A method for protecting a signal of a beam measurement of a cyclotron

Abstract

This invention discloses a method for protecting beam measurement signals in a cyclotron accelerator, comprising: suppression of coupled high-frequency signals in the accelerator under normal conditions: measuring and adjusting the parameters of the first set of series resonant circuits S21 using a network analyzer, so that the frequency corresponding to the lowest point of S21 is equal to the accelerator's high-frequency frequency f0, and satisfying S21 < -30dB; calibration of the capacitor rotation angle scale range before abnormal condition monitoring; transmission line oscillation monitoring under abnormal conditions: setting the speeds of the first set of motors and the second set of motors, so that the first set of motors and the second set of motors drive the capacitor to move within the calibrated rotation angle scale range; transmission line oscillation control under abnormal conditions: when the signal interlocking device detects a high level input, the interlocking signal prohibits the output of the high-frequency system signal source and the operation of the power source, and the accelerator high-frequency system stops operating; this invention solves the problems of the beam measurement device being greatly interfered with by the accelerator's high-frequency signals and being greatly interfered with by unexpected transmission line oscillations.

Description

Technical Field

[0001] This invention belongs to the field of cyclotrons, specifically relating to a method for protecting beam measurement signals in cyclotrons. Background Technology

[0002] For a quarter-wavelength cyclotron, the asymmetry of the electric field on the upper and lower sides of the central plane makes the cyclotron cavity structure open in the ion acceleration plane, leading to high-frequency field leakage. This results in the high-frequency signal coupled to the target system in the central plane reaching close to the hundreds of watts, causing significant interference to the beam measurement signal and affecting the stability and accuracy of the target system's electronic beam measurement signal. Specifically, the abnormal phenomena caused by the high-frequency field in the target system's electronics often manifest as deviations of the "background" beam measurement signal from zero, measurement errors varying with high-frequency power, and abnormal beam measurement signals under high-power conditions. In severe cases, this can lead to the burnout or failure of electronic devices, affecting the cyclotron's beam output judgment and use.

[0003] Existing beam measurement protection devices address high-frequency field leakage in the central plane of a quarter-wavelength cyclotron accelerator by adding shielding to the inner or stripped target in the accelerator's central plane. This shielding involves adding a metallic shielding structure for electric field signals to the inner or stripped target. This shielding structure can block some high-frequency field leakage, reducing the coupling of high-frequency signals and thus minimizing interference. However, since the inner or stripped target remains within the accelerator environment, even with shielding, the effectiveness is limited because it doesn't completely isolate the high-frequency signals.

[0004] To eliminate interference from the accelerator environment, beam measurement protection devices can be placed outside the accelerator, thus completely escaping its influence. However, this introduces new challenges: transmission line oscillations are inevitable during long-distance signal transmission. Transmission line oscillations are parasitic oscillations caused by impedance transformation when the vacuum tube final-stage cavity amplifier is connected to a long-distance transmission line or a high-quality-factor cavity. Theoretically, these oscillations can be completely suppressed by placing the vacuum tube final-stage cavity amplifier close to the cavity or by adding a circulator for isolation. In practice, due to limitations such as facility space and radiation shielding, the use of long-distance transmission lines is unavoidable. Typically, adjusting the transmission line length is used to reposition the parasitic oscillations away from the accelerator's high-frequency operating frequency. However, this adjustment is static and cannot achieve dynamic monitoring of transmission line oscillations or protection against unexpected oscillations.

[0005] In summary, the design challenge of beam measurement protection devices for high-frequency field leakage in quarter-wavelength cyclotron accelerators lies in simultaneously addressing two protection dimensions: one is resolving high-frequency field leakage under normal accelerator operation, and the other is mitigating abnormal oscillations during long-distance signal transmission under abnormal conditions. These two protection dimensions are interdependent and mutually influential; failure to simultaneously address both dimensions will render all previous efforts futile. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention proposes a method for protecting cyclotron beam measurement signals, aiming to solve the problems of cyclotron beam measurement devices being subjected to huge interference from high-frequency signals from the accelerator and huge interference from unexpected oscillations in the transmission line.

[0007] To solve its technical problem, the present invention adopts the following technical solution:

[0008] A method for protecting a cyclotron beam measurement signal is disclosed, based on a cyclotron beam measurement signal protection device. This device is located outside the cyclotron, with one end connected to a stripping target or inner target inside the cyclotron and the other end connected to a beam measurement device outside the cyclotron. The device includes a rectangular copper shell 3, with a high-power air-cooling device fixed to the upper end and an air convection hole at the lower end. One side of the copper shell 3 serves as a signal input terminal 1, and the other as a signal output terminal 2, directly connected via a copper tube 4 inside the shell. At least three sets of inductor-capacitor series resonant circuits are connected to ground via the copper tube 4. The input terminal 1 is the first set of inductor and capacitor series resonant circuits, while the second and third sets of inductor and capacitor series resonant circuits are located further away from the beam signal input terminal 1. The three sets of inductor and capacitor series resonant circuits are separated by copper plates 6 to reduce coupling interference. A polytetrafluoroethylene block 5 is installed where the copper tube 4 passes through the copper plate 6 to achieve insulation between the copper tube 4 and the copper plate 6. The mechanical interface between the signal input terminal 1 and the signal output terminal 2 is an N-type flange joint. The first set of inductor and capacitor series resonant circuits is used to suppress high-frequency signals coupled from the beam measurement signal drawn from the cyclotron under normal conditions and to prevent such high-frequency signals from entering the beam measurement device. The second and third sets of inductor and capacitor series resonant circuits are used to detect and control transmission oscillations under abnormal conditions.

[0009] Its characteristic is that the method includes the following steps:

[0010] Step 1: Suppression of high-frequency coupled signals in the accelerator under normal conditions: Measure the parameters of the first series resonant circuit S21 using a network analyzer, and adjust the first set of adjustable insulation knobs 11-1 so that the frequency corresponding to the lowest point of S21 is equal to the high-frequency frequency fo of the accelerator, and S21 < -30dB.

[0011] Step 2: Calibration of the capacitor rotation angle scale range before abnormal situation monitoring: Measure the parameters of the second and third series resonant circuits S21, adjust the second group of adjustable insulation knobs 11-2 or adjust the first group of motors 12-1 through the motor controller, and calibrate the capacitor angle scale range within the range of (f0-2) to (f0-0.2)MHz corresponding to the lowest point of S21; adjust the third group of adjustable insulation knobs 11-3 or adjust the motor 12-2 through the motor controller, and calibrate the capacitor angle scale range within the range of (f0+0.2) to (f0+2)MHz corresponding to the lowest point of S21.

[0012] Step 3: Monitoring transmission line oscillations under abnormal conditions, specifically:

[0013] 1) Connect the first set of motors 12-1 to the second set of series resonant circuit capacitor adjustment knob 11-2, set the speed of the first set of motors 12-1 so that the first set of motors 12-1 drives the capacitor to move within the marked rotation angle scale. The change in capacitance value caused by this movement should cover the series resonant frequency (f0-2) to (f0-0.2) MHz within 5 seconds. Connect the third set of motors 12-2 to the third set of series resonant circuit capacitor adjustment knob 11-3, set the speed of the third set of motors 12-2 so that the first set of motors 12-1 drives the capacitor to move within the marked rotation angle scale. The change in capacitance value caused by this movement should cover the series resonant frequency (f0+0.2) to (f0+2) MHz within 5 seconds.

[0014] 2) When the series resonant frequency of the second group reaches one end of the calibrated frequency range, the first group motor 12-1 reverses, so that the change in the capacitance value driven by the first group motor 12-1 can complete the coverage of the series resonant frequency (f0-0.2) to (f0-2) MHz within 5 seconds, and the motor rotates back and forth in this way; when the series resonant frequency of the third group reaches one end of the calibrated frequency range, the second group motor 12-2 reverses, so that the change in the capacitance value driven by the second group motor 12-2 can complete the coverage of the series resonant frequency (f0+2) to (f0+0.2) MHz within 5 seconds, and the motor rotates back and forth in this way;

[0015] Step 4: Transmission line oscillation control under abnormal conditions: Specifically:

[0016] 1) The function of the signal monitoring module 15 is to compare the signals of the first group of capacitive coupling probes 13-1 and the second group of capacitive coupling probes 13-2 with the set reference values, and to record the maximum values ​​of the signals of the first group of capacitive coupling probes 13-1 and the second group of capacitive coupling probes 13-2 in each 5s frequency sweep cycle.

[0017] 2) When the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 are greater than the set reference voltage, the signal monitoring module 15 outputs a high level, and vice versa.

[0018] 3) When the signal interlocking device 16 detects that the input is high level, the interlocking signal prohibits the output of the high-frequency system signal source and the operation of the power source, and the high-frequency system of the accelerator stops running; at the same time, the motor moves quickly to the capacitance scale position corresponding to the maximum value of the first set of capacitor coupling probes 13-1 and the second set of capacitor coupling probes 13-2 within the current 5s sweep frequency cycle, and this movement is required to be achieved within less than 0.5s.

[0019] Furthermore, the first set of inductors and capacitors in series resonant circuit includes a first set of non-adjustable inductors (7-1), a first set of adjustable capacitors (9-1), a first set of adjustable capacitors with a non-grounded terminal (9-1), a first set of adjustable capacitors with a grounded terminal (10-1), and a first set of insulated adjustable knobs (11-1). The upper end of the first set of adjustable capacitors (9-1) is connected to the first set of non-adjustable inductors (7-1) through the non-grounded terminal (9-1), and the lower end is grounded through the grounded terminal (10-1). The inductive reactance of the first set of non-adjustable inductors (7-1) is fixed and non-adjustable. The first set of adjustable capacitors (9-1) is a vacuum adjustable capacitor. The first set of insulated adjustable knobs (11-1) is used to adjust the first set of adjustable capacitors (9-1) so that the frequency corresponding to the lowest point of S21 is equal to the high-frequency frequency f0 of the accelerator, and S21 < -30dB.

[0020] Furthermore, the second set of inductor and capacitor series resonant circuit includes a second set of non-adjustable inductor 7-2, a second set of adjustable capacitor 9-2, a second set of adjustable capacitor non-grounded terminal 9-2, a second set of adjustable capacitor grounded terminal 10-2, a second set of insulated adjustable knob 11-2, and a first set of motor 12-1; the upper end of the second set of adjustable capacitor 9-2 is connected to the second set of non-adjustable inductor 7-2 through the second set of adjustable capacitor non-grounded terminal 9-2, and the lower end is grounded through the second set of adjustable capacitor grounded terminal 10-2; the inductive reactance of the second set of non-adjustable inductor 7-2 is fixed and non-adjustable, the second set of adjustable capacitor 9-2 is a cylindrical vacuum capacitor, and the second set of insulated adjustable knob 11-2 is used to adjust the second set of adjustable capacitor. Device 9-2, so that the lowest point of S21 corresponds to the capacitor rotation angle scale range within the frequency range of (f0-2) to (f0-0.2)MHz; the first set of motors 12-1 is connected to the second set of insulated adjustable knobs 11-2. By setting the speed of the first set of motors 12-1, the change in the capacitance value driven by the first set of motors 12-1 can complete the coverage of the series resonant frequency (f0+0.2) to (f0+2)MHz within 5 seconds. The motor (12-1) rotates back and forth in this way; the calibration of the capacitor rotation angle scale in the frequency range of (f0-2) to (f0-0.2)MHz is adjusted by the motor or by the manual knob. The adjustment by the motor is to adjust the motor by the motor drive controller.

[0021] Furthermore, the third set of inductor and capacitor series resonant circuit includes a third set of non-adjustable inductor 7-3, a third set of adjustable capacitor 9-3, a third set of adjustable capacitor non-grounded terminal 9-3, a third set of adjustable capacitor grounded terminal 10-3, a third set of insulated adjustable knob 11-3, and a second set of motor 12-2; the upper end of the third set of adjustable capacitor 9-3 is connected to the third set of non-adjustable inductor 7-3 through the third set of adjustable capacitor non-grounded terminal 8-3, and the lower end is grounded through the third set of adjustable capacitor grounded terminal 10-3; the inductive reactance of the third set of non-adjustable inductor 7-3 is fixed and non-adjustable, the third set of adjustable capacitor 9-3 is a cylindrical vacuum capacitor, and the third set of insulated adjustable knob 11-3 is used to adjust the third set of adjustable capacitor series resonant circuit. Adjust capacitor 9-3 so that the lowest point of S21 corresponds to the capacitor rotation angle scale range within the frequency range of (f0+0.2) to (f0+2) MHz; the second set of motors 12-2 is connected to the third set of insulated adjustable knobs 11-3. By setting the speed of the second set of motors 12-2, the change in the capacitance value driven by the second set of motors 12-2 can complete the coverage of the series resonant frequency (f0+0.2) to (f0+2) MHz within 5 seconds, and the motor rotates back and forth in this way; the calibration of the capacitor rotation angle scale in the frequency range of (f0+0.2) to (f0+2) MHz is adjusted by the motor or by the manual knob. The adjustment by the motor is to adjust the motor by the motor drive controller.

[0022] Furthermore, a first set of capacitive coupling probes 13-1 is set near the second ungrounded terminal 8-2 of the second set of series resonant circuit capacitors, and leads out to the first set of N-type flange joints 14-1 set on the copper shell structure, wherein the minimum distance between the first set of capacitive coupling probes 13-1 and the second ungrounded terminal 8-2 of the capacitor is 5mm; the first set of N-type flange joints 14-1 connects the signal monitoring module 15 and the subsequent signal interlocking device 16;

[0023] Furthermore, a second set of capacitive coupling probes 13-2 is provided near the ungrounded terminal 8-3 of the third set of series resonant circuit capacitors, and led out to the second set of N-type flange joints 14-2 provided on the copper shell structure. The minimum distance between the second set of capacitive coupling probes 13-2 and the ungrounded terminal 8-3 of the third set of capacitors is 5mm. The second set of N-type flange joints 14-2 is connected to the signal monitoring module 15 and the subsequent signal interlocking device 16.

[0024] Furthermore, the function of the signal monitoring module 15 is to compare the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 with a set reference value. When the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 are greater than the set reference voltage, the signal monitoring module 15 outputs a high level, and vice versa. When the signal interlocking device 16 detects that the input is high, the interlocking signal prohibits the output of the high-frequency system signal source and the operation of the power source, and the accelerator high-frequency system stops operating. At the same time, the motor moves rapidly to the capacitance scale position corresponding to the maximum value of the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 within the current 5s sweep frequency cycle. This movement is required to be completed within less than 0.5s.

[0025] Furthermore, the reference value of the signal monitoring module 15 can be calibrated in the following way: Under normal operating conditions of the accelerator, record the high-frequency signal power values ​​of the capacitively coupled probes of the second and third sets of series resonant circuits in the corresponding ranges of (f0-2) to (f0-0.2) MHz and (f0+0.2) to (f0+2) MHz, denoted as M dBm, and the reference value is (M+3) dBm.

[0026] Furthermore, an air convection hole is provided at the lower end of the copper shell 3, with a diameter greater than 5 mm and less than 0.01 times the wavelength of the high-frequency signal. The signal input terminal 1 and the signal output terminal 2 are directly connected inside the copper shell 3 through a copper tube 4 with a diameter of 2.5 mm.

[0027] Advantages and effects of the present invention

[0028] This invention solves the problem of suppressing high-frequency signals coupled from the beam measurement signal derived from the cyclotron and preventing these high-frequency signals from entering the beam measurement device under normal conditions by setting up a first set of inductor and capacitor series resonant circuits. By setting up a second and third set of inductor and capacitor series resonant circuits to monitor and control oscillations, it solves the problem of oscillations in the ranges of (f0-2) to (f0-0.2) MHz and (f0+0.2) to (f0+2) MHz interfering with the beam measurement signal under abnormal conditions. Furthermore, by setting up high-power air-cooling devices and air convection holes at the top and bottom of the protection device, it addresses the concern that the heat generated when the power is absorbed by the spikes below the first, second, and third sets of series resonant circuits cannot be dissipated in time. The organic combination of these technologies solves the problems of the cyclotron beam measurement device being greatly interfered with by the accelerator's high-frequency signals and by unexpected oscillations in the transmission lines. Attached Figure Description

[0029] Figure 1 This is an application effect diagram of the beam measurement signal protection device of the present invention;

[0030] Figure 2 This is a circuit diagram of the beam measurement signal protection device of the present invention;

[0031] Figure 3 This is a schematic diagram illustrating the principle of suppressing high-frequency signals in this invention.

[0032] Figure 4 This is a flowchart of the cyclotron beam measurement signal protection method of the present invention;

[0033] In the diagram: 1: N-type connector, input terminal of the protection device; 2: N-type connector, output terminal of the protection device; 3: Copper shell of the protection device; 4: Copper tube; 5: PTFE block, through which the copper tube passes; 6: Copper partition, dividing three sets of series resonant circuits; 7-1: First set of non-adjustable inductors; 7-1: Second set of non-adjustable inductors; 7-1: Third set of non-adjustable inductors; 8-1: Non-grounded terminal of the first set of adjustable capacitors; 8-2: Non-grounded terminal of the second set of adjustable capacitors; 8-3: Non-grounded terminal of the third set of adjustable capacitors; 9-1: First set of adjustable capacitors; 9-2: Second set of adjustable capacitors; 9-3: 10-1: Ground terminal of the first adjustable capacitor group; 10-2: Ground terminal of the second adjustable capacitor group; 10-3: Ground terminal of the third adjustable capacitor group; 11-1: Ground terminal of the first insulated adjustable knob; 11-2: Ground terminal of the second insulated adjustable knob; 11-3: Ground terminal of the third adjustable knob; 12-1: Motor group 1; 12-2: Motor group 2; 13-1: Capacitive coupling probe group 1; 13-2: Capacitive coupling probe group 2; 14-1: N-type connector group 1; 14-2: N-type connector group 2; 15: Signal monitoring device; 16: Signal interlock device. Detailed Implementation

[0034] Design principle of this invention:

[0035] 1. Design principle of three sets of parallel inductor and capacitor series resonant circuits. ① The significance of designing the first set of inductor and capacitor series resonant circuits is to suppress high-frequency signals, solving the problem of suppressing high-frequency signals coupled to the beam measurement signal extracted from the cyclotron under normal conditions. ② The significance of designing the second and third sets of inductor and capacitor series resonant circuits is to monitor transmission line oscillations, solving the problem that the suppression of high-frequency signals f0 by the first set of inductor and capacitor series resonant circuits is not affected under abnormal conditions: Since the possible transmission line oscillations in the ranges (f0-2) to (f0-0.2) MHz and (f0+0.2) to (f0+2) MHz of the second and third sets are relatively close to the high-frequency f0, the oscillations in this range will cause instability in the high-frequency system and interfere with the normal operation of the high-frequency system at point f0. For example, the effect of abnormal oscillations will cause the power of the high-frequency signal coupled to the beam measurement signal extracted from the cyclotron to increase abnormally, far exceeding the signal power at f0. Without processing at the frequency corresponding to the abnormal oscillation, the abnormal oscillation high-frequency signal is not absorbed and enters the beam measurement device, or even burns out the beam measurement device. ③ The technical means for monitoring oscillations in this invention is as follows: First, a signal monitoring device 15 and a signal interlocking device 16 are set up. Once abnormal oscillations occur in the ranges of (f0-2) to (f0-0.2) MHz and (f0+0.2) to (f0+2) MHz, the signal interlocking device 16 is used to prohibit the output of the high-frequency system signal source and the operation of the power source, and the accelerator high-frequency system stops operating. Second, if the abnormal oscillations in this range are not temporarily cut off by the interlocking device 16, such as... Figure 3As shown, the motor moves rapidly to the capacitance scale position corresponding to the maximum value of the signals of the first group of capacitive coupling probes 13-1 and the second group of capacitive coupling probes 13-2 within the current 5s sweep frequency cycle. This movement is required to be completed within less than 0.5s. The spike below the series resonant circuit of the second and third groups of inductors and capacitors can absorb the power, forming a protection for the beam measurement device. The reason this spike can absorb the energy of abnormal oscillations is that the resistance is minimum at this point. The resistance is minimum because, by manually adjusting the capacitor or by adjusting the capacitor on the motor, the capacitive reactance and inductive reactance in this range are exactly equal in magnitude and opposite in direction, canceling each other out, resulting in the minimum total reactance and a purely resistive characteristic. At this time, the current in the series resonant circuit is maximum, and the voltage is minimum, showing a downward spike on the frequency response curve of S-parameter S21. However, the location of the abnormal oscillation spike in this range is not fixed but random. The random range of this abnormal oscillation spike is (f0-2) to (f0-0.2)MHz and (f0+0.2) to (f0+2)MHz. ④ The reason for choosing to monitor within the range of (f0-0.2)MHz and (f0+0.2) to (f0+2)MHz is that the accelerator high-frequency amplifier is a narrow-band system. The range where the amplifier gain is relatively large is within ±2MHz of f0. If the range deviates too much, the amplifier gain will be too small and it will not be able to amplify effectively. Only within this range can the amplifier gain be relatively large, and the accelerator high-frequency system can work normally or oscillate abnormally. This range is also defined based on the narrow-band characteristics of the amplifier. In this sense, we are concerned about the oscillation in the range of (f0-2) to (f0-0.2)MHz and (f0+0.2) to (f0+2)MHz.

[0036] 2. Design principle of high-power air cooling and air convection. The principle of the first set of inductor and capacitor series resonant circuits suppressing high-frequency signal f0 is: when the coupled high-frequency signal f0 approaches the level of hundreds of watts, the series resonant circuit can absorb the power; the principle of the second and third sets of inductor and capacitor series resonant circuits monitoring and controlling abnormal oscillations of the transmission line is: if the abnormal oscillation in this range is not temporarily cut off, the series resonant circuit can absorb the coupled abnormal oscillation power. According to the principle of energy conservation, when power is absorbed, a lot of heat will be generated. If the heat is not dissipated in time, it will burn out the equipment. Therefore, this invention has a high-power air cooling device fixed at the upper end of the copper shell 3 of the cuboid protective device, and an air convection hole set at the lower end. The diameter of the hole is greater than 5mm and less than 0.01 times the wavelength of the high-frequency signal.

[0037] A method for protecting beam measurement signals in a cyclotron accelerator, such as Figure 1 , Figure 2 , Figure 3 , Figure 4As shown, this protection method is based on a cyclotron beam measurement signal protection device. This signal protection device is located outside the cyclotron, with one end connected to a stripping target or inner target inside the cyclotron, and the other end connected to a beam measurement device outside the cyclotron. The signal protection device has a rectangular copper shell 3, with a high-power air-cooling device fixed to the upper end and an air convection hole at the lower end. One side of the rectangular copper shell 3 is a signal input terminal 1, and the other side is a signal output terminal 2. The signal input terminal 1 and the signal output terminal 2 are directly connected through a copper tube 4 inside the copper shell. At least three sets of inductor and capacitor series resonant circuits are connected to ground on the copper tube 4, wherein the circuit closest to the beam signal input terminal 1 is... The first set of inductor-capacitor series resonant circuits, and the second and third sets of inductor-capacitor series resonant circuits located away from the beam signal input terminal 1; the three sets of inductor-capacitor series resonant circuits are separated by copper plates 6 to reduce coupling interference; a polytetrafluoroethylene block 5 is installed where the copper tube 4 passes through the copper plate 6 to achieve insulation between the copper tube 4 and the copper plate 6; the mechanical interface between the signal input terminal 1 and the signal output terminal 2 is an N-type flange joint; the first set of inductor-capacitor series resonant circuits is used to suppress high-frequency signals coupled from the beam measurement signal drawn from the cyclotron under normal conditions and prevent such high-frequency signals from entering the beam measurement device; the second and third sets of inductor-capacitor series resonant circuits are used to detect and control transmission oscillations under abnormal conditions.

[0038] Its characteristic is that the method includes the following steps:

[0039] Step 1: Suppression of high-frequency coupled signals in the accelerator under normal conditions: Measure the parameters of the first series resonant circuit S21 using a network analyzer, and adjust the first set of adjustable insulation knobs 11-1 so that the frequency corresponding to the lowest point of S21 is equal to the high-frequency frequency f0 of the accelerator, and S21 < -30dB.

[0040] Step 2: Calibration of the capacitor rotation angle scale range before abnormal situation monitoring: Measure the parameters of the second and third series resonant circuits S21, adjust the second group of adjustable insulation knobs 11-2 or adjust the first group of motors 12-1 through the motor controller, and calibrate the capacitor angle scale range with the frequency corresponding to the lowest point of S21 in the range of (f0-2) to (f0-0.2)MHz; adjust the third group of adjustable insulation knobs 11-3 or adjust the second group of motors 12-2 through the motor controller, and calibrate the capacitor angle scale range with the frequency corresponding to the lowest point of S21 in the range of (f0+0.2) to (f0+2)MHz.

[0041] Step 3: Monitoring transmission line oscillations under abnormal conditions, specifically:

[0042] 1) Connect the first set of motors 12-1 to the second set of series resonant circuit capacitor adjustment knob 11-2, set the speed of the first set of motors 12-1 so that the first set of motors 12-1 drives the capacitor to move within the specified rotation angle scale. The change in capacitance value caused by this movement should cover the series resonant frequency (f0-2) to (f0-0.2) MHz within 5 seconds. Connect the second set of motors 12-2 to the third set of series resonant circuit capacitor adjustment knob 11-3, set the speed of the second set of motors 12-2 so that the first set of motors 12-1 drives the capacitor to move within the specified rotation angle scale. The change in capacitance value caused by this movement should cover the series resonant frequency (f0+0.2) to (f0+2) MHz within 5 seconds.

[0043] 2) When the series resonant frequency of the second group reaches one end of the calibrated frequency range, the first group motor 12-1 reverses, so that the change in the capacitance value driven by the first group motor 12-1 can complete the coverage of the series resonant frequency (f0-0.2) to (f0-2) MHz within 5 seconds, and the motor rotates back and forth in this way; when the series resonant frequency of the third group reaches one end of the calibrated frequency range, the second group motor 12-2 reverses, so that the change in the capacitance value driven by the second group motor 12-2 can complete the coverage of the series resonant frequency (f0+2) to (f0+0.2) MHz within 5 seconds, and the motor rotates back and forth in this way;

[0044] Step 4: Transmission line oscillation control under abnormal conditions: Specifically:

[0045] 1) The function of the signal monitoring module 15 is to compare the signals of the first group of capacitive coupling probes 13-1 and the second group of capacitive coupling probes 13-2 with the set reference value respectively;

[0046] 2) When the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 are greater than the set reference voltage, the signal monitoring module 15 outputs a high level, and vice versa.

[0047] 3) When the signal interlocking device 16 detects a high-level input, the interlocking signal prohibits the output of the high-frequency system signal source and the operation of the power source, and the accelerator high-frequency system stops operating; simultaneously, the motor rapidly moves to the capacitance scale position corresponding to the maximum value of the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 within the current 5s sweep frequency cycle, and this movement is required to be completed within less than 0.5s.

[0048] Furthermore, the first set of inductors and capacitors in series resonant circuit includes a first set of non-adjustable inductors (7-1), a first set of adjustable capacitors (9-1), a first set of adjustable capacitors with a non-grounded terminal (9-1), a first set of adjustable capacitors with a grounded terminal (10-1), and a first set of insulated adjustable knobs (11-1). The upper end of the first set of adjustable capacitors (9-1) is connected to the first set of non-adjustable inductors (7-1) through the non-grounded terminal (9-1), and the lower end is grounded through the grounded terminal (10-1). The inductive reactance of the first set of non-adjustable inductors (7-1) is fixed and non-adjustable. The first set of adjustable capacitors (9-1) is a vacuum adjustable capacitor. The first set of insulated adjustable knobs (11-1) is used to adjust the first set of adjustable capacitors (9-1) so that the frequency corresponding to the lowest point of S21 is equal to the high-frequency frequency f0 of the accelerator, and S21 < -30dB.

[0049] Furthermore, the second set of inductor and capacitor series resonant circuit includes a second set of non-adjustable inductor 7-2, a second set of adjustable capacitor 9-2, a second set of adjustable capacitor non-grounded terminal 9-2, a second set of adjustable capacitor grounded terminal 10-2, a second set of insulated adjustable knob 11-2, and a first set of motor 12-1; the upper end of the second set of adjustable capacitor 9-2 is connected to the second set of non-adjustable inductor 7-2 through the second set of adjustable capacitor non-grounded terminal 9-2, and the lower end is grounded through the second set of adjustable capacitor grounded terminal 10-2; the inductive reactance of the second set of non-adjustable inductor 7-2 is fixed and non-adjustable, the second set of adjustable capacitor 9-2 is a cylindrical vacuum capacitor, and the second set of insulated adjustable knob 11-2 is used to adjust the second set of adjustable capacitor. Device 9-2, so that the lowest point of S21 corresponds to the capacitor rotation angle scale range within the frequency range of (f0-2) to (f0-0.2)MHz; the first set of motors 12-1 is connected to the second set of insulated adjustable knobs 11-2. By setting the speed of the first set of motors 12-1, the change in the capacitance value driven by the first set of motors 12-1 can complete the coverage of the series resonant frequency (f0+0.2) to (f0+2)MHz within 5 seconds. The motor (12-1) rotates back and forth in this way; the calibration of the capacitor rotation angle scale in the frequency range of (f0-2) to (f0-0.2)MHz is adjusted by the motor or by the manual knob. The adjustment by the motor is to adjust the motor by the motor drive controller.

[0050] Furthermore, the third set of inductor and capacitor series resonant circuit includes a third set of non-adjustable inductor 7-3, a third set of adjustable capacitor 9-3, a third set of adjustable capacitor non-grounded terminal 9-3, a third set of adjustable capacitor grounded terminal 10-3, a third set of insulated adjustable knob 11-3, and a second set of motor 12-2; the upper end of the third set of adjustable capacitor 9-3 is connected to the third set of non-adjustable inductor 7-3 through the third set of adjustable capacitor non-grounded terminal 8-3, and the lower end is grounded through the third set of adjustable capacitor grounded terminal 10-3; the inductive reactance of the third set of non-adjustable inductor 7-3 is fixed and non-adjustable, the third set of adjustable capacitor 9-3 is a cylindrical vacuum capacitor, and the third set of insulated adjustable knob 11-3 is used to adjust the third set of adjustable capacitor series resonant circuit. Adjust capacitor 9-3 so that the lowest point of S21 corresponds to the capacitor rotation angle scale range within the frequency range of (f0+0.2) to (f0+2) MHz; the second set of motors 12-2 is connected to the third set of insulated adjustable knobs 11-3. By setting the speed of the second set of motors 12-2, the change in the capacitance value driven by the second set of motors 12-2 can complete the coverage of the series resonant frequency (f0+0.2) to (f0+2) MHz within 5 seconds, and the motor rotates back and forth in this way; the calibration of the capacitor rotation angle scale in the frequency range of (f0+0.2) to (f0+2) MHz is adjusted by the motor or by the manual knob. The adjustment by the motor is to adjust the motor by the motor drive controller.

[0051] Furthermore, a first set of capacitive coupling probes 13-1 is set near the second ungrounded terminal 8-2 of the second set of series resonant circuit capacitors, and leads out to the first set of N-type flange joints 14-1 set on the copper shell structure, wherein the minimum distance between the first set of capacitive coupling probes 13-1 and the second ungrounded terminal 8-2 of the capacitor is 5mm; the first set of N-type flange joints 14-1 connects the signal monitoring module 15 and the subsequent signal interlocking device 16;

[0052] Furthermore, a second set of capacitive coupling probes 13-2 is provided near the ungrounded terminal 8-3 of the third set of series resonant circuit capacitors, and led out to the second set of N-type flange joints 14-2 provided on the copper shell structure. The minimum distance between the second set of capacitive coupling probes 13-2 and the ungrounded terminal 8-3 of the third set of capacitors is 5mm. The second set of N-type flange joints 14-2 is connected to the signal monitoring module 15 and the subsequent signal interlocking device 16.

[0053] Furthermore, the function of the signal monitoring module 15 is to compare the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 with a set reference value. When the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 are greater than the set reference voltage, the signal monitoring module 15 outputs a high level, and vice versa. When the signal interlocking device 16 detects that the input is high, the interlocking signal prohibits the output of the high-frequency system signal source and the operation of the power source, and the accelerator high-frequency system stops operating. At the same time, the motor moves rapidly to the capacitance scale position corresponding to the maximum value of the signals of the first set of capacitive coupling probes 13-1 and the second set of capacitive coupling probes 13-2 within the current 5s sweep frequency cycle. This movement is required to be completed within less than 0.5s.

[0054] Furthermore, the reference value of the signal monitoring module 15 can be calibrated in the following way: Under normal operating conditions of the accelerator, record the high-frequency signal power values ​​of the capacitively coupled probes of the second and third sets of series resonant circuits in the corresponding ranges of (f0-2) to (f0-0.2) MHz and (f0+0.2) to (f0+2) MHz, denoted as M dBm, and the reference value is (M+3) dBm.

[0055] Furthermore, an air convection hole is provided at the lower end of the copper shell 3, with a diameter greater than 5 mm and less than 0.01 times the wavelength of the high-frequency signal. The signal input terminal 1 and the signal output terminal 2 are directly connected inside the copper shell 3 through a copper tube 4 with a diameter of 2.5 mm.

[0056] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A method for protecting a beam measurement signal of a cyclotron accelerator, the method being based on a beam measurement signal protection device for a cyclotron accelerator; the signal protection device is located outside the cyclotron accelerator, with one end connected to a stripping target inside the cyclotron accelerator and the other end connected to a beam measurement device outside the cyclotron accelerator; the signal protection device is provided with a cuboid protective copper shell (3), the upper end of which is fixed with a high-power air-cooling device, and the lower end is provided with an air convection hole; one end of the side of the cuboid protective copper shell (3) is a signal input terminal (1), and the other end is a signal output terminal (2), the signal input terminal (1) and the signal output terminal (2) are directly connected through a copper tube (4) inside the copper shell; at least three sets of inductors and capacitors are connected in series to ground on the copper tube (4), wherein, The first set of inductor and capacitor series resonant circuits is located near the signal input terminal (1), while the second and third sets of inductor and capacitor series resonant circuits are located away from the signal input terminal (1). The three sets of inductor and capacitor series resonant circuits are separated by a copper plate (6) to reduce coupling interference. A polytetrafluoroethylene block (5) is provided where the copper tube (4) passes through the copper plate (6) to achieve insulation between the copper tube (4) and the copper plate (6). The first set of inductor and capacitor series resonant circuits is used to suppress high-frequency signals coupled from the beam measurement signal drawn from the cyclotron under normal conditions and prevent the high-frequency signals from entering the beam measurement device. The second and third sets of series resonant circuits of inductors and capacitors are used to detect and control transmission oscillations under abnormal conditions; The method is characterized by the following steps: Step 1: Suppression of high-frequency coupled signals in the accelerator under normal conditions: Measure the parameters of the first series resonant circuit S21 using a network analyzer, and adjust the first set of insulating adjustable knobs (11-1) so that the frequency corresponding to the lowest point of S21 is equal to the high-frequency frequency f0 of the accelerator, and S21 < -30dB. Step 2: Calibration of the capacitor rotation angle scale range before abnormal situation monitoring: Measure the parameters of S21 in the second and third series resonant circuits, adjust the second set of adjustable insulation knobs (11-2) or adjust the first set of motors (12-1) through the motor controller, and calibrate the capacitor angle scale range with the frequency corresponding to the lowest point of S21 in the range of (f0-2) to (f0-0.2)MHz; adjust the third set of adjustable insulation knobs (11-3) or adjust the second set of motors (12-2) through the motor controller, and calibrate the capacitor angle scale range with the frequency corresponding to the lowest point of S21 in the range of (f0+0.2) to (f0+2)MHz. Step 3: Monitoring transmission line oscillations under abnormal conditions, specifically: 1) Connect the first set of motors (12-1) to the second set of series resonant circuit capacitor adjustment knob (11-2), set the speed of the first set of motors (12-1) so that the first set of motors (12-1) drives the capacitor to move within the specified rotation angle scale. The change in capacitance value caused by this movement should cover the series resonant frequency (f0-2) to (f0-0.2)MHz within 5 seconds. Connect the second set of motors (12-2) to the third set of series resonant circuit capacitor adjustment knob (11-3), set the speed of the second set of motors (12-2) so that the second set of motors (12-2) drives the capacitor to move within the specified rotation angle scale. The change in capacitance value caused by this movement should cover the series resonant frequency (f0+0.2) to (f0+2)MHz within 5 seconds. 2) When the series resonant frequency of the second group reaches one end of the calibrated frequency range, the first group of motors (12-1) reverses, so that the change in the capacitance value driven by the first group of motors (12-1) can complete the coverage of the series resonant frequency (f0-0.2) to (f0-2) MHz within 5 seconds, and the motors rotate back and forth in this way; when the series resonant frequency of the third group reaches one end of the calibrated frequency range, the second group of motors (12-2) reverses, so that the change in the capacitance value driven by the second group of motors (12-2) can complete the coverage of the series resonant frequency (f0+2) to (f0+0.2) MHz within 5 seconds, and the motors rotate back and forth in this way; Step 4: Transmission line oscillation control under abnormal conditions: Specifically: 1) The function of the signal monitoring module (15) is to compare the signals of the first group of capacitive coupling probes (13-1) and the second group of capacitive coupling probes (13-2) with the set reference value respectively; 2) When the signals of the first set of capacitive coupling probes (13-1) and the second set of capacitive coupling probes (13-2) are greater than the set reference voltage, the signal monitoring module (15) outputs a high level, and vice versa. 3) When the signal interlock device (16) detects that the input is high level, the interlock signal prohibits the output of the high frequency system signal source and the operation of the power source, and the high frequency system of the accelerator stops running; at the same time, the motor moves quickly to the capacitance scale position corresponding to the maximum value of the first set of capacitor coupling probes (13-1) and the second set of capacitor coupling probes (13-2) within the current 5s sweep frequency cycle, and this movement is required to be achieved in less than 0.5s.

2. The method for protecting the beam measurement signal of a cyclotron accelerator according to claim 1, characterized in that: The first set of inductors and capacitors in series resonant circuit includes a first set of non-adjustable inductors (7-1), a first set of adjustable capacitors (9-1), a first set of adjustable capacitors with non-grounded terminals (8-1), a first set of adjustable capacitors with grounded terminals (10-1), and a first set of insulated adjustable knobs (11-1). The upper end of the first set of adjustable capacitors (9-1) is connected to the first set of non-adjustable inductors (7-1) through the first set of adjustable capacitors with non-grounded terminals (8-1), and the lower end is grounded through the first set of adjustable capacitors with grounded terminals (10-1). The inductive reactance of the first set of non-adjustable inductors (7-1) is fixed and non-adjustable. The first set of adjustable capacitors (9-1) is a vacuum adjustable capacitor. The first set of insulated adjustable knobs (11-1) is used to adjust the first set of adjustable capacitors (9-1) so that the frequency corresponding to the lowest point of S21 is equal to the high frequency f0 of the accelerator, and S21 < -30dB.

3. The method for protecting the beam measurement signal of a cyclotron accelerator according to claim 1, characterized in that: The second set of inductor and capacitor series resonant circuit includes a second set of non-adjustable inductors (7-2), a second set of adjustable capacitors (9-2), a second set of adjustable capacitor non-grounded terminals (8-2), a second set of adjustable capacitor grounded terminals (10-2), a second set of insulated adjustable knobs (11-2), and a first set of motors (12-1). The upper end of the second set of adjustable capacitors (9-2) is connected to the second set of non-adjustable inductors (7-2) through the non-grounded terminal (8-2), and the lower end is grounded through the grounded terminal (10-2). The inductive reactance of the second set of non-adjustable inductors (7-2) is fixed and non-adjustable. The second set of adjustable capacitors (9-2)... -2) is a cylindrical vacuum capacitor. The second set of insulated adjustable knobs (11-2) is used to adjust the second set of adjustable capacitors (9-2) so that the capacitor rotation angle scale range corresponding to the lowest point of S21 is within the range of (f0-2) to (f0-0.2)MHz. The first set of motors (12-1) is connected to the second set of insulated adjustable knobs (11-2). By setting the speed of the first set of motors (12-1), the change in the capacitance value driven by the first set of motors (12-1) can complete the coverage of the series resonant frequency (f0+0.2) to (f0+2)MHz within 5 seconds. The first set of motors (12-1) rotates back and forth in this way. The calibration of the capacitor rotation angle scale in the frequency range of (f0-2) to (f0-0.2)MHz is adjusted by the motor or by the manual knob. The adjustment by the motor means adjusting the motor by the motor drive controller.

4. The method for protecting the beam measurement signal of a cyclotron accelerator according to claim 1, characterized in that: The third set of inductor and capacitor series resonant circuit includes a third set of non-adjustable inductors (7-3), a third set of adjustable capacitors (9-3), a third set of adjustable capacitor non-grounded terminals (8-3), a third set of adjustable capacitor grounded terminals (10-3), a third set of insulated adjustable knobs (11-3), and a second set of motors (12-2). The upper end of the third set of adjustable capacitors (9-3) is connected to the third set of non-adjustable inductors (7-3) through the non-grounded terminal (8-3), and the lower end is grounded through the grounded terminal (10-3). The inductive reactance of the third set of non-adjustable inductors (7-3) is fixed and non-adjustable. The third set of adjustable capacitors (9-3)... The capacitor is a cylindrical vacuum capacitor. The third set of insulated adjustable knobs (11-3) is used to adjust the third set of adjustable capacitors (9-3) so that the lowest point of S21 corresponds to a frequency range of (f0+0.2) to (f0+2)MHz, which is within the range of the capacitor rotation angle scale. The second set of motors (12-2) is connected to the third set of insulated adjustable knobs (11-3). By setting the speed of the second set of motors (12-2), the change in the capacitance value driven by the second set of motors (12-2) can complete the coverage of the series resonant frequency (f0+0.2) to (f0+2)MHz within 5 seconds. The motor rotates back and forth in this way. The calibration of the capacitor rotation angle scale in the frequency range of (f0+0.2) to (f0+2) MHz is adjusted by the motor or by the manual knob. The adjustment by the motor means adjusting the motor by the motor drive controller.

5. The method for protecting the beam measurement signal of a cyclotron accelerator according to claim 3, characterized in that: A first set of capacitive coupling probes (13-1) is set near the second set of ungrounded terminals (8-2) of the second set of series resonant circuit capacitors and led out to the first set of N-type flange joints (14-1) set on the copper shell structure. The minimum distance between the first set of capacitive coupling probes (13-1) and the second set of ungrounded terminals (8-2) of the capacitor is 5mm. The first set of N-type flange joints (14-1) is connected to the signal monitoring module (15) and the subsequent signal interlocking device (16).

6. The method for protecting the beam measurement signal of a cyclotron accelerator according to claim 4, characterized in that: A second set of capacitive coupling probes (13-2) is set near the ungrounded terminal (8-3) of the third set of series resonant circuit capacitors and led out to the second set of N-type flange joints (14-2) set on the copper shell structure. The minimum distance between the second set of capacitive coupling probes (13-2) and the ungrounded terminal (8-3) of the third set of capacitors is 5mm. The second set of N-type flange joints (14-2) is connected to the signal monitoring module (15) and the subsequent signal interlocking device (16).

7. A method for protecting cyclotron beam measurement signals according to claim 5 or 6, characterized in that: The function of the signal monitoring module (15) is to compare the signals of the first group of capacitive coupling probes (13-1) and the second group of capacitive coupling probes (13-2) with the set reference value. When the signals of the first group of capacitive coupling probes (13-1) and the second group of capacitive coupling probes (13-2) are greater than the set reference voltage, the signal monitoring module (15) outputs a high level, and otherwise outputs a low level. When the signal interlocking device (16) detects that the input is high level, the interlocking signal prohibits the output of the high-frequency system signal source and the operation of the power source, and the high-frequency system of the accelerator stops operating.

8. The method for protecting the beam measurement signal of a cyclotron accelerator according to claim 7, characterized in that: The reference value of the signal monitoring module (15) can be calibrated in the following way: Under normal working conditions of the accelerator, record the high-frequency signal power values ​​of the capacitive coupling probes of the second and third series resonant circuits in the corresponding ranges of (f0-2) to (f0-0.2) MHz and (f0+0.2) to (f0+2) MHz, denoted as M dBm, and the reference value is (M+3) dBm.

9. The method for protecting the beam measurement signal of a cyclotron accelerator according to claim 1, characterized in that: An air convection hole is provided at the lower end of the copper shell. The hole diameter is greater than 5 mm and less than 0.01 times the wavelength of the high-frequency signal. The signal input terminal (1) and the signal output terminal (2) are directly connected inside the copper shell through a copper tube (4) with a diameter of 2.5 mm.

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