System and method for measuring content of metal lithium powder in fusion device

Abstract

The invention discloses a system and a method for measuring the content of metal lithium powder in a fusion device. The system comprises metal lithium powder, a powder chamber, a vacuum chamber, a vacuum electrode feed-in flange, a normally-open microohm meter and a connecting wire. A closed loop is formed by the lithium powder and the normally-open microohm meter outside the vacuum chamber through the connecting wire inserted into the metal lithium powder, the content of the metal lithium powder is gradually reduced along with the use of the metal lithium powder in the fusion device, and when the height of the metal lithium powder in the powder cavity is lower than that of the connecting wire inserted into the powder, the metal lithium powder is separated from the metal lithium powder. The loop is changed from a closed state to an open state, the normally open microohmmeter shows that the resistance is infinite, the lithium powder in the powder chamber is used up, the problem that the content of the metal lithium powder in a fusion device powder system cannot be monitored in real time is solved, and the requirement for controlling boundary particles of the metal lithium powder in the plasma discharging process of the fusion device is met.

Description

Technical Field

[0001] The invention relates to the application field of low atomic number metal material lithium powder in fusion devices, and mainly to a system and method for measuring the content of metal lithium powder in a fusion device. Background Art

[0002] Magnetic confinement controlled nuclear fusion is one of the important ways to solve the energy problem of mankind. As the heating power and discharge time of the fusion device increase, the interaction between the plasma and the surface of the first wall material of the vacuum chamber in the device becomes stronger and stronger. The resulting impurities and wall material damage seriously threaten the safe operation of the fusion device. Real-time injection of low atomic number (low Z) lithium metal powder in high-temperature plasma discharge can effectively alleviate the strong interaction between the plasma and the first wall, realize real-time first wall surface treatment, and help reduce the impurity level in the plasma. At the same time, it can reduce the heat flux bombarding the first wall material and effectively protect the first wall material. Therefore, the real-time injection of low-Z materials can provide a new scientific means for the development of magnetic confinement fusion, which has great application prospects and is increasingly valued by the fusion community.

[0003] At present, low-Z material real-time injection systems have been developed in mainstream fusion devices at home and abroad. For example, EAST, DIII-D and LHD have developed real-time lithium powder injection technology in plasma discharge, which effectively alleviates the strong interaction between plasma and wall and promotes the further improvement of plasma performance. The domestic all-superconducting tokamak EAST device uses real-time continuous injection of metal lithium powder in long pulse discharge to successfully obtain steady-state high-temperature plasma discharge with a core temperature of more than 70 million degrees in the thousands of seconds. The low-Z metal lithium powder real-time injection system uses a piezoelectric ceramic to receive a sinusoidal voltage of a specific frequency to produce a resonance effect, thereby driving the metal lithium powder on the piezoelectric ceramic to fall freely into the plasma. Lithium powder is an alkaline metal with extremely strong physical and chemical activity. It is very easy to oxidize and there is a risk of spontaneous combustion in humid air. Therefore, lithium powder needs to be used in a vacuum environment. High-purity metal lithium powder is silver-gray in color. When stored in a closed ultra-high vacuum stainless steel chamber, it is difficult to observe with the naked eye, especially in a compact lithium powder injector. The glass observation window is only 16mm in size, which makes observation more difficult. In addition, during the discharge of the fusion device, the staff cannot observe the lithium powder content in the injector on site. Therefore, it is urgent to develop a structure to measure the content of metallic lithium powder to achieve remote monitoring of the lithium powder content in the injector and provide protection for the lithium powder injection experiment in the plasma discharge of the fusion device. Summary of the invention

[0004] The purpose of the present invention is to provide a system and method for measuring the residual content of lithium powder in a metal lithium powder system in a fusion device, so as to meet the demand for real-time monitoring of the content of metal lithium powder and provide hardware guarantee for the stable injection of metal lithium powder in tokamak long pulse plasma discharge.

[0005] The present invention is achieved through the following technical solutions: A system for measuring the content of metallic lithium powder in a fusion device, comprising a powder chamber, a vacuum chamber and a measuring circuit; The powder chamber is arranged in the vacuum chamber, and the powder chamber is loaded with metal lithium powder. A ring-shaped piezoelectric ceramic resonance piece with a through hole is arranged at the bottom of the powder chamber, which is used to control the vibration of the metal lithium powder and realize the falling of the metal lithium powder. A calibration line is arranged at a distance (about 0.5-1 cm) from the bottom of the powder chamber; The side wall of the vacuum chamber is provided with a vacuum electrode feeding flange for passing the wire; The measuring circuit comprises a connecting wire a, a connecting wire b, a connecting wire c, a connecting wire d and a normally open micro-ohmmeter which are connected to form a loop; one end of the connecting wire a hangs down to the calibration line of the powder chamber, and the other end is connected to the connecting wire c at the vacuum electrode feeding flange; one end of the connecting wire b is connected to the outer wall of the powder chamber, and the other end is connected to the connecting wire d at the vacuum electrode feeding flange; one end of the connecting wire c is connected to the connecting wire a at the vacuum electrode feeding flange, and the other end is connected to the normally open micro-ohmmeter; one end of the connecting wire d is connected to the connecting wire b at the vacuum electrode feeding flange, and the other end is connected to the normally open micro-ohmmeter.

[0006] Furthermore, the purity of the metallic lithium powder is >99.9%, the powder diameter is ~44 μm, and the density is 0.353 g / cm 3 , melting point 180.5℃, its resistivity is 8.6 μΩ·cm. Using the conductive properties of metal lithium powder itself, a connected circuit is constructed. When the metal lithium powder is consumed to the calibration line position, the circuit is disconnected.

[0007] Furthermore, the powder chamber is a stainless steel chamber for loading metallic lithium powder, which is a cylindrical chamber with a diameter of 73 mm and a height of 80 mm. Four circular holes with a diameter of 16 mm are evenly arranged in a circumferential direction on the top of the chamber for loading metallic lithium powder into the chamber.

[0008] Furthermore, the vacuum chamber is a cylindrical chamber with a diameter of 100 mm and a height of 150 mm. Two glass observation windows with a diameter of 16 mm are installed on the top of the chamber for observing the state of the powder.

[0009] Furthermore, a vacuum pumping port with a diameter of 16 mm is opened on the side wall of the chamber to realize vacuum pumping.

[0010] Furthermore, the vacuum electrode feed flange is a knife-edge sealing flange with a diameter of 35 mm and a leakage rate of <1.0×10 -10 Pa·m 3 / s, meeting the ultra-high vacuum requirements of the vacuum chamber.

[0011] Furthermore, the normally open micro-ohmmeter has a measurement accuracy of 0.1 μΩ and a measurement range of 0-1 mΩ.

[0012] A method for measuring the content of metallic lithium powder in a fusion device is as follows: utilizing the conductive property of metallic lithium powder itself to form a connected circuit among the metallic lithium powder, a powder chamber and a normally open micro-ohmmeter located outside a vacuum chamber; when the metallic lithium powder is consumed to a calibration line position, the circuit is disconnected; and the resistance value on the normally open micro-ohmmeter located outside the vacuum chamber is used to determine whether the content of metallic lithium powder in the powder chamber has dropped to a calibration position.

[0013] Beneficial effects: The present invention provides a simple, economical and effective measurement system for measuring the content of metallic lithium powder in a vacuum powder chamber, which can effectively determine the content of metallic lithium powder in the vacuum powder chamber, provide a stable and reliable powder monitoring system for the real-time injection of metallic lithium powder in a fusion device, and solve the problem that it is difficult to monitor the content of metallic lithium powder in a vacuum chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the present invention.

[0015] In the figure, 1 is metallic lithium powder; 2 is a powder chamber; 3 is a vacuum chamber; 4 is a connecting line a; 5 is a connecting line b; 6 is a vacuum electrode feeding flange; 7 is a connecting line c; 8 is a connecting line d; and 9 is a normally open micro-ohmmeter. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] Example like Figure 1As shown, a system for measuring the content of metallic lithium powder in a fusion device includes metallic lithium powder 1 to be measured, a powder chamber 2 for loading metallic lithium powder, a vacuum chamber 3 for evacuating a vacuum, a connecting line a4, a connecting line b5, a vacuum electrode feeding flange 6 for line connection and vacuum sealing, a connecting line c7, a connecting line d8 and a normally open micro-ohmmeter 9.

[0018] The purity of the metal lithium powder 1 is >99.9%, the diameter of the lithium powder is ~44 μm, and the density is 0.353 g / cm 3 , melting point 180.5℃, its resistivity is 8.6 μΩ·cm. Using the conductive properties of metal lithium powder itself, a connected circuit is constructed. When the metal lithium powder is consumed to the calibrated position, the circuit is disconnected.

[0019] The powder chamber 2 is a stainless steel chamber for loading metal lithium powder. It is a cylindrical chamber with a diameter of 73 mm and a height of 80 mm. Four circular holes with a diameter of 16 mm are evenly arranged in a circular pattern on the top of the chamber for loading metal lithium powder into the chamber. A ring-shaped piezoelectric ceramic resonance piece with a 2.5 mm through hole in the center is installed at the bottom of the chamber to control the vibration of the powder and achieve powder falling.

[0020] The vacuum chamber 3 is a cylindrical chamber with a diameter of 100 mm and a height of 150 mm. Two glass observation windows with a diameter of 16 mm are installed on the top of the chamber for observing the powder state. A vacuum exhaust port with a diameter of 16 mm and a vacuum electrode feed port flange with a diameter of 35 mm are opened on the side wall of the chamber to realize vacuum exhaust and powder signal control.

[0021] The connecting wire a4 is a vacuum-specific copper wire, one end of which is directly inserted into the lower cut-off position of the metal lithium powder 1 , and the other end is connected to the vacuum side electrode of the vacuum electrode feeding flange 6 .

[0022] The connecting wire b5 is also made of vacuum-specific copper wire, one end of which is welded to the outside of the stainless steel powder chamber 2, and the other end is connected to the vacuum side electrode of the vacuum electrode feed flange 6.

[0023] The vacuum electrode feed flange is a knife-edge sealing flange with a diameter of 35 mm and a leakage rate of <1.0×10 -10 Pa·m 3 / s, meeting the ultra-high vacuum requirements of the vacuum chamber. There are two electrodes penetrating the vacuum electrode feed flange 6 to achieve the powder circuit measurement signal output.

[0024] The normally open micro-ohmmeter has a measurement accuracy of 0.1 μΩ and a range of 0-1 mΩ. It is connected to the measurement circuit in the vacuum chamber through a connecting wire and an electrode flange. The resistance value on the normally open micro-ohmmeter is used to determine whether the metal lithium powder content in the powder chamber has dropped to the calibrated position.

[0025] The present invention does not elaborate on some of the common technologies of those skilled in the art. The above-described embodiments are only descriptions of preferred implementations of the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementations described. Without departing from the design spirit of the present invention, various modifications and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A system for measuring the content of metallic lithium powder in a fusion device, characterized in that: It includes a powder chamber, a vacuum chamber and a measuring circuit; The powder chamber is arranged in the vacuum chamber, and the powder chamber is loaded with metal lithium powder. A ring-shaped piezoelectric ceramic resonance piece with a through hole is arranged at the bottom of the powder chamber, which is used to control the vibration of the metal lithium powder and realize the falling of the metal lithium powder. A calibration line is arranged at a distance from the bottom of the powder chamber; The side wall of the vacuum chamber is provided with a vacuum electrode feeding flange for passing the wire; The measuring circuit comprises a connecting wire a, a connecting wire b, a connecting wire c, a connecting wire d and a normally open micro-ohmmeter which are connected to form a loop; one end of the connecting wire a hangs down to the calibration line of the powder chamber, and the other end is connected to the connecting wire c at the vacuum electrode feeding flange; one end of the connecting wire b is connected to the outer wall of the powder chamber, and the other end is connected to the connecting wire d at the vacuum electrode feeding flange; one end of the connecting wire c is connected to the connecting wire a at the vacuum electrode feeding flange, and the other end is connected to the normally open micro-ohmmeter; one end of the connecting wire d is connected to the connecting wire b at the vacuum electrode feeding flange, and the other end is connected to the normally open micro-ohmmeter.

2. A system for measuring the content of metallic lithium powder in a fusion device according to claim 1, characterized in that: The purity of the metallic lithium powder is >99.9%, the powder diameter is ~44μm, and the density is 0.353 g / cm 3 , melting point 180.5℃, its resistivity is 8.6 μΩ·cm.

3. A system for measuring the content of metallic lithium powder in a fusion device according to claim 1, characterized in that: The powder chamber is a stainless steel chamber for loading metallic lithium powder, which is a cylindrical chamber with a diameter of 73 mm and a height of 80 mm. Four circular holes with a diameter of 16 mm are evenly arranged in a circumferential direction on the top of the chamber for loading metallic lithium powder into the chamber.

4. A system for measuring the content of metallic lithium powder in a fusion device according to claim 1, characterized in that: The vacuum chamber is a cylindrical chamber with a diameter of 100 mm and a height of 150 mm. Two glass observation windows with a diameter of 16 mm are installed on the top of the chamber for observing the state of the metallic lithium powder.

5. A system for measuring the content of metallic lithium powder in a fusion device according to claim 1, characterized in that: A vacuum pumping port with a diameter of 16 mm is opened on the side wall of the chamber to achieve vacuum pumping.

6. A system for measuring the content of metallic lithium powder in a fusion device according to claim 1, characterized in that: The vacuum electrode feed flange is a knife-edge sealing flange with a diameter of 35 mm and a leakage rate of <1.0×10 -10 Pa·m 3 / s.

7. A system for measuring the content of metallic lithium powder in a fusion device according to claim 1, characterized in that: The normally open micro-ohmmeter has a measurement accuracy of 0.1 μΩ and a measurement range of 0-1 mΩ.

8. A method for measuring the content of metallic lithium powder in a fusion device, characterized in that: By utilizing the conductive properties of the metallic lithium powder itself, a connected circuit is formed among the metallic lithium powder, the powder chamber and a normally open micro-ohmmeter located outside the vacuum chamber. When the metallic lithium powder is consumed to the calibration line position, the circuit is disconnected, and the resistance value on the normally open micro-ohmmeter located outside the vacuum chamber is used to determine whether the metallic lithium powder content in the powder chamber has dropped to the calibration position.

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