Design Of Radiation Accelerator Low Level Control System

The radiation accelerator in this article is an S-band electron linear accelerator with 27 kW injection power and 1 MeV beam energy.In its high-frequency low-level(LLRF)control system,the operating frequency of the superconducting cavity is 2856 MHz.Nowadays,radiation accelerators are increasingly used in agriculture and food processing industries,such as genetic breeding,food preservation,and special applications in the medical field.The low-level control system,which is the core of its control,has become the focus of research in the field and an urgent problem to be solved.Through the theoretical analysis and combined with the test method,the radiation accelerator low-level control system was designed.The radiation accelerator low-level control system in this article is an all-digital closed-loop feedback control system composed of quadrature demodulation technology based on I/Q sampling.Its main function is to achieve superconducting chamber cavity voltage amplitude stability control,phase stability control and cavity resonance frequency control.Radiation accelerator low-level control system design article,from the overall framework design to each module design,from the theory of the low-level control system theory to each function module FPGA programming design to the functional simulation and test experiments,all carried out Introduction.According to the amplitude-phase feedback loop control principle and the frequency feedback loop control principle,the relevant algorithm to be used by the core control algorithm in the low-level control system is derived,that is,I/Q quadrature demodulation technology,FIR filter technology,CORDIC rotation technology,PID control technology.Through I/Q quadrature demodulation technology,the sampled signal is separated into I signal and Q signal,so that they are compared with the set reference I signal and the reference Q signal to obtain the difference,and the deviation signal is obtained.FIR filter is to filter out high frequency signals due to mixing.CORDIC rotation is used to identify the phase of the signal.Through the deviation signal obtained to correct the phase.The PID control uses the frequency difference signal to control the motor to fine tune the resonant frequency of the cavity,allowing the system to operate more stably.The above functions are implemented through Quartus II programming software and Modelsim simulation tool for logic implementation and simulation debugging.And throughthe FPGA control board for related tests and experiments,in the test results,closed-loop work signal phase fluctuations in the 30 ° ± 0.8 °,the power is stable in the 105 kW ± 1kW range,the operating frequency is stable in the 2856 MHz ± 0.5kHz range,basically meet system work requirements to achieve low-level control.Various problems and results and data occurred during the process were saved in the form of documents,providing experimental data for the subsequent digital low-level control system algorithm upgrade.