A method, device, equipment and medium for online measuring the microphonic effect of a radio frequency cavity

Abstract

The present invention discloses a method, apparatus, device and medium for online measuring the microphonic effect of a radio frequency cavity, including: obtaining the original forward voltage of the radio frequency cavity V f * ; after calibrating and normalizing the original forward voltage V f * , obtaining the forward voltage V f ; calculating the cavity detuning caused by the microphonic effect according to the calibrated and normalized forward voltage V f ; performing preliminary time-frequency analysis on the microphonic to obtain the spectrum of the cavity detuning; decomposing the spectrum of the cavity detuning, and cumulatively calculating the RMS of the time-domain signal and the contribution value of each frequency component to the overall RMS of the cavity detuning from low frequency to high frequency; judging the frequency components of the cavity detuning caused by the microphonic based on the contribution value of the overall RMS of the cavity detuning. Therefore, the present invention can be widely applied to particle accelerators.

Description

Technical Field

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

[0002] The radio frequency cavity is a core component in a superconducting accelerator, mainly used to provide an accelerating field for a particle beam, and has advantages such as 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 dozens 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 affected by external disturbances (such as mechanical vibrations of a vacuum pump, etc.), the cavity is prone to frequency detuning, resulting in cavity failures. Therefore, the radio frequency cavity needs to be equipped with a real-time digital low-level system to maintain its stable operation.

[0003] Microphonics refers to that after the radio frequency cavity absorbs the energy of external mechanical waves, the cavity wall undergoes forced oscillation, resulting in periodic fluctuations in the resonant frequency of the cavity, and further causing periodic changes in the amplitude and phase of the electromagnetic field in the cavity. Microphonics will affect the stability of the electromagnetic field in the radio frequency cavity, and in severe cases, it may even cause phase unlocking of the low-level feedback loop, resulting in cavity failures.

[0004] Currently, traditional microphonics measurement methods equate it with the measurement of radio frequency cavity detuning. However, microphonics is not the only cause of cavity detuning. Beam loading effects, Lorentz forces, 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 microphonics. 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 microphonics.

[0005] Therefore, accurately measuring and evaluating microphonics is crucial for ensuring the stable operation of the radio frequency cavity. There is an urgent need for a more accurate and comprehensive measurement and evaluation method to address the deficiencies of the existing technology. Summary of the Invention

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

[0007] To achieve the above object, the technical solution provided by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for online measuring the microphonics of a radio frequency cavity, including:

[0009] Obtain the original forward voltage of the RF cavity V f * ;

[0010] Calibrate and normalize the original forward voltage V f * to obtain the forward voltage V f ;

[0011] Based on the calibrated and normalized forward voltage V f , calculate the cavity detuning caused by microphonics;

[0012] Based on the cavity detuning, conduct a preliminary time-frequency analysis of microphonics to obtain the spectrum of the cavity detuning;

[0013] 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;

[0014] Based on the contribution value of the overall RMS of the cavity detuning, determine the frequency components of the cavity detuning caused by microphonics.

[0015] Furthermore, calculate the cavity detuning caused by microphonics as:

[0016] ;

[0017] where Δ f micro is the cavity detuning, f 0.5 represents the half bandwidth of the cavity, is the forward voltage V f phase.

[0018] Furthermore, obtain the spectrum of the cavity detuning using FFT analysis or wavelet analysis.

[0019] Furthermore, 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, including:

[0020] Calculate the cumulative RMS value Δ f micro of the cavity detuning Δ F rms ;

[0021] From low frequency to high frequency, sequentially at the cavity detuning Δ f microThe spectral selected frequency components are selected, and the cumulative RMS value of the selected frequency components is calculated until the cumulative RMS values Δ of all selected frequency components are calculated. F rms,1 、Δ F rms,2 …Δ F rms,n ;

[0022] Based on the cumulative RMS values of all selected frequency components, calculate the contribution value of each frequency component to the overall RMS of the cavity detuning.

[0023] Furthermore, calculate the cumulative RMS value Δ of the cavity detuning f micro The calculation formula of is: F rms ;

[0024] ;

[0025] Wherein, is the average value of Δ f micro , represents the value of Δ f micro at the k th sampling point, N Total number of sampling points.

[0026] Furthermore, based on the cumulative RMS values of all selected frequency components, the contribution value of each frequency component to the overall RMS of the cavity detuning is:

[0027] ;

[0028] Wherein, Δ 1 is the contribution value of the first frequency component to the overall RMS of the cavity detuning, Δ n is the contribution value of the n th frequency component to the overall RMS of the cavity detuning, Δ F rms,n and Δ F rms,n-1 correspond to the cumulative RMS values from 0 Hz to the n th and the n -1th frequency points respectively, Δ F rms,1 is the cumulative RMS value from 0 Hz to the first frequency point.

[0029] In a second aspect, the present invention also provides a device for online measuring the microphonics effect of a radio frequency cavity, including:

[0030] A signal acquisition module configured to acquire the original forward voltage of the radio frequency cavityV f * ;

[0031] A signal processing module, configured to calibrate and normalize the original forward voltage V f * to obtain the forward voltage V f ;

[0032] A detuning calculation module, configured to calculate the cavity detuning Δ caused by microphonics in the stable operating state of the cavity f micro ;

[0033] An RMS solving module, configured to 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;

[0034] A microphonic frequency solving module, configured to determine the frequency components of the cavity detuning caused by microphonics based on the contribution value of the overall RMS of the cavity detuning.

[0035] In a third aspect, the present invention further provides an electronic device, including: at least one processor; and a memory communicatively connected to the processor; wherein, the memory stores instructions executable by the processor, and when the instructions are executed by the processor, the processor is enabled to execute the method.

[0036] In a fourth aspect, the present invention further provides a computer-readable storage medium storing one or more programs, the one or more programs including computer instructions for causing a computer to execute the method.

[0037] Due to the above technical solutions adopted by the present invention, it has the following characteristics:

[0038] 1. The present invention can online monitor the dynamic change process of the cavity detuning caused by the microphonic effect. During the operation of the radio frequency cavity, it is not necessary to calculate the differential of the cavity pressure, and its calculation complexity is much lower than that of the traditional method, and the measurement accuracy is better than that of the traditional method.

[0039] 2. By gradually selecting the frequency components of the signal and calculating their RMS values, the present invention can effectively evaluate the contribution of each frequency component to the overall RMS of the signal, and is particularly suitable for the spectral characteristic analysis of the signal and the evaluation of the contribution of the frequency components in the detuning.

[0040] 3. The present invention measures and analyzes the microphonic effect by reading radio frequency signals. Among them, the acquisition, down-conversion, and demodulation of radio frequency signals can all be completed by a general digital low-level system. The control of the amplitude-phase stability of the cavity pressure signal is achieved by adjusting feedback parameters. The processing of core data and model analysis algorithms can be deployed on a general upper computer. None of the above applications require additional hardware devices.

[0041] In summary, the present invention can be widely applied to particle accelerators. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0043] Figure 1a is a flowchart of the method for online measuring the microphonic effect of the radio frequency cavity according to the embodiment of the present invention.

[0044] Figure 1b is a system diagram of the online measuring the microphonic effect of the radio frequency cavity according to the embodiment of the present invention.

[0045] Figure 2a is a measured cavity pressure phase waveform diagram under different PI parameters in the embodiment of the present invention.

[0046] Figure 2b is a waveform diagram of the cavity pressure amplitude and phase with the optimal PI parameters in the embodiment of the present invention.

[0047] Figure 3a is the normalized forward voltage V f vector diagram on the complex plane and V f relationship diagram with detuning Δ ω and half bandwidth ω 0.5 in the embodiment of the present invention.

[0048] Figure 3b is a result comparing the detuning caused by microphony calculated by the method of the present invention with the detuning caused by the traditional method in the embodiment of the present invention.

[0049] Figure 4a is the measurement result of the detuning on the radio frequency cavity CM 1-1 in the superconducting heavy ion accelerator CAFE2 in the embodiment of the present invention. The waveform diagram (upper left), time-frequency diagram (lower left), and spectrogram (lower right) are plotted in sequence.

[0050] Figure 4bFor the radio frequency cavity CM in the superconducting heavy ion accelerator CAFE2 in the embodiments of the present invention 2-6 Regarding the measurement results of detuning on it, waveform diagrams (upper left), time-frequency diagrams (lower left), and spectrograms (lower right) are successively plotted.

[0051] Figure 5 For the calculation process and calculation principle diagram of solving the cumulative RMS value of each frequency component in detuning in the embodiments of the present invention.

[0052] Figure 6 For the embodiments of the present invention Figure 5 Regarding the display of calculation results, from top to bottom are: spectrogram, cumulative RMS diagram, and RMS contribution diagram.

[0053] Figure 7 For the embodiments of the present invention regarding CM 1-1 Regarding the measurement results and evaluation results of the microphonic effect of the cavity, from top to bottom are: waveform diagram of detuning, spectrogram, cumulative RMS diagram, and RMS contribution diagram.

[0054] Figure 8 Regarding the display of the cumulative RMS diagram of 10 measurements of detuning of the cavity CM in the embodiments of the present invention 1-1

[0055] Figure 9 For the structural diagram of the electronic device in the embodiments of the present invention Specific embodiments

[0056] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, as used herein, the singular forms "a", "an", and "the" may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of the stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the particular order described or illustrated, unless the execution order is explicitly stated. It should also be understood that additional or alternative steps may be used.

[0057] ​Although terms such as first, second, and third may 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 may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as "first" and "second" and other numerical terms do not imply an order or sequence when used in the text. Thus, the first element, component, region, layer, or section discussed below may be referred to as the second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0058] For ease of description, spatial relative relationship terms may be used in the text to describe the relationship of one element or feature shown in the figure to another element or feature, such as "inside", "outside", "inner side", "outer side", "below", "above", etc. Such spatial relative relationship terms are intended to include different orientations of the device during use or operation in addition to the orientations depicted in the figure.

[0059] Microphonics is one of the main inducements leading to the operation failure of the RF cavity. Therefore, online measurement of its impact 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 microphonics of the RF cavity provided by the present invention include: obtaining the original forward voltage of the RF cavity V f * ; calibrating and normalizing the original forward voltage V f * to obtain the forward voltage V f ; calculating the cavity detuning caused by microphonics according to the calibrated and normalized forward voltage V f ; performing a preliminary time-frequency analysis on the microphonics according to the cavity detuning to obtain the spectrum of the cavity detuning; decomposing the spectrum of the cavity detuning, calculating the RMS of the time-domain signal cumulatively from low frequency to high frequency and the contribution value of each frequency component to the overall RMS of the cavity detuning; and judging the frequency components of the cavity detuning caused by microphonics 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.

[0060] 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 drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be completely conveyed to those skilled in the art.

[0061] Example 1: As Figure 1a shown, the method for online measuring the microphonics effect of a radio frequency cavity provided in this embodiment includes:

[0062] S1. Baseband signal reading: Based on the cavity sampling signal P t and the cavity incident signal P f , the original cavity pressure V c * and the original forward voltage V f * of the radio frequency cavity are obtained.

[0063] In this embodiment, as Figure 1b shown, a system for online measuring the microphonics effect of a radio frequency cavity 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, and the output end (through port) of the directional coupler 3 is fed into the radio frequency cavity 5 through the input coupler 4. The cavity sampling signal P t is obtained by connecting the radio frequency cavity 5, the signal extraction coupler 6 and the digital low-level system 1. The cavity incident signal P f and the cavity reflection signal P r are obtained by connecting the directional coupler 3 and the digital low-level system 1. The above-mentioned signals ( P t , P f , P r ) are down-converted by the down-conversion module 7 to obtain intermediate-frequency signals, and the intermediate-frequency signals are received by the digital low-level system 1. The digital low-level system 1 demodulates the corresponding digital baseband in-phase quadrature (I / Q) components from the received intermediate-frequency signals and finally uploads them to the host computer 8 through the data bus.

[0064] Furthermore, a Field Programmable Gate Array (FPGA for short) is provided in the digital low-level system 1. A digital signal processing module is provided in the FPGA. The digital signal processing module demodulates the intermediate frequency signal through I / Q to obtain three groups of original digital baseband signals, namely: the original cavity pressure of the radio frequency cavity V c * , the original forward voltage V f * and the original reverse voltage V r * .

[0065] Unless otherwise specified, the parameters involved in this embodiment: voltage (such as V c * , V f * , V r * , V c , V f etc.) and beam current ( I b ) are all in complex form. They can be expressed in the form of amplitude and phase, for example: V =| V | e j∠V , where | V | is the amplitude or modulus, and ∠ V is the phase or argument; they can also be expressed in the form of real part plus imaginary part, for example: V = V I + jV Q , where V I is the real part or in-phase component, V Q is the imaginary part or quadrature component.

[0066] S2. Signal calibration and normalization: After calibrating and normalizing the original cavity pressure V c * and the original forward voltage V f * , the cavity pressure V c and the forward voltage V f are obtained.

[0067] In this embodiment, the process of signal calibration includes:

[0068] Read the original forward voltage V f * , and according to V f, cali = XV f * Solve the calibrated forward signal, where the calibration coefficient X is a complex number used to compensate for the influence of the RF signal transmission cable and high-power RF devices on the measurement results. Note: The original cavity pressure is usually used as the reference signal and does not need to be calibrated.

[0069] Furthermore, the complex multiplication operation can be carried out in the following way:

[0070] ;

[0071] In the formula, V fI,cali and V fQ,cali are the real part and the imaginary part of V f,cali respectively; V fI * and V fQ * are the real part and the imaginary part of V f * respectively; X I and X Q are the real part and the imaginary part of X respectively.

[0072] In this embodiment, the process of signal normalization includes:

[0073] Calculate the average value of the signal during the steady-state operation of the original cavity pressure V c * , and divide the original cavity pressure signal by the average value to obtain the normalized cavity pressure V c ; Similarly, to ensure the consistency of the signal, it is necessary to normalize the calibrated V f,cali to obtain the normalized forward voltage V f , and the specific formula is:

[0074] ;

[0075] In the formula, is the average value during the steady-state operation of the original cavity pressure. The calculation process of finding the average value can directly call the numpy.mean function in the Python language, which will not be elaborated here.

[0076] S3. Calculate the detuning Δ caused by microphonics f micro : Based on the calibrated and normalized cavity pressure V c and the forward voltage V f , calculate the cavity detuning caused by the microphonics effect.

[0077] In this embodiment, the specific process of calculating the cavity detuning caused by the microphonics effect is as follows:

[0078] S31. Based on the normalized cavity pressure V c and the normalized forward voltage V f establish a cavity differential equation:

[0079] ;

[0080] where t is time, is the differential of the cavity pressure V c , β is the coupling coefficient of the cavity (for a radio-frequency cavity, 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 are in units of radians per second. f 0.5 and Δ f are also used to represent the half-bandwidth and detuning of the cavity, but their units are different from ω 0.5 and Δ ω . f 0.5 and Δ f are both in units of hertz. I b is the beam current, r / Q is the geometric factor of the cavity, which is related to the shape of the radio-frequency cavity. The corresponding relationships of the above physical quantities are as follows: .

[0081] Before measuring the microphonics, it is necessary to turn off the beam current first to avoid the influence of the beam current load effect on the measurement. Therefore, the last term of the above differential equation can be deleted. Considering that β is much greater than 1, the above differential equation can be further simplified to:

[0082] .

[0083] S32. Adjust the control closed-loop gain of the digital low-level system 1 to obtain the steady-state cavity pressure.

[0084] 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 commissioning phase and the initial operation phase of the accelerator, conservative PI parameters generally need to be selected to meet the application requirements such as fast phase sweeping and automatic cavity loading. In these phases, generally, the cavity pressure V c is not always in a steady state. As Figure 2a shows, the measured results of the cavity pressure phase during commissioning (gray) and operation (dark blue) are compared. It can be seen that the cavity pressure phase fluctuates significantly with time.

[0085] When performing microphonics measurement, since there is no need to consider the requirements such as fast phase sweeping and automatic cavity loading, the PI parameters can be optimized to maximize the interference suppression ability of the feedback loop. Under the action of the optimal PI parameters, the cavity pressure phase is as shown by the red waveform in Figure 2a . It can be seen that the cavity pressure phase hardly changes with time. Further, Figure 2b more clearly shows the amplitude and phase of the cavity pressure under the optimal PI parameters, and both are approximately non-fluctuating with time. To establish a quantization standard, it is necessary to calculate the RMS value of the cavity pressure amplitude A rms and the RMS value of the cavity pressure phase , and the calculation formulas are as follows:

[0086] ;

[0087] where, k is the position of the sampling point, N is the total number of sampling points. (| V c |) k represents the value of the normalized cavity pressure amplitude at the k th sampling point ( Figure 2b ), and correspondingly, (∠ V c ) k represents the value of the normalized cavity pressure phase at the k th sampling point ( Figure 2b ).

[0088] According to the above formula, Figure 2b in A rms and the values are 0.01% and 0.025 degrees respectively. In the present invention, the cavity pressure being 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, it can be approximately considered that the cavity pressure is in a steady state.

[0089] S33. Calculate the detuning Δ f micro .

[0090] On the premise of the steady-state cavity pressure, substitute , V c ≡ 1 + 0 j into formula (4) and it can be further simplified to:

[0091] ;

[0092] wherein, ω 0.5 is the half-bandwidth of the cavity, generally a constant. Divide both sides of the above formula by ω 0.5 to obtain:

[0093] ;

[0094] It can be seen from the above formula that the real part of the complex signal 2 V f is 1 and the imaginary part is -Δω / ω 0.5 . Figure 3a is the coordinate diagram of the vector 2 V f in the complex coordinate system. Note that the argument angles of the vector 2 V f and the vector V f are both ∠ V f .

[0095] .

[0096] Furthermore, the calculation formula for the detuning Δ ω under the condition of the steady-state cavity pressure can be obtained:

[0097] ;

[0098] wherein, is the phase of the normalized forward voltage, f 0.5 The cavity half-bandwidth can be measured by existing technologies and is usually regarded as a constant.

[0099] It should be noted that the above detuning Δ f mainly consists of three parts: the detuning Δ f micro caused by microphonics, the Lorentz detuning Δ f LFD and the detuning Δ f beam caused by beam loading. Among them, Δ f LFD depends on the change of the cavity pressure. In the present invention, by using the optimal PI parameters, the cavity pressure reaches a steady state, that is, the cavity pressure approximately no longer changes with time. Therefore, Δ f LFD ≈0. In addition, since the beam has been turned off before measuring microphonics, the detuning Δ f beam caused by beam loading ≈0. It can be seen that in this embodiment:

[0100] .

[0101] Equation (9) is the calculation formula for the detuning Δ f micro caused by microphonics in this embodiment. It should be noted that: the traditional method for calculating detuning requires solving the differential of the cavity pressure V c . In this embodiment, by optimizing the PI parameters, the numerical differential link is avoided. Therefore, its calculation accuracy is generally better than that of the traditional method. Figure 3b compares the Δ f micro calculated by the present invention with the Δ f micro calculated by the traditional method. It can be seen that the calculation accuracy of the method of the present invention is higher.

[0102] S4. Obtain the spectrum of the detuning Δ f micro : According to the calculated detuning, perform a preliminary time-frequency analysis on microphonics to obtain the spectrum of the detuning Δ f micro .

[0103] In this embodiment, a preliminary time-frequency analysis of microphonics can be used to obtain the spectrum of Δ f micro by using the existing FFT analysis or the time-frequency characteristics of Δ f micro by using wavelet analysis.

[0104] Figure 4a and Figure 4b respectively show the Δ 1-1 and Δ 2-6 on two radio frequency cavities of the CAFE2 device CM f micro Measurement results. Among them, Figure 4a and Figure 4b the upper sub - graphs (waveform diagrams) show the change of the detuning Δ f micro waveform over time, and the right - hand vertical sub - graphs (spectrum diagrams) represent the spectrum diagrams after taking the fast Fourier transform (FFT) of Δ f micro The square sub - graphs (time - frequency diagrams) in the middle area represent the time - frequency diagrams after taking the continuous wavelet transform (CWT) of Δ f micro In the time - frequency diagram, the color represents the magnitude of the amplitude of the frequency components corresponding to Δ f micro The abscissa represents the time of Δ f micro , and the ordinate represents the frequency components included in Δ f micro The above results can reflect some preliminary characteristics of the microphonics. Taking CM 1-1 as an example, according to the waveform diagram and the time - frequency diagram, every 1 second, Δ f micro will be significantly enhanced, which indicates that there may be a strong vibration source with a period of 1 second in the radio frequency system. According to the time - frequency diagram and the spectrum diagram, it can be clearly seen that the main frequency components of Δ f micro are concentrated in the range of 50 - 150 Hz.

[0105] Furthermore, when taking the FFT or wavelet transform of Δ f micro , it is necessary to first remove the average value in Δ f micro to avoid the influence of the DC component on the measurement results. Calculating the FFT or wavelet transform can directly call the fft or cwt functions provided by MATLAB.

[0106] It should be noted that although the FFT and wavelet transform can clearly obtain the spectrum of Δ f micro , they cannot accurately reflect the contribution of the frequency components to the overall RMS of Δ f micro . Since the RMS value of Δ f micro is the final index for evaluating the microphonics effect, clarifying the contribution of the frequency components to Δ fmicro Analysis of the contribution ratio of the overall RMS Δ f micro has a more important spectrum.

[0107] S5. Calculate the cumulative RMS value and RMS contribution value of the detuning: Use FFT to decompose the spectrum of Δ f micro and calculate the RMS of the time-domain signal cumulatively from low frequency to high frequency to obtain the cumulative RMS value of Δ f micro . Calculate the difference to obtain the contribution value of each frequency component to the overall RMS of Δ f micro .

[0108] In this embodiment, Δ f micro usually contains multiple frequency components with different amplitudes, and the contributions of these components to Δ f micro are different. Even for two frequency components with exactly the same amplitude, their contributions to Δ f micro may still be different. The embodiment of the present invention proposes a general method for evaluating the contribution value of a frequency component to the overall RMS of Δ f micro . For the sake of convenience of explanation, taking the simulation diagram ( Figure 5 ) as an example, the specific process is as follows:

[0109] S51. Calculate the cumulative RMS value Δ f micro of Δ F rms .

[0110] In this embodiment, it is assumed that the waveform of Δ f micro (this waveform is a simulation waveform generated by MATLAB) is as shown in the left sub-diagram of the top two sub-diagrams in Figure 5 . Taking the FFT of Δ f micro can obtain the spectrum as shown in the right sub-diagram at the top. Obviously, Δ f micro contains 8 frequency components, which are 80 Hz, 20 Hz to 70 Hz respectively. Among them, at 10 Hz and 70 Hz, there are two largest frequency components, and their amplitudes are both 3.5 Hz (see the spectrum diagram of Figure 6 ). The cumulative RMS value of Δ f micro can be calculated according to the following formula:

[0111] ;

[0112] Among them, is Δ f micro 's average value ( Figure 5 In the left sub - figure of the above two sub - figures, is preset to 0), represents Δ f micro 's value at the k th sampling point, N the total number of sampling points. According to the above formula, the cumulative RMS value Δ Figure 5 of Δ f micro in F rms can be calculated. As Figure 5 shows, Δ F rms = 4.28 Hz. It can be seen from the following text that Δ F rms 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 the cumulative RMS value.

[0113] S52. From low frequency to high frequency, sequentially select frequency components in the spectrum of Δ f micro and calculate the cumulative RMS value of the selected frequency components.

[0114] In this embodiment, as Figure 5 shown in the right sub - figure of the second row, first select the 10 - Hz frequency point (represented by the purple spectral line, and the unselected frequency points are represented by gray). Take the inverse FFT of the selected frequency components to obtain the time - domain waveform corresponding to the selected frequency components (since only a single 10 - Hz frequency component is selected, the corresponding time - domain waveform is a 10 - Hz sine wave), denoted as Δ f micro1 ; finally, use formula (10) to calculate the cumulative RMS value Δ f micro1 of Δ F rms,1 to be 2.48 Hz.

[0115] Furthermore, the inverse FFT is the inverse Fourier transform, which can convert the spectrum in the frequency domain into a time - domain waveform. The inverse transform of the FFT can be calculated by calling the ifft function in MATLAB.

[0116] S53. Repeat step S52, continue to select frequency components from the spectrum of Δ f micro and calculate the cumulative RMS value of the selected frequency components, and so on, until the cumulative RMS values of all selected frequency components are calculated.

[0117] In this embodiment, as shown in the sub - figure on the right of the third row, two frequency points of 10 Hz and 20 Hz are selected (represented by the cyan spectral line, and the unselected frequency points are represented by gray). The inverse FFT is obtained for the selected frequency components, and the time - domain waveform corresponding to the selected frequency components is obtained (since two frequency points of 10 Hz and 20 Hz are selected simultaneously, the corresponding time - domain waveform is a sine wave of 10 Hz superimposed on a sine wave of 20 Hz), denoted as Δ Figure 5 。 f micro2 。

[0118] Continue to call the ifft function of MATLAB to obtain Δ f micro2 ,and calculate the cumulative RMS value Δ f micro2 of Δ F rms,2 using formula (10).

[0119] And so on, until the last frequency point (80 Hz). At this time, the inverse FFT result is Δ f micro8 。Since all frequency components have been selected at this time (see the dark - red spectrogram), the inverse - transformed time - domain waveform is the same as the original signal, that is, Δ f micro8 =Δ f micro ,and their corresponding cumulative RMS values are both 4.28 Hz, that is, Δ F rms,8 =Δ F rms =4.28 Hz.

[0120] S54. Using the frequencies of the selected frequency points (i.e., 10 Hz to 80 Hz) as the abscissa and the cumulative RMS values (i.e., Δ F rms,1 , Δ F rms,2 to Δ F rms,8 ) as the ordinate, a cumulative RMS value graph (the cumulative RMS graph of Figure 6 ) can be obtained. Further, the RMS contribution value Δ n of the n th frequency component can be calculated (the RMS contribution graph of Figure 6 ):

[0121] ;

[0122] where, Δ F rms,n and Δ Frms,n-1 respectively corresponding to the cumulative RMS values from 0 Hz to the n and the n -1 frequency points. By comparing Figure 6 the spectrogram and the RMS contribution diagram, it can be seen that although the frequency components at 10 Hz and 70 Hz have the same amplitude (both 3.5 Hz) in the spectrogram, however, their RMS contributions to Δ f micro are not the same. The RMS contribution value of the 10 Hz component exceeds three times that of the 70 Hz component, that is . At the same time, it can also be seen that although the frequency components at 20 Hz and 50 Hz have relatively large amplitudes in the spectrogram, according to the RMS contribution diagram, their actual overall RMS contributions to Δ f micro are not significant. In practical applications, the influence of the above two frequency components on the RF system can usually be ignored.

[0123] S6. Judging the frequency components causing detuning due to microphonics: Judging the frequency components of the cavity detuning caused by microphonics based on the contribution value of the overall RMS of the cavity detuning.

[0124] The following verifies the method for online measuring the microphonic effect of RF cavities of the present invention through specific embodiments.

[0125] The test results of this embodiment on the RF cavity CM 1-1 of the superconducting heavy ion accelerator CAFE2 device are as Figure 7 shown. According to formula (9), the detuning Δ 1-1 caused by microphonics of CM f micro can be calculated. The waveform diagram and spectrogram thereof are respectively shown in the first sub-diagram and the second sub-diagram of Figure 7 . According to the spectrogram, the main frequency components of Δ f micro are concentrated in the range of 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 relatively large peaks and bandwidths. In addition, there is a relatively large single-frequency component near 155 Hz.

[0126] According to the method provided in this embodiment, the cumulative RMS diagram and the RMS contribution diagram can be obtained in sequence. According to Figure 7From the RMS contribution diagram, it can be seen that the cumulative RMS contribution value of the 0 - 30 Hz frequency component to the detuning is approximately 3.5 Hz, the cumulative RMS contribution value of the 0 - 90 Hz frequency component to the detuning is 9.5 Hz, and the cumulative RMS contribution value of the 0 - 150 Hz frequency component to the detuning is 12.5 Hz. Therefore, the RMS contribution value of the main peak 1 to the detuning is approximately 6 Hz (i.e., 9.5 Hz minus 3.5 Hz), and the RMS contribution value of the main peak 2 to the detuning is approximately 3 Hz (12.5 Hz minus 9.5 Hz). Obviously, the contribution of the first main peak to the RMS is relatively larger. The RF engineer needs to optimize the control loop to ensure that there is a sufficiently large feedback gain at the position of the main peak 1. At the same time, it can also be seen that the contribution of the 155 Hz component in the spectrogram to the RMS can be approximately ignored. Finally, in order to investigate the consistency problem of the measurement of the present invention, as Figure 8 shown, the present invention conducted 10 independent experiments on the CM 1-1 radio frequency cavity and plotted the cumulative RMS diagrams for all of them. The results show that the cumulative RMS curves fit well, verifying the consistency of the present invention.

[0127] Embodiment 2: The above Embodiment 1 provides a method for online measuring the microphonics effect of a radio frequency cavity. Correspondingly, this embodiment provides an apparatus for online measuring the microphonics effect of a radio frequency cavity. The apparatus provided in this embodiment can implement the method for online measuring the microphonics effect of the radio frequency cavity in Embodiment 1, and this apparatus can be implemented in a software, hardware, or a combination of software and hardware manner. For the convenience of description, when describing this embodiment, it is described by dividing it into various units according to functions. Of course, in implementation, the functions of each unit can be implemented in the same or multiple software and / or hardware. For example, this apparatus can include integrated or separate functional modules or functional units to execute the corresponding steps in the methods of Embodiment 1. Since the apparatus in this embodiment is basically similar to the method embodiment, the description process in this embodiment is relatively simple, and the relevant parts can refer to the partial description of Embodiment 1. The embodiment of the apparatus for online measuring the microphonics effect of the radio frequency cavity provided by the present invention is only illustrative.

[0128] Specifically, the apparatus for online measuring the microphonics effect of a radio frequency cavity provided in this embodiment includes:

[0129] A signal processing module, configured to calibrate and normalize the original forward voltage V f * and obtain the forward voltage V f ;

[0130] A detuning calculation module, configured to calculate the cavity detuning Δ f micro caused by microphonics under the stable operating state of the cavity;

[0131] The RMS solving module is configured to 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;

[0132] The flutter frequency solving module is configured to determine the frequency component of the cavity detuning caused by flutter based on the contribution value of the overall RMS of the cavity detuning.

[0133] Embodiment 3: This embodiment provides an electronic device corresponding to the method for online measuring the flutter effect of a radio frequency cavity provided in Embodiment 1. The electronic device can 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.

[0134] As Figure 9 shown, the electronic device includes a processor, a memory, a communication interface, and a bus. The processor, the memory, and the communication interface are connected through the bus to complete communication with each other. A computer program that can run on the processor is stored in the memory. When the processor runs the computer program, it executes the method of Embodiment 1. The implementation principle and technical effects are similar to those of Embodiment 1 and will not be elaborated here. Those skilled in the art can understand that Figure 9 the structure shown in

[0135] is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computing device to which the solution of this application is applied. The specific computing device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0136] In a preferred embodiment, the logical instructions in the above-mentioned memory can be implemented in the form of a software functional unit and sold or used as an independent product. When stored in a computer-readable storage medium, based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application. The foregoing storage medium includes: various media such as a USB flash drive, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), and an optical disc that can store program codes.

[0136] In a preferred embodiment, the processor can be a general-purpose processor of various types such as a central processing unit (CPU) and a digital signal processor (DSP), which is not limited here.

[0137] Example 4: This example provides a computer-readable storage medium storing one or more programs, where the one or more programs include computer instructions which, when executed by a computer, cause the computer to execute the method provided in the above Example 1.

[0138] In a preferred example, the computer-readable storage medium may be a tangible device for holding and storing instructions executed, 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 of the above. The computer-readable storage medium stores computer program instructions which cause the computer to execute the method provided in the above Example 1.

[0139] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatus (devices), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general computer, a special computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in one or more flows in the flowchart and / or one or more blocks in the block diagram.

[0140] These computer program instructions can also be stored in a computer-readable memory capable of guiding a computer or other programmable data processing devices to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device realizes the functions specified in one or more flows in the flowchart and / or one or more blocks in the block diagram.

[0141] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, such that a series of operation steps are executed on the computer or other programmable devices to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable devices provide steps for realizing the functions specified in one or more flows in the flowchart and / or one or more blocks in the block diagram.

[0142] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In the description of this specification, the descriptions referring to terms such as "a preferred embodiment", "furthermore", "specifically", "in this embodiment", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of this specification. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0143] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate 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 as: ； in, is the cavity detuning, f 0.5 represents the half bandwidth of the cavity, is the forward voltage V f The phase of 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 frequency spectrum of cavity detuning is obtained by FFT analysis or wavelet analysis.

3. The method for online measurement of radio frequency cavity microphonic effect according to claim 2, 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.

4. The method for online measurement of radio frequency cavity microphonic effect according to claim 3, 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.

5. The method for online measurement of radio frequency cavity microphonic effect according to claim 3, 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: ； in, 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 accumulated RMS value of 1 frequency point, It is the cumulative RMS value from 0 Hz to the first frequency point.

6. 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 for: ； in, f 0.5 represents the half bandwidth of the cavity, is the forward voltage V f The phase of 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.

7. 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 1-5.

8. 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 1-5.

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