blocked by ice slag, resulting in the unsmooth circulation of liquid nitrogen in the liquid nitrogen circulation system of the molecular beam epitaxy device, and further making the fluctuation of the system vacuum during the molecular beam epitaxy growth process larger, which is not conducive to growing high-quality thin film materials by epitaxy; in addition, the low-temperature gaseous nitrogen sprayed outdoors is lower than the atmospheric temperature itself, and it is easy to absorb water molecules in the atmosphere at the exhaust port of the liquid nitrogen circulation system, forming a nitrogen and water mixed fog mass in a local area, blocking the line of sight of pedestrians and endangering the safety of pedestrians. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 Shows the main structure diagram of a heating device for the exhaust pipe of the liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention;

[0017] Figure 2a and Figure 2bShows the exhaust pipe sleeve and its groove structure diagram of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention;

[0018] Figure 3 Shows the honeycomb heating tube group structure diagram of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention;

[0019] Figure 4 Shows the distribution diagram of temperature measurement points in the first transition region of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention;

[0020] Figure 5 Shows the distribution diagram of temperature measurement points in the second transition region of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention;

[0021] Figure 6a and Figure 6b Shows the structure diagrams of the first metal heating wire mesh and the second metal heating wire mesh of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention;

[0022] Figure 7 Shows the distribution diagram of the metal heating wire mesh group and temperature measurement points in the third heating region of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention;

[0023] Figure 8 Shows the silencer cover structure diagram of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention.

[0024] Figure 9 Shows the liquid nitrogen storage container structure diagram of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention.

[0025] Figure 10 Shows the layout diagram of the heat insulation jacket of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention.

[0026] Figure 11 Shows the heat insulation jacket structure diagram of a heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device provided by an embodiment of the present invention.

[0027] Description of reference numerals: 1 - Exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment; 2 - First heating zone; 3 - First transition zone; 4 - Second heating zone; 5 - Second transition zone; 6 - Third heating zone; 7 - Silencer; 8 - Liquid nitrogen storage container; 9 - Controller; 10 - Exhaust pipe sleeve; 11 - Metal heating wire; 12 - Honeycomb heating tube group; 13 - Metal heating wire mesh group; 14 - Circuit integration box; 15 - Cable; 16 - Groove; 17 - Barrier strip; 18 - Cylindrical heating long tube; 19 - Heating patch; 20 - First temperature measuring thermocouple; 21 - Second temperature measuring thermocouple; 22 - First metal heating wire mesh; 23 - Second metal heating wire mesh; 24 - Third temperature measuring thermocouple; 25 - Sound-absorbing cotton; 26 - Metal heating plate; 27 - Liquid nitrogen level gauge; 28 - Thermal insulation jacket; 29 - Aluminum foil; 30 - Flame-retardant cotton; 31 - Thermal insulation cotton; 32 - Waterproof cloth. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0029] As Figure 1 shown, the present invention provides a heating device for the exhaust pipe of the liquid nitrogen circulation system of a molecular beam epitaxy equipment, including the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment, a first heating zone 2, a first transition zone 3, a second heating zone 4, a second transition zone 5, a third heating zone 6, a silencer 7, a liquid nitrogen storage container 8, a controller 9, an exhaust pipe sleeve 10, a metal heating wire 11, a honeycomb heating tube group 12, a metal heating wire mesh group 13, a circuit integration box 14, a cable 15, a groove 16, a barrier strip 17, a cylindrical heating long tube 18, and a heating patch 19;

[0030] When the liquid nitrogen circulation system of the molecular beam epitaxy equipment is working, liquid nitrogen is continuously poured into the molecular beam epitaxy equipment system to ensure a stable high-vacuum system, providing a solid foundation for growing high-quality thin film materials by epitaxy. Since each source furnace of the molecular beam epitaxy equipment is in a high-temperature state during the epitaxial growth of thin film materials (generally, the source furnace temperature is 600°C to 1200°C), the liquid nitrogen poured into the molecular beam epitaxy equipment system absorbs heat and then is discharged to the outside through the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment in a gaseous form. The discharged gaseous nitrogen has a low temperature, about below -150°C (the temperature of the liquid nitrogen before flowing into the molecular beam epitaxy equipment is about below -180°C), and it will absorb water molecules in the atmosphere at the pipe orifice (the atmospheric temperature is 25°C - 30°C), condensing into ice slag at the orifice of the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment, hindering the discharge of the low-temperature gaseous nitrogen, and then forming a certain gas resistance, affecting the circulation of liquid nitrogen in the molecular beam epitaxy equipment system, causing large fluctuations in the vacuum of the molecular beam epitaxy equipment system, and seriously affecting the output of high-quality thin film materials. To solve this problem, a heating device for the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment is provided.

[0031] First, the exhaust pipe sleeve 10 in the first heating zone 2 is tightly sleeved on the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. Two metal heating wires 11 are placed in the groove 16 on the outer wall of the exhaust pipe sleeve 10, and the two metal heating wires 11 are separated by a barrier strip 17, as Figure 2a and Figure 2b shown. On the one hand, it is to prevent the two metal heating wires 11 from contacting each other and causing a short-circuit phenomenon, ensuring the safety of the metal heating wires 11 and the stability of their heating; on the other hand, if one of them is damaged, the other heating wire can still work, extending the service life of the first heating zone 2. The two metal heating wires 11 are evenly distributed on the exhaust pipe sleeve. The exhaust pipe sleeve 10 made of ceramic material is selected for two considerations. On the one hand, it is easier to make the groove 16 and the barrier strip 17 on the outer wall of the exhaust pipe sleeve 10 made of ceramic material; on the other hand, the heat transfer coefficient of the ceramic material is good and the manufacturing cost is low. Turn on the power of the controller 9 and set the heating temperature (the temperature set here is 0°C). The heating power will be transmitted to the line integration box 14 through the cable 15 to heat the metal heating wires 11 in the first heating zone 2, and then the heat will be evenly transferred to the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment through the exhaust pipe sleeve 10 made of ceramic material, so that the ejected low-temperature gaseous nitrogen is heat-treated and then discharged to the outside. A first temperature-measuring thermocouple 20 is installed in the first transition zone 3, and the first temperature-measuring thermocouple 20 is directly opposite to the orifice of the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment to measure the temperature of the heated low-temperature gaseous nitrogen flowing out of the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. Its temperature is 0°C ± 1°C, which is directly fed back to the controller 9, as Figure 4As shown. If the temperature is lower than -1°C, the controller 9 will increase the power and deliver a greater power to the metal heating wire 11 to ensure that the low-temperature gaseous nitrogen discharged from the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment can reach about 0°C. Then, the heated low-temperature gaseous nitrogen flowing out of the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment passes through the first transition zone 3 and enters the second heating zone 4. The second heating zone 4 contains a honeycomb heating tube group 12, a cylindrical heating long tube 18, and a heating patch 19. The honeycomb heating tube group 12 is composed of multiple cylindrical heating long tubes 18 combined together, and the tube diameter of each cylindrical heating long tube 18 is the same, and it is 1 / 5 of the tube diameter of the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. This is to divide the large agglomerated low-temperature gaseous nitrogen flowing out of the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment into many small agglomerates in the second heating zone 4 and heat them separately, making it easier for the low-temperature gaseous nitrogen to be heated to the target temperature, such as Figure 3 As shown. The temperature of 20°C set by the controller 9 is used to heat the heating patch 19 on the honeycomb heating tube group 12, conduct the heat to the cylindrical heating long tube 18, and heat the low-temperature gaseous nitrogen flowing through the inside of the cylindrical heating long tube 18. Of course, the material of the cylindrical heating long tube 18 is also a ceramic material because the heat transfer coefficient of the ceramic material is better, the heat distribution is more uniform, and the manufacturing cost is lower. A second temperature measuring thermocouple 21 is provided in the second transition zone 5, and the second temperature measuring thermocouple 21 is placed directly below the second heating zone 4, as Figure 5 As shown. After being processed by the honeycomb heating tube group 12, the measured temperature of the flowing out low-temperature gaseous nitrogen is 20°C ± 1°C, and this data will be directly fed back to the controller 9. Similarly, if the measured temperature of the low-temperature gaseous nitrogen is lower than 19°C, the controller 9 will make adjustments and output a greater power to ensure that the temperature of the heated low-temperature gaseous nitrogen is stable at 20°C ± 1°C. Immediately afterwards, after the heat treatment in the first heating zone 2 and the second heating zone 4, the low-temperature gaseous nitrogen enters the third heating zone 6. The third heating zone 6 consists of a metal heating wire mesh group 13 and a third temperature measuring thermocouple 24, as Figure 7 As shown. The metal heating wire mesh group 13 is composed of a first metal heating wire mesh 22 and a second metal heating wire mesh 23 with two different aperture sizes, as Figure 6a and Figure 6bAs shown in the figure. The aperture size of the first metal heating wire mesh 22 is 1 cm × 1 cm, and the aperture size of the second metal heating wire mesh 23 is 0.5 cm × 0.5 cm. The arrangement order is the first metal heating wire mesh 22 first, followed by the second metal heating wire mesh 23, and finally the third temperature-measuring thermocouple 24. The distance between the first metal heating wire mesh 22 and the second metal heating wire mesh 23 is 4 - 6 cm. The third temperature-measuring thermocouple 24 is far from the second metal heating wire mesh 23 and closer to the soundproof cover 7. On the one hand, the two metal heating wire meshes will not touch each other and affect the use; on the other hand, after the low-temperature gaseous nitrogen flows through the first metal heating wire mesh 22, it can still be affected by the remaining heat emitted by the first metal heating wire mesh 22, increasing the heating time. After the low-temperature gaseous nitrogen enters the third heating zone 6, it is divided into smaller agglomerates again, making the heating of the low-temperature gaseous nitrogen more uniform. When the low-temperature gaseous nitrogen flows through the second metal heating wire mesh 23, since its aperture is already very small, it can be considered that the low-temperature gaseous nitrogen has been fully heated, and the low-temperature gaseous nitrogen in the small agglomerates is heated very evenly. The reduction of the aperture from the first metal heating wire mesh 22 to the second metal heating wire mesh 23 is to better and more fully heat the low-temperature gaseous nitrogen to 40°C ± 1°C. Of course, the low-temperature gaseous nitrogen ejected from the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment has a certain impact force and is likely to damage the second metal heating wire mesh 23. However, through the stroke buffering of the first transition zone 3, the second heating zone 4, and the second transition zone 5, and the division of the low-temperature gaseous nitrogen into small pieces by the honeycomb heating tube group 12 in the second heating zone 4, the impact force of the low-temperature gaseous nitrogen is further weakened, thereby extending the service life of the second metal heating wire mesh 23. The temperature of the low-temperature gaseous nitrogen is measured by the third temperature-measuring thermocouple 24 to be 40°C and fed back to the controller 9. Similarly, if the temperature is lower than 39°C, the controller 9 will make adjustments to ensure that the low-temperature gaseous nitrogen processed by the third heating zone 6 is about 40°C. The low-temperature gaseous nitrogen heated to about 40°C is discharged to the outside through the soundproof cover 7. The outlet of the soundproof cover 7 is twice as large as the inlet to reduce the generation of noise. Changing from a small pipe diameter to a large pipe diameter effectively reduces the noise generated by the flow of low-temperature gaseous nitrogen; at the same time, sound-absorbing cotton 25 is attached to the inner wall of the soundproof cover 7, which can also well eliminate noise, such as Figure 8 As shown in the figure. In order to better heat the low-temperature gaseous nitrogen and prevent heat loss and waste, a heat-insulating jacket 28 is put on the outside of the heating device of the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment, such as Figure 10 As shown in the figure. The heat-insulating jacket 28 is composed of aluminum foil 29, flame-retardant cotton 30, heat-insulating cotton 31, and waterproof cloth 32, such as Figure 11Since this device is placed outdoors for a long time and is exposed to wind, rain, and intense sunlight, it is extremely prone to rust and aging. Therefore, the thermal insulation jacket on the exhaust pipe heating device of the liquid nitrogen circulation system of the molecular beam epitaxy equipment must be waterproof and fireproof, which can extend its service life. In addition, the thermal insulation layer composed of multiple layers of aluminum foil can, on the one hand, reflect the heat dissipated back by the aluminum foil and reheat the area where it is located; on the other hand, the low price of aluminum foil can further reduce its cost.

[0032] As Figure 9 shown, if too much liquid nitrogen flows into the molecular beam epitaxy equipment system due to a malfunction and cannot be completely vaporized, it will directly flow out from the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. Since the temperature of liquid nitrogen is extremely low, below -180°C, after passing through the first heating zone 2 and the second heating zone 4, not all of the liquid nitrogen can be vaporized into low-temperature gaseous nitrogen at 20°C, and part of it will directly flow into the liquid nitrogen storage container 8. The liquid nitrogen storage container 8 is made of stainless steel with a vacuum interlayer. In this way, the liquid nitrogen flowing into the liquid nitrogen storage container 8 is blocked by the vacuum interlayer (heat cannot be conducted in a vacuum), and the outer wall of the liquid nitrogen storage container 8 cannot form a temperature difference with the atmospheric temperature to absorb water molecules in the atmosphere, thus freezing the liquid nitrogen storage container 8. There are two parts in the liquid nitrogen storage container 8, namely a metal heating plate 26 and a liquid nitrogen level gauge 27. The liquid nitrogen level gauge 27 is installed 0.2 - 0.3 cm above the metal heating plate 26, that is, the float in the liquid nitrogen level gauge 27 hangs inside the liquid nitrogen storage container 8 and is higher than the metal heating plate 26, with a distance of 0.2 - 0.3 cm. Generally, the metal heating plate 26 is controlled by the controller 9 and will keep the metal heating plate 26 at about 30°C. In this way, the waste heat dissipated by the heated metal heating plate 26 can also affect the low-temperature gaseous nitrogen heat-treated in the second heating zone 4 and more easily raise the low-temperature gaseous nitrogen above 20°C. If the liquid nitrogen flowing into the liquid nitrogen storage container 8 is lower than the detection position of the liquid nitrogen level gauge 27 (that is, the flowing liquid nitrogen has not floated the float), then the heated metal heating plate 26 can well handle the small amount of liquid nitrogen flowing in (heating and vaporizing it into low-temperature gaseous nitrogen). If the liquid nitrogen flowing into the liquid nitrogen storage container 8 is higher than the detection position of the liquid nitrogen level gauge 27, that is, the float touches the liquid nitrogen and floats upward, which is detected by the liquid nitrogen level gauge 27, its signal will be transmitted to the controller 9, and the controller 9 will heat the metal heating plate 26 to 200°C to heat the liquid nitrogen below -180°C flowing into the liquid nitrogen storage container 8 to low-temperature gaseous nitrogen at about 20°C, and then pass through the third heating zone 6 and be discharged outdoors. Of course, after the liquid nitrogen level gauge 27 detects the liquid nitrogen, it will feedback to the controller 9, and the controller 9 will issue an alarm.

[0033] Since the low-temperature gaseous nitrogen discharged outdoors has been heated to about 40°C after heat treatment in the first heating zone 2, the second heating zone 4, and the third heating zone 6, which is higher than the atmospheric temperature (generally 25°C), it will not adsorb water molecules in the atmosphere. Therefore, it will not form a visual blind area caused by a nitrogen-water mixed fog mass, which endangers the safety of pedestrians. Moreover, the temperature of the ejected low-temperature gaseous nitrogen is high after heating, and it will not form ice slag in the exhaust pipe 1 of the liquid nitrogen circulation system of the molecular beam epitaxy equipment, hindering the circulation of liquid nitrogen in the molecular beam epitaxy equipment system. At the same time, this device can also reduce noise interference.

[0034] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those of ordinary skill in the art to understand the content of the present invention and implement it. However, the protection scope of the present invention cannot be limited thereby. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A heating device for the exhaust pipe of a liquid nitrogen circulation system of a molecular beam epitaxy device, characterized in that, Including the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment, the first heating zone, the first transition zone, the second heating zone, the second transition zone, the third heating zone, the silencer cover, the liquid nitrogen storage container, the controller, the exhaust pipe sleeve, the metal heating wire, the honeycomb heating tube group, the metal heating wire mesh group, the circuit integration box, the cable, the groove, the barrier strip, the cylindrical heating long tube, the heating patch; The exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment is wrapped by the first heating zone. Inside the first heating zone, there are an exhaust pipe sleeve, a metal heating wire, a groove, and a barrier strip. The groove is engraved on the outer wall of the exhaust pipe sleeve, and the barrier strip is arranged in the middle of the groove. Two metal heating wires are placed in the groove on the outer wall of the exhaust pipe sleeve, separated by the barrier strip, and the two metal heating wires do not entangle with each other and are evenly wound on the exhaust pipe sleeve. The exhaust pipe sleeve is tightly sleeved on the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. The material of the exhaust pipe sleeve is ceramic material. The first heating zone is connected to the first transition zone, and the first transition zone is connected to the second heating zone. Inside the second heating zone, there are a honeycomb heating tube group, a cylindrical heating long tube, and a heating patch. The honeycomb heating tube group is composed of multiple cylindrical heating long tubes, and the material of the cylindrical heating long tube is ceramic material. The pipe orifice diameter of the cylindrical heating long tube is 1 / 5 smaller than the pipe orifice diameter of the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. The honeycomb heating tube group is wrapped by the heating patch. The second heating zone is connected to the second transition zone, and the second transition zone is connected to the third heating zone, the liquid nitrogen storage container, and the circuit integration box. Inside the third heating zone, there is the metal heating wire mesh group. Inside the circuit integration box, there are the heating wire groups of the first heating zone, the heating wire groups of the second heating zone, and the heating wire groups of the third heating zone. The circuit integration box is connected to the controller through the cable. The third heating zone is connected to the silencer cover.

2. The exhaust pipe heating device of the liquid nitrogen circulation system of the molecular beam epitaxy equipment according to claim 1, characterized in that, Inside the first transition zone, there is a first temperature measuring thermocouple, which is placed facing the pipe orifice of the exhaust pipe of the liquid nitrogen circulation system of the molecular beam epitaxy equipment. The communication wire of the first temperature measuring thermocouple is connected to the circuit integration box.

3. The exhaust pipe heating device of the liquid nitrogen circulation system of the molecular beam epitaxy equipment according to claim 1, characterized in that, Inside the second transition zone, there is a second temperature measuring thermocouple, which is arranged directly below the second heating zone. The communication wire of the second temperature measuring thermocouple is connected to the circuit integration box.

4. The exhaust pipe heating device of the liquid nitrogen circulation system of the molecular beam epitaxy equipment according to claim 1, characterized in that A metal heating wire mesh group and a third temperature measuring thermocouple are provided in the third heating zone. The metal heating wire mesh group is composed of a first metal heating wire mesh and a second metal heating wire mesh with different pore sizes. The pore size of the first metal heating wire mesh is larger, which is 1 cm × 1 cm, and it is placed in front of the second metal heating wire mesh. The pore size of the second metal heating wire mesh is smaller, which is 0.5 cm × 0.5 cm. The first metal heating wire mesh is 4 - 6 cm away from the second metal heating wire mesh. The third temperature measuring thermocouple is placed directly behind the second metal heating wire mesh, and the communication wire of the third temperature measuring thermocouple is connected to the line integration box.

5. The exhaust pipe heating device of the liquid nitrogen circulation system of the molecular beam epitaxy equipment according to claim 1, characterized in that, The diameter of the air inlet of the muffler is twice as large as the diameter of the air outlet. Sound-absorbing cotton is provided inside the muffler, and the sound-absorbing cotton is closely attached to the inner wall of the muffler.

6. The exhaust pipe heating device of the liquid nitrogen circulation system of the molecular beam epitaxy equipment according to claim 1, characterized in that A metal heating plate and a liquid nitrogen level gauge are provided inside the liquid nitrogen storage container. The metal heating plate is placed at the bottom of the liquid nitrogen storage container, and the control wire of the metal heating plate is connected into the line integration box. The liquid nitrogen level gauge is installed above the metal heating plate, and the height from the metal heating plate is 0.2 - 0.3 cm.

7. The exhaust pipe heating device of the liquid nitrogen circulation system of the molecular beam epitaxy equipment according to claim 1, characterized in that, Heat-insulating clothes are provided on the outer surfaces of the first heating zone, the first transition zone, the second heating zone, the second transition zone, the third heating zone, the muffler, and the liquid nitrogen storage container. The heat-insulating clothes wrap the first heating zone, the first transition zone, the second heating zone, the second transition zone, the third heating zone, the muffler, and the liquid nitrogen storage container, and the heat-insulating clothes are made of aluminum foil, flame-retardant cotton, heat-insulating cotton, and waterproof cloth.

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