Method, device, equipment and medium for measuring flutter noise effect of radio frequency cavity on line

Abstract

The invention discloses a method, a device, equipment and a medium for on-line measurement of a flutter noise effect of a radio frequency cavity. The method comprises the following steps: acquiring an original forward voltage Vf * of the radio frequency cavity; performing calibration and normalization processing on the original forward voltage Vf * to obtain a forward voltage Vf; according to the calibrated and normalized forward voltage Vf, cavity detuning caused by a flutter noise effect is calculated; performing preliminary time-frequency analysis on the flutter noise according to the cavity detuning to obtain a frequency spectrum of the cavity detuning; decomposing the cavity detuning frequency spectrum, and accumulatively calculating the RMS of the time domain signal and the contribution value of each frequency component to the cavity detuning overall RMS from low frequency to high frequency; and based on the contribution value of the overall RMS of the cavity detuning, judging the frequency component of the cavity detuning caused by the flutter noise. Therefore, the invention can be widely applied to particle accelerators.

Description

Technical Field

[0001] The present invention relates to a method, a device, a equipment and a medium for online measuring radio frequency cavity microphonics, and relates to the field of particle accelerators. Background Art

[0002] The radio frequency cavity is a core component in a superconducting accelerator. It is mainly used to provide an acceleration field for particle beams. It has the advantages of low loss and high gradient, and is suitable for accelerating high-intensity beams in continuous wave (CW) or long pulse mode. However, the bandwidth of the radio frequency cavity is very narrow, usually only tens to hundreds of hertz. Although this helps to improve the acceleration efficiency, it also makes the cavity extremely sensitive to changes in the resonant frequency. When subject to external interference (such as mechanical vibration of the vacuum pump, etc.), the cavity is prone to frequency detuning, resulting in cavity failure. Therefore, the radio frequency cavity needs to be equipped with a real-time digital low-level system to maintain its stable operation.

[0003] The microphonic effect refers to the forced oscillation of the cavity wall after the RF cavity absorbs external mechanical wave energy, which causes the cavity resonant frequency to fluctuate periodically, and then causes the amplitude and phase of the electromagnetic field in the cavity to change periodically. The microphonic effect will affect the stability of the electromagnetic field in the RF cavity, and in severe cases may even cause the low-level feedback loop to lose phase lock, causing cavity failure.

[0004] At present, the traditional method of measuring microphonic noise is equivalent to the measurement of RF cavity detuning. However, microphonic noise is not the only cause of cavity detuning. Beam loading effect, Lorentz force, etc. may also cause cavity detuning. In addition, existing methods usually use FFT (Fast Fourier Transform) to analyze the spectrum to evaluate the frequency components of microphonic noise. However, spectrum analysis cannot objectively reflect the contribution of different frequency components to the root mean square (RMS) of detuning, and cannot comprehensively and accurately evaluate the impact of microphonic noise.

[0005] Therefore, accurate measurement and evaluation of the microphonic effect is crucial to ensure the stable operation of the RF cavity, and a more accurate and comprehensive measurement and evaluation method is urgently needed to address the shortcomings of existing technologies. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, in view of the above problems, the purpose of the present invention is to provide a method, device, equipment and medium for online measuring the microphonic effect of a radio frequency cavity, which can improve the operating stability of the radio frequency cavity.

[0007] In order to achieve the above object, the technical solution provided by the present invention is: In a first aspect, the present invention provides a method for online measuring radio frequency cavity microphonic effect, comprising: Get the original forward voltage of the RF cavity Vf * ; The original forward voltage V f * After calibration and normalization, the forward voltage is obtained V f ; According to the calibrated and normalized forward voltage V f , calculate the cavity detuning caused by the microphonic effect; According to the cavity detuning, a preliminary time-frequency analysis is performed on the microphonic noise to obtain the frequency spectrum of the cavity detuning; Decompose the frequency spectrum of cavity detuning, and calculate the RMS of the time domain signal and the contribution of each frequency component to the overall RMS of cavity detuning from low frequency to high frequency. The frequency component of the cavity detuning caused by the microphonic noise is determined based on the contribution value of the overall RMS of the cavity detuning.

[0008] Furthermore, the cavity detuning caused by the microphonic effect is calculated as: ; Among them, Δ f micro is the cavity detuning, f 0.5 represents the half bandwidth of the cavity, is the forward voltage V f phase.

[0009] Furthermore, the frequency spectrum of the cavity detuning is obtained by using FFT analysis or wavelet analysis.

[0010] Furthermore, the spectrum of the cavity detuning is decomposed, and the RMS of the time domain signal and the contribution of each frequency component to the overall RMS of the cavity detuning are cumulatively calculated from low frequency to high frequency, including: Calculate the cavity detuning Δ f micro The cumulative RMS value of Δ F rms ; From low frequency to high frequency, the cavity is detuned in turn by Δ f micro The frequency spectrum of the selected frequency component is selected, and the cumulative RMS value of the selected frequency component is calculated until the cumulative RMS value of all selected frequency components is calculated. F rms,1 , Δ F rms,2 …Δ F rms,n ; Based on the cumulative RMS values ​​of all selected frequency components, the contribution of each frequency component to the overall RMS of the cavity detuning is calculated.

[0011] Further, the cavity detuning Δ is calculated f micro The cumulative RMS value of Δ F rms The calculation formula is: ; in, is Δ f micro The average value of Represents Δ f micro In the k The value of the sampling point, N Total number of sampling points.

[0012] Furthermore, based on the cumulative RMS values ​​of all selected frequency components, the contribution of each frequency component to the overall RMS of the cavity detuning is calculated as: ; Where Δ1 is the contribution of the first frequency component to the overall RMS of the cavity detuning, Δ n For the n The contribution of a frequency component to the overall RMS of the cavity detuning, Δ F rms,n and Δ F rms,n-1 Corresponding to the frequency from 0 Hz to n and n -The cumulative RMS value of 1 frequency point, Δ F rms,1 It is the cumulative RMS value from 0 Hz to the first frequency point.

[0013] In a second aspect, the present invention further provides a device for online measuring the microphonic effect of a radio frequency cavity, comprising: A signal acquisition module configured to acquire the original forward voltage of the RF cavity V f * ; The signal processing module is configured to convert the raw forward voltage V f * After calibration and normalization, the forward voltage is obtained V f ; The detuning calculation module is configured to calculate the cavity detuning Δ caused by microphonics in the stable operation state of the cavity f micro ; An RMS solver module is configured to decompose the frequency spectrum of the cavity detuning, and cumulatively calculate the RMS of the time domain signal from low frequency to high frequency and the contribution value of each frequency component to the overall RMS of the cavity detuning; The howling frequency solving module is configured to determine the frequency component of the cavity detuning caused by the howling based on the contribution value of the overall RMS of the cavity detuning.

[0014] In a third aspect, the present invention also provides an electronic device, comprising: at least one processor; and a memory communicatively connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to execute the described method.

[0015] In a fourth aspect, the present invention further provides a computer-readable storage medium storing one or more programs, wherein the one or more programs include computer instructions, and the computer instructions are used to enable a computer to execute the described method.

[0016] The present invention adopts the above technical solution, and has the following characteristics: 1. The present invention can monitor the dynamic change process of cavity detuning caused by the microphonic effect online. During the operation of the RF cavity, there is no need to calculate the differential of the cavity pressure. Its calculation complexity is much lower than that of the traditional method, and its measurement accuracy is better than that of the traditional method.

[0017] 2. The present invention can effectively evaluate the contribution of each frequency component to the overall RMS of the signal by gradually selecting the frequency components of the signal and calculating their RMS values. It is particularly suitable for analyzing the spectral characteristics of the signal and evaluating the contribution of frequency components in detuning.

[0018] 3. The present invention measures and analyzes the microphonic effect by reading the radio frequency signal, wherein the acquisition, down-conversion and demodulation of the radio frequency signal can be completed by a general digital low-level system, the control of the amplitude and phase stability of the cavity pressure signal is achieved by adjusting the feedback parameters, and the core data processing and model analysis algorithm can be deployed on a general host computer. The above applications do not require the addition of additional hardware equipment.

[0019] In summary, the present invention can be widely used in particle accelerators. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings: Figure 1a The present invention is a flowchart of a method for online measurement of radio frequency cavity microphonic effect according to an embodiment of the present invention.

[0021] Figure 1b 4 is a diagram of a system for online measurement of radio frequency cavity microphonic effect according to an embodiment of the present invention.

[0022] Figure 2a 3 is a waveform diagram of the cavity pressure phase measured under different PI parameters in an embodiment of the present invention.

[0023] Figure 2b 3 is a waveform diagram of the optimal PI parameter cavity pressure amplitude and phase in an embodiment of the present invention.

[0024] Figure 3a is the normalized forward voltage in the embodiment of the present invention V f Vector diagrams in the complex plane and V f With detuning Δ ω and half bandwidth ω 0.5 relationship diagram.

[0025] Figure 3b The detuning caused by the howling calculated by the method of the present invention is compared with the detuning caused by the traditional method in the embodiment of the present invention.

[0026] Figure 4a The radio frequency cavity CM in the superconducting heavy ion accelerator CAFE2 in the embodiment of the present invention 1-1 The measurement results of the upper detuning are plotted in the waveform diagram (upper left), time-frequency diagram (lower left) and spectrum diagram (lower right).

[0027] Figure 4b The radio frequency cavity CM in the superconducting heavy ion accelerator CAFE2 in the embodiment of the present invention 2-6 The measurement results of the upper detuning are plotted in the waveform diagram (upper left), time-frequency diagram (lower left) and spectrum diagram (lower right).

[0028] Figure 5 The figure is a diagram showing the calculation process and principle of solving the cumulative RMS value of each frequency component in the detuning in the embodiment of the present invention.

[0029] Figure 6 In the embodiment of the present invention Figure 5 The calculation results are displayed from top to bottom as follows: spectrum graph, cumulative RMS graph, and RMS contribution graph.

[0030] Figure 7 In the embodiment of the present invention, CM 1-1 The measurement and evaluation results of the cavity microphonic effect, from top to bottom: detuned waveform, spectrum, cumulative RMS, and RMS contribution.

[0031] Figure 8To show the cavity CM in the embodiment of the present invention 1-1 Cumulative RMS plot of 10 detuned measurements.

[0032] Fig. 9 FIG. 4 is a structural diagram of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0034] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0035] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside", "outside", "inner side", "outer side", "below", "above", etc. Such spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0036] The microphonic effect is one of the main causes of RF cavity operation failure. Therefore, online measurement of its influence on the electromagnetic field in the RF cavity is the basis for troubleshooting the source of the failure and thus reducing or avoiding such failures. The method, device, equipment and medium for online measurement of the microphonic effect of the RF cavity provided by the present invention include: obtaining the original forward voltage of the RF cavity V f *; The original forward voltage V f * After calibration and normalization, the forward voltage is obtained V f ; According to the calibrated and normalized forward voltage V f , calculate the cavity detuning caused by the microphonic effect; perform a preliminary time-frequency analysis on the microphonic according to the cavity detuning to obtain the spectrum of the cavity detuning; decompose the spectrum of the cavity detuning, and cumulatively calculate the RMS of the time domain signal from low frequency to high frequency and the contribution value of each frequency component to the overall RMS of the cavity detuning; and judge the frequency component of the cavity detuning caused by the microphonic based on the contribution value of the overall RMS of the cavity detuning. Therefore, the computational complexity of the present invention is much lower than that of the traditional method, and the measurement accuracy is better than that of the traditional method.

[0037] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0038] Embodiment 1: Figure 1a As shown, the method for online measuring the microphonic effect of a radio frequency cavity provided in this embodiment includes: S1. Baseband signal reading: cavity sampling signal based on online measurement P t and the cavity incident signal P f , the original cavity pressure of the RF cavity is obtained V c * and the original forward voltage V f * .

[0039] In this embodiment, Figure 1b As shown, a system for online measurement of radio frequency cavity microphonic effect is provided, including a digital low-level system 1, a solid-state power source 2, a directional coupler 3, an input coupler 4, a radio frequency cavity 5, a signal extraction coupler 6, a down-conversion module 7 and a host computer 8. The output end of the digital low-level system 1 is connected to the input end of the solid-state power source 2, the output end of the solid-state power source 2 is connected to the input end of the directional coupler 3, the output end (through port) of the directional coupler 3 is fed into the radio frequency cavity 5 through the input coupler 4, and the cavity sampling signal P t The incident signal of the cavity is obtained by connecting the RF cavity 5 and the signal extraction coupler 6 to the digital low-level system 1.P f and cavity reflection signal P r The directional coupler 3 is connected to the digital low-level system 1 for acquisition. P t , P f , P r ) is down-converted by the down-conversion module 7 to obtain an intermediate frequency signal, which is received by the digital low-level system 1. The digital low-level system 1 demodulates the corresponding digital baseband in-phase and quadrature (I / Q) components from the received intermediate frequency signal, and finally uploads them to the host computer 8 through the data bus.

[0040] Furthermore, a field programmable gate array (FPGA) is provided in the digital low-level system 1, and a digital signal processing module is provided in the FPGA. The digital signal processing module obtains three groups of original digital baseband signals by I / Q demodulation of the intermediate frequency signal, namely: the original cavity pressure of the radio frequency cavity V c * , original forward voltage V f * and the original reverse voltage V r * .

[0041] Unless otherwise specified, the parameters involved in this embodiment are: voltage (such as V c * , V f * , V r * , V c , V f etc.) and beam current ( I b ) are all in complex form, which can be expressed in the form of amplitude and phase, for example: V =| V | e j∠V , where | V | is the amplitude or modulus, ∠ V is the phase or argument; it can also be expressed as the real part plus the imaginary part, for example: V = V I + JbXj Q ,in,V I is the real part or the in-phase component, V Q is the imaginary part or the orthogonal component.

[0042] S2. Signal calibration and normalization: The original cavity pressure V c * and the original forward voltage V f * After calibration and normalization, the cavity pressure is obtained V c and forward voltage V f .

[0043] In this embodiment, the signal calibration process includes: Read the raw forward voltage V f * ,according to V f, cali = XV f * Solve for the calibrated forward signal, where the calibration coefficient X It is a complex number used to compensate for the influence of RF signal transmission cables and high-power RF devices on the measurement results. Note: The original cavity pressure is usually used as a reference signal and does not require calibration.

[0044] Furthermore, the complex multiplication operation can be performed as follows: ; In the formula, V fI,cali and V fQ,cali They are V f,cali The real and imaginary parts of V fI * and V fQ * They are V f * The real and imaginary parts of X I and X Q They are X The real and imaginary parts of .

[0045] In this embodiment, the process of signal normalization includes: Calculate the original cavity pressure V c* The normalized cavity pressure is obtained by dividing the original cavity pressure signal by the average value during steady-state operation. V c Similarly, to ensure the consistency of the signal, the calibrated V f,cali Normalize to get the normalized forward voltage V f , the specific formula is: ; In the formula, is the average value of the original cavity pressure during steady-state operation. The calculation process of the average value can be directly called by Python language numpy.mean Function, I will not go into details here.

[0046] S3. Calculate the detuning Δ caused by microphonics f micro : According to the calibrated and normalized cavity pressure V c and forward voltage V f , calculate the cavity detuning caused by the microphonic effect.

[0047] In this embodiment, the specific process of calculating the cavity detuning caused by the microphonic effect is: S31, according to the normalized cavity pressure V c and the normalized forward voltage V f Establish the cavity differential equation: ; Where t is time, Cavity pressure V c The differential of β is the cavity coupling coefficient (for RF cavities, β is much greater than 1), is the resonant frequency of the cavity, ω 0.5 is the half bandwidth of the cavity, Δ ω is the detuning of the cavity. ω 0.5 and Δ ω The unit is radians per second. f 0.5 With Δ f Also used to indicate the half-bandwidth and detuning of a cavity, but they are not the same as ω 0.5 and Δ ω The units are different. f 0.5 With Δ fThe unit is Hertz. I b For beam flow, r / Q is the geometric factor of the cavity, which is related to the shape of the RF cavity. The corresponding relationship of the above physical quantities is as follows: .

[0048] Before measuring the microphonic noise, the beam needs to be turned off to avoid the influence of beam loading effect on the measurement. Therefore, the last term of the above differential equation can be deleted. Considering β is much greater than 1, the above differential equation can be further simplified as: .

[0049] S32, adjusting the control closed-loop gain of the digital low-level system 1 to obtain a steady-state cavity pressure.

[0050] In this embodiment, the digital low-level system 1 uses a proportional integral (PI) feedback control loop to ensure the stability of the cavity pressure. During the debugging stage and the initial operation stage of the accelerator, it is generally necessary to select conservative PI parameters to meet application requirements such as fast phase scanning and cavity automatic loading. In these stages, the cavity pressure is generally V c It is not always in steady state. Figure 2a The figure shows a comparison of the measured results of the cavity pressure phase during debugging (gray) and operation (dark blue). It can be seen that the cavity pressure phase fluctuates significantly over time.

[0051] When measuring microphonic noise, since there is no need to consider the requirements of fast phase scanning and automatic cavity loading, the PI parameters can be optimized to maximize the interference suppression capability of the feedback loop. Under the action of the optimal PI parameters, the cavity pressure phase is Figure 2a As shown in the red waveform in , it can be seen that the cavity pressure phase hardly changes with time. Furthermore, Figure 2b The amplitude and phase of the cavity pressure under the optimal PI parameters are more clearly shown, and both are approximately constant over time. In order to establish a quantitative standard, it is necessary to calculate the RMS value of the cavity pressure amplitude separately. A rms RMS value of the phase with cavity pressure , the calculation formula is as follows: ; in, k is the location of the sampling point, N is the total number of sampling points. (| V c |) k represents the normalized cavity pressure amplitude at k The value of the sampling point ( Figure 2b On the top), correspondingly, (∠ V c )k represents the normalized cavity pressure phase at k The value of the sampling point ( Figure 2b Down).

[0052] According to the above formula, Figure 2b middle A rms and The values ​​of are 0.01% and 0.025 degrees respectively. In the present invention, the cavity pressure is in a steady state means that the cavity pressure no longer changes with time, that is, , V c ≡ 1+0 j Generally speaking, when the RMS values ​​of the cavity pressure amplitude and phase are less than 0.05% and 0.05 degrees, the cavity pressure can be approximately considered to be in a steady state.

[0053] S33. Calculate the detuning Δ caused by microphonics f micro .

[0054] Under the premise of steady-state cavity pressure, , V c ≡ 1+0 j Substituting into formula (4) can be further simplified as: ; in, ω 0.5 is the half bandwidth of the cavity, which is generally a constant. Divide both sides of the above formula by ω 0.5 We can get: ; From the above formula, we can know that: complex signal 2 V f The real part is 1, and the imaginary part is -Δω / ω 0.5 . Figure 3a is the vector 2 in the complex coordinate system V f Coordinate diagram of the vector 2. V f and vector V f The angles are ∠ V f .

[0055] .

[0056] Furthermore, the detuning Δ under steady-state cavity pressure conditions can be obtained ω The calculation formula is: ; in, is the phase of the normalized forward voltage, f 0.5 The cavity half bandwidth can be measured using existing technology and can usually be regarded as a constant.

[0057] It should be noted that the above detuning Δ f It mainly consists of three parts: detuning Δ caused by microphonics f micro , Lorenz detuning Δ f LFD and the detuning Δ caused by beam loading f beam . Among them, Δ f LFD Depending on the change of the cavity pressure, the present invention uses the optimal PI parameters to make the cavity pressure reach a steady state, that is, the cavity pressure approximately no longer changes with time, so Δ f LFD ≈0. In addition, since the beam was turned off before measuring the microphonic noise, the detuning Δ f beam ≈0. It can be seen that in this embodiment: .

[0058] Formula (9) is used to calculate the detuning Δ caused by the microphonic noise in this embodiment. f micro It is worth noting that the traditional method of calculating detuning requires solving the cavity pressure V c The present embodiment avoids the numerical differentiation step by optimizing the PI parameters, so its calculation accuracy is usually better than that of the traditional method. Figure 3b Compared with the Δ f micro Compared with the Δ calculated by traditional method f micro It can be seen that the calculation accuracy of the method of the present invention is higher.

[0059] S4. Obtain detuning Δ f micro Spectrum: Based on the calculated detuning, a preliminary time-frequency analysis of the howling noise is performed to obtain the detuning Δ f micro spectrum.

[0060] In this embodiment, the preliminary time-frequency analysis of the howling noise can be performed using the existing FFT analysis to obtain Δ f micro The spectrum of Δ f micro time-frequency characteristics.

[0061] Figure 4a and Figure 4b The CAFE2 device CM was displayed 1-1 and CM 2-6 Δ on the two RF cavities f micro Measurement results. Among them, Figure 4a and Figure 4b The upper sub-graph (waveform graph) shows the detuning Δ f micro The waveform changes over time. The vertical sub-graph on the right (spectrum graph) represents the change of Δ f micro Obtain the spectrum after the fast Fourier transform (FFT). The square sub-graph in the middle area (time-frequency graph) represents the f micro Obtain the time-frequency diagram after wavelet transform (CWT). In the time-frequency diagram, the color represents Δ f micro The amplitude of the corresponding frequency component, red represents the frequency component with a larger amplitude, and blue represents the frequency component with a smaller amplitude. The horizontal axis represents Δ f micro The vertical axis represents the time of f micro The above results can reflect some preliminary characteristics of howling noise, with CM 1-1 For example, according to the waveform and time-frequency diagram, every 1 second, Δ f micro It will be significantly enhanced, which indicates that the RF system may contain a strong vibration source with a period of 1 second. According to the time-frequency diagram and spectrum diagram, it can be clearly seen that Δ f micro The main frequency components are concentrated in 50~150 Hz.

[0062] Furthermore, in the f micro When obtaining FFT or wavelet transform, you need to remove Δ f micro The average value in the calculation can avoid the influence of DC component on the measurement result. The calculation of FFT or wavelet transform can directly call the fft or cwt function provided by MATLAB.

[0063] It is worth noting that although FFT and wavelet transform can clearly obtain Δ f micro The spectrum of Δ f micro The overall RMS contribution is due to Δ f micro The RMS value is the ultimate indicator for evaluating the microphonic effect, which clearly defines the effect of frequency components on Δ fmicro Analysis of contribution ratio of overall RMS f micro The spectrum is more important.

[0064] S5. Calculate the cumulative RMS value and RMS contribution value of the detuning: Use FFT to calculate Δ f micro The spectrum is decomposed, and the RMS of the time domain signal is calculated from low frequency to high frequency to obtain Δ f micro The cumulative RMS value of each frequency component is calculated by difference to obtain Δ f micro The contribution to the overall RMS.

[0065] In this embodiment, Δ f micro Usually contains multiple frequency components of different amplitudes, which have an impact on Δ f micro Even if there are two frequency components with exactly the same amplitude, their contribution to Δ f micro The contribution of Δ may still be different. The embodiment of the present invention proposes a method for evaluating the effect of frequency components on Δ f micro A general method for calculating the overall RMS contribution. For ease of illustration, the simulation diagram ( Figure 5 ) as an example, the specific process is: S51, calculate Δ f micro The cumulative RMS value of Δ F rms .

[0066] In this embodiment, it is assumed that Δ f micro The waveform (this waveform is a simulation waveform generated by MATLAB) is as follows Figure 5 As shown in the left sub-figure of the top two sub-figures, for Δ f micro Taking FFT, we can get the spectrum as shown in the upper right sub-figure. Obviously, Δ f micro It contains 8 frequency components, namely 80 Hz, 20 Hz to 70 Hz. Among them, there are two largest frequency components at 10 Hz and 70 Hz, and their amplitudes are both 3.5 Hz (see Figure 6 Spectrum diagram of Δ f micro The cumulative RMS value can be calculated using the following formula: ; in, is Δ fmicro The average value ( Figure 5 In the left sub-image of the two sub-images above, The default value is 0). Represents Δ f micro In the k The value of the sampling point, N The total number of sampling points. According to the above formula, it can be calculated Figure 5 Δ f micro The cumulative RMS value of Δ F rms ,like Figure 5 As shown, Δ F rms =4.28 Hz. It can be seen from the following text that Δ F rms It can be regarded as the cumulative RMS value of multiple frequency components (from 0 Hz to the current frequency), also known as Δ F rms is the cumulative RMS value.

[0067] S52, from low frequency to high frequency, in turn in Δ f micro The frequency spectrum of the selected frequency component is selected and the cumulative RMS value of the selected frequency component is calculated.

[0068] In this embodiment, Figure 5 As shown in the right sub-figure of the second row, the 10 Hz frequency point is first selected (represented by the purple spectrum line, and the unselected frequency points are represented by gray). The inverse FFT transform is performed on the selected frequency component to obtain the time domain waveform corresponding to the selected frequency component (since only a single 10 Hz frequency component is selected, the corresponding time domain waveform is a 10 Hz sine wave), which is calculated as Δ f micro1 ; Finally, use formula (10) to calculate Δ f micro1 The cumulative RMS value of Δ F rms,1 is 2.48 Hz.

[0069] Furthermore, the inverse transform of FFT is the inverse Fourier transform, which can transform the spectrum in the frequency domain into a waveform in the time domain. To calculate the inverse transform of FFT, you can call the ifft function of MATLAB.

[0070] S53, repeat step S52, continue from Δ f micro The frequency spectrum of the selected frequency component is selected, and the cumulative RMS value of the selected frequency component is calculated. Similarly, the cumulative RMS values ​​of all the selected frequency components are calculated.

[0071] In this embodiment, Figure 5 As shown in the right sub-figure of the third row, two frequency points of 10 Hz and 20 Hz are selected (indicated by cyan color spectrum, and unselected frequency points are indicated by gray). The inverse FFT transform is performed on the selected frequency components to obtain the time domain waveform corresponding to the selected frequency components (since the two frequency points of 10 Hz and 20 Hz are selected at the same time, the corresponding time domain waveform is a 10 Hz sine wave superimposed on a 20 Hz sine wave), which is calculated as Δ f micro2 .

[0072] Continue to call MATLAB's ifft function to get Δ f micro2 , and use formula (10) to calculate Δ f micro2 The cumulative RMS value of Δ F rms,2 .

[0073] And so on, until the last frequency point (80 Hz), the inverse FFT transform result at this time is Δ f micro8 Since all frequency components have been selected at this time (see the dark red spectrum), the inverted time domain waveform is the same as the original signal, that is, Δ f micro8 =Δ f micro , the corresponding cumulative RMS value is 4.28 Hz, that is, Δ F rms,8 =Δ F rms =4.28 Hz.

[0074] S54, taking the frequency of the selected frequency point (i.e. 10 Hz to 80 Hz) as the horizontal axis, and the cumulative RMS value (i.e. Δ F rms,1 , Δ F rms,2 to Δ F rms,8 ) as the vertical axis, we can get the cumulative RMS value graph ( Figure 6 Further, the cumulative RMS graph of n The RMS contribution of the frequency component Δ n ( Figure 6 RMS contribution graph): ; Among them, Δ F rms,n and Δ F rms,n-1 Corresponding to the frequency from 0 Hz to n and n-1 frequency point cumulative RMS value. Figure 6 The spectrum and RMS contribution graphs show that although the 10 Hz and 70 Hz frequency components have the same amplitude in the spectrum (both 3.5 Hz), their contribution to Δ f micro The RMS contribution of the 10 Hz component is more than three times that of the 70 Hz component, that is, At the same time, it can be seen that although the frequency components of 20 Hz and 50 Hz have larger amplitudes in the spectrum diagram, according to the RMS contribution diagram, the actual contribution of the two to Δ f micro The overall RMS contribution of is not significant. In practical applications, the impact of the above two frequency components on the RF system can usually be ignored.

[0075] S6. Determine the frequency component of the detuning caused by the howling: Determine the frequency component of the cavity detuning caused by the howling based on the contribution value of the overall RMS of the cavity detuning.

[0076] The method for online measurement of radio frequency cavity microphonic effect of the present invention is verified by specific examples below.

[0077] In this embodiment, the radio frequency cavity CM of the superconducting heavy ion accelerator CAFE2 is used. 1-1 The test results on Figure 7 As shown. According to formula (9), CM can be calculated 1-1 The detuning Δ caused by the microphonic noise f micro The waveform and spectrum diagram are shown in Figure 7 The first and second sub-graphs of . According to the spectrum graph, Δ f micro The main frequency components of are concentrated in 30~150 Hz. Among them, there is a main peak (main peak 1) from 30 Hz to 90 Hz, and another main peak (main peak 2) from 90 Hz to 150 Hz. From the spectrum, both have large peaks and bandwidths. In addition, there is a large single-frequency frequency component near 155 Hz.

[0078] According to the method provided in this embodiment, the cumulative RMS graph and the RMS contribution graph can be obtained in sequence. Figure 7From the RMS contribution graph, we can see that the cumulative RMS contribution of the 0-30 Hz frequency component to the detuning is about 3.5 Hz, the cumulative RMS contribution of the 0~90 Hz frequency component to the detuning is 9.5 Hz, and the cumulative RMS contribution of the 0~150 Hz frequency component to the detuning is 12.5 Hz. Therefore, the RMS contribution of main peak 1 to the detuning is about 6 Hz (i.e. 9.5 Hz minus 3.5 Hz), and the RMS contribution of main peak 2 to the detuning is about 3 Hz (12.5 Hz minus 9.5 Hz). Obviously, the contribution of the first main peak to the RMS is relatively greater. RF engineers need to optimize the control loop to ensure that there is a sufficiently large feedback gain at the position of main peak 1. It can also be seen that the contribution of the 155 Hz component in the spectrum graph to the RMS can be approximately ignored. Finally, in order to examine the consistency of the measurement of the present invention, as Figure 8 As shown, the present invention is in CM 1-1 The RF cavity was subjected to 10 independent experiments, and cumulative RMS graphs were drawn for all of them. The results showed that the cumulative RMS curves matched well, verifying the consistency of the present invention.

[0079] Embodiment 2: Embodiment 1 above provides a method for online measurement of radio frequency cavity microphonic effect. Correspondingly, this embodiment provides a device for online measurement of radio frequency cavity microphonic effect. The device provided in this embodiment can implement the method for online measurement of radio frequency cavity microphonic effect of embodiment 1, and the device can be implemented by software, hardware, or a combination of software and hardware. For the convenience of description, this embodiment is described by functions divided into various units and described separately. Of course, the functions of each unit can be implemented in the same or one or more software and / or hardware during implementation. For example, the device may include integrated or separate functional modules or functional units to perform the corresponding steps in each method of embodiment 1. Since the device of this embodiment is basically similar to the method embodiment, the description process of this embodiment is relatively simple. For the relevant parts, please refer to the partial description of embodiment 1. The embodiment of the device for online measurement of radio frequency cavity microphonic effect provided by the present invention is only schematic.

[0080] Specifically, the device for online measuring the microphonic effect of a radio frequency cavity provided in this embodiment includes: The signal processing module is configured to convert the raw forward voltage V f * After calibration and normalization, the forward voltage is obtained V f ; The detuning calculation module is configured to calculate the cavity detuning Δ caused by microphonics in the stable operation state of the cavity f micro ; An RMS solver module is configured to decompose the frequency spectrum of the cavity detuning, and cumulatively calculate the RMS of the time domain signal from low frequency to high frequency and the contribution value of each frequency component to the overall RMS of the cavity detuning; The howling frequency solving module is configured to determine the frequency component of the cavity detuning caused by the howling based on the contribution value of the overall RMS of the cavity detuning.

[0081] Embodiment 3: This embodiment provides an electronic device corresponding to the method for online measuring the radio frequency cavity microphonic effect provided in this embodiment 1. The electronic device may be an electronic device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of embodiment 1.

[0082] like Fig. 9 As shown, the electronic device includes a processor, a memory, a communication interface and a bus, and the processor, the memory and the communication interface are connected through the bus to complete mutual communication. The memory stores a computer program that can be run on the processor. When the processor runs the computer program, it executes the method of embodiment 1. Its implementation principle and technical effect are similar to those of embodiment 1, and will not be repeated here. Those skilled in the art can understand that Fig. 9 The structure shown in the figure is only a block diagram of a part of the structure related to the scheme of the present application, and does not constitute a limitation on the computing device to which the scheme of the present application is applied. The specific computing device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0083] In a preferred embodiment, the logic instructions in the above-mentioned memory can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), optical disk and other media that can store program codes.

[0084] In a preferred embodiment, the processor may be a central processing unit (CPU), a digital signal processor (DSP) or other general-purpose processors of various types, which are not limited herein.

[0085] Embodiment 4: This embodiment provides a computer-readable storage medium storing one or more programs, wherein the one or more programs include computer instructions. When the computer instructions are executed by a computer, the computer executes the method provided in the above-mentioned embodiment 1.

[0086] In a preferred embodiment, the computer-readable storage medium may be a tangible device that holds and stores instructions executed by the instructions, such as but not limited to an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof. The computer-readable storage medium stores computer program instructions that enable the computer to execute the method provided in the first embodiment.

[0087] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (apparatus), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate a device for implementing the functions specified in one process or multiple processes in the flowchart and / or one box or multiple boxes in the block diagram.

[0088] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0089] These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0090] Each embodiment in this specification is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In the description of this specification, the description of reference terms "a preferred embodiment", "further", "specifically", "in the present embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for online measurement of radio frequency cavity microphonic effect, characterized in that: include: Get the original forward voltage of the RF cavity V f * ; The original forward voltage V f * After calibration and normalization, the forward voltage is obtained V f ; According to the calibrated and normalized forward voltage V f , calculate the cavity detuning caused by the microphonic effect; According to the cavity detuning, a preliminary time-frequency analysis is performed on the microphonic noise to obtain the frequency spectrum of the cavity detuning; Decompose the spectrum of cavity detuning, and calculate the RMS of the time domain signal and the contribution of each frequency component to the overall RMS of cavity detuning from low frequency to high frequency. The frequency component of the cavity detuning caused by the microphonic noise is determined based on the contribution value of the overall RMS of the cavity detuning.

2. The method for online measurement of radio frequency cavity microphonic effect according to claim 1, characterized in that: The cavity detuning caused by the microphonic effect is calculated as: ； Among them, Δ f micro is the cavity detuning, f 0.5 represents the half bandwidth of the cavity, is the forward voltage V f phase.

3. The method for online measurement of radio frequency cavity microphonic effect according to claim 2, characterized in that: The frequency spectrum of cavity detuning is obtained by FFT analysis or wavelet analysis.

4. The method for online measurement of radio frequency cavity microphonic effect according to claim 3, characterized in that: The spectrum of cavity detuning is decomposed, and the RMS of the time domain signal and the contribution of each frequency component to the overall RMS of cavity detuning are calculated from low frequency to high frequency, including: Calculate the cavity detuning Δ f micro The cumulative RMS value of Δ F rms ; From low frequency to high frequency, the cavity is detuned in turn by Δ f micro The frequency spectrum of the selected frequency component is selected, and the cumulative RMS value of the selected frequency component is calculated until the cumulative RMS value of all selected frequency components is calculated. F rms,1 , Δ F rms,2 …Δ F rms,n ; Based on the cumulative RMS values ​​of all selected frequency components, the contribution of each frequency component to the overall RMS of the cavity detuning is calculated.

5. The method for online measurement of radio frequency cavity microphonic effect according to claim 4, characterized in that: Calculate the cavity detuning Δ f micro The cumulative RMS value of Δ F rms The calculation formula is: ； in, is Δ f micro The average value of Represents Δ f micro In the k The value of the sampling point, N Total number of sampling points.

6. The method for online measurement of radio frequency cavity microphonic effect according to claim 4, characterized in that: Based on the cumulative RMS values ​​of all selected frequency components, the contribution of each frequency component to the overall RMS of the cavity detuning is calculated as: ； Where Δ1 is the contribution of the first frequency component to the overall RMS of the cavity detuning, Δ n For the n The contribution of a frequency component to the overall RMS of the cavity detuning, Δ F rms,n and Δ F rms,n-1 Corresponding to the frequency from 0 Hz to n and n -The cumulative RMS value of 1 frequency point, Δ F rms,1 It is the cumulative RMS value from 0 Hz to the first frequency point.

7. A device for online measurement of radio frequency cavity microphonic effect, characterized in that: include: A signal acquisition module configured to acquire the original forward voltage of the RF cavity V f * ; The signal processing module is configured to convert the raw forward voltage V f * After calibration and normalization, the forward voltage is obtained V f ; The detuning calculation module is configured to calculate the cavity detuning Δ caused by microphonics in the stable operation state of the cavity f micro ; An RMS solver module is configured to decompose the frequency spectrum of the cavity detuning, and cumulatively calculate the RMS of the time domain signal from low frequency to high frequency and the contribution value of each frequency component to the overall RMS of the cavity detuning; The howling frequency solving module is configured to determine the frequency component of the cavity detuning caused by the howling based on the contribution value of the overall RMS of the cavity detuning.

8. An electronic device, characterized in that: include: at least one processor; and a memory communicatively connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor can execute the method according to any one of claims 1-6.

9. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include computer instructions for causing a computer to execute the method according to any one of claims 1-6.

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