CN116027101A - On-line discriminating method and system for ignition type of radio frequency superconducting cavity - Google Patents
On-line discriminating method and system for ignition type of radio frequency superconducting cavity Download PDFInfo
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Abstract
The invention relates to an on-line discriminating method and system for the type of the firing of a radio frequency superconducting cavity, comprising the following steps: cavity sampling signal P based on-line measurement t Cavity incident signal P f Cavity reflection signal P r Obtaining the cavity pressure V of the superconducting cavity c Forward voltage V f And reverse voltage V r The method comprises the steps of carrying out a first treatment on the surface of the Based on forward voltage V f And reverse voltage V r Reconstructing the superconducting cavity pressure U c The method comprises the steps of carrying out a first treatment on the surface of the Chamber pressure V based on superconducting Chamber c Determining whether a firing event has occurred; when the ignition time is determined, the pressure U is based on the superconducting cavity c The amount of change before and after the firing event identifies the firing type. The invention can realize the on-line screening of the sparking type of the superconducting cavity and provides preconditions for inhibiting the group fault of the superconducting cavity.
Description
Technical Field
The invention relates to an on-line screening method and an on-line screening system for a firing type of a radio frequency superconducting cavity, and relates to the field of particle accelerators.
Background
The radio frequency superconducting cavity (superconducting cavity) is very suitable for accelerating high average flow Jiang Shu flow in Continuous Wave (CW) or long pulse mode due to the advantages of low loss, high gradient and the like. In recent years, the radio frequency superconducting technology is taken as a preferred scheme in the current important project of the accelerator front field in construction, planning and planning at home and abroad. The operating bandwidth of a superconducting cavity is typically tens to hundreds of Hz, and the extremely narrow bandwidth results in a cavity that is extremely prone to failure when detuned by disturbances (e.g., mechanical vibrations). Therefore, each superconducting cavity needs to be equipped with a real-time digital radio frequency low-level control system (hereinafter referred to as a low-level system) to maintain its operation stability.
Spark failure is a serious problem that is common in superconducting cavities in high gradient operation. The firing event can be classified into two cases, a flashover and an electrical quench, according to the type of firing. Both of which result in field emission electrons striking the signal extraction coupler of the superconducting cavity, resulting in characterizationSuperconducting cavity pressure (V) c ) Is sampled (P) t ) Abnormal signal (expressed as P t Transient strong interference occurs in the signal). The flash event does not have a large impact on the real cavity pressure and can be solved by a low-level digital signal algorithm. However, electrical quench events typically consume a significant amount of the cavity energy, causing V on the order of microseconds c The number of the superconducting cavities is greatly reduced, and other cavity faults (such as electromechanical oscillation or thermal quench) can be triggered, so that the occurrence of group faults of a plurality of superconducting cavities is finally caused.
Therefore, when it is determined that the superconducting cavity frequently loses time out, necessary countermeasures (e.g., lowering the radio frequency electric field of the fault cavity, shutting down the fault cavity, etc.) are taken. Due to both flash and electrical quench, the device is in P t Similar instantaneous strong interference is formed in the signal, and a low-level system cannot distinguish the two types of sparking events on line, so that a solution cannot be formulated for the electrical quench event in a targeted manner. In conclusion, the type of the superconducting cavity sparking event is screened on line, the precondition of relieving the group fault of the superconducting cavity is achieved, and the running stability of the high-power high-current high-intensity radio frequency superconducting accelerator in the future is further related.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, aiming at the problems, the invention aims to provide the on-line discriminating method and the system for the type of the spark of the radio frequency superconducting cavity, which can accurately discriminate the type of the spark of the superconducting cavity and lay a foundation for improving the operation stability of the superconducting cavity.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the method for on-line discriminating the sparking type of the radio frequency superconducting cavity provided by the invention comprises the following steps:
cavity sampling signal P based on-line measurement t Cavity incident signal P f Cavity reflection signal P r Obtaining the cavity pressure V of the superconducting cavity c Forward voltage V f And reverse voltage V r ；
Based on forward voltage V f And reverse voltage V r Reconstructing the superconducting cavity pressure U c ；
Chamber pressure V based on superconducting Chamber c Determining whether a firing event has occurred;
when the ignition is judged to occur, the pressure U is based on the superconducting cavity c The amount of change before and after the firing event identifies the firing type.
Further, the cavity sampling signal P based on-line measurement t Cavity incident signal P f Cavity reflection signal P r Obtaining the cavity pressure V of the superconducting cavity c Forward voltage V f And reverse voltage V r Comprising:
sampling the cavity with the signal P t Cavity incident signal P f Cavity reflection signal P r Down-converting to an intermediate frequency signal;
respectively obtaining three groups of digital baseband signals, namely the cavity pressure V of the superconducting cavity, by performing quadruple frequency sampling on the intermediate frequency signals c Forward voltage V f And reverse voltage V r 。
Further, the superconducting cavity pressure U c By formula U c ＝X V f +Y V r A configuration is made in which X and Y are both correction coefficients.
Further, cavity pressure V based on superconducting cavity c Determining whether a fire event has occurred, comprising: calculating the cavity pressure V of the superconducting cavity c The magnitude of the change in magnitude at the set time is considered to occur if the absolute value of the change is greater than a set threshold value of 0.
Further, when it is determined that the sparking occurs, the superconducting cavity pressure U is based on c The method for distinguishing the ignition type by the variation before and after the ignition event comprises the following steps:
calculating the superconducting cavity pressure U c The change amounts of the amplitude of the pulse before and after the ignition event are respectively recorded as delta A, if delta A is smaller than a threshold value 1, the pulse is identified as a flash event, and the event is considered to not trigger the superconducting cavity fault;
if ΔA is greater than threshold 2, then an electrical quench event is identified, which is believed to induce a cavity quench, wherein threshold 2> threshold 1;
ΔA is between threshold 1 and threshold 2, and is identified as a partial electrical quench, which is believed to trigger electromechanical oscillations, but not evolve into a cavity quench.
In a second aspect, the invention provides an on-line discriminating system of the type of a radio frequency superconducting cavity fire striking, comprising a digital low-level system, a solid-state power source, a directional coupler, an input coupler and a signal extraction coupler;
the output end of the digital low-level system is connected with the input end of the solid-state power source, the output end of the solid-state power source is connected with the input end of the directional coupler, the output end of the directional coupler is fed into the superconducting cavity through the input coupler, and the directional coupler measures the cavity incident signal P on line f Reflected signal P r ；
The signal extraction coupler is used for connecting the superconducting cavity to measure the superconducting cavity sampling signal P on line t ；
The digital low-level system receives a superconducting cavity sampling signal P t Cavity incident signal P f Reflected signal P r Reconstructing the superconducting cavity pressure U c Based on superconducting cavity pressure U c The amount of change before and after the firing event identifies the type of firing.
Further, an FPGA is arranged in the digital low-level system, and a digital signal processing module, a cavity pressure reconstruction module, a sparking detection module and a sparking type screening module are arranged in the FPGA;
the digital signal processing module is used for sampling the cavity body signal P t Cavity incident signal P f Reflected signal P r P t 、P f And P r Signal processing to cavity pressure V of superconducting cavity c Forward voltage V f And reverse voltage V r ；
A cavity pressure reconstruction module for utilizing the forward voltage V f And reverse voltage V r Reconstructing the superconducting cavity pressure U c ；
The ignition detection module is used for judging the occurrence of an ignition event and sending a trigger signal;
the ignition type screening module is used for receiving the trigger signal according to the superconducting cavityPressure U c The amount of change before and after the firing event identifies the type of firing.
Further, the ignition type screening module is used for screening the ignition type according to the superconducting cavity pressure U c The method for judging the ignition type by the variation before and after the ignition event comprises the following steps:
calculating the superconducting cavity pressure U c The change amounts of the amplitude of the pulse before and after the ignition event are respectively recorded as delta A, if delta A is smaller than a threshold value 1, the pulse is identified as a flash event, and the event is considered to not trigger the superconducting cavity fault;
if ΔA is greater than threshold 2, then an electrical quench event is identified, which is believed to induce a cavity quench, wherein threshold 2> threshold 1;
ΔA is between threshold 1 and threshold 2, and is identified as a partial electrical quench, which is believed to trigger electromechanical oscillations, but not evolve into a cavity quench.
Further, the cavity pressure reconstruction module utilizes a forward voltage V f And reverse voltage V r By the formula U c ＝X V f +Y V r Reconstructing the superconducting cavity pressure U c Wherein X and Y are correction coefficients.
Further, the system also comprises an upper computer which is connected with the digital low-level system.
The invention adopts the technical proposal and has the following characteristics:
1. according to the invention, the on-line screening of the superconducting cavity sparking type is realized by constructing a real-time signal processing algorithm in the FPGA, a precondition is provided for inhibiting the group fault of the superconducting cavity, and a foundation is laid for realizing the long-term stable operation of the radio frequency superconducting accelerator in the future.
2. Because the new generation particle accelerator system generally adopts a digital low-level technical scheme based on the FPGA, the screening algorithm of the invention can be completely deployed inside the low-level system without adding additional hardware equipment.
3. The long-term statistics of the sparking type of the present invention provide data support for further clear coupling correlations between quench frequency and other physical quantities (e.g., beam intensity, cavity pressure, etc.).
In conclusion, the invention can be widely applied to high-power and high-current strong radio frequency superconducting accelerators.
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Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Like parts are designated with like reference numerals throughout the drawings. In the drawings:
fig. 1 is a block diagram of an on-line discriminating system for the type of firing of a radio frequency superconducting cavity according to an embodiment of the present invention.
FIG. 2 is a raw cavity pressure signal V under three types of firing events according to an embodiment of the present invention c 。
Fig. 3 is an example of an electromechanical oscillation fault triggered by a partial electrical quench event according to an embodiment of the present invention, and after the partial electrical quench event occurs, the cavity resonant frequency (i.e. cavity detuning in the case of baseband) oscillates, and the oscillation signal frequency coincides with the frequency of the cavity mechanical mode.
FIG. 4 shows an example of an electrical quench event developed as a thermal quench fault in accordance with an embodiment of the present invention, (a) is the cavity pressure signal U throughout the evolution process c (after reconstruction), (b) is the forward and reverse voltage signals U in the evolution process f And U r (after correction) according to U after RF cut-off c Attenuation curve of amplitude: q of cavity L The temperature is reduced to 1/10 of the normal value, and the characteristics of thermal quench are met.
Fig. 5 (a) is a block diagram of an algorithm for discriminating the type of the superconducting cavity spark according to the embodiment of the present invention, and fig. 5 (b) is a specific implementation form of complex multiplication in the FPGA.
FIG. 6 (a) shows an embodiment of the invention of the primary cavity voltage signal V for the occurrence of a flash event c And the reconstructed cavity pressure signal U c FIG. 6 (b) is a raw cavity pressure signal V at partial electrical quench event c And the reconstructed cavity pressure signal U c 。
Fig. 7 shows a measurement channel delay reconstruction cavity pressure signal U according to an embodiment of the present invention c Influence of accuracy.
Detailed Description
It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "includes," "including," and "having" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless an order of performance is explicitly stated. It should also be appreciated that additional or alternative steps may be used.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
For ease of description, spatially relative terms, such as "inner," "outer," "lower," "upper," and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.
Due to flashing and powerQuench will be at P t Similar instantaneous strong interference is formed in the signal, and a digital low-level system cannot distinguish the two types of ignition events on line, so that a solution cannot be formulated for the electrical quench event in a targeted manner. The invention provides a method and a system for on-line screening of the type of the spark of a radio frequency superconducting cavity, which comprise the following steps: cavity sampling signal P based on-line measurement t Cavity incident signal P f Cavity reflection signal P r Obtaining the cavity pressure V of the superconducting cavity c Forward voltage V f And reverse voltage V r The method comprises the steps of carrying out a first treatment on the surface of the Based on forward voltage V f And reverse voltage V r Reconstructing the superconducting cavity pressure U c The method comprises the steps of carrying out a first treatment on the surface of the Chamber pressure V based on superconducting Chamber c Determining whether a firing event has occurred; when the ignition time is determined, the pressure U is based on the superconducting cavity c The amount of change before and after the firing event identifies the firing type. Therefore, the invention is a precondition for researching the physical mechanism of the superconductive cavity group fault, also provides data support for coupling association between the li qing sparking event and other physical quantities, and lays a foundation for realizing the long-term operation stability of the superconductive cavity.
Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Embodiment one: as shown in fig. 1, the radio frequency superconducting cavity sparking type on-line screening system provided by the embodiment comprises a digital low-level system 1, a solid-state power source 2, a directional coupler 3, an input coupler 4 and a signal extraction coupler 5.
The output end of the digital low-level system 1 is connected with the input end of the solid-state power source 2, the output end of the solid-state power source 2 is connected with the input end of the directional coupler 3, the output end (through port) of the directional coupler 3 is fed into the superconducting cavity through the input coupler 4, and the directional coupler 3 measures the cavity incident signal P on line f Reflection ofSignal P r The signal extraction coupler 5 is used for connecting a superconducting cavity to measure a superconducting cavity sampling signal P on line t The digital low-level system 1 receives a superconducting cavity sampling signal P t Cavity incident signal P f Reflected signal P r Reconstructing the superconducting cavity pressure U c According to the pressure U of the superconducting cavity c The amount of change before and after the firing event identifies the type of firing.
In a preferred embodiment, the system further comprises a host computer 6, and the host computer 6 is connected with the digital low-level system 1 and is used for setting related parameters of the digital low-level system 1.
In a preferred embodiment, a field programmable gate array (FPGA for short) is arranged in the digital low-level system 1, and a digital signal processing module, a cavity pressure reconstruction module, a fire striking detection module and a fire striking type screening module are arranged in the FPGA.
Digital signal processing module for sampling signal P through superconducting cavity t Cavity incident signal P f Reflected signal P r P t 、P f And P r Signal acquisition of the cavity pressure V of the corresponding superconducting cavity c Forward voltage V f And reverse voltage V r 。
Cavity pressure reconstruction module utilizing forward voltage V f And reverse voltage V r By the formula U c ＝X V f +Y V r Reconstructing the superconducting cavity pressure U c Wherein X and Y are correction coefficients.
And the ignition detection module is used for judging whether an ignition event occurs or not, and sending out a trigger signal when the ignition occurs.
The ignition type screening module calculates U when the ignition happens c The magnitude and phase of the (a) change before and after the firing event are denoted as deltaa and deltaθ, respectively. If Δa is smaller than threshold 1, a flash event is recognized, and if Δa is larger than threshold 2 (threshold 2>Threshold 1), then an electrical quench event is identified, and Δa is between threshold 1 and threshold 2, then a partial electrical quench is identified.
Embodiment two: the invention provides an on-line discriminating method for the type of the spark of a radio frequency superconducting cavity, which comprises the following steps:
s1, a digital low level system 1 measures a cavity sampling signal P of a superconducting cavity on line t Cavity incident signal P f Cavity reflection signal P r Processing to obtain cavity pressure V of superconducting cavity c Forward voltage V f And reverse voltage V r 。
Specifically, the cavity is sampled by the signal P t Cavity incident signal P f Cavity reflection signal P r Down-converting the signal into an intermediate frequency signal, and obtaining three groups of digital baseband signals respectively by sampling the intermediate frequency signal by four times (namely, sampling frequency is 4 times of signal frequency), wherein the three groups of digital baseband signals are: cavity pressure V of superconducting cavity c Forward voltage V f And reverse voltage V r . For example, in general P t Representing radio frequency signals, e.g. 162.5MHz, V c Representing the digitized baseband signal, i.e., without radio frequency components, is removed by down-conversion.
In this embodiment, the cavity samples the signal P t The digital low level system 1 is connected with a superconducting cavity signal extraction coupler 5 for extraction. P (P) f And P r The signal is coupled to the digital low level system 1 via a directional coupler 3 for acquisition.
Further, the voltages according to the present embodiment (e.g., V c 、V f 、V r Etc.) are complex forms, they may be represented either in amplitude and phase form, for example: v= |v|e j∠V Where V is amplitude (or modulo), V is phase (or amplitude angle); may also be expressed in terms of real plus imaginary parts, such as: v=v I +jV Q Wherein V is I As the real part, V Q Is imaginary.
S2, based on forward voltage V f And reverse voltage V r Reconstructing the superconducting cavity pressure U c 。
In this embodiment, a real-time signal processing algorithm is designed inside a Field Programmable Gate Array (FPGA) chip of the digital low-level system 1, and the forward voltage V is obtained by measurement f And reverse voltage V r By the formula U c ＝X V f +Y V r Reconstructing the superconducting cavity pressure U c Wherein, correction coefficients X and Y are complex numbers. Due to V f And V r Independent of the signal extraction coupler, reconstruct the cavity pressure U c And no transient strong interference signal is mixed in.
Further, complex coefficients X and Y can be solved using prior art techniques, and coefficients X and Y can also be expressed in terms of amplitude versus phase or real plus imaginary parts.
S3, when the occurrence of the sparking event is judged, a trigger signal is sent out
In this embodiment, the FPGA chip is provided with a sparking detection module, which is derived from the original V c When transient strong interference is detected in the signal (for example, the duration of the interference is 1-10 microseconds, the interference intensity exceeds 1/3 of the amplitude of the steady-state signal), the occurrence of a sparking event is judged, and a triggering signal is sent to a sparking type screening module.
Further, the fire detection module calculates V c The amplitude of the change in the set time, if the absolute value of the change is greater than the set threshold value 0, the ignition event is considered to occur, and a trigger signal Trig1 is sent out. The threshold value 0 is set by the upper computer, and can be generally selected to be 20 to 50 times of the root mean square value of random noise of an analog-to-digital converter (ADC) so as to avoid misjudgment of a sparking event.
S4, calculating U by using a fire type screening module of the FPGA chip c The variation of the amplitude and phase of the (B) before and after the firing event is based on the superconducting cavity pressure U c The amount of change before and after the firing event identifies the type of firing.
In this embodiment, calculate U c The change amounts of the amplitude and the phase of the pulse before and after the ignition event are respectively recorded as delta A and delta theta, wherein the delta A is used for judging the ignition type, the delta theta is mainly used for further determining the phase information of dark current in the electric quench event, and the judgment process for judging the ignition type is as follows:
if ΔA is less than threshold 1, a flashover event is identified, i.e., the event is deemed not to trigger a superconducting cavity fault.
If ΔA is greater than threshold 2 (threshold 2> threshold 1), then an electrical quench event is identified, which is generally believed to be likely to induce a cavity quench. ΔA is between threshold 1 and threshold 2, identified as a partial electrical quench, and this event is generally believed to trigger an electromechanical oscillation, but does not evolve into a cavity quench.
Further, the threshold 1 and the threshold 2 can be set by issuing parameters through an upper computer connected with the digital low level system.
In this embodiment, the amplitude, the phase variation Δa and the phase variation Δθ obtained by online measurement may also be returned to the upper computer 6.
The application of the method for realizing the on-line discrimination of the sparking type of the radio frequency superconducting cavity is described in detail by a specific embodiment.
The solid state power source used in this example was model 2 KFAA-162-1-1, each comprising 24 inserts, the saturation output power of a single insert being about 1.4kW; the superconducting cavity is a half wavelength superconducting cavity (HWR 010, the relativity speed of which is 0.1), the resonant frequency of the cavity is 162.5MHz, and the on-load quality factor (Q) L ) About 5X 10 5 The method comprises the steps of carrying out a first treatment on the surface of the The data sampling rate of the digital low-level system 1 is 100MHz, and the model of the FPGA chip is ZYNQ7100; the model of the directional coupler 3 is EXIR MDIR-2077-33-A, and the directivity is that:>40dB; antenna quality factor Q of signal extraction coupler 5 e About 10 7 。
Based on the above parameter setting, the method for on-line screening of the sparking type of the radio frequency superconducting cavity in this embodiment includes:
1. measurement of the voltage signal.
Cavity pressure V of superconducting cavity c Forward voltage V f And reverse voltage V r Is a measurement stage of (a). As shown in fig. 1, the measurement schematic diagram is that the output of the digital low-level system 1 is connected with the input end of the solid-state power source 2, the output of the solid-state power source 2 is connected with the input end of the directional coupler 3, the output of the directional coupler 3 is fed into the superconducting cavity through the input coupler 4, and the measurement process is as follows:
1. on-line measurement of superconducting cavity sampling signal P using signal extraction coupler 5 t The method comprises the steps of carrying out a first treatment on the surface of the On-line measurement of cavity incident signal P using directional coupler 3 f Reflected signal P r Wherein P is t 、P f P r Are 162.5MHz radio frequency signals.
2. After the radio frequency signals are sequentially down-converted and digitized, a digitized original baseband voltage signal, namely a cavity voltage V, is obtained in the digital low-level system 1 c Forward voltage V f And reverse voltage V r 。
As shown in fig. 2, a flash-off, partial electrical quench, and electrical quench timeout occur, and a transient strong disturbance (typically 7-10 microseconds in duration) is mixed into the original cavity pressure signal. The partial electrical quench event may further trigger the cavity electromechanical coupling oscillation, and the cavity resonant frequency, which is embodied as oscillation, is shown in fig. 3, and the electrical quench event may further be embodied as thermal quench, which is embodied as Q of the cavity L After decreasing, RF is turned off, the time constant of the cavity field decay curve decreases, as shown in fig. 4.
2. Calibration of the baseband voltage signal and reconstruction of the cavity voltage signal.
As shown in FIG. 5, V is obtained at this stage from the above measurement f And V r The real-time signal processing algorithm is designed in the digital low level system 1 to reconstruct the cavity pressure U c Comprising:
1. using the measured baseband voltage signal V f And V r By complex multiplication U f ＝X V f U and U r ＝Y V r Solving for the calibrated forward voltage U f And reverse voltage U r . The calibration coefficients X, Y and the signals U, V are complex, and the complex X may be equivalent to a 2×2 matrix in the following formula (1), and the specific implementation form of the complex multiplication in the FPGA is shown in fig. 5 (b).
In U fI And U fQ Respectively U f Real and imaginary parts of (a); v (V) fI And V fQ V respectively f Real and imaginary parts of (a); x is X I And X Q The real and imaginary parts of the calibration coefficient X, respectively. U (U) rI And U rQ Respectively U r Real and imaginary parts of (a); v (V) rI And V rQ V respectively r Real and imaginary parts of (a); y is Y I And Y Q The real and imaginary parts of the calibration coefficient Y, respectively.
2. By means of corrected U f And U r Reconstruction cavity pressure U c (U c ＝U f +U r As shown in fig. 5 (a). U when no ignition event occurs c And V is equal to c Is completely consistent. In the event of a fire, due to V f And V r Is obtained by measuring a directional coupler (not influenced by a cavity ignition event), and the U is reconstructed c No longer contains the original V c Transient strong interference in the signal as shown in fig. 6.
3. Taking into account P f And P r The delay of the signal measuring channel is different and affects U because the measuring devices (such as cable length) of the two channels cannot be completely consistent c Is used for measuring the precision of the test piece. Therefore, the channel delay needs to be further calibrated before reconstructing the cavity pressure signal. To ensure corrected U f And U r The delay error between is less than one sample period (10 ns).
Specifically, in the FPGA, the delay element may be implemented by a first-in-first-out memory (FIFO) module, and the U before and after channel delay calibration c The signal is shown in fig. 7.
3. Triggering of a firing event.
As shown in FIG. 5 (a), the fire detection module is constructed in the FPGA chip to calculate V c The amplitude is varied within 80 nanoseconds. If the absolute value of the variation is greater than the threshold value 0, a firing event is considered to occur and a trigger signal Trig1 is sent out. The threshold value 0 is issued by the upper computer and can be generally selected to be 20 to 50 times of the root mean square value of random noise of an analog-to-digital converter (ADC) so as to avoid misjudgment of a sparking event.
4. And (5) on-line judging of the sparking type.
After receiving the trigger signal, calculating the variation of the pressure of the reconstruction cavity before and after the sparking event, and judging the sparking type according to the variation, comprising the following steps:
1. calculating the amplitude U of the reconstruction cavity pressure cA And phase U cθ The delta A and delta theta of the change amount in the duration of the ignition event (7-10 microseconds) are uploaded to the upper computer through the data acquisition system.
2. If the delta A is<A threshold value of 1, the type of the sparking event is identified as a flashing event; if the delta A is>Threshold 2 (threshold 2)>Threshold 1), the firing event type is identified as an electrical quench event, which typically further induces cavity quench, as shown in fig. 4; if threshold value 1<ΔA<Threshold 2, the firing event type is identified as a partial electrical quench, which event typically triggers an electromechanical oscillation, but does not evolve into a cavity quench as shown in fig. 3. Wherein, the threshold value 1 and the threshold value 2 can be set by an upper computer. Typically, threshold 1 is selected to be the steady state cavity pressure magnitude value (U cA0 ) 1/100 of (2), threshold 2 is selected to be U cA0 1/3 to 2/3 of the total weight of the product.
3. And (3) online recording the long-term sparking type and the delta A and delta theta data, and analyzing the coupling correlation between the sparking type and other related physical quantities (such as cavity pressure, cavity detuning, beam intensity, power and the like).
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In the description of the present specification, reference to the term "one preferred embodiment", etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the embodiments of the present specification. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. An on-line discriminating method for the type of the spark of a radio frequency superconducting cavity is characterized by comprising the following steps:
cavity sampling signal P based on-line measurement t Cavity incident signal P f Cavity reflection signal P r Obtaining the cavity pressure V of the superconducting cavity c Forward voltage V f And reverse voltage V r ；
Based on forward voltage V f And reverse voltage V r Reconstructing the superconducting cavity pressure U c ；
Chamber pressure V based on superconducting Chamber c Determining whether a firing event has occurred;
when the ignition is judged to occur, the pressure U is based on the superconducting cavity c The amount of change before and after the firing event identifies the firing type.
2. The method for on-line discriminating between radio frequency superconducting cavity sparking types according to claim 1 wherein cavity sampling signal P based on-line measurement t Cavity incident signal P f Cavity reflection signal P r Obtaining the cavity pressure V of the superconducting cavity c Forward voltage V f And reverse voltage V r Comprising:
sampling the cavity with the signal P t Cavity incident signal P f Cavity reflection signal P r Down-converting to an intermediate frequency signal;
respectively obtaining three groups of digital baseband signals, namely the cavity pressure V of the superconducting cavity, by performing quadruple frequency sampling on the intermediate frequency signals c Forward voltage V f And reverse voltage V r 。
3. The method for on-line discriminating a type of radio frequency superconducting cavity fire according to claim 1, wherein the superconducting cavity pressure U is as follows c By formula U c ＝X V f +Y V r A configuration is made in which X and Y are both correction coefficients.
4. The method for on-line discrimination of radio frequency superconducting cavity sparking type according to claim 1, wherein the cavity pressure V based on superconducting cavity c Determining whether a fire event has occurred, comprising: calculating the cavity pressure V of the superconducting cavity c The magnitude of the change in magnitude at the set time is considered to occur if the absolute value of the change is greater than a set threshold value of 0.
5. The method for on-line discrimination of radio frequency superconducting cavity fire type according to claim 1, wherein when it is determined that fire is occurring, based on superconducting cavity pressure U c The method for distinguishing the ignition type by the variation before and after the ignition event comprises the following steps:
calculating the superconducting cavity pressure U c The change amounts of the amplitude of the pulse before and after the ignition event are respectively recorded as delta A, if delta A is smaller than a threshold value 1, the pulse is identified as a flash event, and the event is considered to not trigger the superconducting cavity fault;
if ΔA is greater than threshold 2, then an electrical quench event is identified, which is believed to induce a cavity quench, wherein threshold 2> threshold 1;
ΔA is between threshold 1 and threshold 2, and is identified as a partial electrical quench, which is believed to trigger electromechanical oscillations, but not evolve into a cavity quench.
6. The radio frequency superconducting cavity sparking type on-line screening system is characterized by comprising a digital low-level system, a solid-state power source, a directional coupler, an input coupler and a signal extraction coupler;
the output end of the digital low-level system is connected with the input end of the solid-state power source, the output end of the solid-state power source is connected with the input end of the directional coupler, and the output end of the directional coupler passes through the input endThe in-coupler feeds into the superconducting cavity, and the directional coupler measures the cavity incident signal P on line f Reflected signal P r ；
The signal extraction coupler is used for connecting the superconducting cavity to measure the superconducting cavity sampling signal P on line t ；
The digital low-level system receives a superconducting cavity sampling signal P t Cavity incident signal P f Reflected signal P r Reconstructing the superconducting cavity pressure U c Based on superconducting cavity pressure U c The amount of change before and after the firing event identifies the type of firing.
7. The radio frequency superconducting cavity fire type on-line screening system according to claim 6, wherein an FPGA is arranged in the digital low-level system, and a digital signal processing module, a cavity pressure reconstruction module, a fire detection module and a fire type screening module are arranged in the FPGA;
the digital signal processing module is used for sampling the cavity body signal P t Cavity incident signal P f Reflected signal P r P t 、P f And P r Signal processing to cavity pressure V of superconducting cavity c Forward voltage V f And reverse voltage V r ；
A cavity pressure reconstruction module for utilizing the forward voltage V f And reverse voltage V r Reconstructing the superconducting cavity pressure U c ；
The ignition detection module is used for judging the occurrence of an ignition event and sending a trigger signal;
the ignition type screening module is used for receiving the trigger signal according to the superconducting cavity pressure U c The amount of change before and after the firing event identifies the type of firing.
8. The radio frequency superconducting cavity fire type on-line screening system according to claim 7, wherein the fire type screening module is based on superconducting cavity pressure U c The method for judging the ignition type by the variation before and after the ignition event comprises the following steps:
calculating the superconducting cavity pressure U c The change amounts of the amplitude of the pulse before and after the ignition event are respectively recorded as delta A, if delta A is smaller than a threshold value 1, the pulse is identified as a flash event, and the event is considered to not trigger the superconducting cavity fault;
if ΔA is greater than threshold 2, then an electrical quench event is identified, which is believed to induce a cavity quench, wherein threshold 2> threshold 1;
ΔA is between threshold 1 and threshold 2, and is identified as a partial electrical quench, which is believed to trigger electromechanical oscillations, but not evolve into a cavity quench.
9. The radio frequency superconducting cavity fire type on-line screening system according to claim 7, wherein the cavity pressure reconstruction module utilizes a forward voltage V f And reverse voltage V r By the formula U c ＝X V f +Y V r Reconstructing the superconducting cavity pressure U c Wherein X and Y are correction coefficients.
10. The radio frequency superconducting cavity fire type on-line screening system according to claim 6, further comprising an upper computer, wherein the upper computer is connected with the digital low level system.
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