Alkali atom cell laser non-magnetic heating temperature control device and method

Abstract

The application discloses an alkali metal atom gas chamber laser non-magnetic heating temperature control device and method, and the device comprises a heating laser, an optical fiber, a cylindrical cavity structure, an atom gas chamber, an infrared temperature detector, a temperature control circuit board and an upper computer, the atom gas chamber is arranged in the cylindrical cavity structure, a quantum well mixing system is arranged on the outer wall of the atom gas chamber, light holes are arranged around the cylindrical cavity structure, the heating laser and the infrared temperature detector are connected with the atom gas chamber through the light holes of the cylindrical cavity structure respectively through the optical fiber, the infrared temperature detector is connected with the temperature control circuit board, the temperature control circuit board is connected with the heating laser through the optical fiber, and the temperature control circuit board is connected with the upper computer. The application can avoid magnetic field interference, maintain the stability of the high-temperature heating state, and improve the precision of the magnetic field measurement.

Description

Technical Field

[0001] This invention relates to the field of quantum sensing technology, and in particular to a laser non-magnetic heating temperature control device and method for alkali metal atom gas chambers. Background Technology

[0002] Atomic magnetometers typically use alkali metal atoms as sensing elements. Since alkali metals are solid at room temperature, their gas chambers need to be heated to increase the saturated vapor density and saturated vapor pressure of the alkali metal atoms, thereby increasing the electron spin density. This helps enhance the driving and detection capabilities of nuclear spin. The temperature parameters of the gas chamber are crucial to the performance of the atomic magnetometer, and the density of alkali metal atoms is determined by the heating temperature of the gas chamber. Therefore, to achieve high-precision detection, the heating temperature of the gas chamber must be kept highly stable.

[0003] Heating of alkali metal gas chambers mainly includes methods such as hot gas flow heating, intermittent electric heating, and high-frequency alternating current heating. Atomic magnetometers are extremely sensitive to external magnetic fields; therefore, to reduce the Larmor precession frequency of the atomic gas chamber, the probe must minimize the introduction of interfering magnetic fields. Since alkali metal gas chambers require high-temperature heating, and heating devices are often the main source of interfering magnetic fields, achieving low magnetic field noise and high stability in heating technology is a key challenge for atomic magnetometers. The advent of miniature gas chambers has made the application of laser heating in alkali metal gas chamber heating possible. Laser heating heats the gas chamber by irradiating it with a laser; for miniature gas chambers, laser heating does not generate magnetic noise.

[0004] However, conventional methods for laser heating of alkali metal gas chambers still suffer from low measurement accuracy and unstable high-temperature heating. Summary of the Invention

[0005] To address the problems of high magnetic field noise, low measurement accuracy, and unstable heating in conventional alkali metal gas chamber heating, this invention proposes a laser-based non-magnetic heating temperature control device and method for alkali metal atomic gas chambers, thereby resolving these issues.

[0006] This application discloses a laser-based non-magnetic heating and temperature control device for alkali metal atomic gas chambers, comprising a heating laser, an optical fiber, a cylindrical cavity structure, an atomic gas chamber, an infrared thermometer, a temperature control circuit board, and a host computer. The atomic gas chamber is disposed inside the cylindrical cavity structure, and a quantum well mixing system is disposed on the outer wall of the atomic gas chamber. Light-transmitting holes are disposed around the cylindrical cavity structure. The heating laser and the infrared thermometer are respectively connected to the atomic gas chamber through the light-transmitting holes of the cylindrical cavity structure via optical fibers. The infrared thermometer is connected to the temperature control circuit board, which is connected to the heating laser via an optical fiber and to the host computer.

[0007] Preferably, the cylindrical cavity structure includes a hexagonal boron nitride cylindrical cavity structure and a glass fiber vacuum-insulated cylindrical cavity structure, with the glass fiber vacuum-insulated cylindrical cavity structure covering the outer wall of the hexagonal boron nitride cylindrical cavity structure.

[0008] Preferably, the light-transmitting holes include a first light-transmitting hole penetrating the left side surface of the cylindrical cavity structure, a second light-transmitting hole penetrating the front side surface of the cylindrical cavity structure, a third light-transmitting hole penetrating the right side surface of the cylindrical cavity structure, and a fourth light-transmitting hole penetrating the rear side surface of the cylindrical cavity structure.

[0009] Preferably, the optical fibers include a first optical fiber, a second optical fiber, a third optical fiber, and a fourth optical fiber. One end of the first optical fiber is connected to the output end of the heating laser, and the other end is disposed in a first light-transmitting hole. One end of the second optical fiber is connected to the output end of the heating laser, and the other end is disposed in a third light-transmitting hole. One end of the third optical fiber is connected to the input end of the infrared thermometer, and the other end is disposed in a fourth light-transmitting hole. One end of the fourth optical fiber is connected to the temperature control circuit board, and the other end is connected to the input end of the heating laser.

[0010] Preferably, the quantum well mixing system is disposed on the left and right sides of the outer wall of the atomic gas chamber.

[0011] Preferably, the inner wall of the hexagonal boron nitride cylindrical cavity structure is coated with a black light-absorbing material.

[0012] Preferably, the quantum well hybrid system includes a quantum well and a solution of triangular gold nanosheets coated on the surface of the quantum well.

[0013] This application also discloses a method for temperature control of non-magnetic laser heating in an alkali metal atom gas chamber, characterized by the use of the aforementioned non-magnetic laser heating device for alkali metal atom gas chamber, comprising the following steps:

[0014] S1. Prepare a cylindrical cavity structure and a quantum well mixing system, and place the quantum well mixing system on the left and right sides of the outer wall of the atomic gas chamber, and then place the atomic gas chamber in the cylindrical cavity structure;

[0015] S2. Complete the assembly of the laser non-magnetic heating and temperature control device for the alkali metal atom gas chamber;

[0016] S3. A laser is emitted using a heated laser. The laser shines on the quantum well mixing system through the first and third light-passing holes. Photothermal conversion occurs on the heating surface of the quantum well mixing system, and the heat is transferred to the atomic gas chamber for heating through heat conduction.

[0017] S4. The control program is written by the host computer and burned onto the temperature control circuit board. The infrared thermometer monitors the temperature of the outer wall of the atomic gas chamber in real time and transmits the measured temperature signal to the temperature control circuit board. After receiving the temperature signal, the temperature control circuit board converts the signal and outputs a control signal to the heating laser, thereby adjusting the output power of the heating laser, so that the whole device forms a negative feedback mechanism and maintains the temperature of the atomic gas chamber at 80℃.

[0018] S5. The temperature signal is collected in real time through the temperature control circuit board and transmitted to the host computer. The host computer displays the temperature change curve of the atomic gas chamber and optimizes and adjusts the control algorithm based on the real-time temperature change curve to ensure that the atomic gas chamber can quickly recover stability after external interference.

[0019] Preferably, the preparation of the cylindrical cavity structure includes the following steps:

[0020] A hexagonal boron nitride cylindrical cavity structure was prepared by coating the inner wall of the hexagonal boron nitride cylindrical cavity structure with a black light-absorbing material, and covering the outer wall of the hexagonal boron nitride cylindrical cavity structure with a glass fiber vacuum-insulated cylindrical cavity structure to obtain the cylindrical cavity structure.

[0021] Preferably, the preparation of the quantum well hybrid system includes the following steps:

[0022] A solution of triangular gold nanosheets is dropped onto the surface of a quantum well, where they self-assemble using electrostatics or van der Waals forces, and finally the bonding is enhanced by heat treatment.

[0023] The beneficial effects of this invention are:

[0024] (1) The triangular gold nanosheets in the quantum well hybrid system of the present invention can significantly enhance the absorption of incident light. When combined with the quantum well, the light absorption capacity is greatly improved, the photothermal conversion efficiency is increased, and the energy consumption is reduced.

[0025] (2) The quantum well structure of the present invention can isolate heat transfer and reduce the diffusion of heat energy to the surrounding environment. When the triangular gold nanosheet generates heat energy in the quantum well, it helps to maintain the stability of the high temperature state and extend the service life of the hybrid system.

[0026] (3) The present invention uses laser heating to heat the quantum well mixing system on the opposite surface of the atomic gas chamber, which improves the temperature uniformity of the atomic gas chamber, ensures that the atomic number density distribution at each position inside the atomic gas chamber is uniform, and improves the accuracy and stability of magnetic field measurement.

[0027] (4) The present invention achieves non-magnetic temperature measurement by using an infrared thermometer to measure the temperature of the gas chamber, avoids magnetic field interference, improves the accuracy of the measurement data, and meets the high stability requirements of the atomic magnetometer for the internal temperature of the gas chamber. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the alkali metal atom gas chamber laser non-magnetic heating temperature control device according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the cylindrical cavity structure according to an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the atomic gas chamber according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the quantum well hybrid system structure according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the electric field mode of the quantum well hybrid system under the action of a heated laser, according to an embodiment of the present invention.

[0033] Figure 6 This is a schematic diagram of the temperature of the quantum well hybrid system under the action of a heating laser, according to an embodiment of the present invention.

[0034] The attached figures are labeled as follows:

[0035] 1-Heating laser, 2-First optical fiber, 3-Hexagonal boron nitride cylindrical cavity structure, 4-Glass fiber vacuum insulated cylindrical cavity structure, 5-Atomic gas chamber, 6-First light-transmitting hole, 7-Second light-transmitting hole, 8-Third light-transmitting hole, 9-Fourth light-transmitting hole, 10-Infrared thermometer, 11-Temperature control circuit board, 12-Host computer, 13-Third optical fiber, 14-Second optical fiber, 15-Fourth optical fiber, 16-Quantum well hybrid system. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments.

[0037] This application discloses a laser-based non-magnetic heating and temperature control device for an alkali metal atom gas chamber, such as... Figure 1As shown, the system includes a heating laser 1, an optical fiber, a cylindrical cavity structure, an atomic gas chamber 5, an infrared thermometer 10, a temperature control circuit board 11, and a host computer 12. The atomic gas chamber 5 is located inside the cylindrical cavity structure. A quantum well mixing system 16 is installed on the outer wall of the atomic gas chamber 5. Light-transmitting holes are provided around the cylindrical cavity structure. The heating laser 1 and the infrared thermometer 10 are connected to the atomic gas chamber 5 via optical fibers passing through the light-transmitting holes in the cylindrical cavity structure. The infrared thermometer 10 is connected to the temperature control circuit board 11, which is connected to the heating laser 1 via an optical fiber. The temperature control circuit board 11 is also connected to the host computer 12. In this embodiment, the infrared thermometer 10 is a German KELU PX10 infrared thermometer, the temperature control circuit board 11 uses an Arduino temperature control module, and the host computer 12 uses a Siemens IPC.

[0038] like Figure 2 As shown, the cylindrical cavity structure includes a hexagonal boron nitride cylindrical cavity structure 3 and a glass fiber vacuum-insulated cylindrical cavity structure 4. The inner wall of the hexagonal boron nitride cylindrical cavity structure 3 is coated with a black light-absorbing material; in this embodiment, graphite is used. The glass fiber vacuum-insulated cylindrical cavity structure 4 covers the outer wall of the hexagonal boron nitride cylindrical cavity structure 3. Hexagonal boron nitride has low magnetic properties, meaning it has less influence on external magnetic fields. This is crucial for quantum state manipulation and measurement in the atomic gas chamber 5, as external magnetic fields can cause splitting and drifting of atomic energy levels, affecting the accuracy of experimental results. Furthermore, hexagonal boron nitride has good thermal conductivity, helping to maintain the uniformity of temperature inside the atomic gas chamber 5. The thermal conductivity of the outer glass fiber vacuum insulation material is much lower than that of traditional insulation materials, making it excellent in heat preservation and effectively reducing heat conduction. This is very important for ensuring the uniform distribution and stability of the atomic gas, especially when precise temperature control is required.

[0039] The light-transmitting holes include a first light-transmitting hole 6 penetrating the left side surface of the cylindrical cavity structure, a second light-transmitting hole 7 penetrating the front side surface of the cylindrical cavity structure, a third light-transmitting hole 8 penetrating the right side surface of the cylindrical cavity structure, and a fourth light-transmitting hole 9 penetrating the rear side surface of the cylindrical cavity structure. The optical fibers include a first optical fiber 2, a second optical fiber 14, a third optical fiber 13, and a fourth optical fiber 15. One end of the first optical fiber 2 is connected to the output end of the heating laser 1, and the other end is disposed in the first light-transmitting hole 6. One end of the second optical fiber 14 is connected to the output end of the heating laser 1, and the other end is disposed in the third light-transmitting hole 8. One end of the third optical fiber 13 is connected to the input end of the infrared thermometer 10, and the other end is disposed in the fourth light-transmitting hole 9. One end of the fourth optical fiber 15 is connected to the temperature control circuit board 11, and the other end is connected to the input end of the heating laser 1.

[0040] like Figure 3As shown, the left outer wall of the atomic gas chamber 5 is surface a, the front outer wall is surface b, the right outer wall is surface c, and the rear outer wall is surface d. The quantum well mixing system 16 is encapsulated on the left and right sides of the outer wall of the atomic gas chamber 5, i.e., surfaces a and c. Figure 4 As shown, the quantum well hybrid system 16 includes a quantum well and a solution of triangular gold nanosheets coated on the surface of the quantum well. The triangular gold nanosheets possess unique optical properties that significantly enhance the absorption of incident light. When combined with the quantum well, this enhancement effect is further amplified, resulting in a substantial increase in the light absorption capacity of the quantum well hybrid system 16. This is significant for improving photothermal conversion efficiency and reducing energy consumption. The quantum well structure can isolate heat transfer to a certain extent, reducing the diffusion of heat energy to the surrounding environment. When the gold nanosheets generate heat energy in the quantum well, this thermal isolation helps maintain the stability of the high-temperature state and extends the lifespan of the quantum well hybrid system 16. By reducing the center distance and position between the triangular gold nanosheets and the quantum well in the quantum well hybrid system 16, the light absorption coefficient is increased. This process allows more light energy to be converted into heat energy, reducing energy loss due to reflection, scattering, and other methods. After placing the atomic gas chamber 5 in the cylindrical cavity structure 3, the a-side of the atomic gas chamber faces the first light-transmitting hole 6, the b-side faces the second light-transmitting hole 7, the c-side faces the third light-transmitting hole 8, and the d-side faces the fourth light-transmitting hole 9.

[0041] Heating laser 1 illuminates the quantum well hybrid system 16 on the surface of atomic gas chamber 5a through the first optical fiber 2 and the first optical aperture 6. Heating laser 1 illuminates the quantum well hybrid system 16 on the surface of atomic gas chamber 5c through the second optical fiber 14 and the second optical aperture 7. The atomic number density distribution inside the alkali metal atomic gas chamber 5 is directly related to temperature. Thermal uniformity during heating ensures a uniform atomic number density distribution at various locations inside the gas chamber, thus avoiding uneven atomic number density distribution due to temperature gradients. A uniform atomic number density distribution can improve the accuracy and stability of magnetic field measurement, as the uniformity of the magnetic field sensor signal is affected by the atomic number density distribution. Laser heating of the quantum well hybrid system 16 on the a and c surfaces of the atomic gas chamber 5 improves the temperature uniformity of the atomic gas chamber. In a specific embodiment, the photothermal effect simulation of the quantum well hybrid system 16 is obtained. Figure 5 The diagram shows the electric field mode of the quantum well hybrid system under the action of a heated laser. Figure 6 The diagram shows the temperature of the quantum well hybrid system under the action of a heated laser. Figure 5 and Figure 6 As can be seen from the perspective of temperature uniformity, the temperature distribution of the quantum well is uniform, which indicates that the thermal management of the quantum well hybrid system is well done, which is conducive to maintaining the stability of the temperature performance of the atomic gas chamber.

[0042] The d-surface of the atomic gas chamber 5 is connected to the infrared thermometer 10 via the fourth optical fiber 15 and the fourth light-transmitting aperture 9, enabling the infrared thermometer 10 to measure the temperature of the atomic gas chamber 5 in real time. Traditional methods use thermistors to measure the chamber temperature; however, supplying power to the thermistor introduces magnetic interference, preventing truly non-magnetic heating. The device structure of this application uses the infrared thermometer 10 to measure the chamber temperature via optical fiber, achieving truly non-magnetic heating.

[0043] Another embodiment of this application discloses a method for temperature control of non-magnetic laser heating in an alkali metal atom gas chamber, implemented using the aforementioned non-magnetic laser heating device for an alkali metal atom gas chamber, comprising the following steps:

[0044] S1. Preparation of a cylindrical cavity structure: A hexagonal boron nitride cylindrical cavity structure 3 is prepared. A black light-absorbing material (graphite) is coated on the inner wall of the hexagonal boron nitride cylindrical cavity structure 3. A glass fiber vacuum-insulated cylindrical cavity structure 4 is then placed on the outer wall of the hexagonal boron nitride cylindrical cavity structure 3 to obtain the cylindrical cavity structure.

[0045] Preparation of quantum well hybrid system 16: Triangular gold nanosheet solution is dropped onto the surface of quantum well, and self-assembled by electrostatics or van der Waals force, and finally the bonding is enhanced by heat treatment.

[0046] The quantum well mixing system 16 is placed on the left and right sides of the outer wall of the atomic gas chamber 5, and then the atomic gas chamber 5 is placed in the cylindrical cavity structure.

[0047] S2. Complete the assembly of the laser non-magnetic heating and temperature control device for the alkali metal atom gas chamber.

[0048] S3. A laser is emitted using a heated laser 1. The laser beam is irradiated onto the quantum well mixing system 16 through the first light-transmitting hole 6 and the third light-transmitting hole 8. Photothermal conversion occurs on the heating surface of the quantum well mixing system, and the heat is transferred to the atomic gas chamber 5 for heating.

[0049] S4. The PID temperature control program is input into the host computer 12 and burned onto the temperature control circuit board 11. The infrared thermometer 10 monitors the temperature of the outer wall of the atomic gas chamber 5 in real time and transmits the measured temperature signal to the temperature control circuit board 11. After receiving the temperature signal, the temperature control circuit board 11 converts the signal and outputs a control signal to the heating laser 1, thereby adjusting the output power of the heating laser 1, so that the whole device forms a negative feedback mechanism and maintains the temperature of the atomic gas chamber at 80°C.

[0050] S5. The temperature signal is collected in real time by the temperature control circuit board 11 and transmitted to the host computer 12. The host computer 12 displays the temperature change curve of the atomic gas chamber 5 and optimizes and adjusts the PID temperature control program based on the real-time temperature change curve to ensure that the atomic gas chamber 5 can quickly recover stability after external interference.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A laser-based non-magnetic heating and temperature control device for an alkali metal atom gas chamber, characterized in that, The system includes a heating laser (1), an optical fiber, a cylindrical cavity structure, an atomic gas chamber (5), an infrared thermometer (10), a temperature control circuit board (11), and a host computer (12). The atomic gas chamber (5) is located inside the cylindrical cavity structure. A quantum well mixing system (16) is provided on the outer wall of the atomic gas chamber (5). The quantum well mixing system (16) includes a quantum well and a triangular gold nanosheet solution coated on the surface of the quantum well. Light-transmitting holes are provided around the cylindrical cavity structure. The heating laser (1) and the infrared thermometer (10) are respectively connected to the atomic gas chamber (5) through the light-transmitting holes of the cylindrical cavity structure via optical fibers. The infrared thermometer (10) is connected to the temperature control circuit board (11). The temperature control circuit board (11) is connected to the heating laser (1) via an optical fiber. The temperature control circuit board (11) is connected to the host computer (12).

2. The alkali metal atom gas chamber laser non-magnetic heating and temperature control device according to claim 1, characterized in that, The cylindrical cavity structure includes a hexagonal boron nitride cylindrical cavity structure (3) and a glass fiber vacuum-insulated cylindrical cavity structure (4), with the glass fiber vacuum-insulated cylindrical cavity structure (4) covering the outer wall of the hexagonal boron nitride cylindrical cavity structure (3).

3. The alkali metal atom gas chamber laser non-magnetic heating and temperature control device according to claim 2, characterized in that, The light-transmitting holes include a first light-transmitting hole (6) penetrating the left side surface of the cylindrical cavity structure, a second light-transmitting hole (7) penetrating the front side surface of the cylindrical cavity structure, a third light-transmitting hole (8) penetrating the right side surface of the cylindrical cavity structure, and a fourth light-transmitting hole (9) penetrating the rear side surface of the cylindrical cavity structure.

4. The alkali metal atom gas chamber laser non-magnetic heating and temperature control device according to claim 3, characterized in that, The optical fibers include a first optical fiber (2), a second optical fiber (14), a third optical fiber (13), and a fourth optical fiber (15). One end of the first optical fiber (2) is connected to the output end of the heating laser (1), and the other end is set in the first light-transmitting hole (6). One end of the second optical fiber (14) is connected to the output end of the heating laser (1), and the other end is set in the third light-transmitting hole (8). One end of the third optical fiber (13) is connected to the input end of the infrared thermometer (10), and the other end is set in the fourth light-transmitting hole (9). One end of the fourth optical fiber (15) is connected to the temperature control circuit board (11), and the other end is connected to the input end of the heating laser (1).

5. The alkali metal atom gas chamber laser non-magnetic heating and temperature control device according to claim 4, characterized in that, The quantum well mixing system (16) is located on the left and right sides of the outer wall of the atomic gas chamber (5).

6. The alkali metal atom gas chamber laser non-magnetic heating and temperature control device according to claim 5, characterized in that, The inner wall of the hexagonal boron nitride cylindrical cavity structure (3) is coated with a black light-absorbing material.

7. A method for temperature control using laser-based non-magnetic heating in an alkali metal atom gas chamber, characterized in that, The temperature control device for laser non-magnetic heating of alkali metal atom gas chambers as described in any one of claims 1-6 is implemented by including the following steps: S1. Preparation of a cylindrical cavity structure and a quantum well hybrid system (16), wherein the preparation of the quantum well hybrid system (16) includes: dropping a triangular gold nanosheet solution onto the surface of the quantum well, using electrostatic or van der Waals forces to make it self-assemble, and finally enhancing the bonding through heat treatment; The quantum well mixing system (16) is placed on the left and right sides of the outer wall of the atomic gas chamber (5), and then the atomic gas chamber (5) is placed in the cylindrical cavity structure; S2. Complete the assembly of the laser non-magnetic heating and temperature control device for the alkali metal atom gas chamber; S3. A laser is emitted using a heated laser (1). The laser shines on the quantum well mixing system (16) through the first light-transmitting hole (6) and the third light-transmitting hole (8). Photothermal conversion is performed on the heating surface of the quantum well mixing system (16), and the heat is transferred to the atomic gas chamber (5) for heating. S4. The control program is written by the host computer (12) and burned onto the temperature control circuit board (11). The infrared thermometer (10) monitors the temperature of the outer wall of the atomic gas chamber (5) in real time and transmits the measured temperature signal to the temperature control circuit board (11). After receiving the temperature signal, the temperature control circuit board (11) performs signal conversion and outputs control signal to the heating laser (1), thereby adjusting the output power of the heating laser (1) so that the whole device forms a negative feedback mechanism and keeps the atomic gas chamber temperature at 80°C. S5. The temperature signal is collected in real time by the temperature control circuit board (11) and transmitted to the host computer (12). The host computer (12) displays the temperature change curve of the atomic gas chamber (5). Based on the real-time temperature change curve, the control algorithm is optimized and adjusted to ensure that the atomic gas chamber (5) quickly recovers stability after external interference.

8. The method for laser-based non-magnetic heating and temperature control of an alkali metal atom gas chamber according to claim 7, characterized in that, The preparation of the cylindrical cavity structure includes the following steps: A hexagonal boron nitride cylindrical cavity structure (3) was prepared. A black light-absorbing material was coated on the inner wall of the hexagonal boron nitride cylindrical cavity structure (3), and a glass fiber vacuum insulating cylindrical cavity structure (4) was covered on the outer wall of the hexagonal boron nitride cylindrical cavity structure (3) to obtain the cylindrical cavity structure.

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