CN105807132B - A kind of method and device of detection accelerator radio-frequency cavity off-resonance frequency - Google Patents
A kind of method and device of detection accelerator radio-frequency cavity off-resonance frequency Download PDFInfo
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- CN105807132B CN105807132B CN201610128167.5A CN201610128167A CN105807132B CN 105807132 B CN105807132 B CN 105807132B CN 201610128167 A CN201610128167 A CN 201610128167A CN 105807132 B CN105807132 B CN 105807132B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
Abstract
This application discloses a kind of methods of detection accelerator radio-frequency cavity off-resonance frequency.This method samples to obtain incidence wave and back wave in the radio-frequency power feeder system of accelerator radio-frequency cavity including the use of directional coupler, then the amplitude and reference phase for obtaining two paths of signals are demodulated by IQ, by the impedance of one computation accelerator radio-frequency cavity of formula, then the off-resonance frequency for obtaining accelerator radio-frequency cavity is calculated by formula two.The detection method of the application, can accurately obtain off-resonance frequency to judge the detuning state of system, compared with the existing mode for judging detuning state indirectly, more it is direct effectively.Also, by the way of IQ demodulation, the accurate measurement to the amplitude and phase of incidence wave, back wave is realized, measurement accuracy is increased；It can accurately know detuning degree, the resonant condition accurately to detect and control accelerator radio-frequency cavity is laid a good foundation.
Description
Technical field
This application involves the Detection & Controling fields of accelerator radio-frequency cavity, are penetrated more particularly to a kind of detection accelerator
The method of frequency resonant cavity off-resonance frequency.
Background technology
Accelerator is a kind of device for making charged particle increase speed, and is dissipated in national major science and technology infrastructure projects Program in China
It splits in neutron source, accelerator is divided into linear accelerator and ringotron, and linear accelerator accelerates to proton beam
Proton beam is accelerated to 1.6Gev by 80Mev, ringotron, is then drawn proton beam by line extraction system, is drawn
The line bombardment heavy metal tungsten target gone out, obtains neutron, microstructure of the neutron as probe in detecting a variety of materials.
The main body of accelerator is exactly radio-frequency cavity, after RF power is sent in radio-frequency cavity by power transmission system,
Stable accelerating field, charged particle, such as proton are formed in radio-frequency cavity, by obtaining energy after acceleration fields, are added
Speed.
Under resonance condition, same input power can set up maximum acceleration fields to radio-frequency cavity wherein, and one
Denier radio-frequency cavity is detuning, and the characteristic impedance deviation of resonant cavity load impedance and power transmission system is too far, it will causes to input
Power is largely reflected back, and sufficiently high acceleration fields can not be established in resonant cavity, cause charged particle that can not obtain
Enough energy, are not achieved design requirement.In addition radio-frequency power can be caused by after a large amount of reflect back to radio frequency power source system
The damage of system.
The resonant frequency control system of existing accelerator radio-frequency cavity is for controlling accelerator radio-frequency cavity
Resonant frequency is stablized, and keeps it consistent with the output frequency of radio frequency power source, which mainly passes through incidence
The phase difference of the wave and accelerator radio-frequency cavity chamber field signal foundation whether detuning as cavity is judged is a kind of judgement indirectly
The whether detuning means of resonant cavity, can not directly obtain the off-resonance frequency of accelerator radio-frequency cavity, therefore, it is impossible to accurately sentence
The detuning degree of disconnected accelerator radio-frequency cavity, also just can not accurately use corresponding resonant frequency control program.
Invention content
The purpose of the application is to provide a kind of method of completely new detection accelerator radio-frequency cavity off-resonance frequency.
The application uses following technical scheme：
This application discloses a kind of methods of detection accelerator radio-frequency cavity off-resonance frequency, including the use of directional coupler
Sampling obtains the incidence wave and back wave in the radio-frequency power feeder system of accelerator radio-frequency cavity, is then obtained by IQ demodulation
The amplitude and reference phase for obtaining two paths of signals, by the impedance of one computation accelerator radio-frequency cavity of formula, then pass through formula
Two calculate the off-resonance frequency for obtaining accelerator radio-frequency cavity；
Formula one：
Formula two：
Wherein, ZLFor accelerator radio frequency resonant cavity impedance,For the voltage value of load impedance,For load impedance
Current value, Z0For the characteristic impedance of power transmission system,For Z1The voltage value of incidence wave at position,For Z2Position
Set place back wave voltage value, e be plural number exponential form representation in natural logrithm the truth of a matter, γ (Z1- L) represent edge
The wave that Z axis negative direction is propagated is from Z1Point arrives the phase difference of load end ,-γ (Z2- L) wave propagated along the positive aspect of Z axis is represented from Z2
For point to the phase difference of load end, γ is complex propagation constant；ω is radio frequency power source output signal angular frequency, ω0It is penetrated for accelerator
The natural oscillation angular frequency of frequency resonant cavity；△ ω are the off-resonance frequency of accelerating cavity, that is, radio frequency power source output signal angular frequency
Difference on the frequency between rate and the natural mode shape of accelerating cavity, Q0For the unloaded quality factor of accelerating cavity, YLIndicate load admittance,
Load admittance YLIt is accelerator radio-frequency cavity impedance ZLInverse, YL iFor load admittance YLImaginary part, YL rFor load admittance YL's
Real part, π are pi, and Δ H is off-resonance frequency；
Also, YL、ZL、YL iAnd YL rMeet formula three,
Formula three：
Wherein, j represents the imaginary unit of plural number, is -1 square root.
It should be noted that by the present processes, the value of off-resonance frequency can be accurately calculated, is led to existing
It crosses the phase difference of chamber field wave shape and incidence wave, or by reflection power size, indirectly judges whether are off-resonance frequency or system
It is compared in detuning state, the present processes are more simple direct and more accurate.
Preferably, it samples to obtain entering in the radio-frequency power feeder system of accelerator radio-frequency cavity using directional coupler
Ejected wave and back wave, specifically, using at least two concatenated directional couplers, a directional coupler is for coupling incident letter
Number, a directional coupler is used for coupled reflection signal, and the incoming signal of coupling and reflection signal are transported to analog down
In, it respectively obtains incoming signal and reflects the intermediate-freuqncy signal of signal, intermediate-freuqncy signal, which is transported in AD sampling A/D chips, carries out quadruple
Digital quadrature-sampling, i.e. I, Q sample, and obtain incoming signal and reflect I, Q value of signal.
It should be noted that one of the emphasis of the application is to obtain the signal of incidence wave and back wave, it will be understood that adopt
With directional coupler, coupled reflection signal and incoming signal are one of which realization method respectively, it is other in the prior art can be with
Realize that the device of similar functions can be used for the application.But in the preferred embodiment of the application, it is contemplated that realize difficulty or ease journey
The factors such as degree, cost and detection accuracy, it is preferred to use two concatenated directional couplers are realized reflection signal and entered respectively
Penetrate the coupling of signal.
It should also be noted that, another of the application focuses on, the amplitude for obtaining two paths of signals is demodulated by IQ
And reference phase, it will be understood that distinguish coupled reflection signal and incoming signal in directional coupler, conventional side may be used
Formula sampled I, Q values；But in the preferred scheme of the application, use analog down to the signal of directional coupler at
Reason obtains intermediate-freuqncy signal, then uses AD sampling A/D chips sampled I, Q values.
Preferably, the amplitude and reference phase for obtaining two paths of signals are demodulated by IQ, specifically, by I, Q value of sampling
It is transported to progress IQ demodulation in fpga chip, obtains the amplitude and reference phase of incidence wave and back wave.
It is carried out it should be noted that existing demodulation mode may be used in IQ demodulation, fpga chip is the one of the application
Kind preferred implementation.
Preferably, at least two concatenated directional couplers, forward and reverse coefficient of coup of directional coupler keeps one
It causes, also, the transfer passage of directional coupler to AD sampling A/D chips keeps Striking symmetry.
It should be noted that in order to acquire accurate load impedance, need accurately to measure in radio-frequency power feeder system
The amplitude and phase information of incidence wave and back wave have to reduce measurement error to the greatest extent thus, and therefore, directional coupler is just
The reversed coefficient of coup is consistent, also, the transfer passage of directional coupler to AD sampling A/D chips keeps Striking symmetry.
Preferably, it by the impedance of one computation accelerator radio-frequency cavity of formula, then is calculated and is accelerated by formula two
The off-resonance frequency of device radio-frequency cavity can be calculated in industrial personal computer, and industrial personal computer is by directly exporting detuning frequency after calculating
Rate.
It should be noted that for further easy acquisition off-resonance frequency, it will be understood that according to existing computer skill
Art, any formula can be realized in industrial personal computer, therefore, in the preferred realization method of the application, by computation accelerator radio frequency
The formula one of resonance cavity impedance and the formula two of computation accelerator radio-frequency cavity off-resonance frequency realize automatic meter by industrial personal computer
It calculates, and exports required impedance and off-resonance frequency numerical value.
The another side of the application discloses a kind of device of detection accelerator radio-frequency cavity off-resonance frequency, which includes
IQ sampling components, IQ demodulation chips and industrial personal computer, are connected between IQ sampling components and IQ demodulation chips by signal, and IQ solves aligning
It is connected by signal between piece and industrial personal computer；IQ sampling components include signal connection directional coupler group, analog down and
AD sampling A/D chips；Directional coupler group is made of two concatenated directional couplers, and a directional coupler is for coupling incidence
Signal, another directional coupler are used for coupled reflection signal；The incidence that analog down is used to couple directional coupler group
Signal and reflection signal carry out down-converted, obtain incoming signal respectively and reflect the intermediate-freuqncy signal of signal；AD sampling A/D chips
For carrying out quadruple digital quadrature-sampling to intermediate-freuqncy signal, obtaining incoming signal and reflecting I, Q value of signal；IQ solves aligning
Piece is fpga chip, and I, Q value for obtaining to AD sampling A/D chips carry out IQ demodulation, obtain the amplitude of incidence wave and back wave with
Reference phase；The amplitude and reference phase that industrial personal computer is obtained according to IQ demodulation chips, are penetrated by one computation accelerator of formula
The impedance of frequency resonant cavity passes through the off-resonance frequency of two computation accelerator radio-frequency cavity of formula；
Formula one：
Formula two：
Wherein, ZLFor accelerator radio frequency resonant cavity impedance,For the voltage value of load impedance,For load impedance
Current value, Z0For the characteristic impedance of power transmission system,For Z1The voltage value of incidence wave at position,For Z2Position
Set place back wave voltage value, e be plural number exponential form representation in natural logrithm the truth of a matter, γ (Z1- L) represent edge
The wave that Z axis negative direction is propagated is from Z1Point arrives the phase difference of load end ,-γ (Z2- L) wave propagated along the positive aspect of Z axis is represented from Z2
For point to the phase difference of load end, γ is complex propagation constant；
ω is radio frequency power source output signal angular frequency, ω0For the natural oscillation angular frequency of accelerator radio-frequency cavity；△
ω is the off-resonance frequency of accelerating cavity, that is, between radio frequency power source output signal angular frequency and the natural mode shape of accelerating cavity
Difference on the frequency, Q0For the unloaded quality factor of accelerating cavity, YLIndicate load admittance, load admittance YLIt is accelerator radio-frequency cavity
Impedance ZLInverse, YL iFor load admittance YLImaginary part, YL rFor load admittance YLReal part, π is pi, and Δ H is detuning frequency
Rate；
Also, YL、ZL、YL iAnd YL rMeet formula three,
Formula three：
Wherein, j represents the imaginary unit of plural number, is -1 square root.
It should be noted that the device of the application, each component combines the accurate meter realized to off-resonance frequency
It calculates.It is appreciated that under the directional coupler group of IQ sampling components, IQ demodulation chips and industrial personal computer or even IQ sampling components, simulation
Frequency conversion and AD sampling A/D chips etc., be all each other connected by signal or radio-frequency cable connection, in most simple situation
Under, various components can be self-existent；But use for convenience, various components can also be integrated into a container
Or the unit installation that forms a whole in frame, or IQ sampling components are integrated into a unit, IQ demodulation chips and work
Control machine is as another unit, so as to remote operation；These can not do have herein depending on particular condition in use or demand
Body limits.
The advantageous effect of the application is：
The detection method of the application, can accurately obtain off-resonance frequency to judge the detuning state of system, and existing
Judge that the mode of detuning state is compared indirectly, more it is intuitive effectively.Also, it by the way of IQ demodulation, realizes to incidence
The accurate measurement of wave, the amplitude of back wave and phase, increases measurement accuracy；It can accurately know detuning degree, in order to
Resonant frequency control program is adjusted for different detuning degree.
Description of the drawings
Fig. 1 is sine wave in the embodiment of the present applicationComplex vector in I, Q complex spaces indicates figure；
Fig. 2 is the schematic diagram of AD sampling A/D chips quadruple sampling intermediate-freuqncy signal in the embodiment of the present application；
Fig. 3 is radio frequency power source power feeding system schematic diagram in the embodiment of the present application；
Fig. 4 is the structural schematic diagram of 324MHz analog radio frequencies resonant cavity in the embodiment of the present application；
Fig. 5 is the structural schematic diagram at another visual angle of 324MHz analog radio frequencies resonant cavity in the embodiment of the present application；
Fig. 6 is that resonant cavity Q is simulated in the embodiment of the present application0It is worth test result figure；
Fig. 7 is the schematic diagram of dual-port directional coupler in the embodiment of the present application, and the ends A are radiofrequency signal input port, and the ends B are
Radiofrequency signal delivery outlet, C-terminal are back wave coupling aperture, and the ends D are incidence wave coupling aperture；
Fig. 8 is the internal digital signal Processing Algorithm schematic diagram of fpga chip in the embodiment of the present application.
Specific implementation mode
The main purpose of the application is impedance and the off-resonance frequency of computation accelerator radio-frequency cavity.The present processes have
Body is utilized directional coupler and samples to obtain the incidence wave and back wave transmitted in radio-frequency power feeder system, then passes through number
The mode of IQ demodulation obtains the amplitude and reference phase of two paths of signals, utilizes the amplitude and reference phase of two paths of signals, meter
The impedance of accelerator radio-frequency cavity is calculated, then by the relationship between impedance value and accelerator radio-frequency cavity off-resonance frequency,
Acquire the off-resonance frequency of accelerator radio-frequency cavity.Accelerator radio-frequency cavity can be accurately calculated in the present processes
Off-resonance frequency value, the off-resonance frequency value can as the reference frame of radio-frequency cavity off-resonance frequency control system, realize pair
The closed-loop control of radio-frequency cavity resonant frequency.Also, the present processes are for accelerator low level radio frequency control system
It is unrelated in closed-loop control state or opened loop control state.
It should be noted that the detection method of the application can directly measure the off-resonance frequency of resonant cavity, more intuitively, just
Judge the detuning degree of resonant cavity in operating personnel, and then takes different resonant frequency control programs.In addition, by directly surveying
The value for measuring the off-resonance frequency of cavity, can be used for accelerator radio-frequency cavity during the automatic frequency-conversion in seasoned stage.Adding
The fast device radio-frequency cavity seasoned stage, after the off-resonance frequency value for measuring resonant cavity by the detection method of the application, so that it may
Directly to change the output frequency of radio frequency power source, keeps it consistent with the natural mode shape of resonant cavity at that time, make radio-frequency power
It can be fed into resonant cavity faster, reduce the cavity seasoned time.
The application is described in further detail below by specific embodiment.Following embodiment is only to the application into traveling
One step illustrates, should not be construed as the limitation to the application.
Embodiment
This example proposes a kind of method of the off-resonance frequency of new detection accelerator radio-frequency cavity.This method is using fixed
The incidence wave and back wave transmitted in radio-frequency power feeder system is extracted to coupler, and the amplitude of two waveforms is then calculated
And reference phase, incidence wave, the amplitude of back wave and reference phase are substituted into the calculation formula of load impedance, acquire radio frequency
It is humorous that radio frequency is calculated using the relationship between the load impedance and cavity off-resonance frequency of radio-frequency cavity in the impedance value of resonant cavity
It shakes the off-resonance frequency value of chamber, the technical solution of the method for this example is described in greater detail below.
This example completes I, Q sampling using directional coupler group, analog down and AD sampling A/D chips, then in FPGA into
Row IQ demodulation, obtains the amplitude and reference phase of incidence wave and back wave, then carries out subsequent impedance and off-resonance frequency calculating.
When carrying out I, Q sampling, due to the limitation of AD sampling A/D chip maximum sample frequencys, it is therefore desirable to by directional coupler
The incidence wave and reflection wave signal of coupling pass through analog down, obtain the intermediate-freuqncy signal of two signals, the mistake of analog down
Journey is as follows：
Coupled signal：
Wherein, VRFThe signal that incidence wave or back wave are coupled out by directional coupler is represented,Representation signal
Amplitude, t represent time, ωRFIncidence wave or reflection wave signal oscillation angular frequency are represented,Represent incidence wave or back wave
The initial phase of signal.
Local oscillation signal：
Wherein, VLOLocal oscillation signal is represented,The amplitude of local oscillation signal is represented, t represents time, ωLORepresent local oscillation signal
Angular frequency is vibrated,Represent the initial phase of local oscillation signal.
After the two mixing：
After the low-pass filtering of analog down, the high-frequency components in mixing formula are filtered, intermediate-freuqncy signal V is leftIF：
Wherein, VIFIntermediate-freuqncy signal is represented,The amplitude of intermediate-freuqncy signal is represented, andWhen t is represented
Between, ωIFRepresent intermediate-freuqncy signal oscillation angular frequency, and ωIF=ωLO-ωRF,The initial phase of intermediate-freuqncy signal is represented, and
And
Due to local oscillation signal VLOAmplitude and phase be fixed, so intermediate-freuqncy signal VIFJust contain directional coupler
Coupled signal VRFAmplitude and phase information.
One I of this example, a complex vector in Q complex spaces indicate a sine waveWherein, A is
The amplitude of sine wave, ω represent the oscillation angular frequency of sine wave, and t represents the time,Represent the initial phase of sine wave.Such as Fig. 1
Shown, the amplitude of wherein sine wave is exactly the mould of complex vector, and the phase of sine wave is exactly phase of the complex vector in I, Q complex spaces
Angle, projection of the complex vector on I axis are I component of the sine wave in complex space, and the projection on Q axis is sine wave in complex space
Q component.
By the intermediate-freuqncy signal V of the two-way waveform obtained after analog downIFIt is sent into AD sampling A/D chips and carries out quadruple
Digital quadrature-sampling, i.e. I, Q samplings, obtain the digital I of two signals, Q values.
Assuming that intermediate-freuqncy signal wherein all the way is：As shown in Figure 2, respectively in the t of sine wave0、t1、
t2、t3Instance sample.
In t0Moment, intermediate-freuqncy signalSampled value be：
In t1Moment, sampled value are
In t2Moment, sampled value are
In t3Moment, sampled value are
The then amplitude of intermediate-freuqncy signalPhase
Wherein, A is the amplitude of signal, and t represents time, t0、t1、t2、t3Four different sampling stages points are respectively represented, because
It is to be adopted four times of signal frequency for sample clock frequency, therefore for by the number of accepting and believing, the phase difference between each sampling interval
It is 90 degree.I is represented in complex vector space, the projection of the vector of sine wave on transverse axis.Q is represented in complex vector space, just
The projection of the vector of string wave on longitudinal axis.
The amplitude and reference phase of two-way intermediate-freuqncy signal can thus be calculated.
After carrying out IQ by fpga chip and demodulating to obtain the amplitude of incidence wave and back wave and the reference value of phase, just
The impedance Z of radio-frequency cavity can be acquired by the impedance computation formula of radio-frequency cavityL.As shown in Figure 3, it is assumed that VgFor radio frequency
The output of power source, Z0For the characteristic impedance of waveguide, radio-frequency cavity load impedance is ZL, can be obtained according to microwave engineering principle
The impedance Z of resonant cavity at Z=LL, i.e. radio-frequency cavity load impedance ZL：
That is formula one,
Wherein, Z1And Z2For 0 to appointing take 2 points between L,For the voltage value of load impedance,For load impedance
Current value, Z0For the characteristic impedance of power transmission system,For Z1The vector reference value of incidence wave, i.e. Z at point1Position
Locate the voltage value of incidence wave, wherein the reference value of amplitude and phase comprising incidence wave,For Z2The vector of back wave at point
Reference value, i.e. Z2The voltage value of back wave at position, wherein the reference value of amplitude and phase comprising back wave, γ is multiple propagates
Constant then obtains：
Wherein, YLIndicate load admittance, load admittance YLIt is accelerator radio-frequency cavity impedance ZLInverse, YL iFor load
Admittance YLImaginary part, YL rFor load admittance YLReal part, j represent plural number imaginary unit, be -1 square root；
It regards the load of radio-frequency cavity cavity as a rlc circuit in parallel, can obtain：
Wherein, R represents the resistive component in the equivalent Parallel RLC Circuit of accelerator radio-frequency cavity load； Q0It represents
The nonloaded Q of accelerator radio-frequency cavity, i.e. the unloaded quality factor of accelerating cavity；ω represents the power of accelerator radio-frequency cavity
Source exports the angular frequency of radiofrequency signal, i.e. radio frequency power source output signal angular frequency；ω0Represent consolidating for accelerator radio-frequency cavity
There is oscillation angular frequency；J represents the imaginary unit of plural number, is -1 square root；
WhenWhen,
Δ ω represent accelerator radio-frequency cavity natural oscillation angular frequency and radio frequency power source output signal angular frequency it is blunt
The difference on the frequency connect, the i.e. detuning angular frequency of accelerator radio-frequency cavity.Pass between detuning angular frequency Δ ω and off-resonance frequency Δ H
System is 2 π × Δ H=Δs ω.
It should be noted that by radio-frequency cavity load impedance ZLCalculation formula, i.e. formula one, it is known that, if wanting to acquire
Load impedance needs the amplitude and phase information that accurately measure incidence wave and back wave in radio-frequency power feeder system, in order to
Reducing measurement error to the greatest extent, forward and reverse coefficient of coup of directional coupler must be consistent, the sampling channel of two paths of signals,
I.e. by directional coupler to the input port of AD sampling A/D chips, it is necessary to keep Striking symmetry, additionally need calibration from directional couple
Device signal extraction position is to the phase difference between radio-frequency cavity.
In order to test the detection method of this example, this example is verified using the radio-frequency cavity of a simulation, wherein radio frequency
The center resonant frequency of resonant cavity is designed in 324MHz, and the structure of analog radio frequency resonant cavity simulates resonance as shown in Fig. 4 and Fig. 5
Chamber is formed there are four main part, collet 1, bottom plate 2, resonance cavity main body 3 and resonant frequency adjusting rod 4；Collet 1 is four
Aluminum round bar supports entire resonant cavity；Resonance cavity main body 3, i.e. the copper cylinder of 1 top of collet；In 1 resonant cavity of collet
It is bottom plate 2 between main body 3, resonance cavity main body 3, which shrouds, to be fixed on a base plate 2, and on a base plate 2, there are two SMA interfaces, wherein one
A is radio-frequency power input feed port, the other is the pick-up sample ports of radio-frequency cavity field；Resonant frequency adjusting rod 4 is set
It sets in the top cover of resonance cavity main body 1, there are two resonant frequency adjusting rods altogether, one of them is thick for resonant frequency
It adjusts, the resonant frequency of coarse adjustment resonant cavity is used for, the other is being fine-tuned for resonant frequency.The collet 1 of resonant cavity with
Resonance cavity main body 3 is linked together by screw rod, and two resonant frequency adjusting rods 4 are extend into inside resonance cavity main body 3, by outer
Two threaded rods in portion adjust the length that resonant frequency adjusting rod 4 is extend into resonance cavity main body 3, change the internal junction of resonant cavity
Structure, to change the resonant frequency of resonant cavity.
It can be in the hope of simulating the coefficient of coup of two power coupling apertures of resonant cavity by Fig. 61,2,3,4 four point, and lead to
Overcoupling system and loaded Q can extrapolate the nonloaded Q of simulation resonant cavity, i.e. Q0Represent the nothing of accelerator radio-frequency cavity
Q values are carried, formula is used for：In.Wherein, the point for being labeled as 4 is used for first coupling aperture of measurement
The coefficient of coup 2.32, be used to measure the coefficient of coup 1.59 of second coupling aperture labeled as 1 point.
In order to which the off-resonance frequency of radio-frequency cavity is calculated using the design scheme of this example, it is necessary first to which test obtains chamber
The Q of body0Value.The Q of the radio-frequency cavity0Value tests to obtain by vector network analyzer, specifically, first passing through vector network point
Analyzer test cavity has load QLValue, test results are shown in figure 6, QL=2584.9, the degree of coupling β of two ports1And β2Respectively
For 3.32 and 1.59, pass through formula Q0=QL*(1/β1+1/β2) cavity Q is calculated0Value is 5326.In Fig. 6, abscissa is frequency
The swept frequency range of spectrometer, from 323.901MHz frequency sweep to 324.101MHz；Ordinate is the watt level of signal.The mould of this example
There are one input port and an output ports on quasi- resonant cavity；In Fig. 6, S21 curves indicate to measure the value of S21, S11 curve tables
Show that the value for measuring S11, S22 curves indicate to measure the value of S22, in this example, we only need three values in care figure：Q values,
That is loaded Q 2587.1；1 point of S11 curves, it is 2.32 to be worth；1 point of S22 curves, it is 1.59 to be worth, and is calculated using these three values
Go out to simulate the nonloaded Q of resonant cavity, i.e. Q0Value.
The signal amplitude 7dBm of RF pumping signals, frequency 324MHz, the signal are sent to two series connection by radio-frequency cable
In the directional coupler to get up, directional coupler selects the Coaxial Directional Coupler of NARDA companies production,
Model Narda 3000-10, the degree of coupling are -10dBm, and one of directional coupler is coupled out incoming signal, another
Directional coupler, which is coupled out, reflects signal, and the connection of directional coupler is as shown in fig. 7, the ends A are that radiofrequency signal inputs in Fig. 7
Mouthful, the ends B are radiofrequency signal delivery outlet, and C-terminal is back wave coupling aperture, and the ends D are incidence wave coupling aperture.Then by directional coupler coupling
The two paths of signals of conjunction is sent in analog down, is obtained for sampling intermediate-freuqncy signal.
Two-way intermediate-freuqncy signal is sent into AD sampling A/D chips the digital quadrature-sampling for carrying out quadruple, then send sampled data
Enter into fpga chip, number IQ carried out in fpga chip and is demodulated, then by demodulate come I/Q signal be calculated two
The amplitude and phase of a waveform, the digital signal processing algorithm inside fpga chip are as shown in Figure 8.
In Fig. 8, reverse signal in forward signal and back wave, that is, figure, is sent to AD sampling A/D chips in incidence wave, that is, figure
In, sample frequency is 4 times of signal frequency, then samples the AD to obtain digital signal and is sent in FPGA, to AD in FPGA
The digital quantity of sampling is decoded, and I is generated after decoding, then Q sequences carry out spin matrix and go the operation of direct current, obtain again
The I of the incidence wave and back wave that are sampled, Q value, then according to amplitude formulaPhase formulaThe amplitude and phase information that incidence wave and back wave can be calculated separately out, hinder according to radio-frequency cavity
Anti- calculation formula and off-resonance frequency calculation formula, can be in the hope of the off-resonance frequency of radio-frequency cavity.
In fpga chip, by the amplitude and phase information of incidence wave and back wave that digital IQ demodulation methods obtain, so
Impedance Z is calculated according to formula one afterwardsL, off-resonance frequency is calculated by formula two.This example by what IQ was demodulated specifically, enter
The amplitude and phase information of ejected wave and back wave are sent to by Ethernet in industrial personal computer, and formula one and public affairs are run in industrial personal computer
Formula two completes the calculating of off-resonance frequency, and result of calculation is as shown in table 1.
In order to verify the accuracy of this example detection method, this example also directly tests radio-frequency cavity using Network Analyzer
Off-resonance frequency, test result are as shown in table 1.
It should be noted that Network Analyzer can only be tested the case where cold chamber, that is, the case where no plus radio-frequency power,
Commonly used in analyzing off-line test result, and on-line testing cannot be carried out in real time.And the detection accelerator of this example is penetrated
The method of frequency resonant cavity off-resonance frequency, can be with the off-resonance frequency of on-line testing accelerating cavity, that is, in radio-frequency power is sent to radio frequency
After chamber, the off-resonance frequency of accelerating cavity is directly tested by incidence wave and back wave, is desirably integrated into radio frequency power source system
In, for carrying out on-line analysis, or in accelerator tuning system, being tuned in real time to accelerator radio-frequency cavity.
1 off-resonance frequency test result of table
| The off-resonance frequency (Hz) of the example method detection | The off-resonance frequency (Hz) of Network Analyzer test |
| -51180 | -50000 |
| -44356 | -43000 |
| -41106 | -41000 |
| -38979 | -39000 |
| -32205 | -34500 |
| -28579 | -30000 |
| -24711 | -25500 |
| -20375 | -22500 |
| -16226 | -18000 |
| -12230 | -13500 |
| -9408 | -10500 |
| -5481 | -4500 |
| -2211 | -1500 |
| -1112 | -1250 |
| 2656 | 3000 |
| 5812 | 5500 |
| 8308 | 8500 |
| 10377 | 11000 |
| 13101 | 14500 |
| 15458 | 16500 |
| 17957 | 19500 |
| 21072 | 22500 |
| 25088 | 26500 |
| 28040 | 28500 |
| 32019 | 33000 |
| 36449 | 38500 |
| 40311 | 41000 |
| 43262 | 45500 |
| 47413 | 47000 |
| 51694 | 51000 |
| 57445 | 56000 |
| 59643 | 57000 |
The test result of two methods shows, the measured off-resonance frequency value under the different detuning state of radio-frequency cavity
It coincide, error is within 3KHz, and relative to the radiofrequency signal of 324MHz, measurement accuracy reaches 0.009 ‰.As it can be seen that the inspection of this example
The method for surveying the off-resonance frequency of accelerator radio-frequency cavity can accurately detect the off-resonance frequency of radio-frequency cavity.
The foregoing is a further detailed description of the present application in conjunction with specific implementation manners, and it cannot be said that this Shen
Specific implementation please is confined to these explanations.For those of ordinary skill in the art to which this application belongs, it is not taking off
Under the premise of conceiving from the application, a number of simple deductions or replacements can also be made, all shall be regarded as belonging to the protection of the application
Range.
Claims (6)
1. a kind of method of detection accelerator radio-frequency cavity off-resonance frequency, it is characterised in that：It is adopted including the use of directional coupler
Sample obtains the incidence wave and back wave in the radio-frequency power feeder system of accelerator radio-frequency cavity, is then demodulated and is obtained by IQ
The amplitude and reference phase of two paths of signals by the impedance of one computation accelerator radio-frequency cavity of formula, then pass through formula two
Calculate the off-resonance frequency for obtaining accelerator radio-frequency cavity；
Formula one：
Formula two：
Wherein, ZLFor accelerator radio frequency resonant cavity impedance,For the voltage value of load impedance,For the electric current of load impedance
Value, Z0For the characteristic impedance of power transmission system,For Z1The voltage value of incidence wave at position,For Z2At position
The voltage value of back wave, e be plural number exponential form representation in natural logrithm the truth of a matter, γ (Z1- L) it represents along Z axis
The wave that negative direction is propagated is from Z1Point arrives the phase difference of load end ,-γ (Z2- L) wave propagated along the positive aspect of Z axis is represented from Z2Point arrives
The phase difference of load end, γ are complex propagation constant；
ω is radio frequency power source output signal angular frequency, ω0For the natural oscillation angular frequency of accelerator radio-frequency cavity；△ ω are
The detuning angular frequency of accelerator radio-frequency cavity, that is, radio frequency power source output signal angular frequency and accelerator radio-frequency cavity
Natural oscillation angular frequency between difference on the frequency, Q0For the unloaded quality factor of accelerator radio-frequency cavity, YLIndicate that load is led
It receives, load admittance YLIt is accelerator radio-frequency cavity impedance ZLInverse, YL iFor load admittance YLImaginary part, YL rFor load admittance
YLReal part, π is pi, and Δ H is off-resonance frequency；
Also, YL、ZL、YL iAnd YL rMeet formula three,
Formula three：
Wherein, j represents the imaginary unit of plural number, is -1 square root.
2. according to the method described in claim 1, it is characterized in that：It is described to sample to obtain accelerator radio frequency using directional coupler
Incidence wave and back wave in the radio-frequency power feeder system of resonant cavity, specifically, using at least two concatenated directional couples
Device, a directional coupler is for coupling incoming signal, and a directional coupler is used for coupled reflection signal, by the incidence of coupling
Signal and reflection signal are transported in analog down, are respectively obtained incoming signal and are reflected the intermediate-freuqncy signal of signal, intermediate frequency letter
It number is transported to progress quadruple digital quadrature-sampling in AD sampling A/D chips, i.e. I, Q is sampled, and is obtained incoming signal and is reflected signal
I, Q values.
3. according to the method described in claim 2, it is characterized in that：It is described that the amplitude and phase for obtaining two paths of signals are demodulated by IQ
Position reference value obtains incidence wave and back wave specifically, I, Q value of sampling are transported in fpga chip progress IQ demodulation
Amplitude and reference phase.
4. according to the method described in claim 2, it is characterized in that：In at least two concatenated directional coupler, orientation
Forward and reverse coefficient of coup of coupler is consistent, also, the transfer passage of directional coupler to AD sampling A/D chips keeps tight
Lattice are symmetrical.
5. according to claim 1-4 any one of them methods, it is characterised in that：It is described to pass through one computation accelerator radio frequency of formula
The impedance of resonant cavity, then by formula two calculate obtain accelerator radio-frequency cavity off-resonance frequency, can in industrial personal computer into
Row calculates, and industrial personal computer after calculating by directly exporting off-resonance frequency.
6. a kind of device of detection accelerator radio-frequency cavity off-resonance frequency, it is characterised in that：Described device includes IQ set of samples
Part, IQ demodulation chips and industrial personal computer, are connected between IQ sampling components and IQ demodulation chips by signal, IQ demodulation chips and industry control
It is connected by signal between machine；
The IQ sampling components include directional coupler group, analog down and the AD sampling A/D chips of signal connection；Directional couple
Device group is made of two concatenated directional couplers, and a directional coupler is for coupling incoming signal, another directional couple
Device is used for coupled reflection signal；The incoming signal that analog down is used to couple directional coupler group carries out down with reflection signal
Frequency-conversion processing obtains incoming signal respectively and reflects the intermediate-freuqncy signal of signal；AD sampling A/D chips are used to carry out four to intermediate-freuqncy signal
Frequency multiplication digital quadrature-sampling obtains incoming signal and reflects I, Q value of signal；
The IQ demodulation chips are fpga chip, and I, Q value for being obtained to AD sampling A/D chips carry out IQ demodulation, obtain incidence wave
With the amplitude and reference phase of back wave；
The amplitude and reference phase that the industrial personal computer is obtained according to IQ demodulation chips, it is humorous by one computation accelerator radio frequency of formula
It shakes the impedance of chamber, passes through the off-resonance frequency of two computation accelerator radio-frequency cavity of formula；
Formula one：
Formula two：
Wherein, ZLFor accelerator radio frequency resonant cavity impedance,For the voltage value of load impedance,For the electric current of load impedance
Value, Z0For the characteristic impedance of power transmission system,For Z1The voltage value of incidence wave at position,For Z2At position
The voltage value of back wave, e be plural number exponential form representation in natural logrithm the truth of a matter, γ (Z1- L) it represents along Z axis
The wave that negative direction is propagated is from Z1Point arrives the phase difference of load end ,-γ (Z2- L) wave propagated along the positive aspect of Z axis is represented from Z2Point arrives
The phase difference of load end, γ are complex propagation constant；
ω is radio frequency power source output signal angular frequency, ω0For the natural oscillation angular frequency of accelerator radio-frequency cavity；△ ω are
The detuning angular frequency of accelerator radio-frequency cavity, that is, radio frequency power source output signal angular frequency and accelerator radio-frequency cavity
Natural oscillation angular frequency between difference on the frequency, Q0For the unloaded quality factor of accelerator radio-frequency cavity, YLIndicate that load is led
It receives, load admittance YLIt is accelerator radio-frequency cavity impedance ZLInverse, YL iFor load admittance YLImaginary part, YL rFor load admittance
YLReal part, π is pi, and Δ H is off-resonance frequency；
Also, YL、ZL、YL iAnd YL rMeet formula three,
Formula three：
Wherein, j represents the imaginary unit of plural number, is -1 square root.
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| CN108815723B (en) * | 2018-07-26 | 2024-01-30 | 中国科学院近代物理研究所 | High-frequency cavity detuning detection unit and detection method thereof |
| CN109392234A (en) * | 2018-11-07 | 2019-02-26 | 清华大学 | A kind of method and device that signal generates |
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| CN112057752A (en) * | 2020-09-15 | 2020-12-11 | 散裂中子源科学中心 | All-digital low-level control method and system for boron neutron capture treatment device |
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