Compact RF power source system for BNCT

Abstract

The present invention discloses a compact radio frequency power source system for BNCT, comprising a low-level control and power detection integrated module, a high-frequency protection module, a CPCI chassis, a CompactPCI blade, a solid-state amplifier, a coaxial feed tube, a directional coupler, a high-power coupler, and an accelerating cavity. The low-level control and power detection integrated module is provided with a low-level control and power detection integrated system, which is composed of a low-level control system and a power detection system. The high-frequency protection module is provided with a high-frequency protection system. The CPCI chassis is provided with a backplane bus. By carrying a CompactPCI blade running a Linux operating system and developing a Linux-based driver and EPICS interface program, the system replaces the traditional solution of a CPU board of a VxWorks system and an EPICS control mode of a Linux computer. The low-level control and power monitoring systems are integrated into one system to form an integrated low-level control and power monitoring system.

Description

Technical Field

[0001] The present invention relates to the technical fields of accelerators and high-power microwaves, and in particular to a compact radio frequency power source system for BNCT. Background Art

[0002] Cancer has become one of the biggest threats to human health. Boron neutron capture therapy (BNCT) is the best-established cancer radiotherapy method to date. It is a safe binary targeted radiotherapy technology and an excellent treatment for gliomas and melanomas. It also has a good therapeutic response for recurrent neck cancer and liver metastases. With the development of accelerator technology, accelerator-based boron neutron capture tumor treatment devices have the advantages of precise targeting, low side effects, a wide range of indications, a one-time solution, and easy popularization and use in hospitals in densely populated areas.

[0003] In recent years, extensive research has been conducted both domestically and internationally. The Boron Neutron Capture Therapy (BNCT) device developed by the Spallation Neutron Source Science Center uses a radio frequency quadrupole accelerator (RFQ) to provide a high-current proton beam. The proton beam passes through a beam transmission line and hits a lithium target to produce a high flux of neutrons. The accelerator is designed for a high-repetition-rate pulsed operation mode. The RFQ accelerating cavity has a high-frequency frequency of 180 MHz, a beam duty ratio of 80%, a beam pulse length of 4 ms, a repetition rate of 200 Hz, and a pulse current intensity of 25 mA. In addition to providing sufficient power to compensate for the RFQ accelerating cavity consumption, the RF power source system must also compensate for the beam loading effect to ensure the stability of the RFQ accelerating electric field.

[0004] Traditional radio frequency power source systems used in boron neutron capture therapy (BNCT) devices often have complex system structures and high costs, which are not conducive to the use of BNCT devices. Based on this, we propose a compact radio frequency power source system for BNCT, which can stably and effectively meet the requirements of BNCT devices. Summary of the Invention

[0005] The object of the present invention is to provide a compact radio frequency power source system for BNCT to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Used for a BNCT compact radio frequency power source system, the system includes a low-level control and power detection integrated module, a high-frequency protection module, a CPCI chassis, a CompactPCI blade, a solid-state amplifier, a coaxial feed tube, a directional coupler, a high-power coupler, and an accelerating cavity. The low-level control and power detection integrated module is provided with a low-level control and power detection integrated system, which is composed of a low-level control system and a power detection system. The high-frequency protection module is provided with a high-frequency protection system. The CPCI chassis is provided with a backplane bus. The CompactPCI blade uses a Linux operating system, a Linux system driver, an EPICS interface program, and a CSS. The low-level control and power detection integrated module and the high-frequency protection module both communicate with the CompactPCI blade via the backplane bus of the CPCI chassis for data transmission. The CompactPCI blade is provided with a Linux operating system, a Linux system driver, an EPICS interface program, and a CSS. The CompactPCI blade uses a Linux operating system, a CPCIEPCIS remote control system, and a CSS graphical display interface.

[0008] As a further solution of the present invention: the low-level control and power detection integrated system is used to control the amplitude of the high-frequency field in the accelerator and the stability of the resonant frequency of the accelerating cavity, perform real-time detection of the power entering the accelerating cavity and protect the standing wave ratio. The low-level control and power detection integrated module performs digital signal processing, and after digital-to-analog conversion, sends out the radio frequency signal required by the accelerating cavity. The sent radio frequency signal is amplified into a high-power radio frequency signal by a solid-state amplifier. The high-power radio frequency signal is transmitted to the high-power coupler through the coaxial feed tube, and the radio frequency signal is coupled into the accelerating cavity through the high-power coupler. The directional coupler is used to couple the forward and reverse power signals of the accelerating cavity. The water cooling, vacuum signal and other signals of the accelerating cavity are fed back to the high-frequency protection module. When the accelerating cavity has water cooling, vacuum or the tunnel personal protection system issues a fault alarm, the high-frequency protection module sends a protection signal to the low-level control and power detection integrated module, and cuts off the output of the radio frequency signal in time through low-level control.

[0009] As a further solution of the present invention: the input RF signal source of the accelerating cavity is derived from a low-level control system. In the integrated system of low-level control and power detection, power detection and low-level control share the same FPGA board. The power detection system accurately calculates the power of the RF signal sent to the accelerating cavity by sharing the FPGA with the low-level control system. The power detection method does not require a detector when performing RF power detection within a wide frequency range, and can simultaneously detect the power value of each spectral component contained in the signal.

[0010] As further scheme of the present invention: in the described power detection system, i.e. power detection and standing wave ratio protection system, comprise AD sampling module, IQ demodulation module, IIR filtering module, power calculation module and standing wave ratio protection module, the digital processing method that described power detection and standing wave ratio protection system adopt comprises: at first calculate power through the power calculation module from the radio frequency signal coupled out by directional coupler by AD sampling, IQ demodulation, IIR filtering, then the forward power and reverse power calculated are sent into the standing wave ratio protection module, judge by the standing wave ratio protection module whether to carry out standing wave ratio protection, when judging that need carry out standing wave ratio protection, after standing wave ratio protection takes place, standing wave ratio protection module output protection signal is given to the switch in the low-level control system, the switch cuts off the output of radio frequency signal, next pulse recovers, when the number of times of standing wave ratio protection exceeds set value, will permanently cut off the output of low-level radio frequency signal, up to manual recovery.

[0011] As a further solution of the present invention: the low-level control system includes an AD sampling module, an IQ demodulation module, an IIR filtering module, an amplitude-phase conversion module, a PI feedback controller, an amplitude-phase adjustment module, a digital up-conversion module, a switch, and a DAC chip. The processing method of the low-level control system includes: first, the RF signal coupled from the accelerating cavity is sent to the AD sampling module of the low-level control system; the sampled signal is output through the IQ demodulation module and IIR filtering to output DC I and Q signals; the I and Q signals are sent to the amplitude-phase conversion module to obtain the amplitude and phase information of the acceleration field; then closed-loop control is performed through the PI feedback controller; the closed-loop output signal is respectively sent to the amplitude-phase adjustment module of each channel; the adjusted signal is output through the digital up-conversion module to output the required digital signal; the output digital signal contains the cavity field amplitude, phase, and frequency signal and is transmitted to the DAC chip; the DAC output signal is filtered and amplified, and then the high-power signal is transmitted to the accelerating cavity through the coaxial feed tube; the amplitude, phase, frequency and other parameters of the signal can be set through the CSS graphical display interface.

[0012] As a further solution of the present invention: by introducing an amplitude and phase adjustment module into the low-level control system, the amplitude modulation and phase modulation of each signal entering the acceleration cavity are realized. The amplitude adjustment coefficient and phase shift parameter are set through the CSS graphical display interface. The amplitude signal output from the PI controller is multiplied by the amplitude coefficient set through the CSS interface to complete the amplitude adjustment of the RF signal. If the coefficient is greater than 1, the signal is amplified, and if the coefficient is less than 1, the signal is reduced. The phase signal output from the PI controller is added to the phase offset coefficient set through the CSS interface to complete the phase adjustment of the RF signal.

[0013] As a further solution of the present invention: the solid-state amplifier is used to receive the radio frequency signal from the low-level control system and generate a high-power radio frequency signal. The radio frequency signal output by the low-level control system is sent to the preamplifier for amplification. The signal output by the preamplifier is divided into four paths by a one-to-four power distributor, and provides radio frequency input for four power amplifier cabinets respectively. Each power amplifier cabinet divides the radio frequency signal input by the distributor into thirty-two paths through a one-to-four power distributor and a one-to-eight power distributor. The thirty-two-path final-stage power amplifier plug-in amplifies the signal. The thirty-two-path final-stage power amplifier The signal after the plug-in amplification is then synthesized into 32 channels by an 8-in-1 power combiner and a 4-in-1 power combiner to achieve the power output of a single power amplifier cabinet. The output signals of the four cabinets are then power synthesized by a two-stage 2-in-1 power combiner at the cabinet level. The synthesized output power is higher than 150kW. Among them, the power distribution and synthesis methods in the four power amplifier cabinets are the same. The 8-in-1 power combiner, the 4-in-1 power combiner in the power amplifier cabinet and the synthesizer in the final power amplifier plug-in all use isolated synthesizers. The ports of the power synthesis network are isolated from each other to ensure When the solid-state amplifier works in the full reflection state, the reflected power of the final power amplifier plug-in is only single power, and there will be no situation where it bears several times the power due to power imbalance. The final power amplifier plug-in adopts a two-stage amplification chain, including an RF sampling board, a one-to-two power splitter, two 1200W amplifier modules, a circulator and load, a two-in-one power combiner, a directional coupler, a monitoring board, a water cooling plate and an external interface. The principle of the final power amplifier plug-in is: first, the external RF signal is sampled by the RF, and then amplified in two stages by two 1200W amplifier modules, and then the circulator, two-in-one power combiner and the load are connected. The output power of the one-in-one power combiner and directional coupler reaches more than 2000W. The two-in-one power combiner adopts an isolated orthogonal combiner. The heat source devices such as the pre-amplifier tube, the final power amplifier tube, the circulator and its load are cooled by a professionally designed water-cooling plate. The temperature and current of the final high-power module, the forward and reverse power of the components, etc. are monitored in real time through the monitoring board. The input and output external interfaces on the final power amplifier plug-in include RF input interface, RF output interface, AC power supply interface, status and fault signal interface, and water input and output interfaces.

[0014] As a further aspect of the present invention, the high-frequency electromagnetic energy generated by the solid-state amplifier is directionally transmitted to the BNCT RFQ accelerating cavity via a closed coaxial feed tube of the power feeding system, minimizing or preventing leakage. The entire power feeding system comprises a coaxial feed tube, an elbow, a directional coupler, and a high-power coupler. The transmission line does not require a high-power circulator or load. Because the solid-state amplifier utilizes an isolated synthesis network, the reflected power experienced by the final-stage power amplifier plug-in is only a single times its power. Therefore, in a fully reflected state, the power amplifier tube is not damaged by total reflection, and the entire solid-state amplifier is resistant to total reflection.

[0015] As a further solution of the present invention: the accelerating cavity uses two high-power couplers to complete the feeding of high-frequency power. The high-power coupler isolates the vacuum and feeds the microwaves sent by the power source into the accelerating cavity. The high-power coupler transmits high power, but the ceramic sheet in the ceramic window has limited pressure resistance, which limits the peak power transmitted by the power coupler. In addition, the high power and high duty cycle cause very large heat deposition on the power coupler. At the same time, there is a pressure difference of 1 atmosphere on both sides of the high-power coupler, which will generate large stress on the ceramic window. For the ceramic window of the fragile device, the stress thereon limits the average power of the power coupler. The present invention combines the relevant theories of microwave, thermal, and mechanics to design a high-power and high-duty cycle power coupler for the BNCT RFQ accelerating cavity. After optimization, the high-power coupler has a standing wave ratio of less than 1.1 in the range of 180MHz, ±7MHz, and a temperature rise of less than 2 degrees at an average power of 90kW. The diameter of the optimized ceramic sheet is 262mm and the thickness of the ceramic sheet is 10mm.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention utilizes an integrated low-level control and power detection module, a high-frequency protection module, a CPCI chassis, a CompactPCI blade, a solid-state amplifier, a coaxial feeder, a directional coupler, and a high-power coupler. By installing a CompactPCI blade running a Linux operating system and developing a Linux-based driver and EPICS interface program, the present invention replaces the traditional VxWorks CPU board + Linux computer EPICS control model. By integrating the low-level control and power monitoring systems into one, an integrated low-level control and power monitoring system is formed, simplifying the system structure. Furthermore, a detector is not required for power detection, resulting in a compact overall system structure, reduced costs, and more convenient operation.

[0018] 2. In the present invention, by mounting the low-level control and power detection integrated system board and the high-frequency protection system board in the same CPCI chassis, the CompactPCI blade transmits data with the low-level control and power detection integrated module and the high-frequency protection module via the PCI bus. The CompactPCI blade runs the Linux operating system, adopts EPICS control, and uses a CSS graphical display interface, thereby enabling monitoring and control of the low-level control and power detection integrated system and the high-frequency protection system.

[0019] 3. In the present invention, by using a shared FPGA board for the low-level control and power detection integrated system, low-level control, power detection, and standing wave ratio protection functions can be simultaneously realized. The low-level control system realizes frequency modulation of the radio frequency signal by controlling the frequency of the DDS module, and the radio frequency signal for power detection is exactly the amplified signal output by the low-level control system. The frequencies of the two signals are the same, so the two orthogonal signals output by the low-level control system DDS can be directly sent to the power detection module for I,Q demodulation and calculation of the power value. This system can demodulate signals of any frequency in the system without the need for a detector, thereby calculating the power value, and can measure the power values ​​of different frequencies in a signal containing multiple frequency components in real time.

[0020] 4. In the present invention, the cavity pressure of the accelerating cavity is maximized by adjusting the amplitude and phase of multiple signals. By introducing amplitude and phase adjustment modules into the low-level control system, digital amplitude modulation and phase modulation of each input signal are achieved. The amplitude adjustment coefficient and phase shift parameters can be set through the CSS graphical display interface, thereby making the system highly accurate and easy to operate. At the same time, by adopting digital phase modulation, there is no need to increase the power phase shifter in the transmission path. The use of digital adjustment of the signal amplitude ensures that the input power of each coupler of the accelerating cavity is consistent, achieving improved adjustment accuracy while eliminating the need to add an adjustable attenuator in the transmission line.

[0021] 5. In the present invention, the eight-in-one power combiner, the four-in-one power combiner, and the combiner in the final power amplifier plug-in in the cabinet all adopt isolated combiners, and the ports of the power combining network are isolated from each other. This ensures that when the solid-state amplifier operates in a full reflection state, the reflected power of the final power amplifier plug-in is only a single power, and there will be no situation where the final power amplifier plug-in bears several times the power due to power imbalance. The reflected power is relatively stable, thereby reducing the power borne by the circulator and the load in the final power amplifier plug-in. The circulator and the load in the final power amplifier plug-in only need to be able to withstand a reflected power greater than 1 times the output power. Therefore, there is no need to add a high-power circulator in the RF transmission line to protect the solid-state amplifier, thereby reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure shows the overall composition block diagram of the compact RF power source system for BNCT.

[0023] Figure 2 This is the architecture diagram of the traditional CPCI EPCIS remote control system.

[0024] Figure 3 This is the CPCI EPCIS remote control system architecture for the BNCT compact RF power source system.

[0025] Figure 4This is the algorithm block diagram of the integrated system for low-level control and power detection in the BNCT compact RF power source system.

[0026] Figure 5 This is a block diagram of the amplitude modulation and phase modulation principles used in the BNCT compact RF power source system.

[0027] Figure 6 This is the block diagram of the power distribution and synthesis network for the 150kW solid-state amplifier used in the BNCT compact RF power source system.

[0028] Figure 7 This is the principle block diagram of the final stage power amplifier plug-in used in the BNCT compact RF power source system.

[0029] Figure 8 Schematic diagram of the structure of the high-power coupler used in the BNCT compact RF power source system.

[0030] Figure 9 Schematic diagram of the coupler standing wave ratio used in the BNCT compact RF power source system. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] See also Figures 1 to 9In an embodiment of the present invention, a compact radio frequency power source system for BNCT includes a low-level control and power detection integrated module, a high-frequency protection module, a CPCI chassis, a CompactPCI blade, a solid-state amplifier, a coaxial feed tube, a directional coupler, a high-power coupler, and an accelerating cavity. The low-level control and power detection integrated module is provided with a low-level control and power detection integrated system. The low-level control and power detection integrated system is composed of a low-level control system and a power detection system. The high-frequency protection module is provided with a high-frequency protection system. The CPCI chassis is provided with a backplane bus. The CompactPCI blade uses a Linux operating system, a Linux system driver, an EPICS interface program, and a CSS. The low-level control and power detection integrated module and the high-frequency protection module both transmit data to the CompactPCI blade through the backplane bus of the CPCI chassis. The CompactPCI blade is provided with a Linux operating system, a Linux system driver, an EPICS interface program, and a CSS. The CompactPCI blade uses a Linux operating system, a CPCI EPCIS remote control system, and a CSS graphical display interface.

[0033] The integrated low-level control and power detection system is used to control the amplitude of the high-frequency field in the accelerator and the stability of the resonant frequency of the accelerating cavity, perform real-time detection of the power entering the accelerating cavity and protect the standing wave ratio. The integrated low-level control and power detection module performs digital signal processing and sends out the radio frequency signal required by the accelerating cavity after digital-to-analog conversion. The sent radio frequency signal is amplified into a high-power radio frequency signal by a solid-state amplifier. The high-power radio frequency signal is transmitted to the high-power coupler through the coaxial feed tube, and the radio frequency signal is coupled into the accelerating cavity through the high-power coupler. The directional coupler is used to couple the forward and reverse power signals of the accelerating cavity. The water cooling, vacuum signal and other signals of the accelerating cavity are fed back to the high-frequency protection module. When the accelerating cavity has water cooling, vacuum or the tunnel's personal protection system and issues a fault alarm, the high-frequency protection module sends a protection signal to the integrated low-level control and power detection module, and cuts off the output of the radio frequency signal in time through low-level control, thereby preventing the accelerating cavity from being damaged under high-power conditions.

[0034] The traditional CPCI EPCIS remote control system architecture mainly consists of a host computer, CPU board, CPCI backplane bus, FPGA board and digital I / O board. The CPU board controls the FPGA board through the CPCI bus and transmits data to the host computer for display through the network. The operating system running on the CPU board is vxWorks. Figure 2 shown.

[0035] By developing a driver and EPICS interface program based on the Linux system, it is used to replace the traditional VxWorks system CPU board + Linux computer EPICS control mode, which has a compact structure and is easy to operate. The CPCIEPICS control system structure diagram used in this system is as follows: Figure 3 shown.

[0036] The CompactPCI blade runs the Linux operating system, adopts EPICS control and CSS graphical display interface, and completes the monitoring and control functions of the high-frequency control of the acceleration cavity, power detection and standing wave ratio protection, high-frequency protection, and acceleration cavity fault status.

[0037] Traditional accelerator low-level control and cavity power monitoring systems are usually divided into two systems with complex system structures. The low-level control system is mainly composed of analog up- and down-conversion, local oscillators, and digital signal processing systems. Analog devices are easily affected by temperature, and it is usually necessary to add a constant temperature system to these analog devices to ensure stable performance. The power detection system is mainly composed of: directional couplers, detectors, AD sampling modules, and digital signal processing systems. The system is complex, and the detector can only detect signals with a single spectrum. It is difficult to detect the power of different frequency signals in multiple spectrum components.

[0038] In the present invention, the low-level control and power monitoring systems are combined into one system to form an integrated system of low-level control and power detection, thereby simplifying the system structure. The algorithm block diagram of the integrated system of low-level control and power detection is shown in FIG. Figure 4 shown.

[0039] The RF signal source input to the accelerating cavity comes from a low-level control system. In the integrated system of low-level control and power detection, power detection and low-level control share the same FPGA board to accurately calculate the power of the RF signal sent to the accelerating cavity. The power detection method does not require a detector when performing RF power detection within a wide frequency range, and can simultaneously detect the power value of each spectral component contained in the signal, simplifying the power detection link, reducing system costs while improving system stability. It has advantages in power detection of multiple spectral components mixed in the signal.

[0040] In the power detection system, i.e. the power detection and standing wave ratio protection system, comprises an AD sampling module, an IQ demodulation module, an IIR filtering module, a power calculation module and a standing wave ratio protection module. The digital processing method adopted by the power detection and standing wave ratio protection system comprises: first, the radio frequency signal coupled out from the directional coupler is calculated power through the power calculation module after AD sampling, IQ demodulation and IIR filtering, then the forward power and reverse power calculated are sent to the standing wave ratio protection module, and it is judged by the standing wave ratio protection module whether to carry out standing wave ratio protection, when it is judged that standing wave ratio protection needs to be carried out, after standing wave ratio protection occurs, the standing wave ratio protection module outputs a protection signal and sends it to the switch in the low-level control system, and the switch cuts off the output of the radio frequency signal, and carries out the next pulse recovery, and when the number of times of standing wave ratio protection exceeds a set value, the output of the low-level radio frequency signal will be permanently cut off until manual recovery.

[0041] The low-level control system includes an AD sampling module, an IQ demodulation module, an IIR filtering module, an amplitude-phase conversion module, a PI feedback controller, an amplitude-phase adjustment module, a digital up-conversion module, a switch, and a DAC chip. The processing method of the low-level control system includes: first, the RF signal coupled from the accelerating cavity is sent to the AD sampling module of the low-level control system; the sampled signal is output through the IQ demodulation module and IIR filtering to output DC I and Q signals; the I and Q signals are sent to the amplitude-phase conversion module to obtain the amplitude and phase information of the acceleration field; then closed-loop control is performed through the PI feedback controller; the closed-loop output signal is respectively sent to the amplitude-phase adjustment module of each channel; the adjusted signal is output through the digital up-conversion module to output the required digital signal; the output digital signal contains the cavity field amplitude, phase, and frequency signal and is transmitted to the DAC chip; the DAC output signal is filtered and amplified, and then the high-power signal is transmitted to the accelerating cavity through the coaxial feed tube; the amplitude, phase, frequency and other parameters of the signal can be set through the CSS graphical display interface.

[0042] The accelerating cavity of the Spallation Neutron Source (BNCT) device uses a two-way power feed method. For this multi-feed power feed method, the amplitude and phase of each input signal need to be adjusted to maximize the cavity pressure of the accelerating cavity. In this invention, the amplitude and phase modulation of each input signal are achieved by introducing an amplitude and phase adjustment module into the low-level control system. The amplitude adjustment coefficient and phase shift parameters can be set through the CSS graphical display interface, which has high adjustment accuracy and convenient operation.

[0043] By introducing amplitude and phase adjustment modules into the low-level control system, the amplitude and phase modulation of each signal entering the acceleration cavity can be realized. The amplitude adjustment coefficient and phase shift parameters are set through the CSS graphical display interface. The principle block diagram of amplitude and phase modulation is shown in the figure. Figure 5As shown, the amplitude signal output from the PI controller is multiplied by the amplitude coefficient set on the CSS interface to complete the amplitude adjustment of the RF signal. If the coefficient is greater than 1, the signal is amplified, and if the coefficient is less than 1, the signal is attenuated. The phase signal output from the PI controller is added to the phase offset coefficient set on the CSS interface to complete the phase adjustment of the RF signal. This digital phase adjustment method has high phase shifting accuracy and does not require a larger power phase shifter on the transmission path. The digital adjustment of the signal amplitude ensures that the power entering the cavity of each coupler of the accelerating cavity is consistent. While improving the adjustment accuracy, no adjustable attenuator is required in the transmission line. This adjustment method can be extended to accelerating cavities with multiple power coupling ports, and is not limited to the case of two coupling ports in the present invention.

[0044] Solid-state amplifiers are used to receive radio frequency signals from low-level control systems and generate high-power radio frequency signals. The BNCT device at the Spallation Neutron Source Science Center uses two sets of 150kW all-solid-state amplifiers to feed power to the two power feed ports of the accelerating cavity. The power distribution and synthesis network of the 150kW solid-state amplifier is as follows: Figure 6 As shown, the RF signal output by the low-level control system is sent to the preamplifier for amplification, and the signal output by the preamplifier is divided into four paths by a one-to-four power distributor, providing RF input for four power amplifier cabinets respectively. Each power amplifier cabinet divides the RF signal input by the distributor into thirty-two paths through a one-to-four power distributor and a one-to-eight power distributor, and the thirty-two-path final power amplifier plug-ins amplify the signal. The amplified signals of the thirty-two-path final power amplifier plug-ins are then synthesized by an eight-in-one power combiner and a four-in-one power combiner to realize the power output of a single power amplifier cabinet, and then the output signals of the four cabinets are power synthesized by a two-stage two-in-one power combiner at the cabinet level, and the synthesized output power is higher than 150kW. Among them, the power distribution and synthesis methods in the four power amplifier cabinets are the same, and the eight-in-one power combiner, the four-in-one power combiner and the final power amplifier plug-in in the power amplifier cabinet are The synthesizers all use isolated synthesizers, and the ports of the power synthesis network are isolated from each other to ensure that when the solid-state amplifier works in the full reflection state, the reflected power of the final power amplifier plug-in is only single power, and there will be no situation where it bears several times the power due to power imbalance. The reflected power is relatively stable, which reduces the power requirements of the circulator and load in the final power amplifier plug-in. The circulator and load in the final power amplifier plug-in only need to be able to withstand reflected power greater than 1 times the output power, so that there is no need to add a high-power circulator to the RF transmission line to protect the solid-state amplifier, which reduces the cost. The final power amplifier plug-in adopts a two-stage amplification chain, including an RF sampling board, a one-to-two power splitter, two 1200W amplification modules (final power amplifier tubes), a circulator and load, a two-in-one power synthesizer, a directional coupler, a monitoring board, a water-cooling plate and an external interface. The principle block diagram of the final power amplifier plug-in is as follows: Figure 7As shown, the principle of the final power amplifier plug-in is: first, after the external RF signal is sampled by RF, it is amplified in two stages by two 1200W amplifier modules, and the output power reaches more than 2000W through the circulator, two-in-one power combiner, and directional coupler. Among them, the two-in-one power combiner uses an isolated orthogonal combiner. The heat source devices such as the pre-amplifier tube, the final power amplifier tube, the circulator and its load are cooled by a professionally designed water-cooled plate. The temperature and current of the final high-power module, the forward and reverse power of the components, etc. are monitored in real time through the monitoring board. The input and output external interfaces on the final power amplifier plug-in include RF input Interface, RF output interface, AC power supply interface, status and fault signal interface, water input and output interface, each interface adopts blind plug-in mode, the water cooling plate of the final power amplifier plug-in is made of copper, which improves the heat dissipation efficiency and ensures that the cooling water does not corrode the water cooling plate when it is deionized water, thereby improving the reliability of the system. Microchannel and stir friction welding technology are used to reduce the temperature rise of the power amplifier tube, thereby improving the stability of the power amplifier tube. The water cooling interface from the water cooling main pipe to the final high-power module adopts a high-reliability self-sealed blind plug quick connector to ensure that the final high-power module can be maintained without draining the water when there is water in the pipeline.

[0045] The high-frequency electromagnetic energy generated by the solid-state amplifier is directionally transmitted to the BNCT RFQ accelerating cavity by the enclosed coaxial feed tube of the power feed system, minimizing or preventing leakage. The entire power feed system consists of a coaxial feed tube, an elbow, a directional coupler, and a high-power coupler. The transmission line does not require the installation of a high-power circulator or load. Because the solid-state amplifier uses an isolated synthesis network, the reflected power borne by the final power amplifier plug-in is only a single power. Therefore, in the full reflection state, the power amplifier tube is not damaged by total reflection. The entire solid-state amplifier has the ability to resist total reflection, and the transmission line does not need to install a high-power circulator or load.

[0046] The BNCT RFQ accelerating cavity uses two high-power couplers to complete the feeding of high-frequency power. The high-power coupler isolates the vacuum and feeds the microwaves sent by the power source into the accelerating cavity. The high-power coupler transmits high power, but the ceramic sheet in the ceramic window has limited pressure resistance, which limits the peak power transmitted by the power coupler. In addition, the high power and high duty cycle cause a very large heat deposition on the power coupler. At the same time, there is a pressure difference of one atmosphere on both sides of the high-power coupler, which will generate a large stress on the ceramic window. For the ceramic window of the fragile device, the stress on it limits the average power of the power coupler. The present invention combines the relevant theories of microwave, thermal and mechanics to design a high-power and high-duty cycle power coupler for the BNCT RFQ accelerating cavity. The structure of the high-power coupler is as follows: Figure 8 As shown in Figure 2, after optimization, the standing wave ratio is less than 1.1 in the range of 180MHz, ±7MHz, as shown in Figure 2. Figure 9As shown, the temperature rise is less than 2 degrees when the average power is 90kW. The diameter of the optimized ceramic sheet is 262mm and the thickness of the ceramic sheet is 10mm.

[0047] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Used in BNCT compact RF power source system, including low-level control and power detection integrated module, high-frequency protection module, CPCI chassis, CompactPCI blade, solid-state amplifier, coaxial feed tube, directional coupler, high-power coupler, characterized by: The low-level control and power detection integrated module is provided with a low-level control and power detection integrated system, which is composed of a low-level control system and a power detection system. The high-frequency protection module is provided with a high-frequency protection system. The CPCI chassis is provided with a backplane bus. The CompactPCI blade adopts a Linux operating system, a driver of the Linux system, an EPICS interface program and a CSS. The low-level control and power detection integrated module and the high-frequency protection module both carry out data transmission with the CompactPCI blade via the backplane bus of the CPCI chassis. In the power detection system, i.e., a power detection and standing wave ratio protection system, the system comprises an AD sampling module, an IQ demodulation module, an IIR filtering module, a power calculation module and a standing wave ratio protection module. The method of adopting the power detection and standing wave ratio protection system to carry out digital processing comprises the following steps: First, the RF signal coupled from the directional coupler is sampled by AD, demodulated by IQ, and filtered by IIR, and then the power is calculated by the power calculation module. Then, the calculated forward power and reverse power are sent to the standing wave ratio protection module, which determines whether to perform standing wave ratio protection; When it is determined that standing wave ratio protection is needed, the standing wave ratio protection module outputs a protection signal to the switch in the low-level control system after standing wave ratio protection occurs. The switch cuts off the output of the RF signal and restores the signal with the next pulse. When the number of standing wave ratio protection exceeds the set value, the output of low-level RF signal will be permanently cut off until it is manually restored; The RF signal source input to the accelerating cavity comes from a low-level control system. In the integrated system of low-level control and power detection, power detection and low-level control share the same FPGA board. The power detection system accurately calculates the power of the RF signal sent to the accelerating cavity by sharing the FPGA with the low-level control system. The power detection method does not require a detector when performing RF power detection within a wide frequency range, and can simultaneously detect the power value of each spectral component contained in the signal.

2. The compact radio frequency power source system for BNCT according to claim 1, characterized in that: The integrated low-level control and power detection system is used to control the amplitude of the high-frequency field in the accelerator and the stability of the resonant frequency of the accelerating cavity, and to perform real-time detection of the power entering the accelerating cavity and protect the standing wave ratio. The integrated low-level control and power detection module performs digital signal processing on the data, and after digital-to-analog conversion, sends out the radio frequency signal required by the accelerating cavity. The sent radio frequency signal is amplified into a high-power radio frequency signal by a solid-state amplifier. The high-power radio frequency signal is transmitted to the high-power coupler through the coaxial feed tube, and the radio frequency signal is coupled into the accelerating cavity through the high-power coupler. The directional coupler is used to couple the forward and reverse power signals of the accelerating cavity.

3. The compact radio frequency power source system for BNCT according to claim 1, characterized in that: The water cooling, vacuum signal and other signals of the accelerating chamber are fed back to the high-frequency protection module. When the water cooling, vacuum or personal protection system of the accelerating chamber occurs or a fault alarm is issued, the high-frequency protection module sends a protection signal to the low-level control and power detection integrated module, and cuts off the output of the radio frequency signal in time through low-level control.

4. The compact radio frequency power source system for BNCT according to claim 1, characterized in that: The low-level control system includes an AD sampling module, an IQ demodulation module, an IIR filtering module, an amplitude-phase conversion module, a PI feedback controller, an amplitude-phase adjustment module, a digital up-conversion module, a switch and a DAC chip.

5. A data processing method using the low-level control system for a BNCT compact radio frequency power source system according to claim 1 mainly comprises the following steps, characterized in that: First, the RF signal coupled from the accelerating cavity is sent to the AD sampling module of the low-level control system. The sampled signal is then demodulated by the IQ demodulation module and IIR filtered to output DC I and Q signals. The I and Q signals are then sent to the amplitude and phase conversion module to obtain the amplitude and phase information of the acceleration field. Then, closed-loop control is performed through the PI feedback controller, and the closed-loop output signal is sent to the amplitude and phase adjustment module of each channel respectively. The adjusted signal is output through the digital up-conversion module to output the required digital signal. The output digital signal contains the cavity field amplitude, phase, and frequency signals and is transmitted to the DAC chip; Finally, the DAC output signal is filtered and amplified, and then transmitted to the accelerating cavity through a coaxial feed tube as a high-power signal. The signal's amplitude, phase, frequency and other parameters can all be set through the CSS graphical display interface.

6. The data processing method for a low-level control system in a BNCT compact radio frequency power source system according to claim 5, characterized in that: By introducing amplitude and phase adjustment modules into the low-level control system, amplitude modulation and phase modulation of each signal entering the acceleration cavity can be achieved. The amplitude adjustment coefficient and phase shift parameters are set through the CSS graphical display interface. The amplitude signal output from the PI controller is multiplied by the amplitude coefficient set on the CSS interface to complete the amplitude adjustment of the RF signal of the acceleration cavity. If the coefficient is greater than 1, the signal is amplified, and if the coefficient is less than 1, the signal is reduced. The phase signal output from the PI controller is added to the phase offset coefficient set on the CSS interface to complete the phase adjustment of the RF signal of the acceleration cavity.

7. The compact radio frequency power source system for BNCT according to claim 1, characterized in that: The solid-state amplifier is used to receive radio frequency signals from a low-level control system and generate high-power radio frequency signals. The radio frequency signals output by the low-level control system are sent to a preamplifier for amplification. The signals output by the preamplifier are divided into four paths by a one-to-four power distributor, providing radio frequency inputs for four power amplifier cabinets respectively. Each power amplifier cabinet divides the radio frequency signals input by the distributor into 32 paths by a one-to-four power distributor and a one-to-eight power distributor. The signals are amplified by 32 final-stage power amplifier plug-ins. The signals amplified by the 32 final-stage power amplifier plug-ins are then synthesized by an eight-in-one power synthesizer and a four-in-one power synthesizer to achieve the power output of a single power amplifier cabinet. The output signals of the four cabinets are then power synthesized by a two-stage two-in-one power synthesizer at the cabinet level.

8. The compact radio frequency power source system for BNCT according to claim 7, characterized in that: The power distribution and synthesis methods in the four power amplifier cabinets are the same. The eight-in-one power combiner, four-in-one power combiner in the power amplifier cabinet and the combiner in the final power amplifier plug-in all use isolated combiners, and the ports of the power synthesis network are isolated from each other.

9. The compact radio frequency power source system for BNCT according to claim 7, characterized in that: The final power amplifier plug-in adopts a two-stage amplification chain, including a radio frequency sampling board, a one-to-two power splitter, two 1200W amplifier modules, a circulator and a load, a two-in-one power combiner, a directional coupler, a monitoring board, a water cooling plate and an external interface.

10. The method for final-stage power amplification of a BNCT compact radio frequency power source system according to claim 1, comprising the following steps, characterized in that: First, after the external RF signal is sampled by the RF, it is amplified in two stages by two 1200W amplifier modules; Then, the output power reaches more than 2000W through a circulator, a two-in-one power combiner, and a directional coupler; At the same time, the heat source components such as the preamplifier tube, the final amplifier tube, the circulator and its load are cooled by the water cooling plate. In addition, the monitoring board can be used to monitor the temperature and current of the final high-power module, the forward and reverse power of the components, etc. in real time. The input and output external interfaces on the final power amplifier plug-in include RF input interface, RF output interface, AC power supply interface, status and fault signal interface, and water input and output interfaces.

11. The compact radio frequency power source system for BNCT according to claim 1, characterized in that: The high-frequency electromagnetic energy generated by the solid-state amplifier is directionally transmitted to the BNCT RFQ accelerating cavity via a power feeding system and a closed coaxial feed tube, minimizing leakage. The power feeding system consists of a coaxial feed tube, an elbow, a directional coupler, and a high-power coupler. The transmission line does not require a high-power circulator or load. Because the solid-state amplifier uses an isolated synthesis network, the reflected power borne by the final-stage power amplifier plug-in is only a single power. Therefore, in the total reflection state, the power amplifier tube is not damaged by total reflection, and the entire solid-state amplifier has the ability to resist total reflection. The accelerating cavity uses two high-power couplers to complete the high-frequency power feeding. The high-power couplers isolate the vacuum and feed the microwaves sent by the power source into the accelerating cavity.

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