Purpose The high modularity and redundancy of the solid-state amplifier(SSA)facilitates its flexible output and convenient maintenance,which has made it the main radiofrequency(RF)source at the China Initiative Accele...Purpose The high modularity and redundancy of the solid-state amplifier(SSA)facilitates its flexible output and convenient maintenance,which has made it the main radiofrequency(RF)source at the China Initiative Accelerator Driven System(CiADS)and China Accelerator Facility for superheavy Elements(CAFe2).However,the nonlinear characteristics of high-power RF systems,such as SSA,reduce their potential operational efficiency and increase their operational complexity.In this study,our objective was to accurately measure the SSA nonlinearity and to develop a compensation method.Methods We utilized a field-programmable gate array(FPGA)in a low-level radiofrequency(LLRF)system to generate a sawtooth driving signal with a tunable amplitude and pulse width.We used this driving signal to measure the nonlinear characteristic curve of the SSA online,calculate the corresponding nonlinear compensation curve,and construct a digital predistortion(DPD)algorithm within the FPGA to compensate for SSA nonlinearity.Results Our results demonstrated that the DPD algorithm greatly improved the overall linearity of the RF system and thus enhanced its potential operational efficiency.We also observed that the thermal effect of the SSA had a notable impact on the measurement results and effectiveness of the compensation.展开更多
n accelerator operations,some phase drifts in the reference signals of low-level radiofrequency(LLRF)control systems and analog components can hardly be detected and corrected by the LLRF itself,leading to phase devia...n accelerator operations,some phase drifts in the reference signals of low-level radiofrequency(LLRF)control systems and analog components can hardly be detected and corrected by the LLRF itself,leading to phase deviations in the cavity and exciting sustained longitudinal energy-phase oscillations of the beam during subsequent acceleration.This phenomenon is particularly pronounced in low-β proton/ion linac,significantly impacting operational safety.Methods The longitudinal oscillations of the beam eventually manifest in the measurements of overall beam position/phase monitors(BPM)with a distinct pattern.In this paper,the effects of cavity phase deviations on the particle accelerating process are simulated and analyzed using a trace model,and beam experiments are performed at an upgraded Chinese ADS front-end demo facility(CAFe2)to demonstrate the morphologies and characteristics of longitudinal oscillations in the low-β proton/ion linac.Comparison of BPM measurements with model predictions provides a method for monitoring the stability of beam operation.Results and conclusion Beam experiments on CAFe2 support the results of relevant simulations and confirm the unique correspondence between beam phase oscillation trajectories and phase-deviated cavities,validating the feasibility of a method for detecting and correcting cavity phase anomalies based on longitudinal measurements.展开更多
基金supported by the projects of“Studies of intelligent LLRF control algorithms for superconducting RF cavities(Grant No.E129851YR0)”“National Natural Science Foundation of China(Grant No.U22A20261),”“National Natural Science Foundation of China(Grant No.12205344).”。
文摘Purpose The high modularity and redundancy of the solid-state amplifier(SSA)facilitates its flexible output and convenient maintenance,which has made it the main radiofrequency(RF)source at the China Initiative Accelerator Driven System(CiADS)and China Accelerator Facility for superheavy Elements(CAFe2).However,the nonlinear characteristics of high-power RF systems,such as SSA,reduce their potential operational efficiency and increase their operational complexity.In this study,our objective was to accurately measure the SSA nonlinearity and to develop a compensation method.Methods We utilized a field-programmable gate array(FPGA)in a low-level radiofrequency(LLRF)system to generate a sawtooth driving signal with a tunable amplitude and pulse width.We used this driving signal to measure the nonlinear characteristic curve of the SSA online,calculate the corresponding nonlinear compensation curve,and construct a digital predistortion(DPD)algorithm within the FPGA to compensate for SSA nonlinearity.Results Our results demonstrated that the DPD algorithm greatly improved the overall linearity of the RF system and thus enhanced its potential operational efficiency.We also observed that the thermal effect of the SSA had a notable impact on the measurement results and effectiveness of the compensation.
基金supported by the Large Research Infrastructures“China initiative Accelerator Driven System”(No.2017-000052-75-01-000590)“Youth Innovation Promotion Association Project,CAS”(No.E329851Y)“National Natural Science Foundation of China”(No.12205344).
文摘n accelerator operations,some phase drifts in the reference signals of low-level radiofrequency(LLRF)control systems and analog components can hardly be detected and corrected by the LLRF itself,leading to phase deviations in the cavity and exciting sustained longitudinal energy-phase oscillations of the beam during subsequent acceleration.This phenomenon is particularly pronounced in low-β proton/ion linac,significantly impacting operational safety.Methods The longitudinal oscillations of the beam eventually manifest in the measurements of overall beam position/phase monitors(BPM)with a distinct pattern.In this paper,the effects of cavity phase deviations on the particle accelerating process are simulated and analyzed using a trace model,and beam experiments are performed at an upgraded Chinese ADS front-end demo facility(CAFe2)to demonstrate the morphologies and characteristics of longitudinal oscillations in the low-β proton/ion linac.Comparison of BPM measurements with model predictions provides a method for monitoring the stability of beam operation.Results and conclusion Beam experiments on CAFe2 support the results of relevant simulations and confirm the unique correspondence between beam phase oscillation trajectories and phase-deviated cavities,validating the feasibility of a method for detecting and correcting cavity phase anomalies based on longitudinal measurements.
