A multi-channel microwave diagnostic system

Abstract

The present invention discloses a multi-channel microwave diagnostic system, comprising a multi-channel microwave generation and emission system, a Doppler backscatter meter (DBS) system, a cross-polarization scattering diagnostic (CPS) system, and a frequency-adjustable reference source. The multi-channel microwave generation and emission system is used to generate multi-channel scattered signals. The Doppler backscatter meter (DBS) system and the cross-polarization scattering diagnostic (CPS) system are integrated and share the multi-channel microwave generation and emission system to achieve synchronous measurement of local density fluctuations and magnetic fluctuations at multiple locations within a fusion device. The frequency-adjustable reference source is used to mix the received multi-channel scattered signals, and the target frequency point to be measured is selected according to experimental requirements. This system can solve the problem of synchronously measuring local density fluctuations and magnetic fluctuations at multiple locations within a fusion device, while also addressing the problem of uneven power distribution between frequency peaks in comb spectrum generator solutions.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave diagnosis, and in particular to a multi-channel microwave diagnosis system. Background Art

[0002] Existing microwave diagnostic systems use comb spectrum generators to produce multi-channel schemes, which have the problem of unstable power distribution between multi-channel frequency peaks. Regular adjustment is required to maintain the uniformity of the frequency peaks, and the detection frequency range is fixed, which limits the flexibility of the Doppler backscattering (DBS) diagnostic system. At the same time, the existing DBS diagnostic system can only measure the density fluctuations and velocity fluctuations of the plasma, and cannot measure magnetic fluctuation signals. Diagnostic systems such as magnetic probes and polarization interferometers POINT are also unable to measure local magnetic fluctuation signals. Summary of the Invention

[0003] The purpose of the present invention is to provide a multi-channel microwave diagnostic system that can solve the problem of synchronously measuring local density fluctuations and magnetic fluctuations at multiple locations inside a fusion device, while solving the problem of uneven power distribution between frequency peaks in the comb spectrum generator scheme. The system can select the frequency points that need to be measured in real time according to experimental requirements.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A multi-channel microwave diagnostic system, comprising a multi-channel microwave generation and emission system, a Doppler backscatter meter DBS system, a cross-polarization scattering diagnostic CPS system, and a frequency-adjustable reference source, wherein:

[0006] The multi-channel microwave generation and transmission system is used to generate multi-channel scattered signals;

[0007] The Doppler backscatter meter DBS system is integrated with the cross-polarization scattering diagnosis CPS system, sharing the multi-channel microwave generation and transmission system to achieve synchronous measurement of local density fluctuations and magnetic fluctuations at multiple locations inside the fusion device;

[0008] Use an adjustable frequency reference source to mix with the received multi-channel scattered signals, and select the target frequency point to be measured according to the experimental requirements, where:

[0009] The reference signal from the adjustable frequency reference source is mixed with the received signals from the DBS system and the CPS system to generate an intermediate frequency signal, which serves as the RF input of the IQ mixer. The reference signal is mixed with the transmitted signal in the reference signal mixer to generate an intermediate frequency signal, which is split into two channels through a power divider and enters the DBS system and the CPS system respectively, serving as the LO input of the IQ mixer.

[0010] The intermediate frequency signals of the reference path and the receiving path are both demodulated into IQ signals in the IQ mixer, and the IQ signals are collected by the high-speed data stream system.

[0011] It can be seen from the technical solution provided by the above-mentioned present invention that the above-mentioned system can solve the problem of synchronously measuring local density fluctuations and magnetic fluctuations at multiple locations inside the fusion device, and at the same time solve the problem of uneven power distribution between frequency peaks in the comb spectrum generator solution, and can select the frequency points that need to be measured in real time according to experimental requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 A schematic structural diagram of a multi-channel microwave diagnostic system provided in an embodiment of the present invention;

[0014] Figure 2 Schematic diagram of the relationship between peak value and power at 4f0=54.8GHz for the example of the present invention;

[0015] Figure 3 This is a schematic diagram of the relationship between peak value and power for the example 4f0=66.8GHz given in the present invention. DETAILED DESCRIPTION

[0016] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, and do not constitute a limitation of the present invention. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0017] like Figure 1 This is a schematic diagram of the structure of a multi-channel microwave diagnostic system provided in an embodiment of the present invention. The system includes a multi-channel microwave generation and transmission system (the first part in the figure), a Doppler backscatter meter DBS system (the second part in the figure), a cross-polarization scattering diagnosis CPS system (the third part in the figure), and an adjustable frequency reference source 9, wherein:

[0018] The multi-channel microwave generation and transmission system is used to generate multi-channel scattered signals;

[0019] The Doppler backscatter meter DBS system is integrated with the cross-polarization scattering diagnosis CPS system, sharing the multi-channel microwave generation and transmission system to achieve synchronous measurement of local density fluctuations and magnetic fluctuations at multiple locations inside the fusion device;

[0020] Specifically, microwaves of the same detection frequency undergo Doppler backscattering and cross-polarization scattering simultaneously near the plasma cutoff layer in the fusion device, where:

[0021] For the Doppler backscattering process, according to the Bragg scattering formula:

[0022]

[0023] k i,X-mode is the incident wave number, which can be calculated based on the incident microwave; k s，X-mode is the scattering wave number, k in the backscattering process s,X-mode =-k i，X-mode ; is the measured density fluctuation wave number;

[0024] By tracking and detecting the microwave wave traces in the plasma of the fusion device, the wave number and cutoff position information of the density fluctuation measured by the Doppler backscattering meter can be calculated. At the same time, the movement of the cutoff layer will introduce the Doppler frequency shift f D =(k·u) / 2π, the DBS Doppler shift f is measured D , the velocity u of density fluctuations can be measured, thereby realizing the measurement of local density fluctuations inside the fusion device;

[0025] For the cross-polarization scattering process, according to the conservation of momentum:

[0026]

[0027] The magnetic fluctuations near the cutoff layer will vertically change the polarization direction of the incident microwave, e.g. Figure 1 The middle transmitting antenna 8 transmits microwaves with X-mode polarization into the fusion device, while the magnetic fluctuation signal received by the CPS receiving antenna 12 is with O-mode polarization. Since the time and position of cross-polarization scattering are almost identical to the Doppler backscattering process, the position can be obtained using a ray tracing program, just like the measurement position of density fluctuations.

[0028] Simultaneous magnetic fluctuation wave number Also satisfies the relationship: f D =(k·u) / 2π, and the CPS Doppler frequency shift f is obtained by measurement. D , substituting the velocity u of the density fluctuation measured by the DBS system, the actual density fluctuation wave number can be measured This enables the measurement of local magnetic fluctuations inside the fusion device;

[0029] The present invention is a multi-channel system, and uses a high-speed data acquisition system 15 with the same clock to simultaneously acquire data from a 5-channel DBS system and a 3-channel CPS system, thereby enabling synchronous measurement of local density fluctuations and magnetic fluctuations at multiple locations within a fusion device.

[0030] The cross-polarization scattering diagnostic CPS system can not only be used to measure quasi-local magnetic fluctuations, but also can simultaneously measure the radial distribution of magnetic fluctuations at different radial positions.

[0031] Use the adjustable frequency reference source 9 to mix with the received multi-channel scattered signal, and select the target frequency point to be measured according to the experimental requirements, where:

[0032] The reference signal from the adjustable frequency reference source 9 is mixed with the received signals from the DBS system and the CPS system to generate an intermediate frequency signal, which serves as the RF input of the IQ mixer 16. The reference signal is mixed with the transmitted signal from the reference signal mixer 13 to generate an intermediate frequency signal, which is split into two channels by the power divider 18 and enters the DBS system and the CPS system respectively, serving as the L0 input of the IQ mixer 16.

[0033] The intermediate frequency signals of the reference path and the receiving path are both demodulated into IQ signals in the IQ mixer 16 , and the IQ signals are collected by the high-speed data acquisition system 15 .

[0034] In a specific implementation, the multi-channel microwave generation and transmission system includes a microwave source 1, an amplifier 2, a comb spectrum generator 3, a bandpass filter 4, a frequency multiplier 5, an EH tuner 6, a directional coupler 7 and a transmitting antenna 8, wherein:

[0035] In the multi-channel microwave generation and transmission system, a broadband frequency synthesizer is used as the microwave source 1, with an output frequency range of 2-4 GHz and a minimum adjustable frequency step of 1 MHz. The output of the microwave source 1 is set to 3.0 GHz. By using a bandpass filter 4 with a frequency range of 12-18 GHz, three specific frequencies of 12 GHz, 15 GHz, and 18 GHz are filtered out from the output of the comb spectrum generator 3.

[0036] Then, the three selected specific frequencies are further multiplied and optimized by the frequency multiplier 5 and the EH tuner 6 to reach the frequency range of 48-72 GHz (V band, Δf = 3.0 GHz);

[0037] Therefore, nine microwaves of fixed frequencies are emitted into the plasma, and they can all be regarded as probe microwave beams.

[0038] The Doppler backscatter meter DBS system includes a DBS signal mixer 10, a low-pass filter 17 and five DBS channels, wherein:

[0039] In the receiving part of the Doppler backscatter meter DBS system, the transmitting antenna 8 in the multi-channel microwave generation and transmission system also serves as the receiving antenna of the DBS system, mixing the received signal with the reference signal in the DBS signal mixer 10 to obtain an intermediate frequency signal;

[0040] The down-converted IF signals from the reference signal mixer 13 and the DBS signal mixer 10 are both passed through the low-pass filter 17 and divided into five DBS channels;

[0041] The reference signal and DBS signal of each channel are passed through a narrow broadband filter 14 after the center frequency is selected to filter out the signal frequencies of other channels and maximize the retention of the signal after the frequency selection;

[0042] In the IQ mixer 16 , the reference signal input from the LO and the DBS signal input from the RF are mixed, and down-converted I and Q signals are output. The down-converted signals are then collected and stored by the high-speed data acquisition system 15 .

[0043] like Figure 1 As shown, the receiving part of the cross-polarization scattering diagnostic CPS system includes a separate CPS receiving antenna 12, a CPS signal mixer 11, a narrow broadband filter 14, an IQ mixer 16, a low-pass filter 17, a power divider 18 and three DBS channels, wherein:

[0044] A separate CPS receiving antenna 12 is used to receive the CPS signal, whose polarization direction is perpendicular to the transmitting antenna. The received signal is mixed with the reference signal in the CPS signal mixer 11 to obtain an intermediate frequency signal;

[0045] The down-converted IF signals from the reference signal mixer 13 and passing through the power divider 18 and the DBS signal mixer 10 all pass through the low-pass filter 17 and are divided into three CPS channels;

[0046] The reference signal and CPS signal of each channel are passed through a narrow broadband filter 14 after the center frequency is selected to filter out the signal frequencies of other channels and maximize the retention of the signal after the frequency selection;

[0047] In the IQ mixer 16 , the reference signal input from the LO and the CPS signal input from the RF are mixed, and down-converted I and Q signals are output. The down-converted signals are then collected and stored by the high-speed data acquisition system 15 .

[0048] In a specific implementation, since the power difference between the multi-channel frequency peaks after the comb spectrum generator in the DBS and CPS integrated diagnostic system is large (>10dB), it is necessary to evenly distribute the multi-channel peaks through the EH tuner 6 to solve the problem of uneven power distribution between frequency peaks in the comb spectrum generator solution and ensure that the output power of different frequency peaks is basically consistent. Specifically:

[0049] The system uses a V-band (50-75GHz) EH tuner. Both the E-plane and H-plane arms of the EH tuner have micrometer-driven adjustable shorts to introduce discontinuities into the waveguide transmission line to simultaneously control the phase and amplitude of the RF reflection coefficient, achieving precise tuning and reproduction settings.

[0050] By adjusting the E-plane and H-plane arms of the EH tuner until the power distribution of microwave signals of different frequencies in the V band is balanced, the problem of uneven power distribution of multi-channel microwave signals generated by a comb spectrum generator is solved.

[0051] The internal short circuit is a contactless choked plunger that provides a highly stable electrical short circuit, and the locking mechanism ensures continued set reliability under all normal conditions of test bench shock and vibration.

[0052] For example, Figure 1 The detection frequencies of DBS and CPS systems are:

[0053] 4f0-0.8, 4f0+2.2, 4f0-3.8, 4f0+5.2, 4f0-6.8GHz

[0054] and 4f0-0.8, 4f0+2.2, 4f0+5.2GHz

[0055] By changing f0, the detection frequency can be changed;

[0056] The EH tuner 6 is used to optimize and redistribute the power of different frequencies to ensure that the output power of different frequency peaks is basically consistent, such as Figure 2 The figure shows the relationship between the peak value and power of the example 4f0=54.8GHz in the present invention. Figure 3 The figure shows the relationship between the peak value and power of the example 4f0=66.8 GHz of the present invention. For 4f0=54.8 GHz and 4f0=66.8 GHz, the power difference between the peak values ​​is almost within 5 dB.

[0057] In addition, the frequency-adjustable reference source used is model LMS-183DX, an adjustable microwave source with a frequency range of 6-18 GHz;

[0058] The stabilization time of the adjustable frequency reference source frequency synthesizer (the time required for the frequency to be adjusted to within 50kHz of the target frequency) is 100μs, so the measurement frequency adjustment can be completed within 100μs, allowing the system to change the measurement frequency during different discharge experiment intervals and also during a discharge experiment.

[0059] It should be noted that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A multi-channel microwave diagnostic system, characterized in that: The system includes a multi-channel microwave generation and emission system, a Doppler backscatter meter DBS system, a cross-polarization scattering diagnosis CPS system, and a frequency-adjustable reference source, wherein: The multi-channel microwave generation and transmission system is used to generate multi-channel scattered signals; The Doppler backscatter meter DBS system and the cross-polarization scattering diagnosis CPS system are integrated and share the multi-channel microwave generation and emission system to achieve synchronous measurement of local density fluctuations and magnetic fluctuations at multiple locations inside the fusion device. The process of synchronously measuring local density fluctuations and magnetic fluctuations at multiple locations inside the fusion device by the Doppler backscatter meter DBS system and the cross-polarization scattering diagnosis CPS system is specifically as follows: Microwaves of the same detection frequency undergo Doppler backscattering and cross-polarization scattering simultaneously near the plasma cutoff layer in the fusion device, where: For the Doppler backscattering process, according to the Bragg scattering formula: ； is the incident wave number, calculated from the incident microwave; is the scattered wave number, in the backscattering process ; is the measured density fluctuation wave number; By tracking the microwave wave traces in the plasma of the fusion device, the wave number and cutoff position information of the density fluctuation measured by the Doppler backscattering meter are calculated. At the same time, the movement of the cutoff layer will introduce the Doppler frequency shift. , the DBS Doppler shift is measured , measuring the speed of density fluctuations , thereby realizing the measurement of local density fluctuations inside the fusion device; For the cross-polarization scattering process, according to the conservation of momentum: ； Magnetic fluctuations near the cutoff layer will vertically change the polarization direction of the incident microwave. Since the time and position of cross-polarization scattering are almost consistent with the Doppler backscattering process, it can be obtained using a ray tracing program, just like the measured position of density fluctuations. Simultaneous magnetic fluctuation wave number Also satisfies the relationship: , the CPS Doppler shift is obtained by measuring , substitute the velocity of density fluctuation measured by DBS system into , the actual density fluctuation wave number is measured , thereby realizing the measurement of local magnetic fluctuations inside the fusion device; The cross-polarization scattering diagnostic CPS system is not only used to measure quasi-local magnetic fluctuations, but also to simultaneously measure the radial distribution of magnetic fluctuations at different radial positions. Use an adjustable frequency reference source to mix with the received multi-channel scattered signals, and select the target frequency point to be measured according to the experimental requirements, where: The reference signal from the adjustable frequency reference source is mixed with the received signals from the DBS system and the CPS system to generate an intermediate frequency signal, which serves as the RF input of the IQ mixer. The reference signal is mixed with the transmitted signal in the reference signal mixer to generate an intermediate frequency signal, which is split into two channels through a power divider and enters the DBS system and the CPS system respectively, serving as the LO input of the IQ mixer. The intermediate frequency signals of the reference path and the receiving path are both demodulated into IQ signals in the IQ mixer, and the IQ signals are collected by a high-speed data acquisition system.

2. The multi-channel microwave diagnostic system according to claim 1, characterized in that: The multi-channel microwave generation and transmission system includes a microwave source, an amplifier, a comb spectrum generator, a bandpass filter, a frequency multiplier, an EH tuner, a directional coupler and a transmitting antenna, wherein: A broadband frequency synthesizer is used as a microwave source with an output frequency range of 2-4 GHz and a minimum adjustable frequency step of 1 MHz. The output of the microwave source is set to 3.0 GHz. By using a bandpass filter with a frequency range of 12-18 GHz, three specific frequencies of 12 GHz, 15 GHz, and 18 GHz are filtered out from the output of the comb spectrum generator. The three selected specific frequencies are then further multiplied and optimized through a frequency multiplier and EH tuner to reach a frequency range of 48-72 GHz.

3. The multi-channel microwave diagnostic system according to claim 1, characterized in that: The Doppler backscatter meter DBS system includes a DBS signal mixer, a low-pass filter and five DBS channels, wherein: In the receiving part of the Doppler backscatter meter DBS system, the transmitting antenna in the multi-channel microwave generation and transmission system also serves as the receiving antenna of the DBS system, mixing the received signal with the reference signal in the DBS signal mixer to obtain an intermediate frequency signal; The down-converted IF signals from the reference signal mixer and the DBS signal mixer are both passed through low-pass filters and divided into five channels; The reference signal and DBS signal of each channel are filtered through a narrow broadband filter after selecting the center frequency to filter out the signal frequencies of other channels and maximize the retention of the signal after frequency selection; In the IQ mixer, the reference signal from the LO input and the DBS signal from the RF input are mixed, and the down-converted I signal and Q signal are output and collected and stored by the high-speed data acquisition system.

4. The multi-channel microwave diagnostic system according to claim 1, characterized in that: The receiving part of the cross-polarization scattering diagnostic CPS system includes a separate CPS receiving antenna, a CPS signal mixer, a narrow broadband filter, an IQ mixer, a low-pass filter, a power divider and three DBS channels, wherein: A separate CPS receiving antenna is used to receive the CPS signal, with its polarization direction perpendicular to the transmitting antenna. The received signal is mixed with the reference signal in the CPS signal mixer to obtain an intermediate frequency signal; The down-converted IF signals from the reference signal mixer and through the power divider and DBS signal mixer are all passed through a low-pass filter and divided into three CPS channels; The reference signal and CPS signal of each channel are filtered through a narrow broadband filter after selecting the center frequency to filter out the signal frequencies of other channels and maximize the retention of the signal after frequency selection; In the IQ mixer, the reference signal from the LO input and the CPS signal from the RF input are mixed, and the down-converted I signal and Q signal are output and collected and stored by the high-speed data acquisition system.

5. The multi-channel microwave diagnostic system according to claim 1, characterized in that: The EH tuner evenly distributes multiple peaks to solve the problem of uneven power distribution between frequency peaks in the comb spectrum generator solution, ensuring that the output power of different frequency peaks is basically consistent. Specifically: Both the E-plane and H-plane arms of the EH tuner feature micrometer-driven adjustable shorts that introduce discontinuities into the waveguide transmission line to simultaneously control the phase and amplitude of the RF reflection coefficient, enabling precise tuning and reproduction settings. By adjusting the E-plane and H-plane arms of the EH tuner, the power distribution of microwave signals of different frequencies in the V band is balanced, thereby solving the problem of uneven power distribution of multi-channel microwave signals generated by a comb spectrum generator.

6. The multi-channel microwave diagnostic system according to claim 1, characterized in that: The frequency-adjustable reference source used is model LMS-183DX, an adjustable microwave source with a frequency range of 6-18 GHz; The stabilization time of the frequency change of the adjustable frequency reference source frequency synthesizer is 100μs, so the measurement frequency adjustment can be completed within 100μs, so that the system can change the measurement frequency during the intervals between different discharge experiments, and can also change the measurement frequency during a discharge experiment.

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