Tuning method for four cavities of high-energy accelerator

Abstract

The invention discloses a tuning method for four cavities of a high-energy accelerator, and the method comprises the following steps: arranging a tuning motor and an electronic ruler outside each cavity of a four-cavity resonant cavity, and setting the initial positions of the four tuning motors and the initial positions of the electronic rulers of the four tuning motors; the tuning motor M1 is moved, and the tuning motor M1 is used for completing the searching of a resonance point in the S1 state, the amplitude climbing in the S2 state and the amplitude stable closed loop in the S3 state of the low-level control system; when heat balance is achieved, entering a voltage deviation compensation stage: alternately adjusting the capacitance variation of the tuning motors M1, M2, M3 and M4 by taking the capacitance variation as a step length, so that the voltage deviation among the tuning motors M1, M2, M3 and M4 is close to 0; according to the method, the step length + the electronic ruler + the comparison table + the fitting curve + the alternating adjustment method is adopted, and the problem that deviation compensation is disordered due to signal delay and mechanical transmission errors during multi-motor tuning is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of cyclotron high-frequency systems, and in particular relates to a tuning method for four cavities of a high-energy accelerator. Background Art

[0002] The high-frequency system is one of the important parts of the cyclotron, and its stability and reliability play a key role in the performance of the cyclotron. The high-frequency system of the cyclotron mainly consists of three parts: a high-frequency power source, a resonant cavity, and a low-level system. The high-frequency power source is responsible for providing energy for the movement of particles; the resonant cavity can provide a stable high-frequency electric field for charged particles through resonance; the low-level system is to control and correct the amplitude, phase and other parameters of the acceleration field to ensure the stable operation of the cavity. The four cavities mentioned in this article are directly connected at the head of the Dee plate of each cavity, so for the high-frequency system, it can be equivalent to a set of high-frequency systems, which can be controlled by a transmitter and a set of low-level systems.

[0003] The resonant cavity will generate a lot of heat during high-power operation. Even if it is cooled by water, the cavity will still deform due to temperature changes. When the cavity is deformed, the equivalent capacitance of the cavity will change. The change in equivalent capacitance will cause the resonant frequency of the cavity to change. Therefore, a tuning device is needed to match the frequency of the incident power with the resonant frequency of the resonant cavity. The tuning device is a tuning capacitor plate arranged outside the cavity. The tuning capacitor plate is controlled by a low-level control system. The distance between the tuning capacitor plate and the cavity is changed to change the equivalent capacitance of the cavity, thereby achieving frequency tuning.

[0004] One of the difficulties in tuning the frequency of the four-cavity resonant cavity is: Figure 3a , 3b As shown in the figure, when there is only one tuning capacitor (only one tuning capacitor means: only one of the four cavities has a tuning capacitor plate on the outside, and the tuning capacitor plate is driven by a tuning motor), the beam loss of the resonant cavity of the four cavities will increase a lot. The reason is that the resonant cavity of the four cavities is generally used in high-energy cyclotron accelerators, and the number of beam rotations in high-energy cyclotron accelerators is large. When there is only one tuning capacitor, after CST software simulation, the accelerating gap voltage of the cavity with the tuning capacitor is about 8% higher than that of the other three cavities. When the accelerating gap voltage of the cavity with the tuning capacitor is 8% higher than that of the other three cavities in each circle, it will definitely lead to a decrease in the efficiency of beam extraction. The higher the beam energy, the more the particles rotate in the accelerator, and the more the beam loss increases. From the perspective of accelerator physics, it can be described as follows: when the two high-frequency acceleration gaps in the accelerator are larger than the other six acceleration gaps, the beam will undergo misaligned acceleration during the acceleration process, and the bunch will precess during the acceleration process, which will increase the cyclic emittance of the beam, and ultimately lead to an increase in the beam envelope. When the beam passes through the dangerous resonance region of the magnetic field, the beam oscillation amplitude becomes larger, causing beam loss.

[0005] The second difficulty in frequency tuning of the four-cavity resonant cavity is that when multiple tuning capacitors are used (each of the four cavities is equipped with a tuning motor and a tuning capacitor plate), it is difficult to ensure the consistency of starting, stopping, and turning of multiple tuning motors due to mechanical transmission errors and signal delay errors. The simultaneous movement of multiple motors may cause a very chaotic situation due to mechanical transmission errors and signal delay errors. Summary of the invention

[0006] The present invention aims at the problems existing in the prior art and proposes a tuning method for four cavities of a high-energy accelerator. The first purpose is to solve the problem that when there is only one capacitor, the accelerating gap voltage of the cavity with the capacitor is about 8% higher than that of the other three cavities, which will definitely lead to a decrease in beam efficiency. The higher the beam energy, the more the particles rotate in the accelerator, and the more the beam loss increases. The second purpose is to solve the problem that when multiple tuning capacitors are used, it is difficult to ensure the consistency of starting, stopping, and turning due to mechanical transmission errors and signal delay errors, and multiple motors move at the same time, resulting in a very chaotic situation due to mechanical transmission errors and signal delay errors.

[0007] The present invention adopts the following technical solutions to solve the technical problems:

[0008] A tuning method for four cavities of a high-energy accelerator is based on a four-cavity resonant cavity tuning device, which includes a transmitter, a four-cavity resonant cavity, a low-level control system, a directional coupler and a host computer; the heads of cavity 1, cavity 2, cavity 3 and cavity 4 of the four-cavity resonant cavity are connected by a bridge, and a tuning motor M1, M2, M3 and M4 is arranged outside each cavity, and each tuning motor is also equipped with an electronic ruler, which is used to feedback the position of the motor; the transmitter is used to amplify the signal from the low-level control system and feed it into the four-cavity resonant cavity through a transmission line; its input end is connected to the low-level control system, and its output end is connected to cavity 1 and connected to cavity 2, cavity 3 and cavity 4 through a bridge; the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through resonance; its input end is connected to the transmitter, wherein cavity 2, cavity 3 and cavity 4 are connected through cavity 1 The invention relates to a transmitter; the low-level control system controls the resonant capacitance of the resonant cavity cavity 1, cavity 2, cavity 3, and cavity 4 through motors M1, M2, M3, and M4 respectively, and obtains the internal power signal from cavity 1, cavity 2, cavity 3, and cavity 4 of the four-cavity resonant cavity, obtains the incident power signal from the directional coupler, and the two signals are phase-detected and the tuning motor is controlled to tune the resonant cavity frequency; the directional coupler is arranged on the transmission line between the transmitter and the resonant cavity, and obtains the incident power signal from the transmitter and samples it as one of the signals of each tuning ring; the host computer is bidirectionally connected with the low-level control system; the host computer switches the high-frequency training mode S1-S3 mode and the beam-out mode S1-S5 mode by communicating with the low-level control system, and the host computer controls the tuning of the four tuning rings through the current positions of the four tuning motors, and its characteristic is that the tuning method includes the following steps:

[0009] Step 1: a tuning motor and an electronic ruler are arranged outside each cavity of the four-cavity resonant cavity, and the electronic ruler is used to feedback the current position of the tuning motor;

[0010] Step 2: Set the initial positions of the tuning motors M1, M2, M3, and M4 and their respective electronic rulers. To reduce the motor moving distance and the change of the motor resonance point caused by cavity maintenance, each time, the four motors are reset to the middle of the electronic ruler.

[0011] Step 3, move the tuning motor M1, and use the tuning motor M1 to complete the search for the resonance point of the low-level control system S1 state, the amplitude climbing of the S2 state, and the amplitude stabilization closed loop of the S3 state; the tuning motors M2, M3, and M4 do not move during this period;

[0012] Step 4: The low-level control system remains in the S3 state for a period of time to reach thermal equilibrium. The judgment condition is time, which is set by usual debugging experience;

[0013] Step 5, entering S4 voltage deviation compensation stage: taking the capacitance variation as the step length, alternately adjusting the capacitance variation of the tuning motors M1, M2, M3, and M4, so as to achieve a voltage deviation between the tuning motors M1, M2, M3, and M4 close to 0;

[0014] The method for setting the capacitance variation in step 5 is as follows:

[0015] 1) Establish a comparison table of capacitance value and electronic ruler position and fit it into a mathematical formula curve;

[0016] 2) Capacitance change = capacitance value at the position of the tuning motor that needs to be moved at present - (sum of capacitance values ​​at the position of the tuning motor that needs to be moved at the current stage) ÷ number of motors to be moved at the current stage; the current stage includes S4-1 stage, S4-2 stage, and S4-3 stage, moving 2, 3, and 4 motors respectively;

[0017] 3) Divide the capacitance change of the current tuning motor into several parts, and use the mathematical formula to fit the curve to obtain the moving distance of the electronic ruler corresponding to each capacitance change;

[0018] 4) Move the tuning motor according to the moving distance of the electronic ruler corresponding to each capacitance change.

[0019] Furthermore, the initial positions of the four tuning motor electronic rulers are the same, and the lengths are the same. The same initial positions mean that the distances between the four electronic rulers and the resonant cavity are the same.

[0020] Furthermore, the step 5 alternately adjusts the capacitance variation of the tuning motors M1, M2, M3, and M4, so as to achieve a voltage deviation between the tuning motors M1, M2, M3, and M4 close to 0. The specific process is as follows:

[0021] ⑴ Move the tuning motors M1 and M2. Previously, only the tuning motor M1 was in working state. Now both the tuning motors M1 and M2 are in working state.

[0022] A. Capacitance change of tuning motor M1 = capacitance value at tuning motor M1 - (sum of capacitance value at tuning motor M1 and capacitance value at tuning motor M2) ÷ 2;

[0023] B. Capacitance change of tuning motor M2 = capacitance value at tuning motor M2 - (sum of capacitance value at tuning motor M1 and capacitance value at tuning motor M2) ÷ 2;

[0024] C. Divide the capacitance changes of the tuning motor M1 and the tuning motor M2 into 100 parts respectively, and calculate the moving distance of the electronic ruler corresponding to each capacitance change by fitting curve;

[0025] D. Move the tuning motor M1 and the tuning motor M2 according to the moving distance of the electronic ruler corresponding to each capacitance change;

[0026] (2) Move the tuning motors M1, M2 and M3. Previously, only the tuning motors M1 and M2 were in working state. Now, the tuning motors M1, M2 and M3 are all in working state.

[0027] A. After the tuning motor M1 and the tuning motor M2 reach the desired capacitance change, the tuning motor M1 and the tuning motor M2 are treated as a whole or as a tuning motor group. 12 Treat; tuned motor group 12 The capacitance change of each tuned motor is the same;

[0028] B. Tuning motor group 12 Capacitance change = tuning motor group 12 The capacitance value of any tuned motor in - (the capacitance value at the position of tuned motor M1 + the capacitance value at the position of tuned motor M2 + the capacitance value at the position of tuned motor M3) ÷ 3;

[0029] C. Capacitance change of tuning motor M3 = capacitance value at tuning motor M3 - (capacitance value at tuning motor M1 + capacitance value at tuning motor M2 + capacitance value at tuning motor M3) ÷ 3;

[0030] D. Tune the motor groups separately 12 The capacitance change amount and the capacitance change amount of the tuning motor M3 are evenly divided into 100 parts, and the moving distance of the electronic ruler corresponding to each capacitance change amount is obtained by fitting the curve through a mathematical formula;

[0031] E. Move the tuning motor group according to the moving distance of the electronic ruler corresponding to each capacitance change. 12 Each tuning motor and the tuning motor M3;

[0032] (3) Move the tuning motors M1, M2, M3, and M4. Previously, only the tuning motors M1, M2, and M3 were in working state. Currently, the tuning motors M1, M2, M3, and M4 are all in working state.

[0033] A. After the tuning motors M1, M2 and M3 reach the desired capacitance change, treat the tuning motors M1, M2 and M3 as a whole or as a tuning motor group. 123 Treat; tuned motor group 123 The capacitance change of each tuned motor is the same;

[0034] B. Tuning motor group 123Capacitance change = tuning motor group 123 The capacitance change of any tuned motor in - (the capacitance value of the tuned motor at position M1 + the capacitance value of the tuned motor at position M2 + the capacitance value of the tuned motor at position M3 + the capacitance value of the tuned motor at position M4) ÷ 4; the tuned motor group 123 The capacitance change of each tuned motor is the same;

[0035] C. Capacitance change of tuning motor M4 = capacitance value at tuning motor M4 - (capacitance value at tuning motor M1 + capacitance value at tuning motor M2 + capacitance value at tuning motor M3 + capacitance value at tuning motor M4) ÷ 4;

[0036] D. Tune the motor groups separately 123 The capacitance change and the capacitance change of the tuning motor M4 are evenly divided into 100 parts, and the moving distance of the electronic ruler corresponding to each capacitance change is obtained by fitting the curve with a mathematical formula;

[0037] E. Move the tuning motor group according to the moving distance of the electronic ruler corresponding to each capacitance change. 123 Each tuning motor and the tuning motor M4.

[0038] Advantages and effects of the present invention

[0039] 1. The present invention adopts the method of "step length" + "electronic ruler": it compensates for the error from mechanical transmission or the error from signal delay (the step length in this embodiment is the capacitance change), and tunes according to the "step length". The focus is on the "step length" regardless of whether mechanical transmission error or signal delay error occurs in the middle. Even if there are errors, these errors have been overcome when the "step length" is met. "Electronic ruler" is a means to ensure that the "step length" is executed in place. When the capacitance change of the tuning motor is adjusted alternately with the capacitance change as the step length, there will still be mechanical transmission errors and signal delay errors. Due to the use of an electronic ruler, we are concerned about the moment when the motor on the electronic ruler reaches the target point. If an error occurs, the moment the motor reaches the target point of the electronic ruler may come earlier or later, but it will eventually reach the target point. Due to the alternating operation, when the previous target point is reached, it will continue to the next target point. This solves the problem that when multiple tuning capacitors are used, it is difficult to ensure the consistency of starting, stopping, and turning due to mechanical transmission errors and signal delay errors, and multiple motors move at the same time, resulting in a very chaotic situation due to mechanical transmission errors and signal delay errors.

[0040] 2. The present invention adopts the method of "comparison table" + "fitting curve" to solve the problem of nonlinearity between the capacitance change and the motor moving distance. The comparison table compares the position of the motor and the capacitance value. Although the position of the motor and the capacitance value are nonlinear, the values ​​of the horizontal and vertical coordinates of each point on the nonlinear curve are fixed. The method of fitting the curve by mathematical formula avoids the nonlinear relationship between the position of the motor and the capacitance value, and uses the capacitance change as a bridge in the middle, and finally implements the position of the tuning motor. The method of "comparison table" + "fitting curve" solves the problem of using "step size" to alternately adjust the capacitance change. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of a tuning device for four cavities of a high energy accelerator according to the present invention;

[0042] Figure 2 This is a schematic diagram of the electronic ruler of the present invention;

[0043] Figure 3a This is a schematic diagram of the prior art in which four cavities have only one tuning capacitor;

[0044] Figure 3b It is a schematic diagram showing that the voltage of two accelerating gaps in one cavity with a tuning capacitor is about 8% higher than that of six accelerating gaps in the other three cavities in the prior art;

[0045] Figure 4 This is an effect diagram showing that the voltage deviation of eight accelerating gaps is close to 0 after the voltage deviation of the four cavities is compensated;

[0046] Figure 5 This is a flow chart of a tuning method for four cavities of a high energy accelerator according to the present invention;

[0047] Figure 6 This is a schematic diagram of the approximate relationship between the distance between the tuning capacitor and the resonant cavity and the change in the tuning capacitor of the present invention. DETAILED DESCRIPTION

[0048] Design principle of the present invention

[0049] The innovation of the present invention: The innovation lies in the use of the method of "step length + comparison table + fitting curve + electronic ruler + alternating adjustment" to solve the problem of voltage deviation compensation for multiple cavities. The "step length" is the capacitance change. The significance of "step length" and "electronic ruler" is that when "step length" and "electronic ruler" are used in combination, they can compensate for the error from mechanical transmission error or signal delay. Assuming that the mechanical transmission error causes the tuning motor to not be in place within the specified time, the motor position fed back on the electronic ruler is also not in place at this time. Once the motor position fed back by the electronic ruler reaches the predetermined position, the error caused by mechanical transmission has been compensated; the significance of "comparison table" and "fitting curve" is that it solves the problem that the moving distance of the tuning motor and the capacitance change are non-linear; the relationship between the tuning capacitance value and the distance between the capacitor plate can be regarded as a parallel plate capacitor in a non-ideal state. The mathematical relationship is that the closer the capacitor plate is to the cavity, the faster the capacitance increases. This trend can be approximately fitted into a similar Figure 6 The curve assumes that the electronic ruler's position from the closest to the cavity to the farthest corresponds to 0-100. Figure 6 It can be seen that the electronic ruler moves 10 in the interval of horizontal axis 10 to 20, which has more impact on the capacitance than the electronic ruler moves 30 in the interval of horizontal axis 50 to 80. In other words, the capacitance change rate is not equal when the motor is in different positions, so a "motor position and capacitance value" comparison table is established, and a mathematical curve is fitted. The significance of "alternating adjustment" is to ensure that the calculation result of each step is accurate through serial operation in time. Only when the capacitance change in the previous step is correct can the capacitance change in the next step be correct, because the previous calculation is the basis for the subsequent calculation. This solves the problem of inconsistent steps due to errors when the four tuned motors are operating at the same time.

[0050] In short, the five aspects of step length + comparison table + fitting curve + electronic ruler + alternating adjustment support each other and are indispensable. After their organic combination, the voltage deviation of the multi-cavity is close to 0.

[0051] Based on the above invention principle, the present invention designs a tuning method for four cavities of a high energy accelerator. The method is based on a four-cavity resonant cavity tuning device such as Figure 1 , 2As shown, the four-cavity tuning device includes a transmitter, a four-cavity resonant cavity, a low-level control system, a directional coupler and a host computer; the heads of cavity 1, cavity 2, cavity 3 and cavity 4 of the four-cavity resonant cavity are connected by a bridge, and a tuning motor M1, M2, M3 and M4 are provided outside each cavity, and each tuning motor is also equipped with an electronic ruler, which is used to feedback the position of the motor; the transmitter is used to amplify the signal from the low-level control system and feed it into the four-cavity resonant cavity through a transmission line; its input end is connected to the low-level control system, and the output end is connected to cavity 1 and connected to cavity 2, cavity 3 and cavity 4 through a bridge; the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through resonance; its input end is connected to the transmitter, wherein cavity 2, cavity 3 and cavity 4 are connected to the transmitter through cavity 1; the low-level control system is respectively connected to the transmitter through the motor 1 and the output end is connected to the cavity 1 through the transmission line ... the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through resonance; the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through the transmission line; the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through the transmission line; the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through the transmission line; the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through M1, M2, M3, and M4 control the resonant capacitance of cavity 1, cavity 2, cavity 3, and cavity 4 of the four-cavity resonant cavity, and obtain the internal power signal from cavity 1, cavity 2, cavity 3, and cavity 4 of the four-cavity resonant cavity, and obtain the incident power signal from the directional coupler. The two signals are phase-detected and the tuning motor is controlled to tune the resonant cavity frequency; the directional coupler is arranged on the transmission line between the transmitter and the resonant cavity, which obtains the incident power signal from the transmitter and samples it as one of the signals of each tuning ring; the host computer is bidirectionally connected to the low-level control system; the host computer switches the high-frequency training mode S1-S3 mode and the beam-out mode S1-S5 mode by communicating with the low-level control system, and the host computer controls the tuning of the four tuning rings through the current positions of the four tuning motors, which is characterized in that the tuning method includes the following steps, such as Figure 5 As shown:

[0052] Step 1: a tuning motor and an electronic ruler are arranged outside each cavity of the four-cavity resonant cavity, and the electronic ruler is used to feedback the current position of the tuning motor;

[0053] Step 2: Set the initial positions of the tuning motors M1, M2, M3, and M4 and their respective electronic rulers. To reduce the motor moving distance and the change of the motor resonance point caused by cavity maintenance, each time, the four motors are reset to the middle of the electronic ruler.

[0054] Step 3, move the tuning motor M1, and use the tuning motor M1 to complete the search for the resonance point of the low-level control system S1 state, the amplitude climbing of the S2 state, and the amplitude stabilization closed loop of the S3 state; the tuning motors M2, M3, and M4 do not move during this period;

[0055] Step 4: The low-level control system remains in the S3 state for a period of time to reach thermal equilibrium. The judgment condition is time, which is set by usual debugging experience;

[0056] Step 5, entering S4 voltage deviation compensation stage: taking the capacitance variation as the step length, alternately adjusting the capacitance variation of the tuning motors M1, M2, M3, and M4, so as to achieve a voltage deviation between the tuning motors M1, M2, M3, and M4 close to 0;

[0057] Supplementary Note 1

[0058] The effect of the voltage deviation being close to 0 is as follows Figure 4 As shown, the eight curves of the eight accelerating gaps of the four resonant cavities are almost fitted together, proving that the voltage deviation among the tuned motors M1, M2, M3, and M4 after the improvement of the present invention is close to zero.

[0059] The method for setting the capacitance variation in step 5 is as follows:

[0060] 1) Establish a comparison table of capacitance value and electronic ruler position and fit it into a mathematical formula curve;

[0061] 2) Capacitance change = capacitance value at the position of the tuning motor that needs to be moved at present - (sum of capacitance values ​​at the position of the tuning motor that needs to be moved at the current stage) ÷ number of motors to be moved at the current stage; the current stage includes S4-1 stage, S4-2 stage, and S4-3 stage, moving 2, 3, and 4 motors respectively;

[0062] 3) Divide the capacitance change of the current tuning motor into several parts, and use the mathematical formula to fit the curve to obtain the moving distance of the electronic ruler corresponding to each capacitance change;

[0063] 4) Move the tuning motor according to the moving distance of the electronic ruler corresponding to each capacitance change.

[0064] Furthermore, the initial positions of the four tuning motor electronic rulers are the same, and the lengths are the same. The same initial positions mean that the distances between the four electronic rulers and the resonant cavity are the same.

[0065] Furthermore, the step 5 alternately adjusts the capacitance variation of the tuning motors M1, M2, M3, and M4, so as to achieve a voltage deviation between the tuning motors M1, M2, M3, and M4 close to 0. The specific process is as follows:

[0066] ⑴ Move the tuning motors M1 and M2. Previously, only the tuning motor M1 was in working state. Now both the tuning motors M1 and M2 are in working state.

[0067] A. Capacitance change of tuning motor M1 = capacitance value at tuning motor M1 - (sum of capacitance value at tuning motor M1 and capacitance value at tuning motor M2) ÷ 2;

[0068] B. Capacitance change of tuning motor M2 = capacitance value at tuning motor M2 - (sum of capacitance value at tuning motor M1 and capacitance value at tuning motor M2) ÷ 2;

[0069] C. Divide the capacitance changes of the tuning motor M1 and the tuning motor M2 into 100 parts respectively, and calculate the moving distance of the electronic ruler corresponding to each capacitance change by fitting curve;

[0070] D. Move the tuning motor M1 and the tuning motor M2 according to the moving distance of the electronic ruler corresponding to each capacitance change;

[0071] (2) Move the tuning motors M1, M2 and M3. Previously, only the tuning motors M1 and M2 were in working state. Now, the tuning motors M1, M2 and M3 are all in working state.

[0072] A. After the tuning motor M1 and the tuning motor M2 reach the desired capacitance change, the tuning motor M1 and the tuning motor M2 are treated as a whole or as a tuning motor group. 12 Treat; tuned motor group 12 The capacitance change of each tuned motor is the same;

[0073] B. Tuning motor group 12 Capacitance change = tuning motor group 12 The capacitance value of any tuned motor in - (the capacitance value at the position of tuned motor M1 + the capacitance value at the position of tuned motor M2 + the capacitance value at the position of tuned motor M3) ÷ 3;

[0074] C. Capacitance change of tuning motor M3 = capacitance value at tuning motor M3 - (capacitance value at tuning motor M1 + capacitance value at tuning motor M2 + capacitance value at tuning motor M3) ÷ 3;

[0075] D. Tune the motor groups separately 12 The capacitance change amount and the capacitance change amount of the tuning motor M3 are evenly divided into 100 parts, and the moving distance of the electronic ruler corresponding to each capacitance change amount is obtained by fitting the curve through a mathematical formula;

[0076] E. Move the tuning motor group according to the moving distance of the electronic ruler corresponding to each capacitance change. 12 Each tuning motor and the tuning motor M3;

[0077] (3) Move the tuning motors M1, M2, M3, and M4. Previously, only the tuning motors M1, M2, and M3 were in working state. Currently, the tuning motors M1, M2, M3, and M4 are all in working state.

[0078] A. After the tuning motors M1, M2 and M3 reach the desired capacitance change, treat the tuning motors M1, M2 and M3 as a whole or as a tuning motor group. 123 Treat; tuned motor group 123 The capacitance change of each tuned motor is the same;

[0079] B. Tuning motor group 123 Capacitance change = tuning motor group 123 The capacitance change of any tuned motor in - (the capacitance value of the tuned motor at position M1 + the capacitance value of the tuned motor at position M2 + the capacitance value of the tuned motor at position M3 + the capacitance value of the tuned motor at position M4) ÷ 4; the tuned motor group 123 The capacitance change of each tuned motor is the same;

[0080] C. Capacitance change of tuning motor M4 = capacitance value at tuning motor M4 - (capacitance value at tuning motor M1 + capacitance value at tuning motor M2 + capacitance value at tuning motor M3 + capacitance value at tuning motor M4) ÷ 4;

[0081] D. Tune the motor groups separately 123 The capacitance change and the capacitance change of the tuning motor M4 are evenly divided into 100 parts, and the moving distance of the electronic ruler corresponding to each capacitance change is obtained by fitting the curve with a mathematical formula;

[0082] E. Move the tuning motor group according to the moving distance of the electronic ruler corresponding to each capacitance change. 123 Each tuning motor and the tuning motor M4.

[0083] It should be emphasized that the above specific embodiments are merely explanations of the present invention, and they are not limitations of the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without any creative contribution as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A tuning method for four cavities of a high-energy accelerator, the method is based on a four-cavity resonant cavity tuning device, the four-cavity tuning device includes a transmitter, a four-cavity resonant cavity, a low-level control system, a directional coupler and a host computer; the heads of the cavities 1, 2, 3 and 4 of the four-cavity resonant cavity are connected by a bridge, and a tuning motor M1, M2, M3 and M4 are arranged outside each cavity, and each tuning motor is also equipped with an electronic ruler, which is used to feedback the position of the motor; the transmitter is used to amplify the signal from the low-level control system and feed it into the four-cavity resonant cavity through a transmission line; its input end is connected to the low-level control system, and the output end is connected to cavity 1 and connected to cavity 2, cavity 3 and cavity 4 by a bridge; the four-cavity resonant cavity provides a stable high-frequency electric field for charged particles through resonance; Its input is connected to the transmitter, where Cavity 2, cavity 3, and cavity 4 are connected to the transmitter through cavity 1; the low-level control system controls the resonant capacitance of cavity 1, cavity 2, cavity 3, and cavity 4 through motors M1, M2, M3, and M4 respectively, and obtains the internal power signal from cavity 1, cavity 2, cavity 3, and cavity 4 of the four-cavity resonant cavity, obtains the incident power signal from the directional coupler, and the two signals are phase-detected and control the tuning motor to tune the resonant cavity frequency; the directional coupler is arranged on the transmission line between the transmitter and the resonant cavity, and obtains the incident power signal from the transmitter and samples it as one of the signals of each tuning loop; The host computer is bidirectionally connected with the low-level control system; the host computer switches the high-frequency training mode S1-S3 mode and the beam-out mode S1-S5 mode by communicating with the low-level control system, and the host computer controls the tuning of the four tuning rings through the current positions of the four tuning motors, characterized in that the tuning method comprises the following steps: Step 1: a tuning motor and an electronic ruler are arranged outside each cavity of the four-cavity resonant cavity, and the electronic ruler is used to feedback the current position of the tuning motor; Step 2: Set the initial positions of the tuning motors M1, M2, M3, and M4 and their respective electronic rulers. To reduce the motor moving distance and the change of the motor resonance point caused by cavity maintenance, each time, the four motors are reset to the middle of the electronic ruler. Step 3, move the tuning motor M1, and use the tuning motor M1 to complete the search for the resonance point of the low-level control system S1 state, the amplitude climbing of the S2 state, and the amplitude stabilization closed loop of the S3 state; the tuning motors M2, M3, and M4 do not move during this period; Step 4: The low-level control system remains in the S3 state for a period of time to reach thermal equilibrium. The judgment condition is time, which is set by usual debugging experience; Step 5, entering S4 voltage deviation compensation stage: taking the capacitance variation as the step length, alternately adjusting the capacitance variation of the tuning motors M1, M2, M3, and M4, so as to achieve a voltage deviation between the tuning motors M1, M2, M3, and M4 close to 0; The method for setting the capacitance variation in step 5 is as follows: 1) Establish a comparison table of capacitance value and electronic ruler position and fit it into a mathematical formula curve; 2) Capacitance change = capacitance value at the position of the tuning motor that needs to be moved at present - (sum of capacitance values ​​at the position of the tuning motor that needs to be moved at the current stage) ÷ number of motors to be moved at the current stage; the current stage includes S4-1 stage, S4-2 stage, and S4-3 stage, moving 2, 3, and 4 motors respectively; 3) Divide the capacitance change of the current tuning motor into several parts, and obtain the moving distance of the electronic ruler corresponding to each capacitance change by fitting the curve with a mathematical formula; 4) Move the tuning motor according to the moving distance of the electronic ruler corresponding to each capacitance change.

2. According to claim 1, a tuning method for four cavities of a high energy accelerator is characterized in that: The initial positions of the four tuning motor electronic rulers are the same, and the lengths are the same. The same initial positions mean that the distances between the four electronic rulers and the resonant cavity are the same.

3. According to claim 1, a tuning method for four cavities of a high energy accelerator is characterized in that: The step 5 alternately adjusts the capacitance variation of the tuning motors M1, M2, M3, and M4, so as to achieve a voltage deviation between the tuning motors M1, M2, M3, and M4 close to 0. The specific process is as follows: ⑴ Move the tuning motors M1 and M2. Previously, only the tuning motor M1 was in working state. Now both the tuning motors M1 and M2 are in working state. A. Capacitance change of tuning motor M1 = capacitance value at tuning motor M1 - (sum of capacitance value at tuning motor M1 and capacitance value at tuning motor M2) ÷ 2; B. Capacitance change of tuning motor M2 = capacitance value at tuning motor M2 - (sum of capacitance value at tuning motor M1 and capacitance value at tuning motor M2) ÷ 2; C. Divide the capacitance changes of the tuning motor M1 and the tuning motor M2 into 100 parts respectively, and calculate the moving distance of the electronic ruler corresponding to each capacitance change by fitting curve; D. Move the tuning motor M1 and the tuning motor M2 according to the moving distance of the electronic ruler corresponding to each capacitance change; (2) Move the tuning motors M1, M2 and M3. Previously, only the tuning motors M1 and M2 were in working state. Now, the tuning motors M1, M2 and M3 are all in working state. A. After the tuning motor M1 and the tuning motor M2 reach the desired capacitance change, the tuning motor M1 and the tuning motor M2 are treated as a whole or as a tuning motor group. 12 Treat; tuned motor group 12 The capacitance change of each tuned motor is the same; B. Tuning motor group 12 Capacitance change = tuning motor group 12 The capacitance value of any tuned motor in - (the capacitance value at the position of tuned motor M1 + the capacitance value at the position of tuned motor M2 + the capacitance value at the position of tuned motor M3) ÷ 3; C. Capacitance change of tuning motor M3 = capacitance value at tuning motor M3 - (capacitance value at tuning motor M1 + capacitance value at tuning motor M2 + capacitance value at tuning motor M3) ÷ 3; D. Tune the motor groups separately 12 The capacitance change amount and the capacitance change amount of the tuning motor M3 are evenly divided into 100 parts, and the moving distance of the electronic ruler corresponding to each capacitance change amount is obtained by fitting the curve through a mathematical formula; E. Move the tuning motor group according to the moving distance of the electronic ruler corresponding to each capacitance change. 12 Each tuning motor and the tuning motor M3; (3) Move the tuning motors M1, M2, M3, and M4. Previously, only the tuning motors M1, M2, and M3 were in working state. Currently, the tuning motors M1, M2, M3, and M4 are all in working state. A. After the tuning motors M1, M2 and M3 reach the desired capacitance change, treat the tuning motors M1, M2 and M3 as a whole or as a tuning motor group. 123 Treat; tuned motor group 123 The capacitance change of each tuned motor is the same; B. Tuning motor group 123 Capacitance change = tuning motor group 123 The capacitance change of any tuned motor in - (the capacitance value of the tuned motor at position M1 + the capacitance value of the tuned motor at position M2 + the capacitance value of the tuned motor at position M3 + the capacitance value of the tuned motor at position M4) ÷ 4; the tuned motor group 123 The capacitance change of each tuned motor is the same; C. Capacitance change of tuning motor M4 = capacitance value at tuning motor M4 - (capacitance value at tuning motor M1 + capacitance value at tuning motor M2 + capacitance value at tuning motor M3 + capacitance value at tuning motor M4) ÷ 4; D. Tune the motor groups separately 123 The capacitance change and the capacitance change of the tuning motor M4 are evenly divided into 100 parts, and the moving distance of the electronic ruler corresponding to each capacitance change is obtained by fitting the curve with a mathematical formula; E. Move the tuning motor group according to the moving distance of the electronic ruler corresponding to each capacitance change. 123 Each tuning motor and the tuning motor M4.

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