CN113612012B - Movable grid type surface wave ion cyclotron antenna structure - Google Patents

Abstract

The invention discloses a movable grid type surface wave ion cyclotron antenna structure which comprises a current strip, a Faraday shield, a back plate, a grid plate, ceramics and a movable connecting rod. The current strip is arranged between the Faraday shield and the backboard, one end of the current strip is connected with the inner conductor of the radio frequency transmission line, and the other end of the current strip is fixed on the box body; the grid plate and the ceramic are assembled together through a movable connecting rod and suspended and fixed between the current strip and the backboard; the ceramic-connected metal grid plate is characterized in that the metal grid plate connected with the ceramic is of a grid structure and is fixed with a movable connecting rod, and water cooling loops are arranged in the grid plate and the movable connecting rod; the resonant frequency of the antenna is not changed by the change of the plasma state, the load impedance of the antenna is changed, the reflection coefficient of the antenna is affected to a certain extent, but the resonant frequency of the antenna is not changed, so that the stability of the radiation performance of the antenna is guaranteed, and the high-power steady operation of the antenna is reliably guaranteed.

Description

A movable grid surface wave ion gyro antenna structure

Technical field

The invention relates to the technical field of magnetically confined ion cyclotron wave heating plasma antennas, specifically a movable grid surface wave ion cyclotron antenna structure, used to heat plasma in a tokamak, with an operating frequency range of 30-100MHz.

Background technique

The realization of magnetic confinement fusion requires effective collision of ions with high enough temperature. Ion cyclotron resonance heating is currently one of the important methods of ion heating in magnetic confinement devices and is widely used in various magnetic confinement plasma devices. The frequency of the ion gyro wave is 30-100 MHz, and the wavelength in vacuum is about 3-10 meters. Limited by the size of the tokamak window, the length of the ion gyro antenna is far less than 1/4 wavelength, and the input impedance of the antenna is usually 1-10 ohms, while the characteristic impedance of the transmission line is 30 or 50 ohms. The mismatch in impedance leads to low power transmission efficiency. The scattering parameter S ₁₁ of the traditional ion gyrotron antenna is above -0.2dB. During megawatt-level high-power operation, the reflected power forms a high standing wave on the transmission line, which increases the standing wave voltage of the transmission line and easily leads to breakdown and sparking. In order to effectively improve the radiation performance of the antenna, using the principle of high surface impedance waves, the present invention designs a low-reflection power ion cyclotron antenna: perforations are made on the surface of a high dielectric constant medium (such as ceramics) for connection By adjusting the metal structure and ground via position of the metal and ground components on the ceramic surface, the resonant frequency of the antenna is controlled, and a resonant ion gyro antenna that meets a specific frequency is designed. In the related patents (CN108601190A, CN110278649A) and articles currently applied for, the structures are only Faraday screens, strips and boxes, and there is no movable ceramic and metal grid structure in the ion cyclotron antenna structure.

Contents of the invention

In order to solve the problems of low radiation efficiency and high reflection coefficient of the traditional ion gyro short antenna, the present invention designs a movable ceramic structure based on the surface wave structure to achieve resonance of the antenna within the operating frequency range.

The object of the present invention is to provide a movable grid surface wave ion gyro antenna structure, which is a high surface impedance ion gyro antenna. A movable grid is designed between the antenna current strip and the antenna box. Type metal structure and ceramic structure, opening holes in the ceramic, allowing the metal structure to pass through the via holes in the ceramic to connect to the ground structure, without changing the length of the ion gyro antenna, by adjusting the ceramic and grid plate relative to the current bar The position of the belt is used to change the capacitance and inductance of the antenna to achieve frequency resonance between the ion gyro antenna and the plasma, effectively increasing the radiation power of the antenna, and obtaining the antenna scattering parameter S ₁₁ below -10dB, effectively reducing the reflection coefficient, thereby obtaining high-temperature plasma. Ensure effective heating of tokamak plasma.

The technical solutions adopted by the present invention are as follows:

A movable grid surface wave ion gyro antenna structure includes a Faraday shield 2, a box 5, a current strip 1, a grid plate 3, a ceramic 4, a movable connecting rod 7 and a metal slide base 8. The Faraday shielding box 5 is fixed on the back plate; the current strip 1 is installed between the Faraday shielding box 5 and the back plate. One end of the current strip is connected to the radio frequency coaxial line 10, and the other end is fixed on the Faraday shield. On box 5. A movable ceramic 4 is installed between the antenna current strip 1 and the box 5 . The movable connecting rod 7 passes through the center of the ceramic 4 , and the ceramic 4 and the movable connecting rod 7 fit together.

Further, the antenna structure also includes a backplane. The grid plate 3 and the ceramic 4 pieces are assembled together through the movable connecting rod 7 and suspended between the current strip 1 and the back plate.

Furthermore, the ceramic 4 is made of 99 porcelain, with holes opened at specific positions, the movable connecting rod 7 passes through the center position, and the ceramic 4 and the movable connecting rod 7 are closely fitted.

Further, the grid metal plate connected to the four ceramic pieces adopts a grid structure. The grid plate 3 is fixed with the movable connecting rod 7 and forms a resonance loop with the antenna current strip. The grid plate 3 and The movable connecting rod 7 is designed with a water cooling circuit inside.

Further, the movable ceramic 4 moves through the movable connecting rod 7, and the movable connecting rod 7 is connected to the box body through a fixed sleeve 6 with a metal sliding piece 9.

Further, the 4 ceramic pieces, the grid plate 3 and the movable connecting rod 7 are fixed on the back plate through the fixed sleeve 6, and the grid plate 3 and the ceramic 4 are arranged in the air between the current strip and the back plate. between them, keeping a distance from the box 5 and the current strip respectively. The movable connecting rod and the box 5 are connected through the metal slide 9 on the metal slide base 8. Ensure good electrical contact between the movable connecting rod 7 and the box 5.

Further, the ceramic 4 is made of 99 porcelain.

The advantages of the present invention are:

1. The present invention makes the ion gyration frequency of the plasma resonate with the antenna structure frequency without changing the length of the ion gyration antenna (the antenna length is limited by the actual size of the tokamak window), thereby achieving efficient radiation of the antenna;

2. The reflection coefficient of the ion gyrotron antenna of the present invention is low (theoretical value is less than -10dB). Compared with the power reflection coefficient (greater than -0.2dB) of the ion gyrotron antenna currently operating on the tokamak, it is greatly reduced, thereby effectively Improve the power capacity of the system;

3. The radiation performance of the antenna of the present invention is less affected by the load, that is, it is not changed by changes in the plasma state, thereby ensuring the practical range of the ion gyro antenna. Both theory and simulation have confirmed that the change in the antenna load impedance has a certain impact on the antenna's reflection coefficient, but the resonant frequency does not change. This will ensure that the antenna's radiation efficiency reaches the best effect and achieves effective transmission of high power.

Description of the drawings

Figure 1 is a three-dimensional side view of the structure of the present invention;

Figure 2 is a structural diagram of the grid metal plate of the present invention;

Figure 3 is a structural diagram of the fixed bushing where the movable connecting rod contacts the box body of the present invention;

Figure 4 is a schematic diagram of the structure of the present invention;

Figure 5 is a comparison of scattering parameters between the antenna of the present invention and the traditional antenna.

Reference signs:

1: Current strip; 2: Faraday shield; 3: Grid plate; 4: Ceramic; 5: Box; 6: Fixed bushing; 7: Movable connecting rod; 8: Metal slide base; 9: Metal Slider; 10: Coaxial line.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

Figure 1 is a three-dimensional side view of the structure of the present invention. Figure 3 is a structural diagram of the fixed bushing in which the movable connecting rod 7 of the present invention contacts the box body 5. Referring to Figures 1 and 3, a movable grid surface wave ion gyro antenna structure includes a Faraday shield 2, a box 5, a current strip 1, a grid plate 3, a ceramic 4, a movable connecting rod 7 and Metal slide base 8. The Faraday shielding box 5 is fixed on the back plate; the current strip 1 is installed between the Faraday shielding box 5 and the back plate.

One end of the current strip 1 is connected to the box 5, and one end is connected to the radio frequency coaxial line 10. The grid plate 3 and the ceramic 4 are located between the current strip 1 and the back plate. The grid plate 3 and the ceramic 4 are removably connected. Rod 7 is connected to the back panel of the box.

A movable ceramic 4 is installed between the antenna current strip 1 and the box 5. The ceramic is made of 99 porcelain. The movable connecting rod 7 passes through the center of the ceramic 4, and the ceramic and the movable connecting rod are closely fitted.

The movable ceramic 4 moves through the movable connecting rod. The ceramic 4, together with the grid plate 3 and the movable connecting rod 7, are fixed on the back plate through a fixed sleeve, and the grid plate 3 and the ceramic 4 pieces are arranged in the air between the current strip 1 and the back plate, respectively. Keep a certain distance from the box 5 and the current strip 1. The movable connecting rod 7 is connected to the box 5 through the metal slide (9) on the metal slide base (8) to ensure that the movable connecting rod 7 Good electrical contact with the box 5.

Figure 2 is a structural diagram of the grid metal plate of the present invention. Referring to Figures 1 and 2, the grid plate 3 includes a plurality of horizontal grid plates arranged in parallel and a vertical grid plate intersecting each other. The vertical grid plate has a groove for the horizontal grid plate to be inserted. . See Figures 2 and 3. The grid plate 3 and ceramics 4 are connected to a movable connecting rod 7. The other end of the movable connecting rod 7 passes through the box 5, and is connected to the box 5 by a metal sliding base 8. Through contact, a metal slide 9 is installed between the metal slide base 8 and the box 5 to ensure good electrical contact. The metal slide base 8 is fixed on the box 5 through a fixed bushing 6, which plays a mechanical fixing role.

The grid metal plate connected to the ceramic 4 adopts a grid structure. The grid plate 3 is fixed with the movable connecting rod 7 and forms a resonance loop with the antenna current strip 1. The grid plate 3 and The movable connecting rod 7 is designed with a water cooling circuit inside.

Figure 4 is a schematic diagram of the structure of the present invention. See attached Figures 1 and 4. The radio frequency wave excites the electromagnetic field between the current strip 1 and the box 5. The Faraday shield 2, the grid plate 3, the ceramic 4, and the movable connecting rod 7 function to adjust the capacitance and resistance of the circuit. Function, adjust the movable connecting rod 7 so that the antenna resonates at the working frequency to achieve high-efficiency radiation.

Figure 5 is a comparison of scattering parameters between the antenna of the present invention and the traditional antenna. As shown in Figure 5, the antenna of the present invention has a lower power reflection coefficient than the traditional antenna, and the radiation performance is greatly improved.

The present invention does not elaborate on some of the well-known technologies belonging to those skilled in the art. The above-described embodiments only describe the preferred embodiments 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 those of ordinary skill in the art to the technical solution of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims (3)

1. A movable grid type surface wave ion cyclotron antenna structure, which is characterized in that: comprises a Faraday shield (2), a box body (5), a current strip (1), a grid plate (3), ceramics (4), a movable connecting rod (7) and a metal sliding sheet base (8);the Faraday shielding box body (5) is fixed on the backboard; the current strip (1) is arranged between the Faraday shielding box body (5) and the backboard, one end of the current strip (1) is connected to the radio frequency coaxial line (10), and the other end of the current strip is fixed on the Faraday shielding box body (5); a movable ceramic (4) is arranged between the antenna current strip (1) and the box body (5), the movable connecting rod (7) passes through the center of the ceramic (4), and the ceramic (4) is attached to the movable connecting rod (7); the grid plate (3) and the ceramic (4) are connected with the back plate of the box body through a movable connecting rod (7); the movable ceramic (4) moves through a movable connecting rod (7), and the movable connecting rod (7) is connected with the box body through a fixed shaft sleeve (6) with a metal sliding sheet (9); the ceramic (4) is fixed on the back plate together with the grid plate (3) and the movable connecting rod (7) through the fixed shaft sleeve (6), the grid plate (3) and the ceramic (4) are suspended between the current strip (1) and the back plate, the distance between the ceramic and the box body (5) and the current strip (1) is kept, and the movable connecting rod (7) and the box body are connected through a metal sliding sheet (9) on the metal sliding sheet base (8); the cyclotron antenna structure is an ion cyclotron antenna with high surface impedance, a movable grid type metal structure and a ceramic structure are designed between an antenna current strip and an antenna box body, holes are formed in the ceramic, the metal structure penetrates through holes in the ceramic to be connected with a grounding structure, under the condition that the length of the ion cyclotron antenna is not changed, the capacitance and inductance of the antenna are changed by adjusting the positions of the ceramic and a grid plate relative to the current strip, so that the ion cyclotron antenna and plasma frequency resonance are realized, the radiation power of the antenna is effectively improved, and the antenna scattering parameter S is obtained ₁₁ Below-10 dB.

2. The movable grid type surface wave ion cyclotron antenna structure of claim 1, wherein: the grid metal plate connected with the ceramic (4) adopts a grid structure, the grid plate (3) and the movable connecting rod (7) are fixed together to form a resonant loop with the antenna current strip (1), and a water cooling loop is designed inside the grid plate (3) and the movable connecting rod (7).

3. The movable grid type surface wave ion cyclotron antenna structure of claim 1, wherein: the ceramic (4) adopts 99 porcelain.