Thermal coherent scattering system for measuring ion temperature of magnetic confinement fusion device

Abstract

The invention discloses a thermal coherence scattering system for measuring the ion temperature of a magnetic confinement fusion device, and relates to the technical field of magnetic confinement fusion plasma microwave diagnosis, and the system comprises a gyrotron which is used for generating a millimeter wave light beam; the quasi-optical matching unit is arranged at the output end of the gyrotron and is used for converting the millimeter wave light beam into a TEM00 mode and coupling the millimeter wave light beam into the metal corrugated circular waveguide in an HE11 mode; one of the three metal corrugated circular waveguides is installed at the output end of the quasi-optical matching unit, the two adjacent metal corrugated circular waveguides are connected through a rotatable polarizer elbow, and the two rotatable polarizer elbows jointly form a rotatable polarizer; according to the thermal coherence scattering system for measuring the ion temperature of the magnetic confinement fusion device, a metal corrugated circular waveguide is adopted for transmission. The advantage that the metal corrugated circular waveguide is used for transmission is that the waveguide has a shielding effect, and an additional shielding mode does not need to be considered.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic confinement fusion plasma microwave diagnosis, in particular to a thermal coherent scattering system for measuring the ion temperature of a magnetic confinement fusion device. Background Art

[0002] The primary ion temperature is a key parameter in studying fusion reactions because, in addition to being related to the Lawson criterion, it is also closely related to the fusion reaction rate. It is generally believed that to achieve fusion, the ion temperature must reach above 10 keV, or 100 million degrees Celsius. At such high temperatures, conventional contact measurements are no longer effective, so researchers have developed a series of non-contact measurements to diagnose ion temperature.

[0003] Currently, thermal coherence scattering (TCS) is a known method for directly diagnosing the localized primary ion temperature. The principle of TCS diagnosis is that high-power, highly monochromatic electromagnetic waves are incident on a plasma. Electrons, under the influence of the electromagnetic wave's electric field, radiate photons, known as scattered light. Ions affect the motion of electrons through the Debye screening effect, allowing ion information to be extracted from the TCS spectrum. In magnetic confinement fusion devices, the wavelength of the probe beam (typically in the millimeter wave range) and the scattering angle θ must be designed to meet coherence requirements.

[0004] Based on this, according to the above measurement of the main ion temperature, there are mainly three difficulties: 1. Low-loss transmission of high-power microwaves. The MW-class high-power microwave source used in thermal coherent scattering systems places extremely high demands on the power handling capacity and loss of the transmission path. Commonly used microwave-band lens materials such as high-density polyethylene may face the risk of thermal damage or breakdown under such high power. 2. Actively adjust the polarization direction of high-power microwaves. Depending on experimental conditions (such as magnetic field configuration and plasma density), it is necessary to excite relatively pure X-modes or O-modes in the plasma for detection. The microwaves output by the gyrotron are typically linearly polarized waves, which need to be converted into the specific polarization state required for pure O-mode or X-mode propagation in the plasma.

[0005] 3. Receive extremely weak scattered signals. Since the scattering cross section of thermal coherent scattering is extremely small, the scattering power is usually only on the order of nW. How to detect and extract the scattered signal in the complex plasma radiation background (especially electron cyclotron radiation) is a very challenging problem. Summary of the Invention

[0006] The object of the present invention is to provide a thermal coherent scattering system for measuring the ion temperature of a magnetic confinement fusion device, so as to solve the above-mentioned deficiencies in the prior art.

[0007] To achieve the above-mentioned object, the present invention provides the following technical solution: a thermal coherent scattering system for measuring the ion temperature of a magnetic confinement fusion device, comprising a magnetic confinement fusion device for generating and confining high-temperature plasma; a gyrotron for generating a millimeter-wave beam; and a quasi-optical matching unit installed at the output end of the gyrotron and used to convert the millimeter-wave beam into a TEM. 00 mode, and HE 11 The invention relates to a method for coupling a mode into a metal corrugated circular waveguide; three sections of metal corrugated circular waveguide, one of which is installed at the output end of the quasi-optical matching unit, and two adjacent sections of the metal corrugated circular waveguide are connected by a rotatable polarizer elbow, and the two rotatable polarizer elbows together constitute a rotatable polarizer, which is used to arbitrarily adjust the polarization direction of the light beam; an incident reflector system, which is used to focus the light beam output from the metal corrugated circular waveguide and adjust the beam waist position, and then incident it into the vacuum chamber of the magnetic confinement fusion device; a receiving reflector system, which is used to adjust the circumferential angle of the received light beam so that the beam waist of the received light beam overlaps with the beam waist of the incident light beam; and a heterodyne receiver, which is used to receive the light beam focused by the reflector system and record the thermal coherent scattering signal.

[0008] Preferably, the incident reflector system and the receiving reflector system are both arranged on an external support and located on the mid-plane of the magnetic confinement fusion device.

[0009] Preferably, the incident reflector system includes a first ellipsoidal reflector, a first plane reflector, a second plane reflector, and a second ellipsoidal reflector, which are arranged in sequence along the incident direction of the light beam; the first ellipsoidal reflector and the first plane reflector are both mounted on an external bracket, and the distance between the first ellipsoidal reflector and the first plane reflector is relatively fixed, and the first group of reflectors formed by the first ellipsoidal reflector and the first plane reflector can be synchronously translated along the optical axis of the light beam on the external bracket, and the mirror surface of the first ellipsoidal reflector is arranged opposite to the mirror surface of the first plane reflector to expand the light beam; the second plane reflector and the second ellipsoidal reflector are both mounted on the external bracket, and the second ellipsoidal reflector can rotate around the optical axis to focus the light beam and adjust the direction of the light beam incident into the vacuum chamber of the magnetic confinement fusion device. When the second ellipsoidal reflector rotates around the line connecting its short axis vertex and the focus, the mirror surface of the second ellipsoidal reflector cooperates with the mirror surface of the first group of reflectors to control the focusing position of the light beam in the plasma of the magnetic confinement fusion device.

[0010] Preferably, the receiving reflector system includes a third plane reflector and a third ellipsoidal reflector, and the third ellipsoidal reflector is rotatably connected to the external bracket so that the third ellipsoidal reflector can rotate around the line connecting its short axis vertex and the focus to adjust the circumferential angle of the receiving light beam.

[0011] Preferably, both ends of each rotatable polarizer elbow are fixedly connected to the corresponding metal corrugated circular waveguide.

[0012] Preferably, a grooved metal reflector for adjusting the polarization direction of the light beam is installed in each of the rotatable polarizer elbows.

[0013] Preferably, the rotatable polarizer is rotated by two fluted metal mirrors in the elbows of the rotatable polarizer to achieve continuous adjustment of the polarization direction.

[0014] Preferably, the background radiation generated by the plasma itself in the magnetic confinement fusion device is collected by a receiving reflector system, and the signal is recorded by a heterodyne receiver.

[0015] Preferably, when the gyrotron is turned on, the heterodyne receiver records the superposition signal of the thermal coherent scattering signal and the plasma background radiation of the first duration; when the gyrotron is turned off, the heterodyne receiver records the plasma background radiation signal of the same duration; the two signals are aligned in the time domain and differentially processed to eliminate the background radiation noise and extract a pure thermal coherent scattering signal.

[0016] In the above technical solution, the present invention provides a thermal coherent scattering system for measuring the ion temperature of a magnetic confinement fusion device. 1. The present invention uses a metal corrugated circular waveguide for transmission. The advantages of using a metal corrugated circular waveguide for transmission are that the waveguide itself has a shielding effect, eliminating the need for additional shielding methods; it also has a relatively high power transmission capacity, capable of transmitting microwaves in the MW range.

[0017] 2. The present invention uses a rotatable polarizer to adjust the polarization direction. Two rotatable polarizers are installed on the reversing waveguide, so that the groove directions of the two polarizers can be adjusted to achieve arbitrary polarization of high-power microwaves.

[0018] 3. The present invention uses a heterodyne receiver to measure the scattered signal, verifying it by adjusting the direction of the receiving antenna. Specifically, the receiving antenna is adjusted so that it gradually approaches the probe wave from a position farther away, then moves away from it. If the received signal is observed to gradually increase in strength and then decrease again, it is confirmed to be derived from thermal coherent scattering. To extract the scattered signal from the high-intensity plasma background radiation, the heterodyne receiver collects the scattered signal when the gyrotron is turned on and a background signal of equal duration when the gyrotron is turned off. The difference between the two is then used to extract the scattered signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0020] Figure 1A top view of a thermal coherent scattering system provided in an embodiment of the present invention; Figure 2 A front view of the incident light path of the thermal coherent scattering system provided by an embodiment of the present invention; Figure 3 A front view of the receiving optical path of the thermal coherent scattering system provided in an embodiment of the present invention; Figure 4 A signal flow chart of a heterodyne receiver provided in an embodiment of the present invention; Figure 5 A top view of a heterodyne receiver provided in an embodiment of the present invention; Figure 6 A schematic diagram of shutting down a MOS tube according to an embodiment of the present invention; Figure 7 This is a conduction diagram of a MOS tube provided by an embodiment of the present invention.

[0021] Description of reference numerals: 1. Gyrotron; 2. Quasi-optical matching unit; 3. Metal corrugated circular waveguide; 4. Rotatable polarizer; 5. Incident reflector system; 5.1. First ellipsoidal reflector; 5.2. First plane reflector; 5.3. Second plane reflector; 5.4. Second ellipsoidal reflector; 6. Magnetic confinement fusion device; 7. Receiving reflector system; 7.1. Third ellipsoidal reflector, 7.2. Third plane reflector; 8. Heterodyne receiver; 8.1. Notch filter; 8.2. Bandpass filter; 8.3. RF low-noise amplifier; 8.4. Isolator; 8.5. Mixer; 8.6. Local oscillator; 8.7. Intermediate-frequency low-noise amplifier; 8.8. Low-pass filter. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0023] See also Figure 1-7 An embodiment of the present invention provides a thermal coherent scattering system for measuring the ion temperature of a magnetic confinement fusion device, comprising a magnetic confinement fusion device for generating and confining high-temperature plasma, a gyrotron 1, a quasi-optical matching unit 2, a three-section metal corrugated circular waveguide 3, a rotatable polarizer 4, an incident reflector system 5, a receiving reflector system 7, and a heterodyne receiver 8.

[0024] In the technical solution provided by the embodiment of the present invention, the above-mentioned device is based on Figure 1 Furthermore, the gyrotron 1 is used to generate a millimeter wave beam; the quasi-optical matching unit 2 is installed at the output end of the gyrotron 1 and is used to convert the millimeter wave beam into a TEM 00 mode, and HE 11The mode is coupled into the metal corrugated circular waveguide 3; one section of the metal corrugated circular waveguide 3 is installed at the output end of the quasi-optical matching unit 2; the incident reflector system 5 is used to focus the light beam output from the metal corrugated circular waveguide 3 and adjust the beam waist position, and then inject it into the vacuum chamber of the magnetic confinement fusion device 6; the receiving reflector system 7 is used to adjust the circumferential angle of the received light beam so that the beam waist of the received light beam overlaps with the beam waist of the incident light beam; the heterodyne receiver 8 is used to receive the light beam focused by the reflector system 7 and record the thermal coherent scattering signal.

[0025] It should be noted that the lengths of the three sections of metal corrugated circular waveguides 3 can be changed according to the specific spatial arrangement, and a rotatable polarizer 4 elbow is provided between each of the two adjacent sections of metal corrugated circular waveguides 3. These two rotatable polarizer 4 elbows together constitute a rotatable polarizer 4 that can arbitrarily adjust the polarization direction.

[0026] Furthermore, the two ends of each rotatable polarizer 4 elbow are fixedly connected to the corresponding metal corrugated circular waveguide 3. Each rotatable polarizer 4 elbow is equipped with a grooved metal reflector for adjusting the polarization direction of the light beam. Specifically, to address the problem of adjusting the polarization direction of high-power microwaves, the present invention uses grooved metal reflectors to adjust the polarization direction. Two rotatable polarizer 4 elbows are installed between three metal corrugated circular waveguides 3, and by rotating the two rotatable polarizer 4 elbows, the groove directions of the two grooved metal reflectors are adjusted to achieve arbitrary polarization of the high-power microwaves.

[0027] In an embodiment, the rotatable polarizer 4 is rotated by two grooved metal mirrors in the elbows of the rotatable polarizer 4 to achieve continuous adjustment of the polarization direction.

[0028] The incident reflector system 5 is arranged after the last section of the metal corrugated circular waveguide 3 and consists of two groups of ellipsoidal reflectors and a plane reflector. Along the incident direction of the light beam, they are arranged in order: the first ellipsoidal reflector 5.1, the first plane reflector 5.2, the second plane reflector 5.3, and the second ellipsoidal reflector 5.4. The first group consists of the first ellipsoidal reflector 5.1 and the first plane reflector 5.2. Both the first ellipsoidal reflector 5.1 and the first plane reflector 5.2 are mounted on an external bracket. The distance between the first ellipsoidal reflector 5.1 and the first plane reflector 5.2 is relatively fixed. The mirror surface of the first ellipsoidal reflector 5.1 is arranged opposite the mirror surface of the first plane reflector 5.2, which expands the light beam. The second plane reflector 5.3 and the second ellipsoidal reflector 5.4 in the second group are mounted on an external bracket. The second ellipsoidal reflector 5.4 can rotate about the optical axis to focus the light beam and adjust the direction of the light beam incident on the vacuum chamber of the magnetic confinement fusion device 6. When the second ellipsoidal reflector 5.4 rotates about the line connecting its minor axis vertex and the focal point, the mirror surface of the second ellipsoidal reflector 5.4 cooperates with the mirror surface of the first group of reflectors to control the focus position of the light beam in the plasma of the magnetic confinement fusion device 6. In addition, the first ellipsoidal reflector 5.1 and the first plane reflector 5.2 in the first group can be adjusted along the optical axis as a whole to adjust the position of the light beam waist. The combined effect of translation and rotation enables the light beam to be focused at different positions in the vacuum chamber of the confinement fusion device. The incident and receiving light paths are both arranged in the midplane of the magnetic confinement fusion device 6. This has the advantage of reducing the adjustment freedom of the incident reflector system 5.

[0029] The receiving reflector system 7 includes a third plane reflector 7.2 and a third ellipsoidal reflector 7.1. The third ellipsoidal reflector 7.1 is rotatably connected to an external bracket so that the third ellipsoidal reflector 7.1 can rotate around the line connecting its minor axis vertex and the focus to adjust the circumferential angle of the receiving beam.

[0030] In this embodiment, the joint adjustment of the incident reflective mirror system 5 and the receiving reflective mirror system 7 can realize the measurement of the main ion temperature at any position in the plasma.

[0031] The background radiation generated by the plasma itself in the magnetic confinement fusion device 6 is collected by the receiving reflector system 7 and the signal is recorded by the heterodyne receiver 8 .

[0032] When the gyrotron 1 is turned on, the heterodyne receiver 8 records the superposition signal of the thermal coherent scattering signal and the plasma background radiation of the first duration; when the gyrotron 1 is turned off, the heterodyne receiver 8 records the plasma background radiation signal of the same duration; the two signals are aligned in the time domain and differentially processed to eliminate the background radiation noise and extract the pure thermal coherent scattering signal.

[0033] Specifically, the millimeter wave beam generated by the gyrotron 1 is converted into a high-purity TEM beam after passing through the quasi-optical matching unit 2. 00 mode, and then HE 11 The mode is coupled into the metal corrugated circular waveguide 3, and after being adjusted to the required polarization direction by the rotatable polarizer 4, it is recoupled into TEM at the waveguide outlet. 00 mode, and then after being focused and adjusting the beam waist position by the incident reflector system 5, it is incident on the vacuum chamber of the magnetic confinement fusion device 6, and thermal coherent scattering occurs in the magnetic confinement fusion device 6. After the thermal coherent scattering signal generated in the scattering volume propagates out of the magnetic confinement fusion device 6, it is focused by the receiving reflector system 7 and coupled into the heterodyne receiver 8, and the heterodyne receiver 8 records the thermal coherent scattering signal. During the period when the gyrotron 1 is closed, the background radiation generated by the plasma itself in the magnetic confinement fusion device 6 is collected by the receiving reflector system 7, and the signal of the same duration is recorded by the heterodyne receiver 8. By taking the difference between the two recorded signals, the thermal coherent scattering signal can be extracted from the plasma background radiation. In addition, the extracted thermal coherent scattering signal can be used to extract parameters such as the main ion temperature using algorithms such as least squares fitting.

[0034] It should be noted that in the thermal coherent scattering diagnostic system, the output mode of the emission source gyrotron 1 is TEM 00 We need to use this microwave energy in HE 11 The microwave energy is transmitted in the form of a corrugated circular waveguide, and a reflector antenna is used at the end of the waveguide near the plasma boundary to send the microwave energy into the plasma. HE 11 Mode field structure ( Poloidal electric field and The toroidal electric field can be formally expressed as:

[0035] in, is the Bessel function, r is the distance from the point to the waveguide axis, and a is the inner radius of the waveguide. 11 The mode field components are transformed into rectangular coordinates (i.e. the horizontal electric field and vertical electric field ),have

[0036] Expand the 0th-order Bessel function with a higher-order Laguerre-Gaussian function, that is

[0037] in,

[0038] is the p-th order Laguerre-Gaussian function, is the projection coefficient of the 0th order Bessel function on the orthogonal basis, where (x) is a Laguerre polynomial of order p, where x is a variable and x= , exp(y) describes the field amplitude distribution of the mode in the cross section, which gradually decays from the center to the outside according to the distribution law of the Gaussian function. The y is a variable, and y= .

[0039] The Laguerre-Gaussian function is an orthonormal basis that satisfies:

[0040]

[0041] From this, we can obtain:

[0042] in,

[0043] Among them, the above is an intermediate variable, the purpose is to solve The integral equation is transformed into an integral equation with an analytical expression.

[0044] here is the Gaussian basis model (TEM 00 Since we are only interested in the Gaussian basis modes, we only need to find the maximum value:

[0045] Make Take the maximum value ,for =0.6435a, at this time =0.911a. HE 11 Total power of the mode :

[0046] Maximum total power contained in the Gaussian basis for:

[0047] The maximum power ratio contained in the Gaussian basis is :

[0048] It can be seen that the relationship between Gaoskim and HE 11 The maximum efficiency of mode coupling is 98%.

[0049] Based on the above, we know that TEM 00 Mode is the wave mode transmitted in free space, HE 11 TEM 00 The wave mode transmitted in the metal corrugated circular waveguide 3.

[0050] In an embodiment of the present invention, to address the low-loss transmission of high-power microwaves, a metal corrugated circular waveguide 3 is employed. The advantages of using a metal corrugated circular waveguide 3 for transmission are that the waveguide itself provides shielding, eliminating the need for additional shielding methods. The waveguide also has a relatively high power transmission capacity, capable of transmitting microwaves in the MW range. To minimize the diffraction effect (generating higher-order modes and increasing losses) during microwave transmission within the metal corrugated circular waveguide 3, the groove period should satisfy the following requirements: Where λ is the transmission wavelength. In order to achieve the minimum ohmic loss, the groove depth h should be selected And the groove duty cycle should be selected as 0.7 to reduce processing difficulty and ohmic loss.

[0051] To address the problem of measuring and identifying thermal coherent scattering signals, the present invention uses a heterodyne receiver 8 to measure the scattered signal and verifies the scattered signal by adjusting the direction of the receiving antenna before the formal experiment. The specific method is to adjust the direction of the receiving antenna so that it gradually approaches the detection wave from a position far away from the detection wave, and then moves away from the detection wave; if the received signal is observed to increase from weak to strong and then decrease to weak, it can be confirmed that the signal is from thermal coherent scattering. To extract the scattered signal from the high-intensity plasma background radiation, the heterodyne receiver 8 collects the scattered signal when the gyrotron 1 is turned on and collects the background signal of the same duration when it is turned off. The scattered signal is then extracted by taking the difference between the two.

[0052] Among them, as a preferred embodiment of the present invention, the heterodyne receiver 8 mainly includes a notch filter 8.1, a bandpass filter 8.2, a radio frequency low noise amplifier 8.3, an isolator 8.4, a mixer 8.5, a local oscillator 8.6, an intermediate frequency low noise amplifier 8.7 and a low-pass filter 8.8.

[0053] The present invention uses a MOS tube to control the power supply of the radio frequency low noise amplifier 8.3. Based on this, it should be noted that, in combination with Figure 6-7 As shown in the figure, after receiving an external trigger signal, the N-channel MOS transistor controls the circuit power supply process as follows: when its gate voltage is lower than the threshold voltage, the MOS transistor is in the off state, and a high-impedance state is present between the source and the drain; when the gate voltage is higher than the threshold voltage, the MOS transistor is turned on, and a low-impedance path is formed between the source and the drain.

[0054] Specifically, during the rising edge of the high-voltage power supply for gyrotron 1, no trigger signal is applied to the MOS transistor gate, turning it off and RF low-noise amplifier 8.3 off due to power outage. After gyrotron 1 enters a stable operating state, a trigger signal is applied to the MOS transistor gate, turning it on and powering up RF low-noise amplifier 8.3 to begin operation. This solution achieves a switching time of less than 1μs, effectively preventing the impact of rising-edge noise on RF low-noise amplifier 8.3 and protecting heterodyne receiver 8.

[0055] After the RF signal is received by the antenna, it is first input into notch filter 8.1. Strong spurious signals are significantly attenuated by notch filter 8.1, thereby filtering out spurious interference and producing a relatively pure scattered signal. Next, the initially filtered RF signal passes through bandpass filter 8.2 before reaching RF low-noise amplifier 8.3. The switching state of RF low-noise amplifier 8.3 is controlled by an external trigger signal: during the rising edge of the high-voltage power supply of gyrotron 1, the external trigger signal turns off the MOS transistor, rendering RF low-noise amplifier 8.3 inoperative due to power outage. During the stable operation of gyrotron 1, the external trigger signal turns on the MOS transistor, energizing RF low-noise amplifier 8.3 and amplifying the input RF signal. To ensure unidirectional transmission of the RF signal through RF low-noise amplifier 8.3, an isolator 8.4 is added after RF low-noise amplifier 8.3. Isolator 8.4 transmits the signal in one direction only, while providing high isolation (significantly attenuating the signal) in the reverse direction.

[0056] Furthermore, to capture the scattered signal, the RF signal must be down-mixed. The RF signal, after passing through isolator 8.4, is down-mixed in mixer 8.5 with the local oscillator signal generated by local oscillator 8.6 to generate an intermediate frequency (IF) signal. This IF signal is then further amplified by intermediate frequency low-noise amplifier 8.7 and filtered by low-pass filter 8.8 before being output for acquisition by the data acquisition system.

[0057] In combination with the above preferred embodiments, it can be seen that the present invention adopts a signal processing flow of first low-noise amplification and then mixing. This solution can significantly reduce electronic noise, thereby helping to improve the sensitivity of the heterodyne receiver 8.

[0058] Furthermore, in the present invention, a narrowband notch filter 8.1 with a high attenuation coefficient is added before the RF low-noise amplifier 8.3. The RF low-noise amplifier 8.3 is used to amplify received RF signals and has a maximum receivable power. Exceeding this power will saturate or even damage the RF low-noise amplifier 8.3. Therefore, it is necessary to attenuate spurious signals before they enter the RF low-noise amplifier 8.3.

[0059] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device, characterized in that: include: Magnetic confinement fusion device, which is used to generate and confine high-temperature plasma; Gyrotrons, which are used to generate millimeter-wave beams; Three sections of metal corrugated circular waveguides, where two adjacent sections of the metal corrugated circular waveguides are connected by a rotatable polarizer elbow, and the two rotatable polarizer elbows together constitute a rotatable polarizer, which is used to arbitrarily adjust the polarization direction of the light beam; A quasi-optical matching unit is installed at the output of the gyrotron and is used to transform the millimeter wave beam into a TEM 00 mode, and couple the millimeter wave beam into the metal corrugated circular waveguide; An incident reflector system is used to focus the light beam output from the metal corrugated circular waveguide and adjust the beam waist position before injecting it into the vacuum chamber of the magnetic confinement fusion device; a receiving reflector system for adjusting the circumferential angle of the received light beam so that the waist of the received light beam overlaps with the waist of the incident light beam; A heterodyne receiver is used to receive the light beam focused and coupled by the reflector system and record the thermal coherent scattering signal.

2. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 1, characterized in that: The incident reflector system and the receiving reflector system are both arranged on an external support and located on the mid-plane of the magnetic confinement fusion device.

3. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 1, characterized in that: The incident reflector system includes a first ellipsoid reflector, a first plane reflector, a second plane reflector, and a second ellipsoid reflector, which are sequentially arranged along the incident direction of the light beam; The first ellipsoidal reflector and the first plane reflector are both mounted on an external bracket, and a distance between the first ellipsoidal reflector and the first plane reflector is relatively fixed. A first group of reflectors formed by the first ellipsoidal reflector and the first plane reflector can be synchronously translated along the optical axis of the light beam on the external bracket, and a mirror surface of the first ellipsoidal reflector is arranged opposite to a mirror surface of the first plane reflector, so that the light beam is expanded. The second plane reflector is mounted on an external bracket, and the second ellipsoid reflector can rotate around the optical axis and is connected to the magnetic confinement fusion device to focus the light beam and adjust the direction of the light beam incident on the vacuum chamber of the magnetic confinement fusion device. When the second ellipsoid reflector rotates around the line connecting the vertex of its short axis and the focus, it cooperates with the translation of the first group of reflectors to control the focusing position of the light beam in the plasma of the magnetic confinement fusion device.

4. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 3, characterized in that: The receiving reflector system includes a third plane reflector and a third ellipsoid reflector. The third ellipsoid reflector is rotatably connected to the external bracket so that the third ellipsoid reflector can rotate around the line connecting its short axis vertex and the focus to adjust the circumferential angle of the receiving light beam.

5. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 1, characterized in that: Two ends of each rotatable polarizer elbow are fixedly connected to the corresponding metal corrugated circular waveguide.

6. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 5, characterized in that: A grooved metal reflector for adjusting the polarization direction of the light beam is installed in each of the rotatable polarizer elbows.

7. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 6, characterized in that: The rotatable polarizer is rotated by two fluted metal mirrors within the rotatable polarizer elbows to achieve continuous adjustment of the polarization direction.

8. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 1, characterized in that: The background radiation generated by the plasma itself in the magnetic confinement fusion device is collected by a receiving reflector system, and the signal is recorded by a heterodyne receiver.

9. A thermal coherent scattering system for measuring ion temperature in a magnetic confinement fusion device according to claim 8, characterized in that: During the period when the gyrotron is turned on, the heterodyne receiver records the superposition signal of the thermal coherent scattering signal of the first duration and the plasma background radiation; During the gyrotron shutdown period, the heterodyne receiver records the plasma background radiation signal of the same duration; The two signals are aligned and differentially processed in the time domain to eliminate background radiation noise and extract pure thermal coherent scattering signals.

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