CN116027101A - On-line discriminating method and system for ignition type of radio frequency superconducting cavity - Google Patents

Abstract

The present invention relates to an on-line identification method and system for the sparking type of a radio frequency superconducting cavity, comprising: obtaining the cavity of the superconducting cavity based on the cavity sampling signal P _t , the cavity incident signal P _f and the cavity reflection signal P _r voltage V _c , forward voltage V _f and reverse voltage V _r ; based on the forward voltage V _f and reverse voltage V _r , reconstruct the superconducting cavity pressure U _c ; determine the cavity pressure V _c based on the superconducting cavity Whether a sparking event occurs; when judging the sparking time, the sparking type is judged based on the variation of the superconducting cavity pressure U _c before and after the sparking event. The invention can realize the on-line identification of the ignition type of the superconducting cavity, and provides a precondition for suppressing group faults of the superconducting cavity.

Description

Online identification method and system for radio frequency superconducting cavity spark type

Technical Field

The invention relates to an online identification method and system for radio frequency superconducting cavity sparking types, and relates to the field of particle accelerators.

Background Art

Radio frequency superconducting cavities (superconducting cavities) are very suitable for accelerating high average current beams in continuous wave (CW) or long pulse mode due to their advantages such as low loss and high gradient. In recent years, major projects in the frontier field of accelerators currently under construction, in preparation, or planned at home and abroad have all chosen radio frequency superconducting technology as the preferred option. The operating bandwidth of a superconducting cavity is generally tens to hundreds of Hz. The extremely narrow bandwidth makes it very easy for the cavity to malfunction when it is detuned by interference (such as mechanical vibration). Therefore, each superconducting cavity needs to be equipped with a real-time digital radio frequency low-level control system (hereinafter referred to as the low-level system) to maintain its operational stability.

Sparking failure is a common and serious problem when superconducting cavities are operating at high gradients. According to the type of sparking, sparking events can be divided into two types: flash and electrical quench. Both will cause field-emission electrons to bombard the signal extraction coupler of the superconducting cavity, causing the cavity sampling ( _Pt ) signal representing the cavity pressure ( _Vc ) of the superconducting cavity to be abnormal (manifested as instantaneous strong interference in the _Pt signal). Flash events will not have a significant impact on the actual cavity pressure and can be solved by low-level digital signal algorithms. However, electrical quench events usually consume a large amount of cavity energy storage, causing a significant reduction _{in Vc} at the microsecond level, and may further trigger other cavity faults (such as electromechanical oscillations or thermal quenches), ultimately leading to collective failures in multiple superconducting cavities.

Therefore, when determining that the superconducting cavity frequently quenches, necessary countermeasures need to be taken (for example, reducing the RF electric field of the faulty cavity, closing the faulty cavity, etc.). Since both flash and quench will form similar instantaneous strong interference in the _Pt signal, the low-level system cannot distinguish these two types of sparking events online, and therefore cannot formulate targeted solutions for quench events. In summary, online identification of superconducting cavity sparking event types is a prerequisite for alleviating superconducting cavity group failures, and is also related to the operational stability of future high-power, high-current RF superconducting accelerators.

Summary of the invention

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 method and system for online identification of the spark type of a radio frequency superconducting cavity, which can accurately identify the spark type of the superconducting cavity and lay a foundation for improving the operating stability of the superconducting cavity.

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

In a first aspect, the present invention provides an online identification method for the spark type of a radio frequency superconducting cavity, comprising:

Based on the online measured cavity sampling signal _Pt , cavity incident signal _Pf and cavity reflection signal _Pr, the cavity pressure _Vc , forward voltage _Vf and reverse voltage _Vr of the superconducting cavity are obtained;

Based on the forward voltage V _f and the reverse voltage V _r , the superconducting cavity pressure U _c is reconstructed;

Determine whether the spark event occurs based on the cavity pressure _Vc of the superconducting cavity;

When it is determined that sparking occurs, the sparking type is determined based on the change in the superconducting cavity pressure _Uc before and after the sparking event.

Furthermore, based on the online measured cavity sampling signal _Pt , cavity incident signal _Pf and cavity reflection signal _Pr, the cavity pressure _Vc , forward voltage _Vf and reverse voltage _Vr of the superconducting cavity are obtained, including:

Down-converting the cavity sampling signal _Pt , the cavity incident signal _Pf and the cavity reflected signal _Pr into intermediate frequency signals;

By performing quadruple frequency sampling on the intermediate frequency signal, three groups of digital baseband signals are obtained respectively, namely, the cavity pressure V _c , the forward voltage V _f and the reverse voltage V _r of the superconducting cavity.

Furthermore, the superconducting cavity pressure U _c is constructed by the formula U _c =XV _f +YV _r , wherein X and Y are correction coefficients.

Further, determining whether the spark event occurs based on the cavity pressure _Vc of the superconducting cavity includes: calculating the change in the cavity pressure _Vc of the superconducting cavity within a set time, and if the absolute value of the change is greater than a set threshold value 0, it is considered that the spark event occurs.

Furthermore, when it is determined that a spark occurs, the spark type is determined based on the change in the superconducting cavity pressure _Uc before and after the spark event, including:

Calculate the change in the amplitude of the superconducting cavity pressure U _c before and after the spark event, recorded as ΔA. If ΔA is less than the threshold value 1, it is identified as a flash event, and it is believed that this event will not trigger a superconducting cavity fault.

If ΔA is greater than threshold 2, it is identified as an electrical quench event, which is considered to induce cavity quench, where threshold 2>threshold 1;

When ΔA is between threshold 1 and threshold 2, it is identified as a partial electrical quench, and it is believed that this event will trigger electromechanical oscillation but will not evolve into a cavity quench.

In a second aspect, the present invention provides an online identification system for the spark type of a radio frequency superconducting cavity, the system 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 to the input end of the solid-state power source, the output end of the solid-state power source is connected to 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 _Pf and the reflected signal _Pr online;

The signal extraction coupler is used to connect to the superconducting cavity to measure the superconducting cavity sampling signal P _t online;

The digital low-level system receives the superconducting cavity sampling signal _Pt , the cavity incident signal _Pf and the reflected signal _Pr to reconstruct the superconducting cavity pressure _Uc , and determines the spark type based on the change of the superconducting cavity pressure _Uc before and after the spark event.

Furthermore, the digital low-level system is provided with an FPGA, and the FPGA is provided with a digital signal processing module, a cavity pressure reconstruction module, an ignition detection module and an ignition type identification module;

The digital signal processing module is used to process the cavity sampling signal P _t , the cavity incident signal P _f and the reflected signal P _r P _t , P _f and P _r signals into the cavity pressure V _c , forward voltage V _f and reverse voltage V _r of the superconducting cavity;

A cavity pressure reconstruction module, used to reconstruct the superconducting cavity pressure U _c using the forward voltage V _f and the reverse voltage V _r ;

An ignition detection module is used to determine the occurrence of an ignition event and send a trigger signal;

The spark type identification module is used to identify the spark type according to the change of the superconducting cavity pressure _Uc before and after the spark event when receiving the trigger signal.

Furthermore, the spark type identification module identifies the spark type according to the change in the superconducting cavity pressure _Uc before and after the spark event, including:

Calculate the change in the amplitude of the superconducting cavity pressure U _c before and after the spark event, recorded as ΔA. If ΔA is less than the threshold value 1, it is identified as a flash event, and it is believed that this event will not trigger a superconducting cavity fault.

If ΔA is greater than threshold 2, it is identified as an electrical quench event, which is considered to induce cavity quench, where threshold 2>threshold 1;

When ΔA is between threshold 1 and threshold 2, it is identified as a partial electrical quench, and it is believed that this event will trigger electromechanical oscillation but will not evolve into a cavity quench.

Furthermore, the cavity pressure reconstruction module reconstructs the superconducting cavity pressure U _c by using the forward voltage V _f and the reverse voltage V _r through the formula U _c =XV _f +YV _r , wherein X and Y are correction coefficients.

Furthermore, a host computer is included, and the host computer is connected to the digital low-level system.

The present invention adopts the above technical solution, and has the following characteristics:

1. The present invention realizes online identification of superconducting cavity sparking types by constructing a real-time signal processing algorithm inside the FPGA, which provides a prerequisite for suppressing collective failures of superconducting cavities and lays a foundation for the long-term stable operation of radio frequency superconducting accelerators in the future.

2. Since the new generation of particle accelerator systems generally adopts FPGA-based digital low-level technical solutions, the identification algorithm of the present invention can be completely deployed inside the low-level system without adding additional hardware equipment.

3. The long-term statistical data of the spark types of the present invention provides data support for further clarifying the coupling relationship between the over-frequency of power outages and other physical quantities (for example, beam intensity, cavity pressure, etc.).

In summary, the present invention can be widely applied to high-power, high-current radio frequency superconducting accelerators.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG1 is a block diagram of a system for online identification of radio frequency superconducting cavity sparking types according to an embodiment of the present invention.

FIG. 2 shows the original cavity pressure signal V _c under three types of ignition events according to an embodiment of the present invention.

3 is an example of a partial electrical quench event triggering an electromechanical oscillation fault according to an embodiment of the present invention. After the partial electrical quench event occurs, the cavity resonant frequency (in the baseband case, that is, cavity detuning) oscillates, and the frequency of the oscillation signal coincides with the frequency of the cavity mechanical mode.

FIG4 is an example of an electrical quench event evolving into a thermal quench fault according to an embodiment of the present invention, wherein (a) is the cavity pressure signal U _c (after reconstruction) during the entire evolution process, and (b) is the forward and reverse voltage signals U _f and _Ur (after correction) during the evolution process. According to the attenuation curve of the U _c amplitude after cutting off RF, the Q _L of the cavity drops to 1/10 of the normal value, which meets the characteristics of thermal quench.

FIG5(a) is a block diagram of an algorithm for identifying superconducting cavity sparking types according to an embodiment of the present invention, and FIG5(b) is a specific implementation form of complex number multiplication inside an FPGA.

FIG6(a) shows the original cavity pressure signal _Vc and the reconstructed cavity pressure signal _Uc during a flash event according to an embodiment of the present invention, and FIG6(b) shows the original cavity pressure signal _Vc and the reconstructed cavity pressure signal _Uc during a partial quench event.

FIG. 7 shows the influence of the measurement channel delay on the accuracy of the reconstructed cavity pressure signal U _c according to an embodiment of the present invention.

DETAILED DESCRIPTION

It should be understood that the terms used in the text 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 in the text 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 in the text 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.

Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside", "outside", "inner side", "outside", "below", "above", etc. Such spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures.

Since both flash and electrical quench will form similar instantaneous strong interference in the _Pt signal, the digital low-level system cannot distinguish these two types of sparking events online, and therefore cannot formulate targeted solutions for electrical quench events. The present invention provides a method and system for online identification of the type of RF superconducting cavity sparking, including: obtaining the cavity pressure _Vc , forward voltage Vf and reverse voltage _Vr of the superconducting cavity based on the online measured cavity sampling signal _Pt , cavity incident signal _Pf and cavity reflection signal Pr; reconstructing the superconducting cavity pressure _Uc based on _{the forward voltage Vf and} reverse _{voltage Vr ;} determining whether the sparking event occurs based on the cavity pressure _Vc of the superconducting cavity; when determining the sparking time, the sparking type is determined based on the change in the superconducting cavity pressure _Uc before and after the sparking event. Therefore, the present invention is a prerequisite for studying the physical mechanism of superconducting cavity group failures, and also provides data support for clarifying the coupling relationship between sparking events and other physical quantities, and also lays a foundation for achieving long-term operation stability of superconducting cavities.

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.

Embodiment 1: As shown in FIG1 , the radio frequency superconducting cavity spark type online identification 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 and a signal extraction coupler 5 .

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 superconducting cavity through the input coupler 4, the directional coupler 3 measures the cavity incident signal _Pf and the reflected signal _Pr online, the signal extraction coupler 5 is used to connect the superconducting cavity to measure the superconducting cavity sampling signal _Pt online, the digital low-level system 1 receives the superconducting cavity sampling signal _Pt , the cavity incident signal _Pf and the reflected signal _Pr to reconstruct the superconducting cavity pressure _Uc , and the spark type is determined according to the change amount of the superconducting cavity pressure _Uc before and after the spark event.

In a preferred embodiment, a host computer 6 is further included. The host computer 6 is connected to the digital low-level system 1 and is used to set relevant parameters of the digital low-level system 1 .

In a preferred embodiment, a field programmable gate array (FPGA) is provided in the digital low-level system 1, and a digital signal processing module, a cavity pressure reconstruction module, an ignition detection module and an ignition type identification module are provided in the FPGA.

The digital signal processing module obtains the cavity pressure _Vc , forward voltage _{Vf and reverse voltage Vr of the} corresponding superconducting cavity through the superconducting cavity sampling signal _{Pt ,} cavity incident signal _Pf and reflected _{signal Pr} .

The cavity pressure reconstruction module uses the forward voltage _Vf and the reverse voltage _Vr to reconstruct the superconducting cavity pressure _Uc through the formula _Uc = _XVf + _YVr , where X and Y are correction coefficients.

The ignition detection module is used to determine whether an ignition event occurs and send a trigger signal when an ignition occurs.

The spark type identification module calculates the change in the amplitude and phase of _Uc before and after the spark event when the spark occurs, which are recorded as ΔA and Δθ respectively. If the above ΔA is less than threshold 1, it is identified as a flash event. If ΔA is greater than threshold 2 (threshold 2> threshold 1), it is identified as an electrical quench event. When ΔA is between threshold 1 and threshold 2, it is identified as a partial electrical quench.

Embodiment 2: The method for online identification of the type of ignition of a radio frequency superconducting cavity provided by the present invention comprises:

S1. The digital low-level system 1 measures the cavity sampling signal _Pt , the cavity incident signal _Pf and the cavity reflection signal _Pr of the superconducting cavity online, and processes them to obtain the cavity pressure _Vc , the forward voltage _Vf and the reverse voltage _Vr of the superconducting cavity.

Specifically, the cavity sampling signal _Pt , the cavity incident signal _Pf and the cavity reflection signal _Pr are down-converted into intermediate frequency signals, and three sets of digital baseband signals are obtained by sampling the intermediate frequency signals at four times the frequency (i.e., the sampling frequency is 4 times the signal frequency), namely: the cavity pressure _Vc , the forward voltage _Vf and the reverse voltage _Vr of the superconducting cavity. For example, generally speaking, _Pt represents a radio frequency signal, such as a 162.5MHz radio frequency signal, and _Vc represents a digital baseband signal, that is, there is no radio frequency component, which is removed by down-conversion.

In this embodiment, the cavity sampling signal _Pt is connected to the digital low-level system 1 through the superconducting cavity signal extraction coupler 5 for extraction. The _Pf and _Pr signals are connected to the digital low-level system 1 through the directional coupler 3 for acquisition.

Further, unless otherwise specified, the voltages involved in this embodiment (such as V _c , V _f , V _r, etc.) are all in complex form. They can be expressed in the form of amplitude and phase, for example: V=|V|e ^j∠V , where |V| is the amplitude (or called modulus) and ∠V is the phase (or called angle); they can also be expressed in the form of real part plus imaginary part, for example: V=V _I +jV _Q , where V _I is the real part and V _Q is the imaginary part.

S2. Based on the forward voltage V _f and the reverse voltage V _r , the superconducting cavity pressure U _c is reconstructed.

In this embodiment, a real-time signal processing algorithm is designed inside the field programmable gate array (FPGA) chip of the digital low-level system 1, and the forward voltage _Vf and the reverse voltage _Vr are measured to reconstruct the superconducting cavity pressure _Uc through the formula _Uc = _XVf + _YVr , where the correction coefficients X and Y are both complex numbers. Since the measurement of _Vf and _Vr is independent of the signal extraction coupler, the instantaneous strong interference signal will not be mixed into the reconstructed cavity pressure _Uc .

Furthermore, the complex coefficients X and Y may be solved by using existing technologies, and the coefficients X and Y may also be expressed in the form of amplitude and phase or real part plus imaginary part.

S3: When it is determined that an ignition event occurs, a trigger signal is issued

In this embodiment, the FPGA chip is provided with an ignition detection module. When the ignition detection module detects transient strong interference from the original V _c signal (for example, the interference duration is 1-10 microseconds, and the interference intensity exceeds 1/3 of the steady-state signal amplitude), it determines that an ignition event occurs and sends a trigger signal to the ignition type identification module.

Furthermore, the ignition detection module calculates the change in the amplitude of V _c within a set time. If the absolute value of the change is greater than the set threshold 0, it is considered that an ignition event has occurred and a trigger signal Trig1 is sent. The threshold 0 is set by the host computer and can usually be selected as 20 to 50 times the root mean square value of the random noise of the analog-to-digital converter (ADC) to avoid misjudgment of ignition events.

S4. The spark type identification module of the FPGA chip calculates the change in the amplitude and phase of _Uc before and after the spark event, and identifies the spark type based on the change in the superconducting cavity pressure _Uc before and after the spark event.

In this embodiment, the changes in the amplitude and phase of U _c before and after the ignition event are calculated and recorded as ΔA and Δθ respectively, where ΔA is used to distinguish the ignition type, and Δθ is mainly used to further determine the phase information of the dark current in the electrical quench event. The process of distinguishing the ignition type is as follows:

If ΔA is less than the threshold value 1, it is identified as a flash event, that is, it is considered that the event will not trigger a superconducting cavity fault.

If ΔA is greater than threshold 2 (threshold 2>threshold 1), it is identified as an electrical quench event, which is generally considered to be likely to induce a cavity quench. When ΔA is between threshold 1 and threshold 2, it is identified as a partial electrical quench, which is generally considered to trigger electromechanical oscillations but will not evolve into a cavity quench.

Furthermore, both threshold 1 and threshold 2 can be set by sending parameters from a host computer connected to the digital low-level system.

In this embodiment, the amplitude, phase change ΔA and Δθ obtained by online measurement may also be transmitted back to the host computer 6 .

The application of the method for online identification of the type of sparking in a radio frequency superconducting cavity of the present invention is described in detail below through specific embodiments.

The solid-state power source 2 used in this embodiment is of model KFPA-162-1-1, each power source includes 24 inserts, and the saturated output power of a single insert is about 1.4kW; the superconducting cavity is a half-wavelength superconducting cavity (HWR010, whose relativistic speed is 0.1), the resonant frequency of the cavity is 162.5MHz, and the loaded quality factor ( _QL ) is about 5× ¹⁰⁵ ; the data sampling rate of the digital low-level system 1 is 100MHz, and the FPGA chip model is ZYNQ7100; the directional coupler 3 model is EXIR MDIR-2077-33-A, and the directivity is >40dB; the antenna quality factor _Qe of the signal extraction coupler 5 is about ¹⁰⁷ .

Based on the above parameter settings, the online identification method of the radio frequency superconducting cavity sparking type of this embodiment includes:

1. Measurement of voltage signal.

The measurement stage of the cavity pressure V _c , forward voltage V _f and reverse voltage V _r of the superconducting cavity. The measurement principle diagram is shown in Figure 1. The output of the digital low-level system 1 is connected to the input end of the solid-state power source 2, and the output of the solid-state power source 2 is connected to 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. The measurement process is:

1. The superconducting cavity sampling signal P _t is measured online using the signal extraction coupler 5; the cavity incident signal P _f and the reflected signal P _r are measured online using the directional coupler 3, wherein P _t , P _f and P _r are all 162.5 MHz radio frequency signals.

2. After the above radio frequency signals are down-converted and digitized in sequence, the digital low-level system 1 obtains the digitized original baseband voltage signals, namely the cavity pressure V _c , the forward voltage V _f and the reverse voltage V _r .

As shown in Figure 2, when flash, partial quench and quench occur, instantaneous strong interference (usually lasting 7-10 microseconds) is mixed into the original cavity pressure signal. Partial quench events may further trigger the electromechanical coupling oscillation of the cavity, which is specifically manifested as the oscillating cavity resonance frequency as shown in Figure 3. The electrical quench event may further evolve into a thermal quench, which is specifically manifested as a decrease in the cavity Q _L. After cutting off RF, the time constant of the cavity field decay curve decreases, as shown in Figure 4.

2. Calibration of baseband voltage signal and reconstruction of cavity pressure signal.

As shown in FIG5 , in this stage, according to the V _f and V _r obtained by the above measurements, a real-time signal processing algorithm is designed inside the digital low-level system 1 to reconstruct the cavity pressure U _c , including:

1. Using the measured baseband voltage signals V _f and V _r , the calibrated forward voltage U _f and reverse voltage U _r are solved by complex multiplication U _f = XV _f and U _r = YV _r . Among them, the calibration coefficients X, Y and signals U, V are all in complex form. The above complex number X can be equivalent to the 2×2 matrix in the following formula (1). The specific implementation form of complex multiplication in FPGA is shown in Figure 5(b).

Where, _UfI and _UfQ are the real and imaginary parts of _Uf , _VfI and _VfQ are the real and imaginary parts of _Vf , _Xi and _XQ are the real and imaginary parts of the calibration coefficient X, _UrI and _UrQ are the real and imaginary parts of _Ur , _VrI and _VrQ are the real and imaginary parts of _Vr , and _Yi and _YQ are the real and imaginary parts of the calibration coefficient Y.

2. Reconstruct the cavity pressure _Uc using the corrected _Uf and _Ur ( _Uc = _Uf + _Ur , as shown in Figure 5(a)). When there is no ignition event, _Uc is completely consistent with _Vc . When there is an ignition event, since _Vf and _Vr are measured by the directional coupler (not affected by the cavity ignition event), the reconstructed _Uc no longer contains the transient strong interference in the original _Vc signal, as shown in Figure 6.

3. Considering the delay in the measurement channels of _Pf and _Pr signals, since the measurement devices (such as cable length) of the above two channels cannot be completely consistent, there are differences in their channel delays and will affect the measurement accuracy of _Uc . Therefore, before reconstructing the cavity pressure signal, the channel delay needs to be further calibrated to ensure that the delay error between _Uf and _Ur after correction is less than one sampling period (10 nanoseconds).

Specifically, in FPGA, the delay link can be implemented by a first-in first-out memory (FIFO) module. The U _c signal before and after the channel delay calibration is shown in FIG7 .

3. The triggering of the ignition event.

As shown in Figure 5(a), an ignition detection module is constructed in the FPGA chip to calculate the change in the amplitude of V _c within 80 nanoseconds. If the absolute value of the change is greater than the threshold 0, it is considered that an ignition event has occurred and a trigger signal Trig1 is sent. Among them, the threshold 0 is sent by the host computer and can usually be selected as 20 to 50 times the root mean square value of the random noise of the analog-to-digital converter (ADC) to avoid misjudgment of the ignition event.

4. Online identification of ignition type.

After receiving the trigger signal, the change in the reconstructed chamber pressure before and after the ignition event is calculated, and the ignition type is determined based on the change, including:

1. Calculate the changes ΔA and Δθ of the amplitude U _cA and phase U _cθ of the reconstructed cavity pressure during the duration of the ignition event (7-10 microseconds), and upload the above information to the host computer through the data acquisition system.

2. If the above ΔA<threshold 1, the ignition event type is identified as a flash event; if the above ΔA>threshold 2 (threshold 2>threshold 1), the ignition event type is identified as an electrical quench event, which usually further induces cavity quench, as shown in Figure 4; if threshold 1<ΔA<threshold 2, the ignition event type is identified as a partial electrical quench, which usually triggers electromechanical oscillation, but does not evolve into a cavity quench, as shown in Figure 3. Among them, threshold 1 and threshold 2 can both be set by the host computer. Usually, threshold 1 can be selected as 1/100 of the steady-state cavity pressure amplitude value ( _UcA0 ) when no ignition event occurs, and threshold 2 can be selected as 1/3 to 2/3 of _UcA0 .

3. Online record the long-term ignition type and the above-mentioned ΔA and Δθ data, and analyze the coupling relationship between the ignition type and other related physical quantities (such as cavity pressure, cavity detuning, beam current intensity and power, etc.).

Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In the description of this specification, the reference term "a preferred embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

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 (10)

1. A method for online identification of radio frequency superconducting cavity sparking type, characterized by comprising: Based on the online measured cavity sampling signal _Pt , cavity incident signal _Pf and cavity reflection signal _Pr, the cavity pressure _Vc , forward voltage _Vf and reverse voltage _Vr of the superconducting cavity are obtained; Based on the forward voltage V _f and the reverse voltage V _r , the superconducting cavity pressure U _c is reconstructed; Determine whether the spark event occurs based on the cavity pressure _Vc of the superconducting cavity; When it is determined that sparking occurs, the sparking type is determined based on the change in the superconducting cavity pressure _Uc before and after the sparking event. 2. The method for online identification of the RF superconducting cavity spark type according to claim 1 is characterized in that the cavity pressure V _c , forward voltage V _f and reverse voltage V _r of the superconducting cavity are obtained based on the online measured cavity sampling signal P _t , cavity incident signal P _f and cavity reflection signal P _r , comprising: Down-converting the cavity sampling signal _Pt , the cavity incident signal _Pf and the cavity reflected signal _Pr into intermediate frequency signals; By performing quadruple frequency sampling on the intermediate frequency signal, three groups of digital baseband signals are obtained respectively, namely, the cavity pressure V _c , the forward voltage V _f and the reverse voltage V _r of the superconducting cavity. 3. The online identification method of radio frequency superconducting cavity sparking type according to claim 1 is characterized in that the superconducting cavity pressure U _c is constructed by the formula U _c =XV _f +YV _r , wherein X and Y are correction coefficients. 4. The online identification method of the radio frequency superconducting cavity spark type according to claim 1 is characterized in that determining whether a spark event occurs based on the cavity pressure _Vc of the superconducting cavity comprises: calculating the change in the amplitude of the cavity pressure _Vc of the superconducting cavity within a set time, and if the absolute value of the change is greater than a set threshold value of 0, it is considered that a spark event occurs. 5. The method for online identification of RF superconducting cavity spark type according to claim 1 is characterized in that, when it is determined that spark occurs, the spark type is identified based on the change in superconducting cavity pressure _Uc before and after the spark event, including: Calculate the change in the amplitude of the superconducting cavity pressure U _c before and after the spark event, recorded as ΔA. If ΔA is less than the threshold value 1, it is identified as a flash event, and it is believed that this event will not trigger a superconducting cavity fault. If ΔA is greater than threshold 2, it is identified as an electrical quench event, which is considered to induce cavity quench, where threshold 2>threshold 1; When ΔA is between threshold 1 and threshold 2, it is identified as a partial electrical quench, and it is believed that this event will trigger electromechanical oscillation but will not evolve into a cavity quench. 6. An online identification system for the spark type of a radio frequency superconducting cavity, characterized in that the system comprises 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 to the input end of the solid-state power source, the output end of the solid-state power source is connected to 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 _Pf and the reflected signal _Pr online; The signal extraction coupler is used to connect to the superconducting cavity to measure the superconducting cavity sampling signal P _t online; The digital low-level system receives the superconducting cavity sampling signal _Pt , the cavity incident signal _Pf and the reflected signal _Pr to reconstruct the superconducting cavity pressure _Uc , and determines the spark type based on the change of the superconducting cavity pressure _Uc before and after the spark event. 7. The radio frequency superconducting cavity spark type online identification system according to claim 6 is characterized in that the digital low-level system is provided with an FPGA, and the FPGA is provided with a digital signal processing module, a cavity pressure reconstruction module, a spark detection module and a spark type identification module; The digital signal processing module is used to process the cavity sampling signal P _t , the cavity incident signal P _f and the reflected signal P _r P _t , P _f and P _r signals into the cavity pressure V _c , forward voltage V _f and reverse voltage V _r of the superconducting cavity; A cavity pressure reconstruction module, used to reconstruct the superconducting cavity pressure U _c using the forward voltage V _f and the reverse voltage V _r ; An ignition detection module is used to determine the occurrence of an ignition event and send a trigger signal; The spark type identification module is used to identify the spark type according to the change of the superconducting cavity pressure _Uc before and after the spark event when receiving the trigger signal. 8. The radio frequency superconducting cavity spark type online identification system according to claim 7 is characterized in that the spark type identification module determines the spark type according to the change in the superconducting cavity pressure _Uc before and after the spark event, comprising: Calculate the change in the amplitude of the superconducting cavity pressure U _c before and after the spark event, recorded as ΔA. If ΔA is less than the threshold value 1, it is identified as a flash event, and it is believed that this event will not trigger a superconducting cavity fault. If ΔA is greater than threshold 2, it is identified as an electrical quench event, which is considered to induce cavity quench, where threshold 2>threshold 1; When ΔA is between threshold 1 and threshold 2, it is identified as a partial electrical quench, and it is believed that this event will trigger electromechanical oscillation but will not evolve into a cavity quench. 9. The radio frequency superconducting cavity spark type online identification system according to claim 7 is characterized in that the cavity pressure reconstruction module uses the forward voltage _Vf and the reverse voltage _Vr to reconstruct the superconducting cavity pressure _Uc through the formula _Uc = _XVf + _YVr , wherein X and Y are correction coefficients. 10. The radio frequency superconducting cavity spark type online identification system according to claim 6, characterized in that it also includes a host computer, and the host computer is connected to the digital low-level system.

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