A cyclotron cavity acceleration voltage measurement system and measurement method

Abstract

The present invention relates to the field of particle accelerators, and discloses a cyclotron cavity acceleration voltage measurement system and measurement method. The system includes: a radio frequency front-end module, which completes the filtering and attenuation of the AD module input signal and the filtering and amplification of the DA module output signal; an AD module, which completes the digitization of the input signal after the radio frequency front-end processing; a DA module, which completes the simulation of the output signal after the feedback processing; a signal processing module, which completes the control of the AD module and the DA module, amplitude and phase detection, tuning motor control and cavity voltage measurement, and completes data interaction with the display and control unit through Ethernet; a display and control unit. The present invention can measure the cavity voltage online by designing a cyclotron cavity voltage measurement system. Q The value is calculated, the high-frequency cavity parallel shunt impedance is calculated, and the current cavity voltage value is calculated by measuring the power consumption inside the cavity.

Description

Technical Field

[0001] The present invention relates to the field of particle accelerators, and in particular to a cyclotron cavity acceleration voltage measurement system and a measurement method. Background Art

[0002] A cyclotron is a device that uses magnetic and electric fields to make charged particles perform cyclotron motion, repeatedly accelerating them through high-frequency electric fields during motion. It is an important instrument in high-energy physics.

[0003] With the application of nuclear technology, its application in medicine, materials science, biology and other fields is becoming more and more extensive.

[0004] The high-frequency system of a cyclotron is an important component of the cyclotron. The high-frequency resonant cavity provides an electric field for particle acceleration. The RF voltage of the cavity is difficult to measure directly. In the past, the calibration method of the cavity voltage of cyclotron resonant cavities at home and abroad was mainly through the Bremsstrahlung method. However, the measurement process of the Bremsstrahlung method is relatively complicated and the measurement cost is relatively high. Summary of the Invention

[0005] Purpose of the invention: To provide a cyclotron cavity acceleration voltage measurement system and method to solve the above-mentioned problems existing in the prior art.

[0006] Technical solution: A cyclotron cavity acceleration voltage measurement system, including:

[0007] The RF front-end module completes the filtering and attenuation of the AD module input signal and the filtering and amplification of the DA module output signal;

[0008] AD module, which completes the digitization of the input signal after being processed by the RF front end;

[0009] DA module, completes the simulation of the output signal after feedback processing;

[0010] The signal processing module completes the AD module and DA module control, amplitude and phase detection, tuning motor control, and cavity voltage measurement, and completes data exchange with the display and control unit through Ethernet;

[0011] Display and control unit, used to display data and control the voltage measurement system.

[0012] In a further embodiment, the input signal includes a cavity sampling signal, an incident sampling signal, and a reflected sampling signal.

[0013] In a further embodiment, the output signal comprises a radio frequency output signal.

[0014] A method for measuring the accelerating voltage of a cyclotron cavity, comprising:

[0015] The simulated parallel shunt impedance and no-load impedance are obtained through CST simulation Ratio K ;

[0016] The theoretical cavity parallel shunt impedance value is obtained by CST calculation and no load , parallel shunt impedance and no-load The ratio is

[0017] Calibrate the sampling amplitude value of the cavity sampling port of the voltage measurement system, and measure the loss of the entire sampling cable and the attenuation value of the sampling port;

[0018] Start the voltage measurement system, search for the cavity operating point, and gradually complete the tuning closed loop and amplitude closed loop;

[0019] Calculating the thermal state of a cyclotron during operation by using the cavity damping oscillation time Q The actual cavity loss power is obtained by fitting and calculating the AD sampling value.

[0020] The cavity voltage value is calculated.

[0021] In a further embodiment, further comprising:

[0022] Calibrate the vector network analyzer by connecting port 1 of the vector network analyzer to the RF feed port of the cavity and port 2 of the vector network analyzer to the cavity sampling port to measure the attenuation value of the cavity sampling. , That is the sampling port attenuation value;

[0023] Measure the cable attenuation from the cavity sampling port to the RF control system. Connect the two ends of the cable with port 1 and port 2 of the vector network analyzer respectively. The measured cable attenuation is , This is the sampling cable loss.

[0024] In a further embodiment, further comprising:

[0025] The signal source was calibrated using a power meter. The signal source output varied from -20dBm to +10dBm in 1dB increments, as shown in Table 1. The actual output power of the signal source was measured using the power meter, as shown in Table 2.

[0026] Connect the signal source output to the cavity sampling input port of the voltage measurement system through the same cable. Similarly, change the output from -20dBm to +10dBm in 1dB intervals. Record the AD sampling values ​​of the voltage measurement system in Table 3. Correlate and fit the values ​​in Table 3 with the values ​​in Table 2 to complete the calibration of the cavity sampling amplitude value of the RF control system.

[0027] The voltage measurement system is set to work with a pulse width of 1ms and a repetition rate of 10ms. The output signal amplitude is set to 0dBm. The voltage measurement system is amplified by a high-frequency power source and fed into the cyclotron high-frequency cavity. The tuning loop and amplitude loop are closed by combining the internal automatic operation process to obtain a stable cavity sampling power value. .

[0028] In a further embodiment, further comprising:

[0029] The actual power loss inside the cavity is ;

[0030] go through Calculate the actual internal cavity power loss The actual cavity damping oscillation time is calculated by triggering the falling edge of the pulse, and the cavity quality factor is calculated. The cavity quality factor is the thermal state of the cyclotron when it is working. Q value.

[0031] Beneficial effect: The present invention discloses a cyclotron cavity acceleration voltage measurement system and a measurement method. The present invention can measure the cavity acceleration voltage online by designing a cyclotron cavity voltage measurement system. Q The high-frequency cavity parallel shunt impedance is calculated, and the current cavity voltage is calculated by measuring the power consumption inside the cavity. Compared with the traditional calibration method of the cyclotron resonant cavity voltage, the measurement process is simpler and the measurement cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0033] Figure 2 It is a schematic flow chart of the method of the present invention.

[0034] Figure 3 It is a schematic diagram of measuring the attenuation value of the sampling port of the present invention.

[0035] Figure 4 It is a schematic diagram of measuring the attenuation value of a sampling cable according to the present invention.

[0036] Figure 5 It is a schematic diagram of the equivalent circuit of the accelerator cavity of the present invention.

[0037] Figure 6 It is a schematic diagram of the cavity field waveform of the present invention.

[0038] Figure 7 It is a schematic diagram of the cavity attenuation waveform under pulse operation of the present invention. DETAILED DESCRIPTION

[0039] The present application relates to a cyclotron cavity acceleration voltage measurement system and method, which are explained in detail below through specific implementation methods.

[0040] The high-frequency cavity voltage is calculated by the internal power consumption of the cavity and the parallel shunt impedance value.

[0041] Right now (Formula 1);

[0042] When the high-frequency cavity has a certain shape, its shunt impedance and no load The ratio is fixed. Due to the difference in processing technology, the surface performance of different cavities has certain differences, so it is necessary to introduce This method is based on the analysis of the surface performance difference caused by the cavity manufacturing process. It needs to be based on the early high-frequency system simulation of the cyclotron. First, we use CST calculation to obtain the theoretical cavity parallel shunt impedance value during design. and no load , then the actual accelerator cavity during operation The value can be measured by the voltage measurement system;

[0043] thereby = (Formula 2), and thus combined with Formula 1 we can get the cavity voltage during actual operation.

[0044] A cyclotron cavity acceleration voltage measurement system, comprising:

[0045] The RF front-end module completes the filtering and attenuation of the AD module input signal and the filtering and amplification of the DA module output signal;

[0046] AD module, which completes the digitization of the input signal after being processed by the RF front end;

[0047] DA module, completes the simulation of the output signal after feedback processing;

[0048] The signal processing module completes the AD module and DA module control, amplitude and phase detection, tuning motor control, and cavity voltage measurement, and completes data exchange with the display and control unit through Ethernet;

[0049] Display and control unit, used to display data and control the voltage measurement system.

[0050] The input signal includes a cavity sampling signal, an incident sampling signal, and a reflected sampling signal.

[0051] The output signal comprises a radio frequency output signal.

[0052] A method for measuring the accelerating voltage of a cyclotron cavity, comprising:

[0053] The simulated parallel shunt impedance and no-load impedance are obtained through CST simulation Ratio K ;

[0054] The theoretical cavity parallel shunt impedance value is obtained by CST calculation and no load , the ratio of the parallel shunt impedance to the no-load impedance is

[0055] Calibrate the sampling amplitude value of the cavity sampling port of the voltage measurement system, and measure the loss of the entire sampling cable and the attenuation value of the sampling port;

[0056] Start the voltage measurement system, search for the cavity operating point, and gradually complete the tuning closed loop and amplitude closed loop;

[0057] Calculating the thermal state of a cyclotron during operation by using the cavity damping oscillation time Q The actual cavity loss power is obtained by fitting and calculating the AD sampling value.

[0058] According to formula (1), the cavity voltage value can be calculated as follows:

[0059] The cavity voltage value is calculated.

[0060] Also includes:

[0061] Calibrate the vector network analyzer by connecting port 1 of the vector network analyzer to the RF feed port of the cavity and port 2 of the vector network analyzer to the cavity sampling port to measure the attenuation value of the cavity sampling. , That is the sampling port attenuation value;

[0062] Measure the cable attenuation from the cavity sampling port to the RF control system. Connect the two ends of the cable with port 1 and port 2 of the vector network analyzer respectively. The measured cable attenuation is , This is the sampling cable loss.

[0063] Also includes:

[0064] Calibrate the vector network analyzer by connecting port 1 of the vector network analyzer to the RF feed port of the cavity and port 2 of the vector network analyzer to the cavity sampling port to measure the attenuation value of the cavity sampling. ;

[0065] Measure the cable attenuation from the cavity sampling port to the RF control system. Connect the two ends of the cable with port 1 and port 2 of the vector network analyzer respectively. The measured cable attenuation is .

[0066] Also includes:

[0067] The signal source was calibrated using a power meter. The signal source output varied from -20dBm to +10dBm in 1dB increments, as shown in Table 1. The actual output power of the signal source was measured using the power meter, as shown in Table 2.

[0068] Connect the signal source output to the cavity sampling input port of the voltage measurement system through the same cable. Similarly, change the output from -20dBm to +10dBm in 1dB intervals. Record the AD sampling values ​​of the voltage measurement system in Table 3. Correlate and fit the values ​​in Table 3 with the values ​​in Table 2 to complete the calibration of the cavity sampling amplitude value of the RF control system.

[0069] The voltage measurement system is set to work with a pulse width of 1ms and a repetition rate of 10ms. The output signal amplitude is set to 0dBm. The voltage measurement system is amplified by a high-frequency power source and fed into the cyclotron high-frequency cavity. The tuning loop and amplitude loop are closed by combining the internal automatic operation process to obtain a stable cavity sampling power value. .

[0070] Also includes:

[0071] The actual power loss inside the cavity is ;

[0072] go through Calculate the actual internal cavity power loss The actual cavity damping oscillation time is calculated by triggering the falling edge of the pulse, and the cavity quality factor is calculated. The cavity quality factor is the thermal state of the cyclotron when it is working. Q value.

[0073] The specific principle and method of measuring the cavity quality factor using the voltage measurement system are as follows:

[0074] The equivalent circuit of the accelerator cavity is shown in the attached figure. Figure 5 As shown,

[0075] The cavity is equivalent to RLC Parallel circuits, RF drive provided by the power source, It is a beam;

[0076] The power source provides pulses to the cavity RF power( ), due to the cavity Q The value is large and can be regarded as RLC The energy storage elements are connected in parallel, so when the power source gives a pulse RF The moment the drive ends, that is, the pulse of the power source RF At the moment the power is turned off, the cavity field does not immediately become 0, but it takes a period of damped oscillation to decay ( decay ) The cavity field can be reduced to 0, the cavity Q The larger the value, the longer the damped oscillation time;

[0077] The cavity field waveform is as follows Figure 6 As shown;

[0078] The cavity attenuation waveform under pulse operation is shown in the attached figure. Figure 7 As shown;

[0079] The amplitude envelope can be seen in the attached figure The larger it is, the faster the amplitude of the oscillation decays;

[0080] Angular frequency of decaying oscillation The larger it is, the smaller the period is and the faster the oscillation is.

[0081] When discussing the limiting case, when the resistance tends to infinity, that is, tends to 0, then in physical terms, only LC The parallel resonant network formed by the that is LC Resonant angular frequency of a parallel circuit ;

[0082] The angular frequency of the RF signal given by the power source is , assuming the resonant angular frequency of the cavity is ,pulse RF The angular frequency of the decay oscillation of the cavity field after the driving is ;

[0083] Quality factor of the cavity Q The value is defined as: the ratio of energy storage to energy consumption when the cavity operates at the resonant frequency;

[0084] RLC Parallel circuit Q The value formula is:

[0085] in R is the cavity equivalent resistance, C is the cavity equivalent distributed capacitance, L is the cavity equivalent inductance, is the resonant angular frequency.

[0086] Cavity damped oscillation attenuation ( decay ) The envelope of the curve decays exponentially, and the time constant is introduced , ;

[0087] The exponentially decaying envelope equation is:

[0088]

[0089] again = ,so , that is, we get , The value is related to two factors, namely the time constant of the exponential decay of the envelope , the resonant angular frequency of the cavity in the current state ;

[0090] Generally speaking, we are concerned about The value refers to the acceleration cavity resonance at the physically designed working frequency. value, that is, when the cavity resonates at the angular frequency value;

[0091] Depend on It can be seen that the cavity resonance will have different effects at different resonant frequencies. value, while the resonance at non-angular frequencies Values ​​are meaningless to us;

[0092] So we need to measure When the value is set, the cavity must first be resonated at The physical design of the operating frequency is a prerequisite before measuring the time constant , and then calculate Value, that is = .

[0093] Working principle description: CST simulation is used to obtain the simulated parallel shunt impedance and no-load Ratio K ;

[0094] Calibrate the sampling amplitude value of the cavity sampling port of the voltage measurement system, and measure the loss of the entire sampling cable and the attenuation value of the sampling port;

[0095] Start the voltage measurement system, search for the cavity operating point, and gradually complete the tuning closed loop and amplitude closed loop;

[0096] Calculating the thermal state of a cyclotron during operation by using the cavity damping oscillation time Q The actual cavity loss power is obtained by fitting and calculating the AD sampling value.

[0097] The cavity voltage value is calculated.

[0098] The preferred specific embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above specific embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A method for measuring the accelerating voltage of a cyclotron cavity, characterized in that: Based on a cyclotron cavity acceleration voltage measurement system, the cyclotron cavity acceleration voltage measurement system includes: The RF front-end module completes the filtering and attenuation of the AD module input signal and the filtering and amplification of the DA module output signal; the input signal includes the cavity sampling signal, the incident sampling signal, and the reflected sampling signal; the output signal includes the RF output signal; AD module, which completes the digitization of the input signal after being processed by the RF front end; DA module, completes the simulation of the output signal after feedback processing; The signal processing module completes the AD module and DA module control, amplitude and phase detection, tuning motor control, and cavity voltage measurement, and completes data exchange with the display and control unit through Ethernet; Display and control unit; The cyclotron cavity acceleration voltage measurement method includes: The simulated parallel shunt impedance and no-load impedance are obtained through CST simulation Ratio K ; Calibrate the sampling amplitude value of the cavity sampling port of the voltage measurement system, measure the loss of the entire sampling cable and the attenuation value of the sampling port; calibrate the vector network analyzer, connect the vector network analyzer port 1 to the cavity RF feed port, and connect the vector network analyzer port 2 to the cavity sampling port, and measure the attenuation value of the cavity sampling. , The attenuation value of the sampling port is measured; the attenuation value of the cable from the cavity sampling port to the RF control system is measured by connecting the two ends of the cable with port 1 and port 2 of the vector network analyzer respectively. The measured cable attenuation value is , That is the sampling cable loss; Start the voltage measurement system, search for the cavity operating point, and gradually complete the tuning closed loop and amplitude closed loop; Calculating the thermal state of a cyclotron during operation by using the cavity damping oscillation time The actual cavity loss power is calculated by fitting the AD sampling value; the actual cavity internal loss power is ;in, is the cavity sampling power value; The cavity voltage value is calculated, 。 2. The method for measuring the accelerating voltage of a cyclotron cavity according to claim 1, wherein: include: The signal source was calibrated using a power meter. The signal source output varied from -20dBm to +10dBm in 1dB increments, as shown in Table 1. The actual output power of the signal source was measured using the power meter, as shown in Table 2. Connect the signal source output to the cavity sampling input port of the voltage measurement system through the same cable. Similarly, change the output from -20dBm to +10dBm in 1dB intervals. Record the AD sampling values ​​of the voltage measurement system in Table 3. Correlate and fit the values ​​in Table 3 with the values ​​in Table 2 to complete the calibration of the cavity sampling amplitude value of the RF control system. The voltage measurement system is amplified by the high-frequency power source and fed into the high-frequency cavity of the cyclotron. By combining the internal automatic operation process, the tuning loop and the amplitude loop are closed to obtain a stable cavity sampling power value. .

3. The method for measuring the accelerating voltage of a cyclotron cavity according to claim 2, wherein: Also includes: The actual cavity damping oscillation time is calculated by triggering the falling edge of the pulse, and the cavity quality factor is calculated. The cavity quality factor is the thermal state of the cyclotron when it is working. value.

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