A method for calibrating inter-bunch signal aliasing based on cavity probe

Abstract

The present invention provides a method for calibrating signal aliasing between bunches based on a cavity probe, comprising: obtaining an alias-free reference signal from a high-repetition-rate free electron laser device; extracting the signal waveform of each bunch and its measurement result from the alias-free reference signal; modeling a formula for the residual signal; obtaining a calibration result for the bunch based on the residual signal formula and a vector calibration algorithm according to the measurement result of the aliased signal waveform and the standard waveform of the previous bunch; using the next bunch as the current bunch and returning to the step of obtaining the calibration result; and continuing until all bunches are calibrated, at which point the calibration results for all bunches are obtained. The method of the present invention models and compensates for the amplitude and phase characteristics of the decay tails of adjacent bunches through a vector calibration algorithm, effectively eliminating the time-domain aliasing effect in the high-repetition-rate free electron laser device and reducing the absolute phase deviation of the beam arrival time measurement of the cavity probe to the femtosecond level.

Description

Technical Field

[0001] The present invention relates to a particle accelerator physical beam current diagnosis technology, and more particularly to an inter-bunch signal aliasing calibration method based on a cavity probe. Background Art

[0002] Cavity probes typically employ a resonant cavity design and are suitable for precise measurement of beam parameters, including lateral position measurement (e.g., in CBPM systems) and longitudinal arrival time measurement (e.g., in CBAM systems). Their operating principle is based on the excitation signal generated by the beam in a resonant cavity, which generates a specific electromagnetic mode. When the TM010 mode is excited, the electric field in this mode is axially symmetric, and the magnetic field surrounds the cavity wall. This results in the coupled signal's amplitude and phase primarily representing the beam's charge and longitudinal arrival time, while being insensitive to changes in the beam's lateral position. For lateral beam position measurement, the TM110 mode is primarily utilized. The coupled signal characteristics of this mode are simultaneously a function of the beam's charge, phase, and lateral offset position, with the lateral position information being linearly correlated with the signal strength.

[0003] The excitation signal of the cavity probe is in the form of exponential decay oscillation, and its mathematical expression is:

[0004] ,

[0005] Where V0 represents the initial amplitude of the excitation signal, τ is the decay time constant, is the central angular frequency of the resonant cavity, is the phase shift of the beam passing through the cavity.

[0006] In the above formula, the decay time constant τ is the time required for the excitation signal amplitude to decay to 1 / e of the initial amplitude, where e is the base of the natural logarithm. Figure 1 As shown in Figure 2, when τ is larger, the signal decays slower.

[0007] The relationship between the decay time constant τ and the cavity quality factor Q is:

[0008] ,

[0009] In harmonic cavity design, the choice of decay time constant τ directly impacts signal processing performance. A larger decay time constant τ allows for a longer cavity energy storage time, resulting in a higher extractable effective signal energy, which improves the signal-to-noise ratio and measurement accuracy. Conversely, if the decay time constant τ is too small, the signal decays too quickly, reducing the available effective signal amplitude and, in turn, affecting the system's measurement resolution.

[0010] However, in high-repetition-rate free-electron lasers, if the decay time constant τ is too long, the cavity excitation signal from the previous bunch will not fully decay before the next bunch arrives, causing signal aliasing. Specifically, the residual signal at the tail of the previous bunch overlaps with the signal from the subsequent bunch in the time domain, affecting the accuracy of independent measurements of beam parameters.

[0011] In a specific factual case, taking the Shanghai Hard X-ray Free Electron Laser Facility (SHINE) as an example, its bunch repetition frequency is 1 MHz (i.e., a period of 1 μs). In the beam arrival time measurement system (CBAM) of the device, the cavity probe is designed with a resonant frequency of 3.520 GHz, and the decay time constant τ is set to 200 ns. The RF signal output by the probe is first processed by the RF front-end module, including bandpass filtering, low-noise amplification, and mixing and down-conversion to a 54.2 MHz intermediate frequency signal, and then synchronously acquired by the digital signal processor. Since the decay time constant τ = 200 ns, according to the exponential decay characteristics, after a bunch time interval (T = 1 μs), the signal amplitude of the previous bunch will decay to e of the initial value. -T / τ =e -5 ≈0.67%. Although the residual amplitude is small, in high-precision time measurement, when the subsequent bunch arrives, it will still produce time domain superposition with the residual signal that has not completely decayed (mainly including the decay tail of the bunch in the first 1-2 cycles), forming a cumulative aliasing effect, such as Figure 2 shown.

[0012] Therefore, it is necessary to develop a method for calibrating inter-bunch signal aliasing for cavity probes to eliminate the interference of adjacent bunch decay tails, thereby improving the measurement resolution of signal amplitude and phase. This is crucial for the accuracy of beam arrival time measurements based on CBAM systems, especially in high-repetition-rate accelerators such as the Shanghai Hard X-ray Free Electron Laser (SHINE) facility, which require femtosecond-level time resolution. Summary of the Invention

[0013] The object of the present invention is to provide a method for calibrating inter-bunch signal aliasing based on a cavity probe, so as to effectively eliminate the time domain aliasing effect in a high repetition rate free electron laser device.

[0014] To achieve the above object, the present invention provides a method for calibrating inter-bunch signal aliasing based on a cavity probe, comprising:

[0015] S1: Acquire a bunch signal from a high repetition rate free electron laser device, the starting point of which is in the bunch intermission period and the duration is at least two bunch time intervals, as an alias-free reference signal;

[0016] S2: Extract the signal waveform of the first bunch without aliasing and the signal waveforms of subsequent bunches from the aliasing-free reference signal. The signal waveform of the first bunch is used as the standard waveform of the previous bunch; and obtain the measurement result of the signal waveform of the first bunch when it is not aliased. The measurement results of the signal waveform of the subsequent n-th bunch after aliasing ;

[0017] S3: Based on the signal waveform of the previous bunch before aliasing, a formula for the residual signal of the previous bunch is obtained by modeling;

[0018] S4: Based on the measurement results of the signal waveform of the current n-th bunch after aliasing and the standard waveform of the previous bunch, and based on the formula of the residual signal of the previous bunch and the vector calibration algorithm, the calibration result of the nth bunch is obtained;

[0019] S5: The next bunch is taken as the current n-th bunch, and the process returns to step S4; this continues until all bunches are calibrated, at which point the calibration results of all bunches are obtained.

[0020] The CBAM system is used as the implementation platform. The CBAM system includes a cavity probe, a radio frequency front-end module and a digital signal processor connected in sequence. The digital signal processor collects the continuous time domain signal of the intermediate frequency signal obtained by processing the radio frequency signal, and extracts the bunch signal whose starting point is in the bunch interval period as the aliasing-free reference signal and stores it in the reference waveform database.

[0021] The step S2 specifically includes:

[0022] S21: segmenting the alias-free reference signal according to the bunch time interval, extracting the signal of the first complete bunch time interval as the signal waveform of the first alias-free bunch, and extracting the signal waveform of the subsequent n-th bunch according to the bunch time interval;

[0023] S22: Get the measurement result of the signal waveform of the first bunch when it is not aliased , represents the amplitude of the signal waveform of the first bunch, Indicates the phase of the signal waveform of the first bunch; obtains the measurement result of the signal waveform of the subsequent n-th bunch after aliasing , and are the amplitude and phase of the signal waveform of the nth bunch respectively.

[0024] In step S3, the amplitude of the residual signal of the previous bunch is and phase for:

[0025] ,

[0026] ,

[0027] in, is the attenuation coefficient, , T is the bunch time interval, T = 1μs, t is the current moment, is the decay time constant, is the amplitude of the standard waveform of the previous bunch, is the phase drift, = , is the phase of the standard waveform of the previous bunch, is the resonant angular frequency of the cavity probe.

[0028] The step S3 further includes: obtaining a formula for the signal amplitude of the simulated n-th bunch after aliasing based on a formula for the residual signal of the previous bunch; and repeating the step of obtaining the formula for the signal amplitude until the signal waveforms of all simulated bunches after aliasing are constructed to form a time-domain spliced ​​waveform.

[0029] Based on the vector calibration algorithm, the calibration result of the nth bunch is for:

[0030] ,

[0031] in, and are the amplitude and phase of the signal waveform of the nth bunch, is the attenuation coefficient correction factor; is the amplitude of the residual signal of the previous bunch, is the phase of the residual signal from the previous bunch.

[0032] The step S4 further includes: obtaining the calibration result of the nth bunch The amplitude and phase of

[0033] Calibration results for the nth bunch Amplitude and phase They are:

[0034] ,

[0035] ,

[0036] Where, and represent the real and imaginary parts of a complex number, respectively. is the calibration result of the nth bunch.

[0037] Finally, the calibration results of all bunches are output Amplitude and phase , n=2,3,……N, n is the bunch number, and N is the total number of bunches of alias-free reference signals.

[0038] For the nth bunch when n≥3, when executing step S5, the calibration result of the previous bunch is As the standard waveform of the previous bunch.

[0039] The repetition frequency of the bunch is 1 MHz.

[0040] The present invention provides a method for calibrating signal aliasing between bunches based on a cavity probe. The method models and compensates for the amplitude and phase characteristics of the attenuation tails of adjacent bunches through a vector calibration algorithm, effectively eliminating the time domain aliasing effect in a high repetition rate free electron laser device and reducing the absolute phase deviation of the beam arrival time measurement of the cavity probe to the femtosecond level. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The output signal of a typical cavity probe has different decay time constants ( ), the output signal of the cavity probe can be the excitation signal of TM010 or TM110 mode.

[0042] Figure 2 Figure 3 is a typical multi-bunch time domain waveform of a cavity probe output at a repetition rate of 1 MHz, showing the cumulative aliasing effect.

[0043] Figure 3 The system block diagram is a beam arrival time measurement system applicable to the inter-bunch signal aliasing calibration method based on the cavity probe of the present invention.

[0044] Figure 4 The present invention is a flow chart of a method for calibrating inter-bunch signal aliasing based on a cavity probe.

[0045] Figure 5A and Figure 5B : is a comparison diagram of signal amplitude and phase optimization effects based on the vector calibration algorithm in an embodiment of the present invention, wherein Figure 5A Shows the deviation of the signal amplitude from the alias-free reference before and after calibration. Figure 5B Shows the comparison of the signal phase deviation from the alias-free reference before and after calibration. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0047] The present invention proposes a method for calibrating inter-bunch signal aliasing using a cavity probe. The principle behind this method is to model and compensate for the amplitude and phase characteristics of the decay tails of adjacent bunches using a vector calibration algorithm, effectively eliminating time-domain aliasing effects in high-repetition-rate free-electron laser devices. While the vector calibration algorithm is implemented using complex number operations, the specific application of this method to inter-bunch signal aliasing calibration in a cavity probe is unique to the present invention.

[0048] The present invention provides a cavity probe-based inter-bunch signal aliasing calibration method for a cavity probe, used for measuring bunch parameters. In this embodiment, the bunches used are those from the Shanghai Hard X-ray Free Electron Laser (SHINE) facility, with a repetition rate of 1 MHz (i.e., a 1 μs time interval).

[0049] In this embodiment, the cavity probe-based inter-bunch signal aliasing calibration method of the present invention is applicable to calibrating the output signal of a cavity probe in a beam arrival time measurement (CBAM) system. The resonant frequency is designed to be 3.520 GHz, and the decay time constant τ is set to 200 ns. The cavity probe output signal can be an excitation signal in either the TM010 or TM110 mode.

[0050] In other embodiments, the inter-bunch signal aliasing calibration method based on the cavity probe of the present invention can also be applied to the output signal of the cavity probe in other systems, wherein the cavity probe is used to measure the bunches continuously emitted according to a fixed bunch time interval, and the output signal of the cavity probe can be an excitation signal of the TM010 or TM110 mode.

[0051] The system block diagram of the CBAM system is as follows Figure 3 The CBAM system includes a cavity probe 100, a radio frequency front-end module 200, and a digital signal processor 300, which are connected in series. The radio frequency front-end module 200 includes a bandpass filter 201, an amplifier 202, and one input of a mixer 203, which are connected in series with the cavity probe 100. The other input of the mixer 203 is connected to a synchronization reference signal, and the output of the mixer 203 is connected to the input channel of the digital signal generator 300.

[0052] In this embodiment, since the cavity probe 100 belongs to a CBAM system, it has two electrodes that output two RF signals (i.e., a first RF signal RF1 and a second RF signal RF2). These two RF signals are identical, and each RF signal is connected to a series-connected bandpass filter 201, amplifier 202, and mixer 203 of the RF front-end module 200 to generate an intermediate frequency (IF) signal (i.e., IF1 or IF2). This signal is then transmitted to an input channel of the digital signal generator 300 (i.e., the first input channel CH1 or the second input channel CH2). Consequently, the digital signal generator 300 can calculate the standard deviation of the phase or amplitude difference between the two IF signals, derived from processing the first and second RF signals RF1 and RF2, and thereby evaluate the resolution of the CBAM system electronics.

[0053] Therefore, the RF signal output by the cavity probe 100 is first processed by the RF front-end module 200. The processing of the RF front-end module 200 includes bandpass filtering, low-noise amplification and mixing and down-conversion to a 54.2 MHz intermediate frequency signal. Subsequently, the digital signal processor 300 synchronously collects the two intermediate frequency signals.

[0054] like Figure 4 As shown, the inter-bunch signal aliasing calibration method based on the cavity probe of the present invention specifically includes:

[0055] Step S1: acquiring a bunch signal starting from a high repetition rate free electron laser device in a bunch intermission period and having a duration of at least two bunch time intervals as an alias-free reference signal;

[0056] In this embodiment, the CBAM system is used as the implementation platform, and the continuous time domain signal of the intermediate frequency signal obtained by processing the radio frequency signal is collected by a digital signal processor. The bunch signal with the starting point in the bunch interval period is extracted as the aliasing-free reference signal and stored in the reference waveform database.

[0057] In this embodiment, the bunches used are those from the Shanghai Hard X-ray Free Electron Laser (SHINE) facility, with a repetition rate of 1 MHz (i.e., a 1 μs interval between bunches). The duration of the signal starting at the bunch interval is at least 2 μs, with the first 1 μs serving as the first alias-free bunch signal, and the last 1 μs of the tail signal being superimposed on the next bunch. The bunch interval refers to the time difference between consecutive bunches. Since the bunch interval of FEL emission is 1 μs, a single bunch signal for a complete cycle is a 1 μs single bunch signal.

[0058] In fact, the collected continuous signal will exceed 2μs, but here we do not consider the signals superimposed on the third and fourth bunches.

[0059] Step S2: Extract the signal waveform of the first bunch without aliasing and the signal waveforms of subsequent bunches from the aliasing-free reference signal, and use the signal waveform of the first bunch as the standard waveform of the previous bunch; and obtain the measurement result of the signal waveform of the first bunch when it is not aliased. The measurement results of the signal waveform of the subsequent n-th bunch after aliasing ;

[0060] Step S2 specifically includes:

[0061] Step S21: segmenting the alias-free reference signal according to the bunch time interval, extracting the signal of the first complete bunch time interval as the signal waveform of the first alias-free bunch, and extracting the signal waveform of the subsequent n-th bunch according to the bunch time interval;

[0062] Step S22: Obtain the measurement result of the signal waveform of the first bunch when it is not aliased , represents the amplitude of the signal waveform of the first bunch, Indicates the phase of the signal waveform of the first bunch; obtains the measurement result of the signal waveform of the subsequent n-th bunch after aliasing , and are the amplitude and phase of the signal waveform of the nth bunch respectively.

[0063] Since the bunch repetition frequency is 1 MHz (i.e., the bunch time interval is 1 μs) in this embodiment, the extracted alias-free single bunch signal is the signal of the first 1 μs of the alias-free reference signal, and the residual signal superimposed on the second bunch in step S3 is the tail signal of the last 1 μs of this alias-free single bunch signal.

[0064] Step S3: Based on the signal waveform of the previous bunch before aliasing, a model is built to obtain a formula for the residual signal of the previous bunch;

[0065] Optionally, step S3 further includes: obtaining a formula for the signal waveform of the simulated n-th bunch after aliasing based on a formula for the residual signal of the previous bunch. Further, step S3 may also include: repeating the step of obtaining the formula for the signal waveform until the signal waveforms of all simulated bunches after aliasing are constructed, so as to form the following formula: Figure 2 The time-domain spliced ​​waveform shown is as follows. Since it is currently impossible to directly acquire a signal with aliasing at a bunch repetition frequency of 1 MHz, this method can only be used to obtain a simulation result through splicing, which can then be processed.

[0066] Among them, for the nth bunch (n is the bunch number, n ≥ 2), the signal waveform of the previous bunch when it is not aliased is Attenuation coefficient After weighting, it is used as the residual signal of the previous bunch; then, vector superposition is performed to construct the simulated signal waveform of the nth bunch after aliasing. .

[0067] The amplitude of the residual signal of the previous bunch and phase for:

[0068] ,

[0069] ,

[0070] in, is the attenuation coefficient, , T is the bunch time interval, T = 1μs, t is the current moment, is the decay time constant, is the amplitude of the standard waveform of the previous bunch, is the phase drift, = , is the phase of the standard waveform of the previous bunch, is the resonant angular frequency of the cavity probe.

[0071] The attenuation coefficient where T is the bunch time interval, is the decay time constant. In this embodiment, T=1μs.

[0072] Therefore, the signal waveform of the simulated n-th bunch after aliasing is for:

[0073] ,

[0074] Where, T is the bunch time interval, T = 1μs, t is the current time, is the decay time constant, is the phase drift, is the phase value of the preceding bunch at time (tT), and the position drift is the phase noise added to the current bunch compared to the phase value of the previous bunch at time (tT), = , phase drift The value of is determined by the resonant angular frequency of the cavity probe and the bunch time interval T. , the frequency is 3.520 GHz, T = 1 μs, and it may also contain the random phase jitter of the beam; and is the signal amplitude and phase of the nth bunch when it is not aliased, is the amplitude of the standard waveform of the previous bunch, that is, the signal amplitude of the previous bunch before aliasing; is the phase of the standard waveform of the previous bunch; and is the signal amplitude and phase of the simulated n-th bunch after aliasing.

[0075] Step S4: Based on the measurement result of the signal waveform of the current n-th bunch after aliasing The calibration result of the nth bunch is obtained based on the formula of the residual signal of the previous bunch and the vector calibration algorithm. Thus, the vector calibration algorithm is realized.

[0076] When executing step S4, the following parameters are known:

[0077] (1) Measurement results of the signal waveform of the first bunch when it is not aliased: ,

[0078] (2) Measurement results of the signal waveform of the nth bunch after aliasing: ,

[0079] (3) Resonant angular frequency of cavity probe: . Resonant angular frequency It is determined when the cavity probe is designed and is related to the probe design frequency. , f is the probe design frequency. In this embodiment, the probe design frequency of the CBAM cavity probe is 3.520 GHz.

[0080] The aliasing effect on the nth bunch includes the residual signal of the previous bunch. As described in step S3 above, the residual signal of the previous bunch can be modeled as:

[0081] ,

[0082] ,

[0083] Where T is the bunch time interval, T = 1μs, t is the current time, is the amplitude of the standard waveform of the previous bunch, is the phase of the standard waveform of the previous bunch, is the resonant angular frequency of the cavity probe.

[0084] Based on the vector calibration algorithm, the calibration result of the nth bunch is for:

[0085] ,

[0086] in, and are the amplitude and phase of the signal waveform of the nth bunch, is the attenuation coefficient correction factor, The default value is 1.0, which can be optimized through experimental calibration; is the amplitude of the residual signal of the previous bunch, is the phase of the residual signal from the previous bunch.

[0087] Since the calibration result of the nth bunch is a plural form, so in this embodiment, the step S4 further includes: obtaining the calibration result of the nth bunch amplitude and phase.

[0088] Calibration results for the nth bunch Amplitude and phase They are:

[0089] ,

[0090] ,

[0091] Where, and represent the real and imaginary parts of a complex number, respectively. is the calibration result of the nth bunch.

[0092] By expanding the formula, the calibration result of the nth bunch is Amplitude and phase They are:

[0093] ,

[0094] ,

[0095] in, and are the amplitude and phase of the signal waveform of the nth bunch, is the attenuation coefficient correction factor, The default value is 1.0, which can be optimized through experimental calibration; is the amplitude of the residual signal of the previous bunch, is the phase of the residual signal from the previous bunch.

[0096] Step S5: Take the next bunch as the current nth bunch and return to step S4 to perform iterative calibration until all bunches are calibrated. At this time, the calibration results of all bunches are obtained. , n=2,3,...N, N is the total number of bunches of alias-free reference signals. In this embodiment, since the step S4 further includes: obtaining the calibration result of the nth bunch The amplitude and phase of all bunches are thus finally output. Amplitude and phase , n=2,3,……N.

[0097] In this embodiment, for the nth bunch when n≥3, when executing step S5, the calibration result of the previous bunch (i.e., the n-1th bunch) is converted to As the standard waveform of the previous bunch.

[0098] In other embodiments, for the n-th bunch when n≥3, if the accuracy requirement is lower, the measurement result of the signal waveform of the previous bunch after aliasing may be used as the standard waveform of the previous bunch.

[0099] Experimental results:

[0100] The vector calibration method was used to calibrate 200 consecutive bunch signals of the CBAM system, achieving significant results. Figure 5A and Figure 5B As shown, Figure 5A To compare the deviation of the signal amplitude from the alias-free reference before and after calibration, the ADC reading of the amplitude deviation after calibration is changed from 4×10 4 Reduced to 2×10 4 (reduced by 50%), Figure 5B Comparing the signal phase deviations before and after calibration with those of the alias-free reference, the absolute phase deviation was significantly optimized from 260 fs to 0.3 fs, an improvement of nearly three orders of magnitude. Simultaneously, the phase jitter (RMS) was significantly reduced from 19 fs to 4 fs. These data fully demonstrate the superior performance of the proposed method in eliminating inter-bunch signal aliasing and improving measurement accuracy.

[0101] The present invention's cavity-probe-based inter-bunch signal aliasing calibration method effectively eliminates the time-domain aliasing effect of adjacent bunch signals in a 1MHz high-repetition-rate free-electron laser (HFFREL) instrument through an innovative vector calibration algorithm. Validated by field data from the Shanghai Hard X-ray Free-Electron Laser (SHINE) facility, the vector calibration reduced the amplitude deviation of adjacent bunch signal aliasing interference in the CBAM system by 50%, and the absolute phase deviation from 260 fs to 0.3 fs, enabling the SHINE instrument to achieve a beam arrival time measurement resolution of 20 fs. Compared to traditional optical measurement methods, the equipment cost is reduced by approximately 40%.

[0102] The present invention provides a method for calibrating inter-bunch signal aliasing based on a cavity probe. The method models and compensates for the amplitude and phase characteristics of the attenuation tails of adjacent bunches through a vector calibration algorithm, effectively eliminating the time domain aliasing effect in a high repetition rate free electron laser device, and reducing the absolute phase deviation of the beam arrival time measurement of the cavity probe, especially the cavity probe of the CBAM system, to the femtosecond level.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. In other words, any simple, equivalent changes and modifications made in accordance with the claims and description of the present invention are within the scope of protection of the patent claims. Anything not fully described in this invention constitutes conventional technology.

Claims

1. A method for calibrating inter-bunch signal aliasing based on a cavity probe, characterized in that: include: Step S1: acquiring a bunch signal starting from a high repetition rate free electron laser device in a bunch intermission period and having a duration of at least two bunch time intervals as an alias-free reference signal; Step S2: Extract the signal waveform of the first bunch without aliasing and the signal waveforms of subsequent bunches from the aliasing-free reference signal, and use the signal waveform of the first bunch as the standard waveform of the previous bunch; and obtain the measurement result of the signal waveform of the first bunch when it is not aliased. The measurement results of the signal waveform of the subsequent n-th bunch after aliasing ; Step S3: Based on the signal waveform of the previous bunch before aliasing, a model is built to obtain a formula for the residual signal of the previous bunch; Step S4: Based on the measurement result of the signal waveform of the current n-th bunch after aliasing and the standard waveform of the previous bunch, and based on the formula of the residual signal of the previous bunch and the vector calibration algorithm, the calibration result of the nth bunch is obtained; Step S5: take the next bunch as the current n-th bunch and return to step S4; This process continues until all bunches are calibrated, at which point the calibration results for all bunches are obtained.

2. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, characterized in that: The CBAM system is used as the implementation platform. The CBAM system includes a cavity probe, a radio frequency front-end module and a digital signal processor connected in sequence. The digital signal processor collects the continuous time domain signal of the intermediate frequency signal obtained by processing the radio frequency signal, and extracts the bunch signal whose starting point is in the bunch interval period as the aliasing-free reference signal and stores it in the reference waveform database.

3. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, characterized in that: Step S2 specifically includes: Step S21: segmenting the alias-free reference signal according to the bunch time interval, extracting the signal of the first complete bunch time interval as the signal waveform of the first alias-free bunch, and extracting the signal waveform of the subsequent n-th bunch according to the bunch time interval; Step S22: Obtain the measurement result of the signal waveform of the first bunch when it is not aliased , represents the amplitude of the signal waveform of the first bunch, Indicates the phase of the signal waveform of the first bunch; obtains the measurement result of the signal waveform of the subsequent n-th bunch after aliasing , and are the amplitude and phase of the signal waveform of the nth bunch respectively.

4. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, wherein: In step S3, the amplitude of the residual signal of the previous bunch is and phase for: ， ， in, is the attenuation coefficient, , T is the bunch time interval, T = 1μs, t is the current moment, is the decay time constant, is the amplitude of the standard waveform of the previous bunch, is the phase drift, = , is the phase of the standard waveform of the previous bunch, is the resonant angular frequency of the cavity probe.

5. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, characterized in that: The step S3 further includes: obtaining a formula for the signal amplitude of the simulated n-th bunch after aliasing based on a formula for the residual signal of the previous bunch; and repeating the step of obtaining the formula for the signal amplitude until the signal waveforms of all simulated bunches after aliasing are constructed to form a time-domain spliced ​​waveform.

6. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, characterized in that: Based on the vector calibration algorithm, the calibration result of the nth bunch is for: ， in, and are the amplitude and phase of the signal waveform of the nth bunch, is the attenuation coefficient correction factor; is the amplitude of the residual signal of the previous bunch, is the phase of the residual signal from the previous bunch.

7. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, characterized in that: The step S4 further includes: obtaining the calibration result of the nth bunch The amplitude and phase of Calibration results for the nth bunch Amplitude and phase They are: ， ， Where, and represent the real and imaginary parts of a complex number, respectively. is the calibration result of the nth bunch.

8. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 7, characterized in that: Finally, the calibration results of all bunches are output Amplitude and phase , n=2,3,……N, n is the bunch number, and N is the total number of bunches of alias-free reference signals.

9. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, characterized in that: For the nth bunch when n≥3, when executing step S5, the calibration result of the previous bunch is As the standard waveform of the previous bunch.

10. The method for calibrating inter-bunch signal aliasing based on a cavity probe according to claim 1, characterized in that: The repetition frequency of the bunch is 1 MHz.

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