An absolute calibration system for electron cyclotron emission based on a blackbody source

Abstract

The present application belongs to the technical field of tokamak, and particularly relates to an absolute calibration system of electron cyclotron radiation based on a blackbody source. The present application comprises an adjustable mirror, a blackbody source, a chopper, a microwave antenna, a band-stop filter, a high-pass filter, a low-noise radio frequency amplifier, a directional coupler, a radio frequency mixer, a directional coupler, a voltage-controlled microwave source, a signal generator, a band-pass filter, an intermediate frequency amplifier, a power divider, an intermediate frequency band-pass filter, an intermediate frequency amplifier, an intermediate frequency mixer, an intermediate frequency Gunt oscillator, an adjustable attenuator, a band-pass filter, a detector, a low-pass filter, a video amplifier, a data collector, an electronic antenna and an industrial computer. The present application is simple in method for obtaining electron cyclotron radiation, good in stability, low in difficulty, can be calibrated in real time during discharge, and is very convenient.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tokamak, and particularly relates to an absolute calibration system for electron cyclotron radiation based on a blackbody source. BACKGROUND

[0002] In a tokamak plasma, the measurement of electron temperature is a very important work. The calculation of plasma pressure distribution by electron temperature measurement and other plasma parameters is crucial for the study of magnetic fluid instability, plasma control, disruption, high-energy particles, turbulent instability and plasma transport. As a conventional electron temperature diagnostic technique, the electron cyclotron radiation meter has been fully developed in recent years. Its advantages as an electron temperature diagnostic means lie in its high temporal and spatial resolution, and the simple proportional relationship between signal strength and electron temperature, which makes data processing convenient. In order to realize the absolute measurement of plasma electron temperature, the electron cyclotron radiation meter needs to be absolutely calibrated to obtain the calibration coefficient between signal strength and electron temperature.

[0003] At present, the calibration methods of the electron cyclotron radiation meter include absolute blackbody calibration method and relative calibration method. In order to maintain the independence of the interpretation of electron cyclotron radiation meter diagnostic data, absolute calibration is very necessary. The usual absolute calibration method is based on a calibration temperature radiation source, such as a blackbody radiation source and liquid nitrogen. By simulating the cyclotron radiation in the plasma with the microwave radiation of the blackbody radiation source and emitting it into the electron cyclotron radiation meter, the proportional coefficient of the blackbody radiation temperature and the response amplitude of the electron cyclotron radiation meter can be obtained. The calibration coefficient is applied to the plasma discharge test to calculate the electron temperature in the plasma. Although the absolute calibration method can obtain the absolute calibration coefficient, the absolute calibration coefficient deviates from the true calibration coefficient over time due to many factors. At the same time, due to the very weak intensity of the blackbody radiation, the absolute calibration process needs a long time operation, which increases the difficulty of obtaining the calibration coefficient. Therefore, the traditional blackbody source absolute calibration is complex, has poor stability and is difficult. SUMMARY

[0004] The technical problem solved by the application is that the traditional blackbody source absolute calibration is complex, has poor stability and is difficult. The application provides an absolute calibration system for electron cyclotron radiation based on a blackbody source. The relative change coefficient of the local oscillator frequency hopping electron cyclotron radiation meter is measured by the blackbody source, the absolute calibration coefficient is obtained, and the relative change rate between the frequency hopping frequencies is also obtained. After obtaining the relative change rate between the frequency hopping frequencies, the blackbody source is no longer needed for absolute calibration, but the absolute calibration coefficient of all electron cyclotron radiation channels is obtained according to the relative change rate of the frequency hopping frequencies and the single-point electron temperature information. The method for obtaining the electron cyclotron radiation of the application is simple, has good stability, is less difficult, can be calibrated in real time during discharge, and is very convenient.

[0005] The technical scheme adopted by the present application is as follows:

[0006] An absolute calibration system of electron cyclotron radiation based on a blackbody source, comprising an adjustable reflector, a blackbody source, a chopper, a microwave antenna, a band-stop filter, a high-pass filter, a low-noise radio frequency amplifier, a directional coupler, a radio frequency mixer, a directional coupler, a voltage-controlled microwave source, a signal generator, a band-pass filter, an intermediate frequency amplifier, a power divider, an intermediate frequency band-pass filter, an intermediate frequency amplifier, an intermediate frequency mixer, an intermediate frequency geng oscillator, an adjustable attenuator, a band-pass filter, a detector, a low-pass filter, a video amplifier, a data collector, an electronic antenna, and an industrial computer; the adjustable reflector is placed in front of the electronic antenna, and the reflecting surface of the adjustable reflector is aligned with the radiation surface of the blackbody source; the blackbody source is connected with the chopper; the microwave antenna is placed right behind the chopper; the microwave antenna is connected with the band-stop filter at the rear end; the band-stop filter is connected with the high-pass filter at the rear end; the high-pass filter is connected with the low-noise radio frequency amplifier at the rear end; the signal of the low-noise radio frequency amplifier is connected with the directional coupler; the microwave signal is input to the radio frequency end of the radio frequency mixer through the directional coupler; the local oscillator end of the radio frequency mixer is connected with the directional coupler and the voltage-controlled microwave source in sequence; the intermediate frequency signal generated by the mixing of the radio frequency and local oscillator signals of the radio frequency mixer is connected with the band-pass filter; the filtered intermediate frequency signal is input to the intermediate frequency amplifier and then to the power divider; the intermediate frequency signal is sent to the intermediate frequency channel; the wideband intermediate frequency signal is filtered to the working intermediate frequency band through the intermediate frequency band-pass filter; the narrowband intermediate frequency signal passing through the intermediate frequency band-pass filter is input to the intermediate frequency amplifier and then to the intermediate frequency mixer; the local oscillator end of the intermediate frequency mixer is connected with the intermediate frequency geng oscillator corresponding to the working frequency; the second-order intermediate frequency signal generated by the mixing of the intermediate frequency mixer is input to the adjustable attenuator; the second-order intermediate frequency signal is input to the band-pass filter; the final signal is input to the detector; the detected signal is input to the low-pass filter; the low-pass filtered signal is input to the video amplifier; the signal amplitude is increased, and finally the signal is input to the data collector.

[0007] The microwave antenna receives the signal passing through the chopper from the blackbody source.

[0008] The high-pass filter filters out the mirror frequency signal of the ECE radio frequency, and the low-frequency attenuation is greater than 30 dB.

[0009] The noise coefficient of the low-noise radio frequency amplifier is lower than 5 dB, and the amplification gain is greater than 20 dB; the band-stop of the band-stop filter is greater than 60 dB, so that the microwave signal strength entering the low-noise radio frequency amplifier is weaker than -10 dB.

[0010] The signal outside the intermediate frequency working band is suppressed by more than 30 dB.

[0011] The band-pass filter selects a band-pass frequency band of 30 MHz to 300 MHz, so that the spatial resolution of the ECE measured current distribution reaches 1 to 2 centimeters.

[0012] Through the industrial computer, the square wave voltage value of the signal generator is set to 1, 2V, and the period is 10ms.

[0013] Through the industrial computer, the working temperature of the blackbody source is set to 600 DEG C.

[0014] Compared with the prior art, the beneficial effects of the present application are:

[0015] (1) The absolute calibration system of electron cyclotron radiation based on a blackbody source provided by the present application firstly measures the characteristic curve of the voltage-controlled microwave source, simultaneously sets the signal generator to make the working frequency bands of adjacent channels of the electron cyclotron radiation meter completely consistent, and then uses the blackbody source to calibrate the absolute calibration coefficients and the relative change coefficients before and after frequency hopping; in the formal experimental calibration, with the periodic change of the local oscillator frequency, the received plasma microwave signal also changes periodically, and through formula calculation, the absolute calibration coefficients of all channels are obtained, so that the electron cyclotron radiation meter can be calibrated in real time.

[0016] (2) The absolute calibration system of electron cyclotron radiation based on a blackbody source provided by the present application overcomes the problems of complex operation, poor stability and great difficulty in traditional calibration, and is a very practical electron cyclotron radiation meter calibration method. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The structure schematic diagram of the absolute calibration system of electron cyclotron radiation based on a blackbody source provided by the present application is shown in the figure.

[0018] In the figure: 1-adjustable mirror, 2-blackbody source, 3-chopper, 4-microwave antenna, 5-band elimination filter, 6-high pass filter, 7-low noise radio frequency amplifier, 8-directional coupler, 9-radio frequency mixer, 10-directional coupler, 11-voltage-controlled microwave source, 12-signal generator, 13-band pass filter, 14-intermediate frequency amplifier, 15-power divider, 16-intermediate frequency band pass filter, 17-intermediate frequency amplifier, 18-intermediate frequency mixer, 19-intermediate frequency Gunn oscillator, 20-adjustable attenuator, 21-band pass filter, 22-detector, 23-low pass filter, 24-video amplifier, 25-data acquisition device, 26-electronic antenna, 27-industrial computer. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0021] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0022] As Figure 1 As shown in the figure, the present application provides an absolute calibration system for electron cyclotron radiation based on blackbody source, which comprises an adjustable mirror 1, a blackbody source 2, a chopper 3, a microwave antenna 4, a band-stop filter 5, a high-pass filter 6, a low-noise RF amplifier 7, a directional coupler 8, an RF mixer 9, a directional coupler 10, a voltage-controlled microwave source 11, a signal generator 12, a band-pass filter 13, an intermediate frequency amplifier 14, a power divider 15, an intermediate frequency band-pass filter 16, an intermediate frequency amplifier 17, an intermediate frequency mixer 18, an intermediate frequency Gunt oscillator 19, an adjustable attenuator 20, a band-pass filter 21, a detector 22, a low-pass filter 23, a video amplifier 24, a data acquisition device 25, an industrial computer 27,

[0023] The adjustable reflector 1 is placed in front of the electronic antenna 26, the reflecting surface of the adjustable reflector 1 is aligned with the radiation surface of the black body source 2, the black body source 2 is connected with the chopper 3, the microwave antenna 4 is placed in front of the chopper 3, receives the signal from the black body source 2 through the chopper 3, the rear end of the microwave antenna 4 is connected with the band elimination filter 5 for filtering the frequency band of the electron cyclotron heating, the rear end of the band elimination filter 5 is connected with the high-pass filter 6 for filtering the mirror frequency signal of the ECE radio frequency, the low frequency attenuation is greater than 30dB. The rear end of the high-pass filter 6 is connected with the low-noise radio frequency amplifier 7 for improving the signal-to-noise ratio of the signal, the noise coefficient of the low-noise radio frequency amplifier 7 is less than 5dB, the amplification gain is greater than 20dB, the band elimination of the band elimination filter 5 should be greater than 60dB, so that the microwave signal entering the low-noise radio frequency amplifier 7 is weaker than -10dB. The signal passing through the low-noise radio frequency amplifier 7 is connected with the directional coupler 8 for preventing the reflected standing wave from damaging the low-noise amplifier 7. The microwave signal is input to the radio frequency end of the radio frequency mixer 9 through the directional coupler 8, and the local oscillator end of the radio frequency mixer 9 is sequentially connected with the directional coupler 10 and the voltage-controlled microwave source 11.

[0024] The radio frequency and the local oscillator signal of the radio frequency mixer 9 are mixed to generate an intermediate frequency signal, which is input to the band-pass filter 13 for filtering the stray signals outside the working frequency band. The filtered intermediate frequency signal is input to the intermediate frequency amplifier 14 and then to the power divider 15, and then the intermediate frequency signal is sent to the intermediate frequency channel. The intermediate frequency signal is filtered to the working intermediate frequency band by the intermediate frequency band-pass filter 16. In order to ensure the interpretability of the intermediate frequency signal, the signal outside the intermediate frequency working frequency band needs to be suppressed by more than 30dB. The narrowband intermediate frequency signal passing through the intermediate frequency band-pass filter 16 is input to the intermediate frequency amplifier 17 to improve the signal-to-noise ratio of the intermediate frequency signal, and then input to the intermediate frequency mixer 18, and the local oscillator end of the intermediate frequency mixer 18 is connected with the intermediate frequency Gunn oscillator 19 corresponding to the working frequency. The second intermediate frequency signal generated by mixing is input to the adjustable attenuator 20 to adjust the strength of the signal. The second intermediate frequency signal with appropriate signal strength is input to the band-pass filter 21 to filter out the low-frequency interference signal, and the band-pass frequency band of 30MHz to 300MHz is usually selected, so that the spatial resolution of the ECE current distribution reaches 1 to 2 centimeters. The final signal is input to the detector 22 to measure the strength of the signal, the detected signal is input to the low-pass filter 23 to filter out the high-frequency interference signal, and a low-pass filter of 300kHz is generally selected. The low-pass filtered signal is input to the video amplifier 24 to increase the signal amplitude and finally input to the data collector 25.

[0025] The working principle of the application is as follows:

[0026] Firstly, the characteristic curve of the voltage-controlled microwave source 11 is tested to obtain the relationship between the input voltage and the output microwave frequency, and the voltage value of the square wave voltage output by the signal generator 12 is set according to the working frequency of the electronic system channel. For example, when the initial local oscillator of the multi-channel electron spin resonance meter is 60 GHz, the working frequency is 61, 62,..., 90, 91 GHz, and when the frequency hopping local oscillator is 61 GHz, the working frequency is 62, 63,..., 91, 92 GHz, the output voltage of the voltage-controlled microwave source 11 is required to be 1 V and 2 V respectively when the output frequency is 60 GHz and 61 GHz, so the square wave voltage value of the signal generator 12 is set to 1 V and 2 V respectively by the industrial computer 27, and the period is 10 ms. Then, the working temperature of the blackbody source 2 is set to 600°C by the industrial computer 27, the adjustable mirror 1 is set so that the reflecting surface is aligned with the radiation surface of the blackbody source 2, and the rotation period of the chopper 3 is set to 1 ms.

[0027] The calibration is performed by frequency hopping method, which has the characteristic that the measurement positions of adjacent two channels can be completely consistent through frequency hopping. However, due to the problems such as electronic response before and after frequency hopping, the calibration result has certain error. However, by evaluating the response coefficients before and after frequency hopping through the blackbody source, the accurate absolute calibration coefficient can be obtained. At the same time, due to the similarity of the time evolution of the calibration coefficients of adjacent channels, after evaluating the relative change coefficient of frequency hopping, the absolute calibration coefficient can be obtained by using the frequency hopping method plus the single-point electron temperature information. In the following formula, i is the channel number of the electron spin resonance meter, f i is the working frequency of the electron spin resonance meter i channel, I i (f i ) and I bi (f i ) are respectively the electron spin resonance signal intensities received by the i channel at the frequency f i of the plasma and the blackbody source, C i (f i ) is the absolute calibration coefficient of the i channel at the frequency f i , T e (f i ) and T b (f i ) are respectively the plasma electron temperature and the radiation temperature of the blackbody source corresponding to the frequency f i , and S i is the relative change coefficient of the i channel before and after frequency hopping. Firstly, the characteristic curve of the voltage-controlled microwave source is tested to obtain the relationship between the input voltage and the frequency; the square wave voltage output by the signal source is set according to the working frequency of the electron spin resonance meter, so that the output frequency of the local oscillator end is just enough to make the adjacent two channels work in the same frequency band; the mirror is adjusted so that the radiation of the blackbody source is incident on the electronic antenna, and the signal source is turned on. Through formula (4) and formula (5), the absolute calibration coefficients before and after frequency hopping and the relative change coefficient S are obtained.i After the correlation coefficient is obtained, the experiment calibration is carried out to obtain the intensity of the plasma microwave radiation before and after frequency hopping, and the absolute calibration coefficient is obtained through formula (7) and the frequency hopping calibration method; the subsequent calibration work no longer needs the blackbody source, and the relative change coefficient S is still used i , the accurate relative calibration coefficient is obtained, and the absolute calibration coefficient of the entire electron cyclotron radiometer is obtained through the absolute temperature information of a single point.

[0028] I i (f i )×C i (f i )= T e (f i ) (1)

[0029] I i (f i+1 )×C i (f i+1 )= T e (f i+1 ) (2)

[0030] I i+1 (f i+1 )×C i+1 (f i+1 )= T e (f i+1 ) (3)

[0031] I bi (f i )×C i (f i )= T b (f i ) (4)

[0032] I bi (f i+1 )×C i (f i+1 )= T b (f i+1 ) (5)

[0033]

[0034]

[0035] The control signal and the blackbody radiation signal I bi (f i ) collected by the data collector 25 are processed. Since the blackbody radiation signal intensity is weak, a long time of calibration is required, and then the blackbody radiation signals I bi (f i) time average, absolute calibration coefficients and relative variation coefficients S of different local oscillators are obtained i .

[0036] Finally, the real experiment calibration is carried out, the tunable mirror 1 and the chopper 3 are adjusted by the industrial computer 27 so that the electron cyclotron emission signal of the plasma enters the electronic system without loss. The output square wave voltage value of the signal generator 12 is still set to 1V and 2V respectively, and the control signal and the plasma electron cyclotron emission signal I i (f i ) are collected by the data collector 25, and the absolute calibration coefficients of all channels are calculated by using formula (7) and the relative variation coefficients obtained before.

[0037] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the present application being defined by the appended claims rather than the above description, and it is intended to embrace all changes and modifications that fall within the meaning and range of equivalents of the claims. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

[0038] Furthermore, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the present specification is described in this way only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A blackbody source based absolute calibration system for electron cyclotron emission, characterized in that, The adjustable mirror (1), blackbody source (2), chopper (3), microwave antenna (4), band-stop filter (5), high-pass filter (6), low-noise RF amplifier (7), first directional coupler (8), RF mixer (9), second directional coupler (10), voltage-controlled microwave source (11), signal generator (12), first band-pass filter (13), first IF amplifier (14), power divider (15), IF band-pass filter (16), second IF amplifier (17), IF mixer (18), IF geng oscillator (19), adjustable attenuator (20), second band-pass filter (21), detector (22), low-pass filter (23), video amplifier (24), data collector (25), electronic antenna (26), industrial computer (27), the adjustable mirror (1) is placed at the front end of the electronic antenna (26), the reflecting surface of the adjustable mirror (1) is aligned with the radiation surface of the blackbody source (2), the blackbody source (2) is connected with the chopper (3), the microwave antenna (4) is placed right behind the chopper (3), the rear end of the microwave antenna (4) is connected with the band-stop filter (5), the rear end of the band-stop filter (5) is connected with the high-pass filter (6), the rear end of the high-pass filter (6) is connected with the low-noise RF amplifier (7), the signal passing through the low-noise RF amplifier (7) is connected with the first directional coupler (8), the microwave signal is input to the RF end of the RF mixer (9) through the first directional coupler (8), the local oscillator end of the RF mixer (9) is connected with the second directional coupler (10) and the voltage-controlled microwave source (11) in sequence; the IF signal is generated by mixing the RF and local oscillator signals of the RF mixer (9) and is connected with the first band-pass filter (13), the IF signal is filtered by the first band-pass filter (13) and is input to the first IF amplifier (14) and then to the power divider (15), the IF signal is sent to the IF channel, the wideband IF signal is filtered to the working IF band by the IF band-pass filter (16), the narrowband IF signal passing through the IF band-pass filter (16) is connected with the second IF amplifier (17) and then with the IF mixer (18), the local oscillator end of the IF mixer (18) is connected with the IF geng oscillator (19) corresponding to the working frequency, the second-order IF signal generated by mixing is connected with the adjustable attenuator (20), the second-order IF signal is input to the second band-pass filter (21), the final signal is input to the detector (22), the detected signal is input to the low-pass filter (23), the low-pass filtered signal is input to the video amplifier (24), the signal amplitude is increased and finally input to the data collector (25).

2. The blackbody source based electron cyclotron radiation absolute calibration system of claim 1, wherein, The microwave antenna (4) receives the signal passing through the chopper (3) from the blackbody source (2).

3. The blackbody source based electron cyclotron radiation absolute calibration system of claim 1, wherein, The high-pass filter (6) filters out the mirror frequency signal of the ECE RF, and the low-frequency attenuation is greater than 30 dB.

4. The blackbody source based electron cyclotron radiation absolute calibration system of claim 1, wherein, The noise coefficient of the low-noise RF amplifier (7) is less than 5 dB, and the amplification gain is greater than 20 dB, the band-stop of the band-stop filter (5) is greater than 60 dB, so that the microwave signal entering the low-noise RF amplifier (7) is weaker than -10 dB.

5. The blackbody source based electron cyclotron radiation absolute calibration system of claim 1, wherein, The signal outside the intermediate frequency working band is suppressed by more than 30dB.

6. The blackbody source based electron cyclotron radiation absolute calibration system of claim 1, wherein, The second band-pass filter (21) selects a band-pass frequency band of 30MHz to 300MHz, so that the spatial resolution of the ECE measurement current distribution reaches 1 to 2 centimeters.

7. The blackbody source based electron cyclotron radiation absolute calibration system of claim 1, wherein, The square wave voltage value of the signal generator (12) is set to 1, 2V respectively by the industrial computer (27), and the period is 10ms.

8. The blackbody source based electron cyclotron radiation absolute calibration system of claim 1, wherein, The working temperature of the black body source (2) is set to 600 DEG C by the industrial computer (27).

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