A high-frequency cavity firing safety interlock protection method and low-level control system

Abstract

The application discloses a high-frequency cavity firing safety interlocking protection method and system, and the method comprises the following steps: 1) two FIFOs are arranged in a low-level control system, the incident power, the reflected power and the cavity field power of a high-frequency cavity are collected in real time, and the signals are stored in the two FIFOs, wherein the signals stored in one of the FIFOs are the signals of T time before the current time, and the signals stored in the other FIFO are the signals of 2T time before the current time; 2) a firing event monitoring unit collects the signals of the high-frequency cavity at the current time, and compares the signals with the signals collected at the T time and the 2T time before the current time, and if the signals meet the set conditions, a firing event trigger signal is generated; 3) when the number of firing event trigger signals received by a firing event interlocking processing unit within a set time period is less than N times, the forward power excitation signal is temporarily cut off and then quickly restored; and when the number of firing event trigger signals received by the firing event interlocking processing unit within the set time period is more than N times, the forward power excitation signal is completely cut off.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of accelerator physics, and particularly relates to a high-frequency cavity arcing safety interlock protection method and a low-level control system, which is used for timely monitoring the arcing phenomenon of a cavity and protecting the normal-temperature high-frequency cavity device to prevent the performance of the high-frequency cavity from being degraded or damaged due to arcing. BACKGROUND

[0002] A newly-made high-frequency copper cavity without high-power seasoning or a long-stored copper cavity is prone to arcing when power is fed into the high-frequency cavity. Only after the power seasoning process from low power to high power and from pulse to continuous wave, the probability of arcing of the copper cavity is greatly reduced.

[0003] Arcing of the cavity may cause the vacuum in the cavity to rise, the cavity frequency to be out of tune, the copper cavity window and the surface of the copper cavity to be damaged, the performance of the cavity to be affected, and even the copper cavity to be damaged. Therefore, it is crucial to monitor the arcing of the cavity and take timely and effective suppression measures.

[0004] In order to prevent arcing from damaging the high-frequency cavity, a corresponding suppression method needs to be taken to protect the cavity. An arc probe can be usually installed on the cavity, which can detect whether arcing occurs in the region near the arc probe in the cavity. When the arc detector detects arcing, an interlock signal is generated to timely turn off the main RF switch of the high-frequency system to cut off the forward power. This method has certain limitations:

[0005] Firstly, the detection region of the arc probe is limited and cannot completely cover the inner surface of the cavity, and the arc probe can only be installed in the region prone to arcing.

[0006] Secondly, the arc detector has a certain sensitivity to the arc, and slight arcing may not be detected.

[0007] Thirdly, after arcing is detected, the forward power is directly turned off, which causes the water temperature to rapidly drop. Since the frequency of the normal-temperature cavity is greatly affected by the water temperature, when the power is added again after the cavity is restarted, the cavity frequency is seriously out of tune due to the change of the water temperature, which further causes a long time to be required for restarting, and thus the work efficiency is greatly reduced. SUMMARY

[0008] In view of the deficiencies of the arc detector, the present application provides a high-frequency cavity arcing safety interlock protection method and a low-level control system. The high-frequency low-level system judges whether arcing occurs in the cavity by monitoring the changes of the incident power, the reflected power and the cavity field power in real time. When the arcing judgment condition is met, the low-level control system generates an arcing processing logic, turns off the low-level excitation for a certain time or completely turns off the low-level excitation, and sends an arcing interlock signal to the high-frequency safety interlock device to cut off the main RF switch of the high-frequency system.

[0009] The high-frequency cavity firing safety interlock protection method of the present application is divided into two parts according to functions: firing event monitoring and firing event interlock processing. The firing event monitoring function is responsible for real-time monitoring of the related radio frequency signals of the high-frequency cavity, and when these signals meet the set conditions, a firing event trigger signal is generated, and the firing event interlock processing function is responsible for taking corresponding action responses after receiving the firing event trigger signal to avoid serious damage to the high-frequency cavity.

[0010] 1) Firing event monitoring function:

[0011] During the high-power seasoning of the high-frequency cavity, under normal circumstances, the incident power is maintained at a certain power value to establish a certain cavity field in the cavity. In order to more effectively season the cavity, the cavity is in a resonant state, and the reflected power at this time is maintained at a small power value, which is much lower than the incident power. If an arc firing event occurs suddenly in the cavity at this time, the cavity will be detuned, and if the forward power is continued to be maintained, the reflected power will rapidly increase due to the detuning of the cavity, and the high-frequency cavity pressure will begin to decay. According to the above analysis, it can be determined that the incident power, reflected power and cavity field power signals satisfy certain relationship conditions before and after arc firing. Therefore, by setting the corresponding relationship conditions, it can be determined whether arc firing has occurred at present.

[0012] The high-frequency cavity firing safety interlock protection system monitors the incident power, reflected power and cavity field power signals in real time, and then sends them into 3us and 6us delay FIFOs, respectively. The incident power, reflected power and cavity field power at the current time are Pf, Pr and Pt, respectively. The incident power, reflected power and cavity field power 3us before are Pf_delay1, Pr_delay1 and Pt_delay1, respectively. The incident power, reflected power and cavity field power 6us before are Pf_delay2, Pr_delay2 and Pt_delay2, respectively. When these power quantities simultaneously satisfy certain relationships, the low-level control system determines that an arc firing event has occurred, and arc firing interlock protection processing is required.

[0013] The cavity firing protection monitoring judgment conditions are as follows:

[0014] 1. After the cavity arc firing, the reflected power will rapidly increase, so the current reflected power Pr will be more than k1 times of the reflected power 6us before, i.e. Pr>k1*Pr_delay2, which is a necessary condition for cavity arc firing protection, wherein k1 is greater than 5.

[0015] 2. After arc, the reflected power will increase rapidly, so the reflected power Pr_delay1 before 3us is k1 times of the reflected power Pr_delay2 before 6us, i.e. Pr_delay1>k1*Pr_delay2 is a necessary condition for arc protection.

[0016] 3. After arc, the high frequency cavity will be detuned, the forward power Pf cannot be sent into the high frequency cavity to build field, which results in the cavity field power Pt decaying by e index, the decay coefficient depends on the cavity quality factor of the high frequency cavity. So the current cavity field power Pt is less than the cavity field power Pt_delay1 before arc, i.e. Pt*10<k2*Pt_delay1 is a necessary condition for arc protection, where k2 is less than 10.

[0017] 4. After arc, if the forward power Pf decreases a lot compared with the forward power Pf_delay1 before 3us, no safety protection is needed, otherwise safety protection is needed, i.e. Pf*10>k3*Pf_delay1 is a necessary condition for arc protection, where k3 is less than 10.

[0018] 5. The cavity forward power Pf needs to exceed a certain threshold H1 to need safety protection, i.e. no safety protection is needed in the case of small or no forward power.

[0019] 6. The cavity field power Pt needs to exceed a certain threshold H2 to need safety protection, i.e. no safety protection is needed in the case of small or no electric field in the cavity.

[0020] When the above 6 conditions are met at the same time, i.e. arc phenomenon occurs, safety protection is needed; otherwise, if any one of the conditions is not met, no safety protection is needed. When arc phenomenon is monitored, the system will generate an arc event trigger signal, which will be sent to the arc event interlock processing part for subsequent safety interlock protection processing.

[0021] 2) Arc event interlock processing function:

[0022] When arc sparking event is monitored, quick response is made, that is, high frequency cavity is well protected from damage, and high frequency cavity high power conditioning efficiency is ensured. From the perspective of protecting high frequency cavity, when arc sparking event occurs, triggering safety interlock and cutting off forward power is the best response. On the other hand, due to the influence of temperature effect on high frequency cavity, once the interlock cuts off power for a long time, the cavity will cool down quickly, resulting in that the cavity frequency detuning is far beyond the bandwidth range, so that a long time is needed for cavity tuning and normal field building when power is started to be added, which will greatly reduce the efficiency of high power conditioning. In view of this, a specific arc sparking event interlock processing mechanism is formed, when the number of received sparking event trigger signals is within 3 times within a certain time period, the low-level control system only cuts off the forward power excitation signal for a short time, such as 100us, and then quickly recovers, since the cutting-off power time is very short, the cavity temperature effect has not yet responded, so that the sparking phenomenon is eliminated, and the state of the high frequency cavity can also be quickly recovered; only when more than 4 times of sparking event trigger signals are received, the safety interlock is triggered, so that the forward power is completely cut off.

[0023] The cavity sparking safety protection algorithm is realized based on the FPGA firmware algorithm of the low-level control system.

[0024] The two FIFO delay times can be adjusted according to the characteristics of the high frequency cavity.

[0025] The k1, k2 and k3 parameters of the cavity sparking protection monitoring and judgment condition can be adjusted online.

[0026] The power cut-off times after the first three cavity sparkings can be adjusted online respectively.

[0027] The first three cavity sparkings do not perform interlock latching, so as to prevent the cavity from cooling down and detuning.

[0028] The fourth sparking event triggers the safety interlock, and the interlock latching is performed, and the interlock state can be released only by resetting the low-level control system.

[0029] The technical scheme of the present application is:

[0030] A high frequency cavity sparking safety interlock protection method, comprising the following steps:

[0031] 1) Two FIFOs are set in the low-level control system, the incident power, the reflected power and the cavity field power of the high frequency cavity are collected in real time at the sampling clock frequency of the low-level control system, and are stored in the two FIFOs, wherein the signals stored in one FIFO are the signals before T time at the current time, and the signals stored in the other FIFO are the signals before 2T time at the current time;

[0032] 2) The fire event monitoring unit collects the incident power Pf, the reflected power Pr and the cavity field power Pt at the current time, and compares them with the incident power Pf_delay1, the reflected power Pr_delay1 and the cavity field power Pt_delay1 collected at the time T before the current time, and the incident power Pf_delay2, the reflected power Pr_delay2 and the cavity field power Pt_delay2 collected at the time 2T before the current time. If the set cavity fire protection monitoring judgment condition is met, a fire event trigger signal is generated and sent to the fire event interlocking processing unit;

[0033] 3) When the number of fire event trigger signals received by the fire event interlocking processing unit within the set time period is less than N, the forward power excitation signal is temporarily cut off and then quickly restored to eliminate the fire phenomenon and quickly restore the state of the high-frequency cavity. When the number of fire event trigger signals received by the fire event interlocking processing unit within the set time period is more than N, the forward power excitation signal is completely cut off.

[0034] Further, the set cavity fire protection monitoring judgment condition includes: a) Pr>k1*Pr_delay2; b) Pr_delay1>k1*Pr_delay2; c) Pt*10<k2*Pt_delay1; d) Pf*10>k3*Pf_delay1; e) Pf exceeds the set threshold H1; f) Pt exceeds the set threshold H2; wherein k1 is greater than 5, k2 is less than 10, and k3 is less than 10.

[0035] Further, the set thresholds H1 and H2 need to be set according to the specific physical performance parameters of the high-frequency cavity.

[0036] Further, the interlocking processing method of the fire event interlocking processing unit is: when the i-th fire event trigger signal is received within the set time period and the number of times is less than N, the duration of cutting off the forward power excitation signal is T i When the i+1-th fire event trigger signal is received within the set time period and the number of times is less than N, the duration of cutting off the forward power excitation signal is T i+1 ; wherein T i+1 is greater than T i .

[0037] Further, T=3us; N=3.

[0038] A low-level control system, characterized in that it comprises a fire event monitoring unit and a fire event interlocking processing unit.

[0039] The spark event monitoring unit is used for collecting the incident power, the reflected power and the cavity field power of the high-frequency cavity in real time with low level control system sampling clock frequency, and storing them into two FIFOs, wherein the signals stored in one of the FIFOs are the signals of T time before the current time, and the signals stored in the other FIFO are the signals of 2T time before the current time; and the incident power Pf, the reflected power Pr and the cavity field power Pt of the high-frequency cavity at the current time are compared with the signals in the two FIFOs, if the set cavity spark protection monitoring judgment condition is met, a spark event trigger signal is generated and sent to the spark event interlock processing unit;

[0040] The spark event interlock processing unit is used for temporarily cutting off the forward power excitation signal and then quickly restoring the forward power excitation signal when the number of received spark event trigger signals within a set time period is not more than N times, so as to eliminate the spark phenomenon and quickly restore the state of the high-frequency cavity; and the forward power excitation signal is completely cut off when the number of received spark event trigger signals within a set time period is more than N times.

[0041] The advantages of the present application are as follows:

[0042] 1) The arc detector can only monitor the arc spark for safety protection in a local area, but the present method can monitor the arc spark in any place in the cavity, thereby improving the safety.

[0043] 2) The sensitivity of the arc detector is not easy to adjust, but the present method can adjust the arc spark monitoring condition on line, and set different arc spark monitoring conditions for different cavity states.

[0044] 3) The arc detector will directly cut off the power after monitoring the arc spark, but the present method will cut off the power for different lengths of time or completely cut off the power according to the different arc spark states.

[0045] 4) Compared with the arc detector spark protection, the present method has higher working efficiency.

[0046] 5) The arc spark monitoring condition can be adjusted on line according to different cavity states. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 It is a cavity spark safety protection algorithm framework.

[0048] Figure 2 It is a timing diagram of the spark event interlock processing function. DETAILED DESCRIPTION

[0049] The present application will be further described in detail below with reference to the drawings, and the examples are only used to explain the present application, and are not used to limit the scope of the present application.

[0050] The present application comprises two parts as follows:

[0051] 1. Program development

[0052] The digital signal processing board based on low-level control system develops cavity arcing safety protection firmware algorithm. The cavity arcing safety protection algorithm block diagram is shown in Figure 1

[0053] Cavity arcing monitoring function part:

[0054] The system collects cavity incident power, reflected power, cavity field back signal, and obtains I / Q quantities of the signals, which are I_pf, Q_pf, I_pr, Q_pr, I_pt and Q_pt respectively. The calculation method is P = I*I+Q*Q, and the power amplitude is obtained by operation, which is Pf, Pr and Pt respectively.

[0055] The obtained power quantities Pf, Pr and Pt are sent to the FIFO with a delay of 3us to obtain Pf_delay1, Pr_delay1 and Pt_delay1.

[0056] The obtained power quantities Pf, Pr and Pt are sent to the FIFO with a delay of 6us to obtain Pf_delay2, Pr_delay2 and Pt_delay2.

[0057] When the measured power quantity meets the conditions of (1.1)-(1.6), it indicates that arcing phenomenon occurs, and the arcing event trigger signal Arc is output. Wherein k1, k2, k3, H1 and H2 are constant parameters, which can be set through the upper OPI interface of the low-level system. H1 and H2 are the threshold values of forward power Pf and cavity field power Pt respectively, and the set values can be set according to the specific physical characteristics of the high-frequency cavity.

[0058]

[0059] Arcing event interlock processing function part:

[0060] The timing diagram of arcing event interlock processing function is shown in Figure 2 ​The rising edge of the arc ignition signal (ignition event trigger signal) triggers the generated fixed-length pulse ignition trigger signal Arc_trig. When the Arc_trig signal is detected to be high, the count signal Count is incremented by 1, and the initial state of the Count signal is 0. When the count signal Count is zero, if the rising edge of the ignition event trigger signal is monitored at this time, the cycle signal Cycle is set to high, and maintained for a time length of Tc. When the Cycle signal becomes low, the count signal Count is reset to zero, and the arc ignition counting is restarted. The Shut is a power-off signal. During the period when the Cycle is high, when the first ignition event occurs, the Count signal is set to 1, the Shut signal is set to 0, and the time length is T1. During the time length T1, the forward power is cut off, and then the forward power is immediately restored. By analogy, the second cut-off time length is T2, and the third cut-off time length is T3. When the fourth ignition event occurs, the ignition interlock signal Interlock is triggered, causing safety interlock protection, and the low-level excitation is directly cut off. Only after the high-frequency system reset is reset, the normal state can be restored. The cut-off time lengths T1, T2, and T3 are register set values, which can be adjusted and set in real time through the upper OPI.

[0061] 2. Hardware and software implementation

[0062] After the cavity ignition safety protection algorithm is integrated into the firmware algorithm of the low-level control system, the low-level system is restarted, the low-level system is connected to the high-frequency cavity incident power, the reflected power, the cavity field power signal, and the arc ignition safety interlock output signal is connected to the low-level interlock cabinet.

[0063] The adjustable parameters K1, K2, K3, T1, T2, and T3 corresponding to the PV quantities in the database db file of the low-level IOC application are added, the addresses correspond to the register addresses of the corresponding parameters in the FPGA algorithm, and the PV control is added on the upper OPI to realize the setting of the K1, K2, K3, T1, T2, and T3 parameters.

[0064] Taking the low-level system as the control main body, the high-power aging and ignition safety interlock protection of the high-frequency cavity are realized, and the K1, K2, K3, T1, T2, and T3 are adjusted online to set appropriate high-frequency cavity ignition safety interlock protection algorithm parameters.

[0065] Although specific embodiments of the present application are disclosed for purposes of illustration and description, it will be understood by those skilled in the art that various alternatives, modifications, and equivalents can be used. It should be especially noted that the present application is not limited to the best embodiments disclosed, but is intended to cover any alternatives, modifications, and equivalents falling within the spirit and scope of the present application as defined by the claims.

Claims

1. A high-frequency cavity firing safety interlock protection method, comprising the steps of: 1) setting two FIFOs in a low-level control system, collecting the incident power, reflected power and cavity field power of the high-frequency cavity in real time at the sampling clock frequency of the low-level control system, and storing them in the two FIFOs, wherein the signals stored in one of the FIFOs are signals T time ago, and the signals stored in the other of the FIFOs are signals 2T time ago; 2) a firing event monitoring unit collecting the incident power Pf, reflected power Pr and cavity field power Pt of the high-frequency cavity at the current time, and comparing them with the incident power Pf_delay1, reflected power Pr_delay1 and cavity field power Pt_delay1 collected T time ago and the incident power Pf_delay2, reflected power Pr_delay2 and cavity field power Pt_delay2 collected 2T time ago, and if the set cavity firing protection monitoring judgment condition is met, a firing event trigger signal is generated and sent to a firing event interlock processing unit; 3) when the number of firing event trigger signals received by the firing event interlock processing unit within a set time period is not more than N, the firing event interlock processing unit temporarily cuts off the forward power excitation signal and then quickly restores the forward power excitation signal, so as to eliminate the firing phenomenon and quickly restore the state of the high-frequency cavity; when the number of firing event trigger signals received by the firing event interlock processing unit within a set time period is more than N, the firing event interlock processing unit completely cuts off the forward power excitation signal.

2. The method of claim 1, wherein, The set cavity firing protection monitoring judgment condition includes: a) Pr > k1*Pr_delay2; b) Pr_delay1 > k1*Pr_delay2; c) Pt*10 < k2*Pt_delay1; d) Pf*10 > k3*Pf_delay1; e) Pf exceeds a set threshold H1; f) Pt exceeds a set threshold H2; wherein k1 is greater than 5, k2 is less than 10, and k3 is less than 10. The set thresholds H1 and H2 need to be set according to the specific physical performance parameters of the high-frequency cavity.

3. The method of claim 2, wherein, T = 3us; N = 3.

4. The method according to claim 1 or 2 or 3, characterized in that, The interlocking processing method of the striking event interlocking processing unit is: when the i-th striking event trigger signal is received within a set time period and the number of times does not exceed N, the time length of cutting off the forward power excitation signal is T i When the i+1-th striking event trigger signal is received within a set time period and the number of times does not exceed N, the time length of cutting off the forward power excitation signal is T i+1 ; wherein T i+1 is greater than T i .

5. The method according to claim 1 or 2 or 3, characterized in that, including a firing event monitoring unit and a firing event interlock processing unit; 6. A low-level control system, characterized by The firing event monitoring unit is configured to collect the incident power, reflected power and cavity field power of the high-frequency cavity in real time at the sampling clock frequency of the low-level control system, and store them in the two FIFOs, wherein the signals stored in one of the FIFOs are signals T time ago, and the signals stored in the other of the FIFOs are signals 2T time ago; and compare the incident power Pf, reflected power Pr and cavity field power Pt of the high-frequency cavity at the current time with the signals in the two FIFOs, and if the set cavity firing protection monitoring judgment condition is met, a firing event trigger signal is generated and sent to the firing event interlock processing unit. ​ The spark event interlocking processing unit is used for cutting off the forward power excitation signal for a short time and then quickly restoring the forward power excitation signal when the number of received spark event trigger signals within a set time period is not more than N, so as to eliminate the spark phenomenon and quickly restore the state of the high-frequency cavity; and the forward power excitation signal is completely cut off when the number of received spark event trigger signals within the set time period is more than N.

7. The system of claim 6, wherein, The set cavity spark protection monitoring judgment conditions include: a) Pr>k1*Pr_delay2; b) Pr_delay1>k1*Pr_delay2; c) Pt*10<k2*Pt_delay1; d) Pf*10>k3*Pf_delay1; e) Pf exceeds a set threshold H1; f) Pt exceeds a set threshold H2; wherein k1 is greater than 5, k2 is less than 10, k3 is less than 10, Pf_delay1, Pr_delay1 and Pt_delay1 are respectively the incident power, the reflected power and the cavity field power collected at T time before the current time, and Pf_delay2, Pr_delay2 and Pt_delay2 are respectively the incident power, the reflected power and the cavity field power collected at 2T time before the current time.

8. The system of claim 7, wherein, The set thresholds H1 and H2 need to be set according to the specific physical performance parameters of the high-frequency cavity.

9. The system according to claim 6 or 7 or 8, characterized in that, The interlocking processing method of the striking event interlocking processing unit is: when the i-th striking event trigger signal is received within a set time period and the number of times does not exceed N, the time length of cutting off the forward power excitation signal is T i When the i+1-th striking event trigger signal is received within a set time period and the number of times does not exceed N, the time length of cutting off the forward power excitation signal is T i+1 ; wherein T i+1 is greater than T i .

10. The system of claim 6 or 7 or 8, wherein, T=3us; N=3.

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