CN220475974U - Static probes and static probes - Google Patents

Abstract

The utility model discloses an electrostatic probe and an electrostatic probe, the electrostatic probe comprises: a first electrode (6) for measuring a levitation potential at a first location; a second electrode (7); a third electrode (8) and a second electrode (7) form a group of double probes; a fourth electrode (9) for measuring a floating potential at the second location, the first electrode (6) and the fourth electrode (9) together measuring electrostatic information of the plasma; the electrostatic probe further comprises a probe main body, wherein the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9) are arranged on the probe main body, and the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9) are arranged and designed into square shapes with equal intervals. The static probe is simple in structure and accurate in measurement result.

Description

Static probes and static probes

Technical field

The utility model relates to the field of plasma diagnosis technology, and in particular to an electrostatic probe and an electrostatic probe.

Background technique

Controlled nuclear fusion refers to a technology that fuses hydrogen elements to release energy for purposes such as power generation. Unlike currently commercially available fission-based nuclear energy technologies, the reaction products of controllable nuclear fusion are relatively environmentally friendly and do not produce a large amount of radioactive waste. However, it is not easy to achieve controllable nuclear fusion. Due to the strict requirements of reaction conditions, scientists have been working hard to find feasible methods. Among them, nuclear fusion research based on tokamak devices has always been in the leading position. In the past 20 years, a low-ring-diameter-ratio tokamak device, also called a spherical tokamak, has been rapidly developed. Compared with the conventional tokamak device, the low ring diameter tokamak device has a small ring diameter ratio, a thin central column, a simple device structure and low cost. The plasma it generates has the characteristics of a conventional tokamak in addition to In addition to its unique plasma characteristics, it also has the advantages of strong ring effect, large deformation, high elongation ratio, high beta, and large current.

The Nanchang Spherical Tokamak (NCST), which was built and successfully discharged in 2020, is a low-ring-ratio tokamak device designed to explore methods of plasma-initiated fusion compression. The large radius R=0.4m, the small radius a=0.24m, the toroidal magnetic field (TF) BT=0.36T, and the plasma current (Ip) can reach 100kA.

The electrostatic probe, also known as the Langmuir probe, is a solid probe widely used in low-temperature plasma and the boundary area of high-temperature plasma or in the divertor. The theoretical basis of electrostatic probe is plasma sheath theory. In particular, for tokamak devices, electrostatic probes are one of the most commonly used diagnostic tools to measure parameters such as density, temperature, velocity, and potential of the plasma. Due to the instability of plasma motion, electrostatic probes need to be used for real-time monitoring and control. Electrostatic probes are usually implemented by selecting a smaller metal ball or cylinder. The diameter of the ball generally ranges from a few millimeters to several centimeters. The probe places the probe near the plasma, and the potential on the probe surface will be affected by the plasma potential. When the plasma moves or changes, the potential on the probe surface also changes. By measuring the potential changes on the surface of the ball, the relevant parameters of the plasma can be obtained.

As a commonly used diagnostic tool, the electrostatic probe on the tokamak device has the following functions and significance:

1. Measure plasma parameters: Parameters such as plasma density, temperature, speed and potential are very important information for plasma research and control. Electrostatic probes can use changes in plasma potential and charge to measure these parameters, providing important parameters for the study of plasma physics.

2. Monitor the stability of plasma: Plasma motion is unstable, and phenomena such as eddy currents, oscillations and irregular movements often occur. The electrostatic probe can monitor the movement of plasma in real time to ensure the stability of the plasma.

3. Auxiliary device control: The electrostatic probe can reflect the state changes of the plasma. By controlling parameters such as plasma discharge, heating and boundary conditions, the control and regulation of the plasma can be achieved.

In the process of implementing the technical solutions of the embodiments of the present application, the inventor of the present application at least discovered that there are the following technical problems in the prior art:

Electrostatic probes generally consist of multiple electrodes placed around the plasma. Its main structure is as follows: 1. Electrode: an exposed wire, connected to the energized instrument at the back end; 2. Shell: an insulator material wrapped around the wire to support the conductor. The working principle of electrostatic probes is based on the charge collection effect. When the electrode of the electrostatic probe enters the plasma, the ions and electrons in the plasma will be adsorbed to the electrode surface, and the potential of the electrode will change accordingly. Through this change, the electrostatic parameter information of the plasma can be obtained.

Currently, existing electrostatic probes have multi-step probes and three-probe structures. The multi-step probe can measure plasma parameters at multiple points, as shown in Figure 1, but the structure is relatively complex. Due to the single electrode used to measure the suspension potential of the three-probe, there is a certain error in the measurement results.

In summary, existing electrostatic probes have technical problems such as complex structures and inaccurate measurements.

Utility model content

Embodiments of the present application provide an electrostatic probe and an electrostatic probe, which solve the technical problems of complex structure and inaccurate measurement of existing electrostatic probes.

An embodiment of the present application provides an electrostatic probe. The electrostatic probe includes: a first electrode (6), used to measure the suspension potential at a first position; a second electrode (7); a third electrode (8), and the The second electrode (7) constitutes a set of dual probes; the fourth electrode (9) is used to measure the suspension potential at the second position, and the first electrode (6) and the fourth electrode (9) jointly measure plasma Electrostatic information of the body; wherein, the electrostatic probe also includes a probe body, the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9 ) are arranged on the probe body, and the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9) are arranged and designed to have equal spacing. square.

Optionally, the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9) are specifically tungsten electrodes.

An embodiment of the present application also provides an electrostatic probe. The electrostatic probe includes: the electrostatic probe described in the previous embodiment; a CF250 flange, the electrostatic probe is arranged on the CF250 flange; and the KF150 flange, which is connected to the CF250 flange. The CF250 flange is connected with screws; the guide rail is connected with the KF150 flange with screws; the stepper motor is connected with the guide rail with screws.

Optionally, the electrostatic probe also includes: a connector; a support rod, which is provided on the CF250 flange, and the support rod is connected to the electrostatic probe through screws; a guide rod, which is provided on the KF150 flange. Connected to the support rod through the connector.

One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

In this application, the electrodes of the electrostatic probe are arranged in a square shape with equal spacing, and the structure is simple. The first electrode and the fourth electrode of the electrostatic probe of the present application can measure the floating potential at different positions, which can reduce the measurement error to a certain extent and make the measurement results accurate.

Existing electrostatic probes are not suitable for high-temperature plasma due to material limitations. Their electrodes and support structures may cause thermal expansion problems in high-temperature plasma environments, and may even cause the electrodes to melt. For example, a graphite probe will begin to soften at about 3000°C in a vacuum environment. However, the electrode of the electrostatic probe of this application uses a tungsten electrode, whose melting point reaches 3400°C, and the probe body uses a gallium nitride body, whose melting point is 1500°C. The temperature resistance of the electrostatic probe has been greatly improved.

The electrostatic probe in this application has a reserved KF150 flange window, and the electrostatic probe can be easily replaced through the connector according to subsequent experimental requirements, making the design more flexible.

Description of drawings

Figure 1 is a schematic structural diagram of a stepped probe in the prior art;

Figure 2 is a schematic structural diagram of an electrostatic probe in an embodiment of the present application;

Figure 3 is a cross-sectional view of an electrostatic probe in an embodiment of the present application;

Figure 4 is a schematic structural diagram of an electrostatic probe in an embodiment of the present application;

Figure 5 is a circuit diagram of an electrostatic probe in an embodiment of the present application.

Detailed ways

Embodiments of the present application provide an electrostatic probe and an electrostatic probe, which solve the technical problems of complex structure and inaccurate measurement of existing electrostatic probes.

The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model.

As shown in Figure 2, 1 is the electrostatic probe; part 2 is the CF250 flange; part 3 is the KF150 flange, which is used to observe the inside and facilitate the replacement of the head; part 4 is the guide rail with a stroke of 20cm; part 5 is the stepper motor , used to drive the movement of the electrostatic probe. The processing materials of the electrostatic probe except the electrostatic probe electrode are made of 304 stainless steel, the processing material of the electrode is tungsten, and the probe body is made of gallium nitride material (used for insulation between the electrode and its supporting material).

As shown in Figure 3, CF250 flange 2, KF150 flange 3, guide rail 4 and stepper motor 5 are connected with screws. The electrostatic probe 1 has M2 screws on the four corners to connect to the support rod. Component 10 is a connector, which is used to connect the support rod and the guide rod. The function of the connector is to facilitate the disassembly of the electrostatic probe.

As shown in Figure 4(c), 6, 7, 8 and 9 are the four electrodes of the electrostatic probe. The first electrode 6 and the fourth electrode 9 are used to measure the suspension potential at different positions; the second electrode 7 and the third electrode 8 form a set of dual probes, and measure the plasma together with the first electrode 6 and the fourth electrode 9 Electrostatic information, including plasma potential, electron density, electron temperature and other parameter information. The size of the four electrodes is shown in Figure 4(a) and Figure 4(b). Its shape is a cylinder, the bottom surface is a circle with a diameter of 1mm, and the length of the exposed part contacting the plasma is 2mm.

As shown in Figure 5, the dotted box is a representation of the plasma region, R1, R2 and R3 are resistors, and the power supply is used to apply a large enough voltage to the second electrode 7 and the third electrode 8. The hollow circle indicates that it is used to connect the downstream collector to facilitate data storage and subsequent data processing.

Data processing process:

First, the power supply is applied to a voltage large enough so that the current flowing through the second electrode 7 and the third electrode 8 is a saturated ion flow. The voltages of the four electrodes are:

Electron density:

where κ _B is Boltzmann’s constant.

Electronic temperature:

Among them, _ID is the current flowing through electrodes 7 and 8, _ID = (V ₁ -V ₂ )/2; α is generally 0.61; C _s is the ion sound speed, C _s = (κ _B T _e /m _i ) ^1/2 ; A _p is the collection area of the probe, and the design A _p =7.07mm ² .

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and variations of the present utility model fall within the scope of the claims of the present utility model and equivalent technologies, the present utility model is also intended to include these modifications and variations.

Claims (5)

1. An electrostatic probe, the electrostatic probe comprising:

a first electrode (6) for measuring a levitation potential at a first location;

a second electrode (7);

a third electrode (8) forming a set of double probes with the second electrode (7);

a fourth electrode (9) for measuring a levitation potential at a second location, the first electrode (6) and the fourth electrode (9) together measuring electrostatic information of the plasma;

the static probe further comprises a probe main body, wherein the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9) are arranged on the probe main body, and the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9) are arranged and designed into squares with equal intervals.

2. The electrostatic probe according to claim 1, characterized in that the first electrode (6), the second electrode (7), the third electrode (8) and the fourth electrode (9) are in particular tungsten electrodes.

3. An electrostatic probe according to claim 1, wherein the probe body is in particular a gallium nitride body.

4. An electrostatic probe, the electrostatic probe comprising:

an electrostatic probe as claimed in any one of claims 1 to 3;

the CF250 flange is provided with the electrostatic probe;

the KF150 flange is connected with the CF250 flange through screws;

the guide rail is connected with the KF150 flange through screws;

and the stepping motor is connected with the guide rail through a screw.

5. The electrostatic probe of claim 4, wherein the electrostatic probe further comprises:

a connector;

the support rod is arranged on the CF250 flange and is connected with the electrostatic probe through a screw;

the guide rod is arranged on the KF150 flange and is connected with the support rod through the connector.