A beam synchronization phase online measurement method, device, equipment and medium

Abstract

The present invention discloses a beam synchronization phase online measurement method, device, equipment and medium, including: obtaining the original cavity pressure of the radio frequency cavity; V c * and the original forward voltage V f * ; For the original cavity pressure V c * and the original forward voltage V f * Processing is performed to obtain the normalized cavity pressure V c and forward voltage V f ; Calculate cavity pressure V c and forward voltage V f The steady-state value U C and U F , and find the detuning Δ in steady state oh ; The cavity pressure change caused by the beam V cb Linear fitting gives the phase ∠ V cb ; According to the selected time window T W , calculated from the detuning Δ oh The phase ∠ V cb Deflection angle α th ; In phase ∠ V cb Deduct the deflection angle α th , we can get the phase of beam equivalent voltage ∠ V b ; Based on the phase of the beam equivalent voltage ∠ V b Extract beam phase #imgabs0#. The calculation result of the present invention is no longer affected by the phase drift caused by environmental factors, and is also no longer affected by cavity detuning.

Description

Technical Field

[0001] The invention relates to an online measurement method, device, equipment and medium for beam synchronization phase based on instantaneous beam load effect, and relates to the field of particle accelerators. Background Art

[0002] In a particle accelerator, the energy gain of the beam depends on the acceleration cavity pressure of the RF cavity and the synchronization phase of the beam. In order to ensure that the beam can obtain the required energy gain, accurate beam synchronization phase is crucial. Therefore, before the beam is officially operated, a "phase sweep" operation is usually required to calibrate the synchronization phase. However, changes in the operating environment (such as temperature, humidity, etc.) will cause phase drift. Over time, the phase of the RF cavity gradually becomes inaccurate and needs to be recalibrated regularly.

[0003] The existing phase-sweeping procedure is not only time-consuming and affects the availability of the accelerator, but also relies on expensive beam diagnostic instruments, making it difficult to fully deploy in large accelerators. In recent years, some foreign research institutions (such as the German Center for Electron Synchrotron Radiation Research—DESY) have proposed a beam phase measurement method based on the transient beam load effect in open-loop mode, which can achieve calibration without phase sweeping, thereby saving machine time. However, this method faces some challenges in specific applications. For example, the open-loop operation of the RF cavity may cause beam loss, and the cavity is required to work in a resonant state as much as possible, otherwise its measurement results will be affected by detuning. Especially in room temperature cavities, the impact of detuning on the measurement results is more significant.

[0004] Therefore, developing a synchronous phase measurement method that can overcome the limitations of existing methods is of great significance for improving accelerator availability, reducing operating costs, and its widespread application in the field of particle accelerators. Summary of the invention

[0005] 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 beam synchronization phase online measurement method, device, equipment and medium, which can realize the online extraction of beam synchronization phase information, and no longer requires the RF cavity to work in a resonant state, and is still applicable in a detuned state.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a beam synchronization phase online measurement method, the method comprising: obtaining an original cavity pressure of a radio frequency cavity; V c * and the original forward voltage V f * ; For the original cavity pressureV c * and the original forward voltage V f * Processing is performed to obtain the normalized cavity pressure V c and forward voltage V f ; Calculate cavity pressure V c and forward voltage V f The steady-state value U C and U F , and find the detuning Δ of the RF cavity in steady state ω ; The cavity pressure change caused by the beam V cb Linear fitting gives the phase ∠ V cb ; The time window selected based on the calculation of the synchronization phase T W , calculated from the detuning Δ ω The phase ∠ V cb Deflection angle α th ; In phase ∠ V cb Deduct the deflection angle α th , we can get the phase of beam equivalent voltage ∠ V b ; Based on the phase of the beam equivalent voltage ∠ V b Extracting beam phase .

[0008] Furthermore, the detuning Δ ω The calculation formula is:

[0009] ;

[0010] ;

[0011] In the formula, is the detuning angle, and Cavity pressure V c and forward voltage V f The steady-state value U C and U F The phase angle, is the half bandwidth of the cavity.

[0012] Furthermore, the cavity pressure change caused by the beam V cb Linear fitting gives the phase ∠ V cb , the specific process is:

[0013] Based on the normalized cavity pressure V c and forward voltage V f Establish the cavity differential equation:

[0014] ;

[0015] In the formula, t is the sampling time, and are the cavity pressures without and with beam, respectively. V c The differential of V c0 and V c1 are the cavity pressures without and with beam, respectively. V c , V f0 and V f1 are the forward voltages without beam current and with beam current respectively. V f , V b is the beam equivalent voltage; and are the cavity detuning Δ without beam and with beam respectively. ω , is the half bandwidth of the cavity, β is the coupling coefficient;

[0016] Beam-induced cavity pressure changes in open-loop operation V cb = V c1 -V c0 , V f0 and V f1 Equal, Δ ω 0=Δ ω 1=Δ ω , we can obtain the following by subtracting the differential equation without beam from the differential equation with beam:

[0017] ;

[0018] The step response of the differential equation is:

[0019] ;

[0020] in, is the cavity pressure change caused by the beam V cb The differential of

[0021] In the detuned Δ ω = 0, the above formula is simplified to:

[0022] ;

[0023] Since the vector V cb and V b have the same direction, i.e., vector V cb The phase angle and beam equivalent voltage V b The phase of the vector V cb Linear fitting gives V cb The phase ∠ V cb ;

[0024] When the detuning Δ ω When it is not equal to 0, V cb Will no longer be with V b Keeping the same direction, detuning causes V cb There is a deflection angle α , in ∠ V cb Deduction α Theoretical value α th The phase of the beam equivalent voltage is obtained V b .

[0025] Further, according to the time window selected by calculating the synchronization phase T W , calculated from the detuning Δ ω Caused by V cb Deflection angle α th , and its calculation formula is:

[0026] ;

[0027] In the formula, For vector V cb In the time window T w The calculation results below are plural U CB The phase angle.

[0028] Furthermore, based on the phase of the beam equivalent voltage ∠ V b Extract the beam phase :

[0029] .

[0030] Furthermore, in open-loop operation mode, the time window for calculating the synchronization phase T W must be less than the beam pulse time; in closed-loop operation mode, the time window T W It must not only be shorter than the beam pulse time, but also shorter than the loop delay time. τ d .

[0031] In a second aspect, the present invention further provides a beam synchronization phase online measurement device, the device comprising:

[0032] The signal acquisition module is configured to obtain the original cavity pressure of the radio frequency cavity. V c * and the original forward voltage V f * ;

[0033] The signal processing module is configured to process the raw cavity pressure V c * and the original forward voltage V f * Processing is performed to obtain the normalized cavity pressure V c and forward voltage V f ;

[0034] The detuning calculation module is configured to calculate the cavity pressure V c and forward voltage V f The steady-state value U C and U F, and find the detuning Δ of the RF cavity in steady state ω ;

[0035] The deflection angle calculation module is configured to calculate the time window selected according to the synchronization phase T W , calculated from the detuning Δ ω The phase ∠ V cb Deflection angle α th ;

[0036] The phase calculation module is configured to calculate the cavity pressure change caused by the beam current. V cb Linear fitting gives the phase ∠ V cb , in ∠ V cb Deduct the deflection angle α th , we can get the phase of beam equivalent voltage ∠ V b ;

[0037] The beam information extraction module is configured to be based on the phase ∠ of the beam equivalent voltage V b Extracting beam phase .

[0038] 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 so that the processor can execute any one of the methods described.

[0039] 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 any one of the methods described.

[0040] Since the present invention adopts the above technical scheme, it has the following characteristics: 1. The present invention can directly solve the phase of the beam relative to the cavity pressure (i.e., the beam synchronization phase), and the calculation result is no longer affected by the phase drift caused by environmental factors. 2. The present invention demodulates the beam information by reading the transient RF signal caused by the beam load effect, wherein RF signal acquisition, down-conversion and I / Q demodulation can all be completed by a general digital low-level system, and the core signal processing algorithm can be deployed on a general host computer without adding additional hardware equipment. 3. Regardless of whether the RF cavity operates in open-loop mode or closed-loop mode, the present invention can obtain beam information online. The online measurement of beam information in closed-loop mode is of great significance to the stable operation of the heavy ion accelerator. 4. The measurement result of the present invention is not affected by the detuning of the cavity. Even if the cavity is far away from the resonant state, the present invention can accurately solve the beam information. In summary, the present invention can be widely used in particle accelerators. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] 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:

[0042] Figure 1 This is a flow chart of a beam synchronization phase online measurement method according to an embodiment of the present invention.

[0043] Figure 2 This is a block diagram of online measurement of beam synchronization phase according to an embodiment of the present invention.

[0044] Figure 3a is a schematic diagram of solving the normalized cavity pressure in an embodiment of the present invention, Figure 3b and Figure 3c is a basic principle diagram for calculating beam phase in an embodiment of the present invention; wherein, Figure 3b is the cavity pressure change caused by the beam during the flat-top time V cb , Figure 3c is the I / Q coordinate diagram of the cavity pressure change. By solving V cb The angle of the vector gives the beam phase.

[0045] Figure 4a The cavity pressure with beam current (red) and without beam current (blue) and the corresponding forward voltage (green) in the open-loop operation mode measured in the embodiment of the present invention. Note that in the open-loop operation mode, the forward voltage remains unchanged with or without beam current; Figure 4b for Figure 4a Enlarged detail of the gray rectangular area. Figure 4c for Figure 4bI / Q plot of cavity pressure signal.

[0046] Figure 5a The cavity pressure signals in the open-loop operation mode (red) and the closed-loop operation mode (blue) and the forward voltage in the closed-loop mode (green) measured in the embodiment of the present invention when there is a beam current are shown. Figure 5b for Figure 5a A magnified detail of the gray rectangular area. Note that in closed-loop operation, the forward voltage undergoes a loop delay ( τ d ) will change only after the beam passes through. V cb The sampling values ​​of are represented by red and blue dots in open-loop and closed-loop modes respectively. Figure 5c is the I / Q coordinate diagram of the cavity pressure signal, where V cb The sampled values ​​of the vector are represented by red and blue dots.

[0047] Figure 6a : The measured results of the cavity pressure signal caused by the beam in the embodiments of the present invention with and without detuning. The black curve represents a detuning angle of 45 degrees, the dark gray curve represents no detuning, and the light gray curve represents a detuning angle of -30 degrees. Figure 6b for Figure 6a I / Q plot of the cavity pressure signal shown.

[0048] Figure 7a is the simulation result of the step response of the cavity differential equation with and without detuning. Figure 7b for Figure 7a The details of the enlarged medium gray rectangular area. Figure 7c for Figure 7a The I / Q coordinate diagram of the simulation results, Figure 7d for Figure 7c Detailed image of the mid-grey area after enlargement.

[0049] Figure 8 This is a schematic diagram of rotating the simulation result of the step response of an embodiment of the present invention to the beam direction.

[0050] Fig. 9 Different calibration time windows in the embodiments of the present invention T W and different detuning angles Δ θ In the case of V cb Theoretical value of vector deflection angle α th Scanned image of .

[0051] Fig.10aThe actual measurement results of the cavity pressure in the closed-loop mode with beam in the embodiment of the present invention, wherein the actual beam phases are approximately -86 degrees, -41 degrees, -15 degrees and +4 degrees; Fig.10b for Fig.10a The details of the medium gray rectangular area after enlargement; in order to facilitate the display of the results, Fig.10a The steady-state bias value in the phase has been subtracted (only the dynamic change result caused by the beam current is retained); Fig.10c Based on τ d In range V cb Vector calculated beam phase.

[0052] Fig.11a In the closed-loop mode of the embodiment of the present invention, the measurement results of the beam phase before and after calibration are compared. The measurement results before calibration are greatly affected by detuning, while the measurement results after calibration are not affected by detuning. Fig.11b The measurement results of the beam phase before and after calibration are compared in the open-loop mode in the embodiment of the present invention. DETAILED DESCRIPTION

[0053] 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.

[0054] Due to the limitations of the existing methods in terms of operation mode, it is difficult to obtain accurate phase information of the beam when the RF cavity is detuned. The beam synchronization phase online measurement method, device, equipment and medium provided by the present invention include: obtaining the original cavity pressure of the RF cavity; V c * and the original forward voltage V f * ; For the original cavity pressure V c * and the original forward voltage V f *Processing is performed to obtain the normalized cavity pressure V c and forward voltage V f ; Calculate cavity pressure V c and forward voltage V f The steady-state value U C and U F , and find the detuning Δ of the RF cavity in steady state ω ; The cavity pressure change caused by the beam V cb Linear fitting gives the phase ∠ V cb ; The time window selected based on the calculation of the synchronization phase T W , calculated from the detuning Δ ω The phase ∠ V cb Deflection angle α th ; In phase ∠ V cb Deduct the deflection angle α th , we can get the phase of beam equivalent voltage ∠ V b ; Based on the phase of the beam equivalent voltage ∠ V b Extracting beam phase Therefore, the present invention can directly solve the phase of the beam relative to the cavity pressure, and the calculation result is no longer affected by the phase drift caused by environmental factors, and is also no longer affected by the cavity detuning.

[0055] 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.

[0056] Embodiment 1: Figure 1 As shown, the beam synchronization phase online measurement method provided in this embodiment includes:

[0057] S1. Online measurement of the cavity sampling signal of the RF cavity P t and the cavity incident signal P f , to obtain the original cavity pressure of the RF cavity Vc * and the original forward voltage V f * .

[0058] like Figure 2 As shown, the beam synchronization phase online measurement system provided in this embodiment includes 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 directional coupler 3 is used to extract the cavity incident signal of the radio frequency cavity 5 P f and cavity reflection signal P r The signal extraction coupler 6 is connected to the RF cavity 5 to extract the cavity sampling signal P t , cavity incident signal P f , cavity reflection signal P r and cavity sampling signal P t After down-conversion by down-conversion module 7, it is sent to digital low-level system 1. Digital low-level system 1 is based on cavity incident signal P f , cavity reflection signal P r and cavity sampling signal P t The corresponding digitized baseband in-phase and quadrature (I / Q) components are demodulated and uploaded to the host computer 8 via the data bus.

[0059] Furthermore, for cross-verification, a beam current detector (BCM) 9 may be provided at the entrance of the RF cavity 5 for online measurement of the beam current intensity; and a beam position detector (BPM) 10 may be provided at the exit of the RF cavity 5 for online measurement of the beam phase.

[0060] Furthermore, the down-conversion module 7 converts the cavity sampling signal P t , cavity incident signal P f and cavity reflection signal P r Down-converted to an intermediate frequency signal, the digital low-level system 1 is provided with an FPGA (field programmable gate array), and the FPGA is provided with a digital signal processing module. The digital signal processing module samples the signal of the RF cavity 5.P t , cavity incident signal P f and reflected signal P r Processing is performed to obtain the corresponding three-way original voltage signals, including the original cavity pressure V c * , original forward voltage V f * and the original reverse voltage V r * .

[0061] It should be noted that the parameters involved in this embodiment, such as V c * , V f * , V r * , V c , U C , V f , U F , V cb and V b etc. 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 called the orthogonal component.

[0062] S2. Signal calibration and normalization processing.

[0063] In this embodiment, the original cavity pressure V c * After normalization, the cavity pressure is obtainedV c . The original forward voltage V f * After normalization, we get V f , specifically: using V c = V c * / V c, ss * Get the normalized cavity pressure V c ,in, V c, ss * is the normalization coefficient; similarly, using V f = V f * / V c, ss * The forward voltage is normalized.

[0064] Furthermore, if Figure 3a As shown, the original cavity pressure V c * After a period of filling time (the time it takes for the RF cavity pressure to reach a steady state from 0), the steady-state cavity pressure will be maintained for a period of time for beam acceleration (flat-top time). The flat-top time is calculated. t 1 and t The average value of the cavity pressure between 2 moments is the normalization coefficient V c, ss * , the calculation formula is as follows:

[0065] .

[0066] After normalization, the cavity pressure V c Steady-state value U C The amplitude is 1 and the phase is 0 degrees. After normalization, the original cavity pressure in the steady state is V c * (You can use U C represents the steady-state value) becomes unity 1 (which is the point "1+0 j ",Right now U C =1+0 j ). In addition, the signal calibration process is a prior art and will not be described in detail here.

[0067] S3. Steady-state detuning calculation: Calculate cavity pressure V c and forward voltage V f The steady-state value U C and U F , and find the detuning angle Δ in the steady state θ and detuning Δ ω , where the signal V ( t ) reaches steady state V ( t ) hardly changes over time, V ( t ) with respect to time is approximately 0, that is, d V ( t ) / d t ≈0.

[0068] In this embodiment, the calculation V f The average value is obtained by taking the average value within a given time interval, that is:

[0069] .

[0070] Using Δ θ =-∠ U F Calculate the detuning angle in steady state to get the detuning Δ in steady state ω . ω 0.5 is known, Δ ω The detuning angle Δ when there is no beam can be θ The steady-state value of is calculated using the following formula:

[0071] .

[0072] In the formula, U C and U F They are V c , V f Since this embodiment has already U C Normalized to 1+0j, therefore, Δ θ =-∠ U F Calculate the detuning angle.

[0073] S4. Deflection angle calibration.

[0074] In this embodiment, the deflection angle calibration first finds the cavity pressure change signal caused by the beam current. V cb , draw the calibration window in the I / Q coordinate system T W In range V cb Vector and fit to get its phase ∠ V cb .

[0075] It should be noted that the I coordinate (In-phase) in the I / Q coordinate system in this embodiment refers to the in-phase component of the signal, which can also be equivalent to the real part of the complex signal. The Q coordinate (Quadrature) in the I / Q coordinate system refers to the orthogonal component of the signal, which can also be equivalent to the imaginary part of the complex signal, which will not be repeated below.

[0076] In this embodiment, the cavity pressure change signal caused by the beam is found V cb , plotted in the I / Q coordinate system V cb Vector. Figure 4c As shown, V cb The vector is approximately linear within the 5 μs range of the beam (i.e., the beam is from 177 μs to 182 μs), and the calibration time window can be selected. T W = 4 μs (i.e., beam current from 177 μs to 181 μs) cavity pressure change signal V cb And the phase ∠ V cb .Notice, T W The value of must be smaller than the width of the beam pulse, that is, T W <5 microseconds, the above steps are detailed as follows:

[0077] S41, based on normalization V c and V f Establish the cavity differential equation:

[0078] ;

[0079] In the formula, t is the sampling time, V c0 and V c1 are the cavity pressures without and with beam, respectively. V c ,V f0 and V f1 are the forward voltages without beam current and with beam current respectively. V f ,Signal V b is the beam equivalent voltage; and are the cavity detuning Δ without beam and with beam respectively. ω , is the half bandwidth of the cavity, which is not affected by the beam current, and β is the coupling coefficient.

[0080] S42, cavity pressure change signal caused by beam current in open-loop operation mode V cb = V c1 -V c0 , V f0 and V f1 Assuming that the tuner is also in a static state, at the moment when the beam pulse passes (usually in the order of microseconds), it can be approximately considered that the cavity is detuned by Δ ω No change, that is, Δ ω 0=Δ ω 1=Δ ω Under the premise of satisfying the above conditions, the differential equation with beam flow minus the differential equation without beam flow can be obtained:

[0081] ;

[0082] S43, such as Figure 3a , Figure 3b As shown, the beam pulse can be approximately regarded as a rectangle. Before it ends, its effect on the cavity is similar to a step signal. The step response of the above differential equation is:

[0083] ;

[0084] (a) At detuning Δ ω =0, the above formula can be simplified to:

[0085] ;

[0086] In the formula, for any sampling time t , V cb and V b are all complex numbers (also called vectors in the I / Q coordinate system), including real and imaginary parts. Vb The first part, namely " " does not contain an imaginary part and can be considered a scalar. Therefore, Figure 3c and Figure 4a As shown, vector V cb and V b have the same direction, i.e., vector V cb The phase angle and beam equivalent voltage V b The phases of V b The phase of generally does not change with time, so V cb In the I / Q coordinate system, it is approximately a straight line. V cb Linear fitting can get the vector V cb It should be noted that if Figure 4c As shown, the linear fit V cb Vector selected time window T W It needs to be greater than 0 but less than the beam time. Figure 4c In the open-loop mode, the beam time is 5 microseconds. T W It can be selected from 0 to 5 microseconds. In actual operation, T W It can be set independently through the external interface without specific limitations.

[0087] Based on beam equivalent voltage V b Phase ∠ V cb Calculate beam phase :

[0088] .

[0089] (b) When the detuning Δ ω When is not equal to 0, the above formula (3) V b The first part contains the real part and the imaginary part and cannot be regarded as a scalar. Figure 6b As shown, V cb Will no longer be with V b Keep the same direction, specifically, V cbThe beam will deflect to the left or right depending on the sign of the detuning. The deflection angle depends on the detuning magnitude and the duration of the beam. Obviously, if we use the same method as the open-loop mode (i.e. linear fitting), V cb Get ∠ V cb ) to calculate the beam phase, the calculation result will be significantly affected by the detuning, such as Fig.11a and Fig.11b If we know in advance the detuning V cb Deflection angle α , that is, it can be V cb Deduction α Theoretical value α th This enables accurate measurement of the beam phase. α Theoretical value α th It can be calculated by the following formula:

[0090] .

[0091] In the formula, For vector V cb In a given calibration window T w The calculation result under ∠ U CB plural U CB The phase angle.

[0092] S5. Beam information extraction.

[0093] In this embodiment, the beam information is extracted as: V cb Deduct the deflection angle α th , and the beam equivalent voltage is obtained V b The phase ∠ V b , and finally the beam phase is converted to .

[0094] In this embodiment, according to a given time window T W , using formula (6) to calculate the detuning Δ ω The deflection angle caused α th . Note that in open loop operation, T W must be less than the beam pulse time; in closed-loop operation mode,T W It must not only be shorter than the beam pulse time, but also shorter than the loop delay time. τ d .like Figure 7b As shown, according to formula (6), in a given time window T W The complex number calculated in the case of U CB and α th .

[0095] exist V cb Compensation of deflection angle in vector α th The beam phase , the formula is as follows:

[0096] .

[0097] It should be noted that, in the detuning Δ ω When it is 0, according to the above formula, we can know U CB The imaginary part of is 0, that is α th =∠ U CB = 0, then the first equation of the above equation group (7) is simplified to ; Correspondingly, the second equation becomes This is completely consistent with the above formula (5).

[0098] Furthermore, when the cavity operates in a closed-loop mode, such as Figure 5a As shown, the closed-loop system will adjust the control loop to change the forward voltage after observing the cavity pressure change caused by the beam current. V f To compensate for the beam loading effect, even if the cavity is not detuned (or Δ ω ≈ 0, for example, the detuning angle Δ θ< 5 degrees) V cb The vector still deflects. However, since the loop takes a certain amount of time to respond, this is commonly referred to as loop delay. τ d Before the loop delay is reached, the loop will not respond, and the loop working mode at this time is similar to the open loop mode. Figure 5b As shown, during the loop delay τ d In the range of open loop and closed loop V cb Approximately coincident. Figure 5cIn the I / Q coordinate system, τ d In range V cb The vectors are almost completely overlapped. Therefore, when the RF cavity works in closed-loop mode, it is necessary to select T W Less than or equal to τ d Under this condition, the calculation process of the closed-loop mode refers to the open-loop mode and will not be repeated here.

[0099] The application and verification process of the beam synchronization phase online measurement method of the present invention are described in detail below through specific embodiments.

[0100] The solid-state power source 2 used in this embodiment has an output power of about 30 kW; the radio frequency cavity 5 is a room temperature focusing cavity of the European Scattered Neutron Source (ESS), with a cavity resonant frequency of 352.21 MHz and a loaded quality factor of Q L About 10000, geometric factor r / Q is 74; the clock frequency of the FPGA in the digital low-level system 1 is 117.402 MHz; the original cavity pressure transmitted to the host computer 8 is V c * , original forward voltage V f * The data sampling rate is 8.3859 MHz; the coupling coefficient of the signal extraction coupler 6 β is about 1. For further cross-verification, this embodiment also uses beam measurement equipment, including a beam current intensity detector 9 (BCM, digital board model: SIS8300-KU MTCA.4, sampling rate: 5.49 MHz) and a beam position detector 10 (BPM, digital board model: SIS8300-KU MTCA.4: sampling rate: 5.87 MHz).

[0101] Based on the above parameter settings, the beam synchronization phase online measurement method of this embodiment includes:

[0102] 1. Measuring the original cavity pressure of the RF cavity V c * , original forward voltage V f * and the original reverse voltage V r * .

[0103] like Figure 2As shown, the output of the digital low-level system 1 is connected to the input end of the solid-state power source 2, the output of the solid-state power source 2 is connected to the input end of the directional coupler 3, and the output of the directional coupler 3 is fed into the radio frequency cavity 5 through the input coupler 4. The measurement process is:

[0104] 1. Use the signal extraction coupler 6 to extract the cavity pressure signal online P t , using directional coupler 3 to measure the cavity incident signal online P f and reflected signal P r , where the cavity pressure signal P t , cavity incident signal P f and reflected signal P r They are all 352.21 MHz radio frequency signals, and this is taken as an example but is not limited to this.

[0105] 2. After the above RF signal is down-converted, digitized and I / Q demodulated in sequence, the digital low-level system 1 obtains the digitized original baseband voltage signal, i.e., the original cavity pressure V c * , original forward voltage V f * and the original reverse voltage V r * The digital low-level system 1 uploads the above baseband signal to the host computer 8 .

[0106] 2. Signal calibration, normalization and standardization.

[0107] According to the original cavity pressure V c * and the original forward voltage V f * The signal calibration and normalization are realized inside the host computer 8, including:

[0108] 1. Original forward voltage V f * calibration.

[0109] The host computer 8 reads the current raw cavity pressure from the data bus V c * and the original forward voltage V f * First, according to Vf, cali = XV f * Solve for the calibrated forward signal. Note: The cavity pressure signal is usually used as a reference signal and does not need to be calibrated. The complex multiplication operation can be performed as follows:

[0110] ;

[0111] In the formula, V f, caliI and V f, caliQ 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 The calibration coefficients are X The real and imaginary parts of .

[0112] 2. Normalization and standardization of original cavity pressure V c * and the original forward voltage V f * .

[0113] like Figure 4a As shown in the figure, after a period of filling time, the original cavity pressure V c * exist t = 100 microseconds to reach steady state. Figure 4b As shown in Figure 1, the beam arrives at 177 microseconds, lasts for 5 microseconds, and ends at 182 microseconds. V c Generate instantaneous fluctuations. Figure 3a Select two points before the beam reaches t 1 and t 2. Calculation V c * exist t 1 and t The average value between 2 V c,ss * ,Right now Note that to ensure the accuracy of calculation,t 1 and t The interval between 2 must be greater than 20 microseconds. t 1 must be selected after the chamber pressure reaches a steady state, for example: t 1 can be selected from a value between 100 and 156 microseconds. t 2 can be selected as 176 microseconds. Taking this as an example, the calculation process of finding the average value can be directly called by Python. numpy.mean function.

[0114] Original cavity pressure V c * , original forward voltage V f * Normalization:

[0115] .

[0116] Normalized cavity pressure V c The steady-state value U C 1+0 j .

[0117] 3. Calculate the steady-state detuning.

[0118] Calculate the forward voltage signal in both the absence and presence of beam current. U f ( t )exist t 1 and t 2, and the steady-state value is obtained U F . Using np.angle( U F ) is calculated U F The phase of the steady-state detuning Δ is obtained according to the above formula. ω .

[0119] 5. Calculate the deflection angle caused by detuning.

[0120] When the cavity is detuned, U CB The vector will be deflected (e.g. Figure 6a as shown). Figure 7a and Figure 7b is the step response of the cavity differential equation. Figure 7c and Figure 7d This is the result in the I / Q coordinate system. Figure 7d Equivalent voltage of medium beam V b=1+0j. In practice, Figure 8 As shown in the figure, the simulation results need to be rotated and scaled according to the direction of the real beam. α th The calibration time window can be T W and detuning Δ ω (or detuning angle Δ θ ) is calculated using the above formula. Note that in open-loop operation mode, T W must be smaller than the beam pulse width; in closed-loop operation mode, T W Need to be less than the loop delay time τ d .

[0121] The embodiment of the present invention is a normal temperature chamber, ω 0.5 ≈1.1×10 5 Radians per second. Its corresponding time constant τ (Time constant τ =1 / ω 0.5 ) is about 9 microseconds. In open-loop operation mode, assuming the beam pulse width is 5 microseconds, if you select T W =3.6 microseconds, corresponding to 0.4 τ .like Figure 7d As shown, the detuning angle Δ θ When it is 45 degrees, U CB =0.3224+0.061 j , through np.angle( U CB ) can calculate its deflection angle α th About 10.7 degrees. Fig. 9 As shown, for a given area T W and Δ θ , for example 0< T W <0.5 τ, - 45°<Δ θ <45°, the formula can be used to calculate each ( T W , Δ θ ) Combination correspondence α th For example, when ( T W , Δ θ )=( 0.4 τ, 45°), corresponding α th That is 10.7 degrees (near the 10-degree contour line).

[0122] It is worth noting that, in general, the ω 0.5 Much smaller than the normal temperature chamber ω 0.5 Assuming that the superconducting cavity ω 0.5 =1000, then the corresponding τ About 1 millisecond, 5 microseconds beam pulse width corresponds to 0.005 τ .like Figure 7d As shown, no matter how large the detuning angle is, U CB The imaginary parts of U CB The vector is almost on the real axis). In the above case, it can be approximately considered that detuning will not cause U CB The vector is deflected (i.e. ∠ U CB ≈0), so there is no need to calculate the deflection angle in the calculation α th , which also explains why the influence of detuning does not need to be considered in DESY's radio frequency superconducting accelerator.

[0123] 6. Calculation of beam synchronization phase .

[0124] Based on a given time window T W , the cavity pressure change caused by the beam V cb Linear fitting, determined by the slope of the fitted line V cb Phase ∠ V cb .like Figure 6b As shown, T W , Δ θ ) = (5 microseconds , 45°) as an example, V cb Linear fitting gives the red straight line y = kx +b. Figure 6b The phase ∠ V cb =180°+arctan( k ). V cbDeduct the deflection angle calculated in the previous step from α th , and the beam equivalent voltage is obtained V b The phase ∠ V b , and finally the beam phase is converted to .

[0125] 7. Online experimental verification.

[0126] The experiment of this example has been verified at the European Spallation Neutron Source (Lund, Sweden). Figure 2 As shown, a beam current detector (BCM) 9 is installed upstream of the RF cavity for online measurement of the beam current; a beam position detector (BPM) 10 is installed downstream of the RF cavity for online measurement of the beam phase. Further, the beam current and phase calculated in this embodiment are compared with the measured values ​​of BCM and BPM.

[0127] 1. If Fig.10a The loop delay in this embodiment is the actual measurement result of the cavity pressure in the closed loop mode. τ d About 1.5 microseconds, calibration time window T W The beam pulse width is 5 microseconds, also selected at 1.5 microseconds. The reference beam phases (measured at BPM) are approximately -86 degrees, -41 degrees, -15 degrees, and +4 degrees. Fig.10b for Fig.10a A magnified detail of the medium gray rectangular area. Note that in order to facilitate the display of the results, Fig.10a The steady-state offset value of the phase has been subtracted (only the dynamic change caused by the beam current is retained). Fig.10c Based on T W = 1.5 microseconds V cb In this embodiment, since the cavity detuning is approximately equal to 0, it is basically unnecessary to calculate the deflection angle caused by the detuning.

[0128] 2. Fig.11a In the embodiment of the present invention, the closed loop mode and the detuning condition are α th Results before and after calibration. T W is selected as 1.5 microseconds (equal to the loop delay τ d ), the reference value of the beam phase (BPM measurement value) is -44 degrees, and the beam pulse width is about 5 microseconds. The blue square is the measurement result of the beam phase before the detuning calibration. It can be seen that the detuning Δ ωFrom -30 kHz to 35 kHz ( ω 0.5 ≈18 kHz), the beam phase measurement results are obviously affected by the detuning, and only when the detuning is equal to 0, the results are consistent with the BPM measurement values. α th From the results after calibration, it can be seen that the measured value of the beam phase will not be affected by the detuning after calibration and will always be consistent with the measured value of BPM. Fig.11b In the embodiment of the present invention, the open loop mode and the detuning condition are α th Results before and after calibration. T W The reference value of the beam phase (BPM measurement value) is -44 degrees. T W The beam phase measurement results before calibration (blue squares) are more significantly affected by detuning than those in closed-loop mode. The beam phase measurement results after calibration (red circles) are no longer affected by detuning.

[0129] Embodiment 2: The above-mentioned embodiment 1 provides an online measurement method of beam synchronization phase based on instantaneous beam load effect. Correspondingly, this embodiment provides an online measurement device of beam synchronization phase based on instantaneous beam load effect.

[0130] Specifically, the present invention also provides a beam synchronization phase online measurement device, the device comprising: a signal acquisition module, configured to obtain the original cavity pressure of the radio frequency cavity; V c * and the original forward voltage V f * ; A signal processing module is configured to process the original cavity pressure V c * and the original forward voltage V f * Processing is performed to obtain the normalized cavity pressure V c and forward voltage V f ; A detuning calculation module configured to calculate the cavity pressure V c and forward voltage V f The steady-state value U C and U F , and find the detuning Δ of the RF cavity in steady state ω ; The deflection angle calculation module is configured to calculate the time window selected according to the synchronization phase T W , calculated from the detuning Δ ω The phase ∠ V cb Deflection angle α th ; Phase calculation module, configured to calculate the cavity pressure change caused by the beam V cb Linear fitting gives the phase ∠ V cb , in ∠ V cb Deduct the deflection angle α th , we can get the phase of beam equivalent voltage ∠ V b ; The beam information extraction module is configured to be based on the phase ∠ of the beam equivalent voltage V b Extracting beam phase .

[0131] Embodiment 3: This embodiment provides an electronic device corresponding to the online measurement method of beam synchronization phase based on instantaneous beam load effect provided in 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.

[0132] 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.

[0133] 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 beam synchronization phase online measurement method, characterized in that: The method includes: Get the original cavity pressure of the RF cavity V c * and the original forward voltage V f * ; Original cavity pressure V c * and the original forward voltage V f * Processing is performed to obtain the normalized cavity pressure V c and forward voltage V f ; Calculate cavity pressure V c and forward voltage V f The steady-state value U C and U F , and find the detuning Δ of the RF cavity in steady state ω ; The change of cavity pressure caused by beam current V cb Linear fitting gives the phase ∠ V cb ; The time window selected based on the calculation of the synchronization phase T W , calculated from the detuning Δ ω The phase ∠ V cb Deflection angle α th ; In phase ∠ V cb Deduct the deflection angle α th , we can get the phase of beam equivalent voltage ∠ V b ; Based on the phase of the beam equivalent voltage V b Extracting beam phase .

2. The beam synchronization phase online measurement method according to claim 1, characterized in that: Detuning Δ ω The calculation formula is: ； ； In the formula, is the detuning angle, and Cavity pressure V c and forward voltage V f The steady-state value U C and U F The phase angle, is the half bandwidth of the cavity.

3. The beam synchronization phase online measurement method according to claim 1, characterized in that: The change of cavity pressure caused by beam current V cb Linear fitting gives the phase ∠ V cb , the specific process is: Based on the normalized cavity pressure V c and forward voltage V f Establish the cavity differential equation: ； In the formula, t is the sampling time, and are the cavity pressures without and with beam, respectively. V c The differential of V c0 and V c1 are the cavity pressures without and with beam, respectively. V c , V f0 and V f1 are the forward voltages without beam current and with beam current respectively. V f , V b is the beam equivalent voltage; and are the cavity detuning Δ without beam and with beam respectively. ω , is the half bandwidth of the cavity, β is the coupling coefficient; Beam-induced cavity pressure changes in open-loop operation V cb = V c1 -V c0 , V f0 and V f1 Equal, Δ ω 0=Δ ω 1=Δ ω , we can obtain the following by subtracting the differential equation without beam from the differential equation with beam: ； in, is the cavity pressure change caused by the beam V cb The differential of The step response of the differential equation is: ； In the detuned Δ ω =0, the above formula is simplified to: ； Since the vector V cb and V b have the same direction, i.e., vector V cb The phase angle and beam equivalent voltage V b The phase of the vector V cb Linear fitting gives V cb The phase ∠ V cb ; When the detuning Δ ω When it is not equal to 0, V cb Will no longer be with V b Keeping the same direction, detuning causes V cb There is a deflection angle α , in ∠ V cb Deduction α Theoretical value α th The phase of the beam equivalent voltage is obtained V b .

4. The beam synchronization phase online measurement method according to claim 3, characterized in that: The time window selected based on the calculation of the synchronization phase T W , calculated from the detuning Δ ω Caused by V cb Deflection angle α th , and its calculation formula is: ； In the formula, For vector V cb In the time window T w The calculation results below are plural U CB The phase angle.

5. The beam synchronization phase online measurement method according to claim 4, characterized in that: Based on the phase of the beam equivalent voltage V b Extract the beam phase : 。 6. The beam synchronization phase online measurement method according to claim 1, characterized in that: In open-loop operation mode, the time window for calculating the synchronization phase T W It needs to be shorter than the beam pulse time; In closed-loop operation mode, the time window T W It must not only be shorter than the beam pulse time, but also shorter than the loop delay time. τ d .

7. A beam synchronization phase online measurement device, characterized in that: The device includes: The signal acquisition module is configured to obtain the original cavity pressure of the radio frequency cavity. V c * and the original forward voltage V f * ; The signal processing module is configured to process the raw cavity pressure V c * and the original forward voltage V f * Processing is performed to obtain the normalized cavity pressure V c and forward voltage V f ; The detuning calculation module is configured to calculate the cavity pressure V c and forward voltage V f The steady-state value U C and U F , and find the detuning Δ of the RF cavity in steady state ω ; The deflection angle calculation module is configured to calculate the time window selected according to the synchronization phase T W , calculated from the detuning Δ ω The phase ∠ V cb Deflection angle α th ; The phase calculation module is configured to calculate the cavity pressure change caused by the beam current. V cb Linear fitting gives the phase ∠ V cb , in ∠ V cb Deduct the deflection angle α th , we can get the phase of beam equivalent voltage ∠ V b ; The beam information extraction module is configured to be based on the phase ∠ of the beam equivalent voltage V b Extracting beam phase .

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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