The China initiative Accelerator Driven System,CiADS,physics design adopts 162.5 MHz,325 MHz,and 650 MHz cavities,which are driven by the corresponding radio frequency(RF)power system,requiring frequency translation f...The China initiative Accelerator Driven System,CiADS,physics design adopts 162.5 MHz,325 MHz,and 650 MHz cavities,which are driven by the corresponding radio frequency(RF)power system,requiring frequency translation front-end for the RF station.For that application,a general-purpose design front-end prototype has been developed to evaluate the multi-frequency point supported design feasibility.The difficult parts to achieve the requirements of the general-purpose design are reasonable device selection and balanced design.With a carefully selected low-noise wide-band RF mixer and amplifier to balance the performance of multi-frequency supported down-conversion,specially designed LO distribution net to increase isolation between adjacent channels,and external band-pass filter to realize expected up-conversion frequencies,high maintenance and modular front-end generalpurpose design has been implemented.Results of standard parameters show an R2 value of at least 99.991%in the range of-60-10 dBm for linearity,up to 18 dBm for P1dB,and up to 89 dBc for cross talk between adjacent channels.The phase noise spectrum is lower than 80 dBc in the range of 0-1 MHz;cumulative phase noise is 0.006°;and amplitude and phase stability are 0.022%and 0.034°,respectively.展开更多
This paper describes the design and preliminary test of the low-level radio frequency(LLRF)part of the C band high-gradient test facility for the Shanghai Soft X-ray Free-Electron Laser(SXFEL)-Linear Accelerator(LINAC...This paper describes the design and preliminary test of the low-level radio frequency(LLRF)part of the C band high-gradient test facility for the Shanghai Soft X-ray Free-Electron Laser(SXFEL)-Linear Accelerator(LINAC).Before installation,the accelerating structures should be tested and conditioned.During the conditioning process,breakdown detection is needed to protect the accelerating structures and klystron from damage.The PCI extensions for instrumentation-based LLRF system and auto-conditioning algorithm are designed and applied in the LLRF part of the C band high-gradient test facility.Three C band accelerating structures and 1 pulse compressor have completed conditioning and were installed in the SXFEL-LINAC.展开更多
The ADS Injector II is a linear superconducting accelerator, which is made up of the four vane type RFQ, MEBTand superconducting cavities. The amplitude and phase stability of all RF resonant cavities need to be contr...The ADS Injector II is a linear superconducting accelerator, which is made up of the four vane type RFQ, MEBTand superconducting cavities. The amplitude and phase stability of all RF resonant cavities need to be controlledprecisely by the low level radio frequency (LLRF) control system. Fig. 1 is the block diagram of the LLRF controlsystem, which is composed of the RF synchronous signal distributor, LLRF system and solide state RF high poweramplifier.展开更多
The low level radio frequency(LLRF) system for booster accelerator at Shanghai Synchrotron Radiation Facility(SSRF) was upgraded by a digital controller based on field programmable gate array(FPGA) technology.Paramete...The low level radio frequency(LLRF) system for booster accelerator at Shanghai Synchrotron Radiation Facility(SSRF) was upgraded by a digital controller based on field programmable gate array(FPGA) technology.Parameters of voltage, frequency and field flatness in the two 5-cell cavities are controlled to meet the requirements of booster. In this article, the ramping curve of cavity voltage, amplitude and phase control loop with vector sum of the two 5-cell cavities, tuning loop and field flatness loop are analyzed and discussed in detail.A different method in tuning loop is adopted due to the limitations of ADC channels. The function realizes energy ramping of electron beam from 150 Me V to 3.5 Ge V with a repetition rate of 2 Hz. With the new LLRF controller, the phase stability at ramping mode in 10 hours long operation is improved from ±1.5°(RMS) with open loop to ±0.15°(RMS) with close loop, while the detuning phase and field flatness are maintained to within ±2°and ±1%, respectively.展开更多
The new generation particle accelerator requires a highly stable radio frequency（RF） system. The stability of the RF system is realized by the Low Level RF（LLRF） subsystem which controls the amplitude and phase of...The new generation particle accelerator requires a highly stable radio frequency（RF） system. The stability of the RF system is realized by the Low Level RF（LLRF） subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signal＇s amplitude and phase is fundamental to LLRF controls. High-speed ADC（Analog to Digital Converter） ,DAC（Digital to Analog Converter） and FPGA（Field Programmable Gate Array） play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter,algorithm＇s defects and non-linearity of devices,which is helpful for future work on high precision detection and control.展开更多
This paper describes a field programming gate array （FPGA） based low level radio frequency （LLRF） prototype for the SSRF storage ring RF system： This prototype includes the local oscillator （LO）, analog front e...This paper describes a field programming gate array （FPGA） based low level radio frequency （LLRF） prototype for the SSRF storage ring RF system： This prototype includes the local oscillator （LO）, analog front end, digital front end, RF out, clock distributing, digital signal processing and communication functions. All feedback algorithms are performed in FPGA. The long term of the test prototype with high power shows that the variations of the RF amplitude and the phase in the accelerating cavity are less than 1% and 1° respectively, and the variation of the cavity resonance frequency is controlled within 4-10 Hz.展开更多
The rapid cycling synchrotron （RCS） is part of the China Spallation Neutron Source （CSNS）. The RCS provides 1.6 GeV protons with a repetition rate of 25 Hz. The RF system in RCS is mainly composed of a ferrite loa...The rapid cycling synchrotron （RCS） is part of the China Spallation Neutron Source （CSNS）. The RCS provides 1.6 GeV protons with a repetition rate of 25 Hz. The RF system in RCS is mainly composed of a ferrite loaded RF cavity, a high power tetrode amplifier, a bias supply of 3300 A and a digital low level RF （LLRF） system based on FPGA. The major challenge of the LLRF system is to solve problems caused by rapid frequency sweeping and the heavy beam loading effect. A total of eight control loops are applied to ensure the normal operation. An effective feedforward scheme is widely used to improve the dynamic performance of the system. The design of the LLRF system and high power integration test results with the prototype RF system are presented.展开更多
This paper describes a low level radio frequency control system that was developed by the Institute of Modern Physics Chinese Academy of Sciences, and will be used in Injector II of the China-ADS project. The LLRF con...This paper describes a low level radio frequency control system that was developed by the Institute of Modern Physics Chinese Academy of Sciences, and will be used in Injector II of the China-ADS project. The LLRF control system consists of an RF modulated front end, fast analog-to-digitM converter （ADC） modules, and a digital signal processing board based on a field programmable gate array. The system has been tested on a room temperature cavity with 12-hr, and the results illustrate that the stability of amplitude and phase achieved ~0.32% and 4-0.35 degrees, respectively.展开更多
Objective The China Spallation Neutron Source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first phase.It consists of RFQ,two bunchers of medium-energy beam transmission line,fo...Objective The China Spallation Neutron Source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first phase.It consists of RFQ,two bunchers of medium-energy beam transmission line,four DTL tanks and one debuncher of linac-to-ring beam transmission line.Correspondingly,eight online RF power sources are used to power these accelerators.In order to stabilize the amplitude,phase and resonant frequency of the RF accelerating field,and minimize beam loss,we have established digital low-level RF(LLRF)control system.Methods The LLRF system includes RF reference line,analog module(AM),clock distribution module,digital control module(DCM),high-power protection module,timing and RF interlock module and so on.The DCM is mainly responsible for the stability of the RF field amplitude and phase,and RF interlock module can quickly cut off the RF drive in case of arc in the RF transmission system,VSWR over threshold or cavity vacuum fault and so on.Result During beam commissioning,all of eight online units of LLRF control system were operating stably and reliably.The amplitude and phase variations of the linac fields have been achieved about±0.4%and±0.15°with 10-mA beam loading,much better than the design requirements of±1%in amplitude and±1°in phase.Conclusion With the help of this system,we achieved stable operation under different beam loads.Also,many important progresses have been achieved in the LLRF control system for amore convenient operation and a higher stability performance.This article describes the design and implementation of the LLRF for CSNS linac.展开更多
Objective:The Chinese ADS proton Linac injector I composed of an electron cyclotron resonance ion source,a lowenergy beam transport line,a radio frequency quadrupole(RFQ)accelerator,a medium-energy beam transport(MEBT...Objective:The Chinese ADS proton Linac injector I composed of an electron cyclotron resonance ion source,a lowenergy beam transport line,a radio frequency quadrupole(RFQ)accelerator,a medium-energy beam transport(MEBT)line,a superconducting section and beam dump with design goal to achieve CW proton beam with beam current 10 mA and energy gain around 10 MeV.In order to maintain the stability of the RF system,to compensate for the beam load effect and to provide the GUI required for the operation of the RF power system,we have established a LLRF control system.Methods:This LLRF system for ADS proton Linac injector I in IHEP consists of RF reference system and LLRF controllers for oneRFQcavity,twoMEBTbunching cavities and 14 superconductive spoke cavities.We have adopted a new development mTCA.4-based hardware platform,and it has some characteristics such as faster bandwidth,standardized design,easy operation and maintenance and good expansibility.Results:The LLRF system has been improved and optimized and has now been put into operation.It takes into account the pulse and CW beam flow mode,feedforward and feedback control functions.Conclusion:With the help of this system,we achieved stable operationwith narrowpulses,long pulses,andCWmodes under different beam loads.This article describes the implementation of this system and presents some initial the CW beam acceleration results with the help of this system at the end of 2016.展开更多
Fundamental power couplers are crucial components for feeding radio frequency power to accelerating cavities. Couplers must be tested and conditioned on a room-temperature test stand to evaluate and potentially improv...Fundamental power couplers are crucial components for feeding radio frequency power to accelerating cavities. Couplers must be tested and conditioned on a room-temperature test stand to evaluate and potentially improve their performance before being installed in an accelerating cavity. A new test system has been designed and is under construction at the institute of modern physics.For this test system, multiple conditioning modes, including the pulse mode, CW mode, and amplitude-sweeping mode, have been embedded in the low-level radio frequency system of the test stand. All of these conditioning modes can be run manually or automatically. In addition, a novel test cavity is proposed and has been designed, which facilitates non-contact conditioning and a multi-purpose test stand.展开更多
Very high frequency(VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavi...Very high frequency(VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavity, the VHF gun requires high stability in the amplitude and phase of the cavity field. However, the gun is microwave powered by two solid-state power sources through two separate power couplers. The input difference between the two power couplers will influence the stability of the cavity field. To systematically study this influence and obtain measurement formulae, a multi-port VHF gun LCR circuit model is built and analyzed. During the warm-up condition, the cavity structure will be deformed due to the large-scale change in the cavity temperature. Then, the deformation will result in cavity resonant frequency changes. To prevent the mechanic tuner from suffering damages due to the frequent and long-distance movement for correcting the cavity resonant frequency, a self-excited loop(SEL) control system is considered for changing the loop phase and make the loop frequency follow the resonant frequency. In this study, a steady-state model of the VHF gun cavity is built for obtaining the optimal input coupler coefficient and the stability requirement of the forward voltage. Then, the generator-driven resonator and SEL control system, which combine with the VHF multiport modeling, are modeled and simulated. The simulated results show that the SEL system can perfectly operate in the process of condition and warm-up.展开更多
Swiss FEL is a free electron laser(FEL) under commissioning at the Paul Scherrer Institut(PSI) in Switzerland. Digital low-level RF(LLRF) systems are used in Swiss FEL to control more than 30 RF stations with either s...Swiss FEL is a free electron laser(FEL) under commissioning at the Paul Scherrer Institut(PSI) in Switzerland. Digital low-level RF(LLRF) systems are used in Swiss FEL to control more than 30 RF stations with either standing wave cavities(e.g. RF gun) or travelling wave structures working at different frequencies. After conditioned to desired power levels, the RF stations need to be setup for beam operation and the LLRF parameters need to be optimized for maximizing the beam stability. Several beam-based algorithms were developed to facilitate the setup, calibration and optimization of the Swiss FEL RF stations for beam operation. The algorithms were implemented as automation procedures in the framework of Experimental Physics and Industrial Control System(EPICS) and were used in commissioning and daily operation of Swiss FEL. In this paper, the algorithms and the implementation will be introduced together with the test results during the commissioning of SwissFEL.展开更多
文摘The China initiative Accelerator Driven System,CiADS,physics design adopts 162.5 MHz,325 MHz,and 650 MHz cavities,which are driven by the corresponding radio frequency(RF)power system,requiring frequency translation front-end for the RF station.For that application,a general-purpose design front-end prototype has been developed to evaluate the multi-frequency point supported design feasibility.The difficult parts to achieve the requirements of the general-purpose design are reasonable device selection and balanced design.With a carefully selected low-noise wide-band RF mixer and amplifier to balance the performance of multi-frequency supported down-conversion,specially designed LO distribution net to increase isolation between adjacent channels,and external band-pass filter to realize expected up-conversion frequencies,high maintenance and modular front-end generalpurpose design has been implemented.Results of standard parameters show an R2 value of at least 99.991%in the range of-60-10 dBm for linearity,up to 18 dBm for P1dB,and up to 89 dBc for cross talk between adjacent channels.The phase noise spectrum is lower than 80 dBc in the range of 0-1 MHz;cumulative phase noise is 0.006°;and amplitude and phase stability are 0.022%and 0.034°,respectively.
基金This work was supported by the National Key R&D Program of China(No.2018YFF0109203).
文摘This paper describes the design and preliminary test of the low-level radio frequency(LLRF)part of the C band high-gradient test facility for the Shanghai Soft X-ray Free-Electron Laser(SXFEL)-Linear Accelerator(LINAC).Before installation,the accelerating structures should be tested and conditioned.During the conditioning process,breakdown detection is needed to protect the accelerating structures and klystron from damage.The PCI extensions for instrumentation-based LLRF system and auto-conditioning algorithm are designed and applied in the LLRF part of the C band high-gradient test facility.Three C band accelerating structures and 1 pulse compressor have completed conditioning and were installed in the SXFEL-LINAC.
文摘The ADS Injector II is a linear superconducting accelerator, which is made up of the four vane type RFQ, MEBTand superconducting cavities. The amplitude and phase stability of all RF resonant cavities need to be controlledprecisely by the low level radio frequency (LLRF) control system. Fig. 1 is the block diagram of the LLRF controlsystem, which is composed of the RF synchronous signal distributor, LLRF system and solide state RF high poweramplifier.
基金Supported by the National Natural Science Foundation of China(No.11335014)
文摘The low level radio frequency(LLRF) system for booster accelerator at Shanghai Synchrotron Radiation Facility(SSRF) was upgraded by a digital controller based on field programmable gate array(FPGA) technology.Parameters of voltage, frequency and field flatness in the two 5-cell cavities are controlled to meet the requirements of booster. In this article, the ramping curve of cavity voltage, amplitude and phase control loop with vector sum of the two 5-cell cavities, tuning loop and field flatness loop are analyzed and discussed in detail.A different method in tuning loop is adopted due to the limitations of ADC channels. The function realizes energy ramping of electron beam from 150 Me V to 3.5 Ge V with a repetition rate of 2 Hz. With the new LLRF controller, the phase stability at ramping mode in 10 hours long operation is improved from ±1.5°(RMS) with open loop to ±0.15°(RMS) with close loop, while the detuning phase and field flatness are maintained to within ±2°and ±1%, respectively.
基金Supported by Knowledge Innovation Program of Chinese Academy of Sciences and National Natural Science Foundation of China (10675142)
文摘The new generation particle accelerator requires a highly stable radio frequency（RF） system. The stability of the RF system is realized by the Low Level RF（LLRF） subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signal＇s amplitude and phase is fundamental to LLRF controls. High-speed ADC（Analog to Digital Converter） ,DAC（Digital to Analog Converter） and FPGA（Field Programmable Gate Array） play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter,algorithm＇s defects and non-linearity of devices,which is helpful for future work on high precision detection and control.
文摘This paper describes a field programming gate array （FPGA） based low level radio frequency （LLRF） prototype for the SSRF storage ring RF system： This prototype includes the local oscillator （LO）, analog front end, digital front end, RF out, clock distributing, digital signal processing and communication functions. All feedback algorithms are performed in FPGA. The long term of the test prototype with high power shows that the variations of the RF amplitude and the phase in the accelerating cavity are less than 1% and 1° respectively, and the variation of the cavity resonance frequency is controlled within 4-10 Hz.
基金Supported by National Natural Science Foundation of China(11175194)
文摘The rapid cycling synchrotron （RCS） is part of the China Spallation Neutron Source （CSNS）. The RCS provides 1.6 GeV protons with a repetition rate of 25 Hz. The RF system in RCS is mainly composed of a ferrite loaded RF cavity, a high power tetrode amplifier, a bias supply of 3300 A and a digital low level RF （LLRF） system based on FPGA. The major challenge of the LLRF system is to solve problems caused by rapid frequency sweeping and the heavy beam loading effect. A total of eight control loops are applied to ensure the normal operation. An effective feedforward scheme is widely used to improve the dynamic performance of the system. The design of the LLRF system and high power integration test results with the prototype RF system are presented.
文摘This paper describes a low level radio frequency control system that was developed by the Institute of Modern Physics Chinese Academy of Sciences, and will be used in Injector II of the China-ADS project. The LLRF control system consists of an RF modulated front end, fast analog-to-digitM converter （ADC） modules, and a digital signal processing board based on a field programmable gate array. The system has been tested on a room temperature cavity with 12-hr, and the results illustrate that the stability of amplitude and phase achieved ~0.32% and 4-0.35 degrees, respectively.
基金The authors would like to sincerely thank the CSNS linac RF team for their hard work and dedication.This work was supported by the China Spallation Neutron Source project.
文摘Objective The China Spallation Neutron Source(CSNS)linac is designed with beam energy of 80 MeV and a peak current of 15 mA in the first phase.It consists of RFQ,two bunchers of medium-energy beam transmission line,four DTL tanks and one debuncher of linac-to-ring beam transmission line.Correspondingly,eight online RF power sources are used to power these accelerators.In order to stabilize the amplitude,phase and resonant frequency of the RF accelerating field,and minimize beam loss,we have established digital low-level RF(LLRF)control system.Methods The LLRF system includes RF reference line,analog module(AM),clock distribution module,digital control module(DCM),high-power protection module,timing and RF interlock module and so on.The DCM is mainly responsible for the stability of the RF field amplitude and phase,and RF interlock module can quickly cut off the RF drive in case of arc in the RF transmission system,VSWR over threshold or cavity vacuum fault and so on.Result During beam commissioning,all of eight online units of LLRF control system were operating stably and reliably.The amplitude and phase variations of the linac fields have been achieved about±0.4%and±0.15°with 10-mA beam loading,much better than the design requirements of±1%in amplitude and±1°in phase.Conclusion With the help of this system,we achieved stable operation under different beam loads.Also,many important progresses have been achieved in the LLRF control system for amore convenient operation and a higher stability performance.This article describes the design and implementation of the LLRF for CSNS linac.
文摘Objective:The Chinese ADS proton Linac injector I composed of an electron cyclotron resonance ion source,a lowenergy beam transport line,a radio frequency quadrupole(RFQ)accelerator,a medium-energy beam transport(MEBT)line,a superconducting section and beam dump with design goal to achieve CW proton beam with beam current 10 mA and energy gain around 10 MeV.In order to maintain the stability of the RF system,to compensate for the beam load effect and to provide the GUI required for the operation of the RF power system,we have established a LLRF control system.Methods:This LLRF system for ADS proton Linac injector I in IHEP consists of RF reference system and LLRF controllers for oneRFQcavity,twoMEBTbunching cavities and 14 superconductive spoke cavities.We have adopted a new development mTCA.4-based hardware platform,and it has some characteristics such as faster bandwidth,standardized design,easy operation and maintenance and good expansibility.Results:The LLRF system has been improved and optimized and has now been put into operation.It takes into account the pulse and CW beam flow mode,feedforward and feedback control functions.Conclusion:With the help of this system,we achieved stable operationwith narrowpulses,long pulses,andCWmodes under different beam loads.This article describes the implementation of this system and presents some initial the CW beam acceleration results with the help of this system at the end of 2016.
基金supported by the National Key Basic Research Program of China(973 Program)(No.2014CB845504)
文摘Fundamental power couplers are crucial components for feeding radio frequency power to accelerating cavities. Couplers must be tested and conditioned on a room-temperature test stand to evaluate and potentially improve their performance before being installed in an accelerating cavity. A new test system has been designed and is under construction at the institute of modern physics.For this test system, multiple conditioning modes, including the pulse mode, CW mode, and amplitude-sweeping mode, have been embedded in the low-level radio frequency system of the test stand. All of these conditioning modes can be run manually or automatically. In addition, a novel test cavity is proposed and has been designed, which facilitates non-contact conditioning and a multi-purpose test stand.
文摘Very high frequency(VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavity, the VHF gun requires high stability in the amplitude and phase of the cavity field. However, the gun is microwave powered by two solid-state power sources through two separate power couplers. The input difference between the two power couplers will influence the stability of the cavity field. To systematically study this influence and obtain measurement formulae, a multi-port VHF gun LCR circuit model is built and analyzed. During the warm-up condition, the cavity structure will be deformed due to the large-scale change in the cavity temperature. Then, the deformation will result in cavity resonant frequency changes. To prevent the mechanic tuner from suffering damages due to the frequent and long-distance movement for correcting the cavity resonant frequency, a self-excited loop(SEL) control system is considered for changing the loop phase and make the loop frequency follow the resonant frequency. In this study, a steady-state model of the VHF gun cavity is built for obtaining the optimal input coupler coefficient and the stability requirement of the forward voltage. Then, the generator-driven resonator and SEL control system, which combine with the VHF multiport modeling, are modeled and simulated. The simulated results show that the SEL system can perfectly operate in the process of condition and warm-up.
文摘Swiss FEL is a free electron laser(FEL) under commissioning at the Paul Scherrer Institut(PSI) in Switzerland. Digital low-level RF(LLRF) systems are used in Swiss FEL to control more than 30 RF stations with either standing wave cavities(e.g. RF gun) or travelling wave structures working at different frequencies. After conditioned to desired power levels, the RF stations need to be setup for beam operation and the LLRF parameters need to be optimized for maximizing the beam stability. Several beam-based algorithms were developed to facilitate the setup, calibration and optimization of the Swiss FEL RF stations for beam operation. The algorithms were implemented as automation procedures in the framework of Experimental Physics and Industrial Control System(EPICS) and were used in commissioning and daily operation of Swiss FEL. In this paper, the algorithms and the implementation will be introduced together with the test results during the commissioning of SwissFEL.
