Surface thermocouple system suitable for active water-cooling all-tungsten divertor of magnetic confinement device

Abstract

The invention discloses a surface thermocouple system suitable for an active water-cooling all-tungsten divertor of a magnetic confinement device, which relates to the field of plasma diagnosis of the magnetic confinement device and comprises a box-shaped supporting structure and a thermocouple assembly. Tungsten copper string pipes of the divertor are fixedly connected with the box-shaped supporting structure through fixing pins, and the thermocouple assembly is composed of a thermocouple probe, a pyrolytic graphite shell, a base, a screw, a nut, a spring washer, a fixing supporting plate and a lead and installed in cylindrical through holes between the adjacent tungsten copper string pipes and gaps between the tungsten copper string pipes and the box-shaped supporting structure. According to the invention, the surface thermocouple can be normally disassembled and maintained, and a direct means is provided for measuring the surface temperature of the active water-cooled all-tungsten divertor target plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of magnetic confinement device plasma diagnosis, and in particular to a surface thermocouple system suitable for a main water-cooled full-tungsten divertor of a magnetic confinement device. BACKGROUND

[0002] A magnetic confinement device uses a special structure of magnetic field to confine a plasma in a vacuum vessel, uses an external neutral beam or a radio frequency wave to improve the temperature of the plasma, and uses a gas filling, an ultrasonic molecular beam or a projectile to improve the density of the plasma, so that the ion temperature, the density and the confinement time of the core plasma reach the ignition condition of fusion, and self-sustaining combustion is achieved, and energy is continuously outputted to the outside. The magnetic confinement device is considered to be an effective way to utilize fusion energy for peaceful purposes. The magnetic confinement fusion energy is a clean energy, and the raw material is abundant in nature, which is a feasible way to solve the future energy problem of human beings. The magnetic confinement device includes a tokamak, a stellarator, a magnetic mirror and a pinch fusion device. At present, the tokamak and the stellarator are considered to be the two devices most likely to achieve controlled thermonuclear fusion.

[0003] The divertor is one of the core components of the tokamak device, is a main area where the plasma directly contacts and interacts with the surface of a solid material, and has important functions of removing heat energy, particles and fusion products helium ash transported from the plasma, shielding impurities generated by the interaction between the plasma and the material, and avoiding impurity pollution of the core plasma. In the magnetic confinement fusion device, a huge amount of energy is transported from the plasma, most of which is deposited on the surface of the divertor target plate, which brings a very high heat load, may erode the target plate material, shorten the service life of the material, and produce a large amount of impurities to pollute the core plasma, so that the nuclear reaction condition is difficult to maintain stably. The measurement and control of the heat load on the surface of the divertor target plate are crucial for the safe operation of the magnetic confinement device. The divertor designs of major international tokamaks are different from each other. The divertor structure of the future fusion reactor ITER is a modular structure of a main water-cooled tungsten divertor based on a box-shaped support structure, and the EAST tokamak in China currently uses a similar divertor structure to ITER.

[0004] The traditional thermocouple is installed inside the divertor target plate. The temperature change on the surface of the target plate needs to penetrate the target plate material to be detected by the thermocouple, which results in that the traditional thermocouple has a long response time to the temperature change on the surface of the target plate and cannot measure the temperature on the surface of the target plate in real time. The surface thermocouple overcomes the shortcoming of the traditional thermocouple embedded in the target plate that has a slow response time. The surface thermocouple can directly face the plasma particle flow and heat flow for measurement and can work normally even under the condition of a high-energy transient heat pulse, which is due to the special welding technology adopted by the surface thermocouple. The special welding technology enables the hot junction of the surface thermocouple to have the function of being automatically renewed after being eroded by the plasma. In addition, the hot electrode of the surface thermocouple significantly reduces the volume, mass and heat capacity of the hot junction by adopting a strip film structure and a layered assembly technology, so that the surface thermocouple can respond more quickly to the change of the temperature and heat flow on the surface of the target plate. The diagnosis has been successfully applied to foreign tokamak devices, such as the C-Mod device and the DIII-D device in the United States, and can provide experimental data for the research on the surface heat load of the divertor target plate. However, the surface thermocouple on the C-Mod device in the United States adopts a non-standard molybdenum / tungsten rhenium as the hot electrode, and the installation structure of the thermocouple is relatively complex. There are multiple un-compensated hot junctions between the thermocouple probe and the wire, which affects the temperature measurement result. The divertor of the DIII-D device in the United States adopts a graphite tile, so it does not need to consider the problem of possible fusion welding between the protective shell material of the thermocouple and the target plate material under a very high temperature environment. Therefore, the surface thermocouple of the DIII-D device selects metal molybdenum as the protective shell material. Unlike the surface thermocouple system on the tokamak device abroad, the surface thermocouple system on the EAST tokamak device in China is installed on the active water-cooled full-tungsten divertor structure similar to the ITER fusion reactor. Under the extremely high temperature environment on the surface of the divertor target plate of the tokamak, the metal material on the surface of the divertor target plate may be fused and welded with the metal material of the protective shell of the thermocouple, which will cause the surface thermocouple to be unable to be normally disassembled and maintained. SUMMARY

[0005] To solve the above technical problems, the present application provides a surface thermocouple system suitable for a full-tungsten divertor of a magnetic confinement device, which uses pyrolytic graphite as a thermocouple protective shell material, thereby effectively avoiding the problem that the surface thermocouple cannot be normally disassembled and maintained. Meanwhile, in the vacuum environment inside the Tokamak device, the temperature resistance of the pyrolytic graphite is stronger than that of molybdenum metal, so that the thermocouple protective shell can withstand a higher temperature to protect the surface thermocouple probe. Since the surface thermocouple directly faces the plasma for measurement, the surface of the measurement end of the surface thermocouple may be affected by impurity sputtering under plasma bombardment, which affects the core plasma confinement performance. However, the low-charge-number carbon impurity has a smaller impact on the core plasma confinement performance than the high-charge-number molybdenum impurity. Therefore, the use of pyrolytic graphite as the thermocouple protective shell material can reduce the impact of impurity sputtering on the core plasma confinement performance. In addition, the EAST device uses a C-type standard tungsten-rhenium thermocouple and a dedicated compensation wire, thereby avoiding the appearance of a new thermal junction in the measurement loop that affects temperature measurement.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solution:

[0007] The surface thermocouple system suitable for a full-tungsten divertor of a magnetic confinement device comprises a box-shaped support structure and a thermocouple assembly. The box-shaped support structure fixedly supports tungsten-copper string tubes of the divertor. The thermocouple assembly comprises a thermocouple probe, a pyrolytic graphite shell, a base, a fixed support plate, a screw, a nut, a spring washer and a lead wire. The thermocouple probe is integrally packaged in the pyrolytic graphite shell, and the surface of the measurement end of the thermocouple probe is flush with the front end surface of the pyrolytic graphite shell. The lead wire is led out from the bottom end surface of the pyrolytic graphite shell. The base is located below the cylindrical through hole between adjacent tungsten-copper string tubes. After the thermocouple probe, the pyrolytic graphite shell and the base are assembled, they are inserted from the rear end of the cylindrical through hole between the tungsten-copper string tubes and connected with the screw. The screw passes through the fixed support plate, the spring washer and the nut, and is connected with the nut. The base is fixed on the fixed support plate by tightening the nut. The two ends of the fixed support plate are welded to the box-shaped support structure. The thermocouple probes of multiple thermocouple assemblies are distributed along the surface of the divertor target plate in the poloidal direction of the surface thermocouple system. The front end surface of the pyrolytic graphite shell is flush with the surface of the divertor target plate.

[0008] Further, the divertor target plate is composed of multiple groups of parallel tungsten-copper string tubes, wherein there are gaps between adjacent tungsten-copper string tubes, and the gaps are provided with cylindrical through holes.

[0009] Further, the rear half of the pyrolytic graphite shell is provided with external threads for connecting with the internal threads of the tubular extension of the base.

[0010] Further, the thermocouple probe is a C-type tungsten-rhenium thermocouple.

[0011] Further, the base is made of stainless steel material.

[0012] Further, the base is composed of a cuboid base and a cylindrical extension, and the base has an inner cavity, and the top and bottom of the base are respectively provided with an inner cavity opening.

[0013] Further, the bottom of the base is provided with a circular inner cavity opening, and two internal thread blind holes are opened on both sides of the circular inner cavity opening at the bottom of the base for screw connection with screws; the top of the base is provided with a tubular extension in communication with the inner cavity of the base, and the tubular extension extends into the cylindrical through hole between the adjacent tungsten-copper string tubes, and the lower end plane of the tubular extension is in close contact with the outer wall of the tungsten-copper string tube.

[0014] Further, the fixed support plate is made of stainless steel material, and three cylindrical through holes are processed on the fixed support plate.

[0015] Further, the lead wire is led out through the bottom end face of the pyrolytic graphite shell, passes through the inner cavity of the base, and is led out from the circular inner cavity opening at the bottom of the base.

[0016] Further, the surface thermocouple system suitable for the active water-cooled full-tungsten divertor of the magnetic confinement device is characterized in that the lead wire is a compensation lead wire of a C-type tungsten-rhenium thermocouple, and glass fiber insulation and stainless steel metal braid are used between the positive electrode and the negative electrode for shielding external interference signals.

[0017] Beneficial effects:

[0018] The surface thermocouple system of the present application makes full use of the narrow space on the full-tungsten divertor to complete the fixed installation of the surface thermocouple probe. Since the base is closely attached to the divertor target plate and the divertor target plate has water-cooled pipes inside, the heat deposited on the thermocouple probe during the discharge process can be taken away, so that the thermocouple system has the working ability under the condition of stable long-pulse discharge. The present application uses pyrolytic graphite material as a protective shell, which can work in a high-temperature environment, and the front surface of the protective shell is flush with the measurement end surface of the thermocouple probe, which can avoid the edge of the measurement end of the thermocouple probe from being directly bombarded by plasma, thereby increasing the service life of the thermocouple probe. The components are connected and fixed by threads, the installation method is simple and easy to operate, and the stability of the thermocouple probe installation is guaranteed, which can work stably under high-temperature conditions, and is convenient for disassembly or replacement of the thermocouple components during maintenance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a front view of the surface thermocouple system suitable for the active water-cooled full-tungsten divertor of the magnetic confinement device of the present application;

[0020] Figure 2A left side sectional view of a surface thermocouple system suitable for a full-tungsten divertor of a magnetic confinement device according to the present application;

[0021] Figure 3 A top view of a surface thermocouple system suitable for a full-tungsten divertor of a magnetic confinement device according to the present application;

[0022] Wherein, the reference signs are: 1 is a pyrolytic graphite shell, 2 is a thermocouple probe, 3 is a base, 4 is a tungsten-copper string tube, 5 is a fixing foot, 6 is a fixing seat, 7 is a box-shaped support structure, 8 is a fixing pin, 9 is a spring washer, 10 is a nut, 11 is a screw, 12 is a fixed support plate, and 13 is a lead wire. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0024] As shown in Figure 1 , Figure 2 and Figure 3 , the surface thermocouple system suitable for a full-tungsten divertor of a magnetic confinement device according to the present application comprises a tungsten-copper string tube 4 of the divertor, a box-shaped support structure 7 and a thermocouple assembly; in the poloidal direction of the surface thermocouple system, a plurality of thermocouple probes 2 of the thermocouple assembly are distributed along the surface of the divertor target plate; the fixing pin 8 passes through the pin hole in the sidewall of the fixing seat 6 on the outer wall of the box-shaped support structure 7 and the fixing foot 5 supporting the tungsten-copper string tube 4, so that the tungsten-copper string tube 4 of the divertor is fixedly connected with the box-shaped support structure 7, the fixing foot 5 is welded to the tungsten-copper string tube 4, and the fixing seat 6 is welded to the outer wall of the box-shaped support structure 7. The divertor target plate is composed of a plurality of parallel tungsten-copper string tubes 4, wherein there is a gap between two adjacent tungsten-copper string tubes 4 and a cylindrical through hole is processed.

[0025] The thermocouple assembly comprises a thermocouple probe 2, a pyrolytic graphite shell 1, a base 3, a fixed support plate 12, a screw 11, a nut 10, a spring washer 9 and a lead wire 13; the thermocouple probe 2 is integrally packaged and fixed in the pyrolytic graphite shell 1, so that the measuring end surface of the thermocouple probe 2 is flush with the front end surface of the pyrolytic graphite shell 1; the front end of the lead wire 13 is connected to the rear end of the thermocouple probe 2 and is led out through the bottom end surface of the pyrolytic graphite shell 1, the bottom through hole of the base 3 and the center through hole of the fixed support plate 12, and the rear end of the lead wire 13 is connected to a thermocouple acquisition system; the rear half of the pyrolytic graphite shell 1 is processed with external threads, is screw-connected with the internal threads of the cylindrical extension of the base 3, and can be adjusted by screwing the length to make the measuring end surface of the thermocouple probe 2 and the front end surface of the pyrolytic graphite shell 1 flush with the surface of the divertor target plate; after the thermocouple probe 2, the pyrolytic graphite shell 1, the lead wire 13 and the base 3 are assembled, they are inserted from the rear end of the cylindrical through hole between the divertor tungsten-copper string tubes 4, and the bottom of the base 3 is processed with threaded holes on both sides, which are screw-connected with the screw 11; the screw 11 passes through the through holes on both sides of the fixed support plate 12, the spring washer 9 and is screw-connected with the nut 10, so that the base 3 is fixedly connected with the fixed support plate 12 by tightening the nut 10, and the upper surface of the cuboid base of the base 3 is tightly attached to the lower surface of the tungsten-copper string tube 4; the both ends of the fixed support plate 12 are welded with the box-shaped support structure 7.

[0026] The installation of the divertor surface thermocouple system needs to ensure the installation accuracy of the surface thermocouple, that is, the measuring end surface of the thermocouple probe is flush with the surface of the divertor target plate, and at the same time, the firmness of the thermocouple probe installation and the detachable maintenance are ensured.

[0027] Preferably, the thermocouple probe 2 adopts a C-type tungsten-rhenium thermocouple (positive electrode: 95% tungsten + 5% rhenium, negative electrode: 74% tungsten + 26% rhenium), the upper limit of temperature measurement is about 2300 degrees Celsius, it can withstand the high temperature environment in the magnetic confinement device, the temperature measurement accuracy of the thermocouple probe 2 is 1% full scale, the frequency response is 50 kHz, and the thermal response time is about several milliseconds. The erosion-resistant probe is adopted, the hot junction has the function of automatic updating after being eroded, can directly face the plasma particle flow and heat flow for measurement, can quickly respond to the changes of the surface temperature and heat flow of the divertor target plate, and can normally work even under the condition of high-energy transient heat pulse.

[0028] The tungsten-rhenium hot electrode inside the thermocouple probe forms a hot junction through welding technology, which can automatically update to form a new hot junction after being eroded by plasma, so as to ensure the continuous and stable work of the thermocouple. In this way, the hot junction of the thermocouple can directly face the plasma for measurement, overcoming the slow response time of the traditional thermocouple embedded in the target plate. In addition, the tungsten-rhenium hot electrode inside the thermocouple probe adopts a strip film structure and a layered assembly technology, so that the volume and mass of the hot junction are very small, and its heat capacity can be almost ignored, which can further reduce the response time of the thermocouple.

[0029] Preferably, the pyrolytic graphite shell 1 encapsulates the thermocouple probe 2 as a whole, the front end surface of the pyrolytic graphite shell 1 is flush with the measuring end surface of the thermocouple probe 2, the rear half of the pyrolytic graphite shell 1 is processed with external threads, which is used for connecting with the internal threads of the tubular extension of the base 3, the pyrolytic graphite shell 1 is located in the cylindrical through hole between the tungsten-copper string tubes 4, and the front end surface of the pyrolytic graphite shell 1 is flush with the surface of the divertor target plate.

[0030] Preferably, the base 3 is made of stainless steel material and is located between the rear end of the divertor target plate and the box-shaped support structure 7, the outer contour of the base 3 is composed of a cuboid base and a cylindrical extension, the base 3 has an internal cavity, the top and bottom of the base 3 are respectively provided with internal cavity openings, the bottom of the base 3 is provided with a circular internal cavity opening, two internal thread blind holes are opened on both sides of the circular internal cavity opening at the bottom of the base 3, which are used for screwing connection with the screws 11; the top of the base 3 is provided with a tubular extension which is in communication with the internal cavity of the base 3, and the tubular extension extends into the cylindrical through hole between the tungsten-copper string tubes 4, the lower end plane of the tubular extension is in close contact with the outer wall of the tungsten-copper string tubes 4 of the divertor target plate, and the tubular extension at the top of the base 3 is processed with internal threads, which is used for screwing connection with the external threads of the rear half of the pyrolytic graphite shell 1.

[0031] Preferably, the fixed support plate 12 is made of stainless steel material and is welded and connected with the box-shaped support structure 7 at both ends, three cylindrical through holes are processed on the fixed support plate 12, the cylindrical through hole located at the center of the fixed support plate 12 is used for the lead wire 13 of the thermocouple to pass out of the internal cavity of the base 3, and the cylindrical through holes on both sides of the center position are used for the screws 11 to pass through the fixed support plate 12, the spring washer 9 and the nut 10, and are screwing connected with the internal thread blind holes at the bottom of the base 3, so as to fix the base 3 at the rear end of the divertor target plate, and the base 3 is fixed by tightening the nut 10. There is a gap between the screw 11 and the fixed support plate 12, which facilitates the fine adjustment of the position of the screw 11 and the base 3 before tightening the nut 10, so that the thermocouple probe 2 can be located at the center of the through hole between the tungsten-copper string tubes 4.

[0032] Preferably, the lead wire 13 is led out through the bottom end surface of the pyrolytic graphite shell 1 and passes out of the circular internal cavity opening at the bottom of the base 3 after passing through the internal cavity of the base 3, the lead wire 13 is a special compensation lead wire for C-type tungsten-rhenium thermocouples, which is composed of positive and negative cores, the positive and negative poles are insulated by glass fiber and wrapped with stainless steel woven mesh for shielding external interference signals.

[0033] Figure 1 、 Figure 2 and Figure 3 The polar direction represents the axial direction along the active water-cooled pipe in the tungsten-copper string tube 4, and the circumferential direction represents the direction perpendicular to the axial direction of the active water-cooled pipe in the tungsten-copper string tube 4 and parallel to the surface of the divertor target plate.

[0034] The surface thermocouple system of the present application is suitable for a magnetic confinement device active water-cooling full-tungsten divertor, and can measure temperature and heat flow of a divertor target plate surface, and provide experimental data for divertor target plate surface heat load related research.

[0035] The portions of the application not specifically set forth herein are considered to be part of the prior art. While the forgoing specification sets forth illustrative specific embodiments of the application it will be apparent to those of ordinary skill in the art that various changes can be made without departing from the spirit and scope of the application as defined in the appended claims. Accordingly, the disclosure of the present application is intended to be illustrative, but not limiting, of the scope of the application, which is set forth in the following claims.

Claims

1. A surface thermocouple system suitable for an active water-cooled all-tungsten divertor in a magnetically confined device, characterized in that, The system includes a box-shaped support structure and a thermocouple assembly. The box-shaped support structure secures the tungsten-copper tubes supporting the divertor. The thermocouple assembly includes a thermocouple probe, a pyrolytic graphite shell, a base, a fixing support plate, screws, nuts, spring washers, and leads. The thermocouple probe is entirely encapsulated within the pyrolytic graphite shell, with the measuring end surface of the probe flush with the front end surface of the pyrolytic graphite shell. The leads extend from the bottom end face of the pyrolytic graphite shell. The base is located below the cylindrical through-hole between adjacent tungsten-copper tubes. After the thermocouple probe, pyrolytic graphite shell, and base are assembled, they are inserted through the rear end of the cylindrical through hole between the tungsten copper tubes and screwed in. The screw passes through the fixed support plate, spring washer, and nut and is screwed in. The base is fixed to the fixed support plate by tightening the nut. The two ends of the fixed support plate are welded to the box-shaped support structure. The thermocouple probes of multiple thermocouple assemblies are distributed along the surface of the divertor target plate with the poles of the surface thermocouple system facing upwards. The front end surface of the pyrolytic graphite shell is flush with the surface of the divertor target plate.

2. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 1, characterized in that, The divertor target plate is composed of multiple sets of parallel tungsten copper tubes, with gaps between adjacent tungsten copper tubes and cylindrical through holes.

3. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 1, characterized in that, The rear half of the pyrolytic graphite shell is machined with external threads for connection with the internal threads of the tubular extension of the base.

4. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 1, characterized in that, The thermocouple probe is a type C tungsten-rhenium thermocouple.

5. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 1, characterized in that, The base is made of stainless steel.

6. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 1, characterized in that, The base consists of a cuboid base and a cylindrical extension. The base has an inner cavity, with openings at the top and bottom of the base.

7. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 6, characterized in that, The base has a circular inner cavity opening at its bottom, and two internally threaded blind holes are opened on both sides of the circular inner cavity opening at the bottom of the base for screwing in with screws; the top of the base has a tubular extension that communicates with the inner cavity of the base, and the tubular extension extends into the cylindrical through hole between adjacent tungsten copper tubes, with the lower end plane of the tubular extension closely attached to the outer wall of the tungsten copper tube.

8. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 1, characterized in that, The fixed support plate is made of stainless steel and has three cylindrical through holes machined on it.

9. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 6, characterized in that, The lead wire is led out through the bottom end face of the pyrolytic graphite shell, passes through the inner cavity of the base, and exits from the circular inner cavity opening at the bottom of the base.

10. The surface thermocouple system for an active water-cooled all-tungsten divertor in a magnetically confined device according to claim 4, characterized in that, The lead wire is a compensating wire for a type C tungsten-rhenium thermocouple. The positive and negative terminals are insulated with glass fiber and wrapped with a stainless steel braided mesh to shield external interference signals.

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