The China Spallation Neutron Source(CSNS) upgrade project(CSNS-Ⅱ) aims to enhance the beam power from 100 to 500 kW. A dual-harmonic accelerating method has been adopted to alleviate the stronger space-charge effect ...The China Spallation Neutron Source(CSNS) upgrade project(CSNS-Ⅱ) aims to enhance the beam power from 100 to 500 kW. A dual-harmonic accelerating method has been adopted to alleviate the stronger space-charge effect in rapid-cycling synchrotrons owing to the increased beam intensity. To satisfy the requirements of dual-harmonic acceleration, a new radiofrequency(RF) system based on a magnetic alloy-loaded cavity is proposed. This paper presents design considerations and experimental results regarding the performance evaluation of the proposed RF system through high-power tests and beam commissioning. The test results demonstrate that the RF system satisfies the desired specifications and affords significant benefits for CSNS-Ⅱ.展开更多
Low-level radio frequency(LLRF)systems stabilize the electromagnetic field in the RF cavities used for beam acceleration in particle accelerators.Reliable,accurate,and precise detection of RF amplitude and phase is pa...Low-level radio frequency(LLRF)systems stabilize the electromagnetic field in the RF cavities used for beam acceleration in particle accelerators.Reliable,accurate,and precise detection of RF amplitude and phase is particularly important to achieve high field stability for pulsed accelerators of free-electron lasers(FEL).The digital LLRF systems employ analog-to-digital converters to sample the frequency down-converted RF signal and use digital demodulation algorithms to calculate the RF amplitude and phase.Different sampling strategies and demodulation algorithms have been developed for these purposes and are introduced in this paper.This article focuses on advanced topics concerning RF detection,including accurate RF transient measurement,wideband RF detection,and RF detection with an asynchronous trigger,local oscillator,or clock.The analysis is based on the SwissFEL measurements,but the algorithms introduced are general for RF signal detection in particle accelerators.展开更多
A longitudinal accumulation scheme based on a triple-frequency RF system,in which the static radio frequency(RF)bucket is lengthened to be compatible with the realizable raise time of a fast pulse kicker,is proposed i...A longitudinal accumulation scheme based on a triple-frequency RF system,in which the static radio frequency(RF)bucket is lengthened to be compatible with the realizable raise time of a fast pulse kicker,is proposed in this paper.With this technique,the bunch from a booster can be captured by the longitudinal acceptance without any disturbance to the stored bunch,which remains at the center.This composite RF system consists of three different frequencies,which can be regarded as the conventional bunch lengthening RF system(usually containing fundamental and third harmonic cavities)extended by an additional second harmonic RF cavity.In this paper,we discuss the RF jitter and the transverse mode-coupling instability(TMCI)when using this special RF system.Considering several different bunch profiles,we discuss the beam stability with regard to the RF jitter.However,for the TMCI we assume an ideal bunch profile,where the bunch is exactly lengthened to the maximum extent.While macroparticle simulation is the main method used to study the impact of the RF jitter,numerical analysis and simulations for the TMCI while using a triple-frequency RF system are also presented in this paper.An approximation formula,based on the existing model,is also derived to estimate the impact of the TMCI on the single bunch current threshold when using harmonic cavities.展开更多
The RF system for TESLA requires a comprehensive interlock system.Usually interlock systems are organized in a hierarchical way,In order to react to different fault conditions in a fast and flexible manner a nonhierar...The RF system for TESLA requires a comprehensive interlock system.Usually interlock systems are organized in a hierarchical way,In order to react to different fault conditions in a fast and flexible manner a nonhierarchical organization seems to be the better solution ,At the TESLA Test Facility (TTF) at DESY we will install a nonhierarchical interlock system that is based on user desgned reprogrammable gate-arrays (FPGA's) which incorporate an embedded microcontroller system.This system could beused later for the TESLA linear collider replacing a strictly hierarchical design.展开更多
Nowadays, we are witnessing an era marked by the autonomy of wireless devices and sensor networks without the aid of batteries. RF energy harvesting therefore becomes a promising alternative for battery dependence. Th...Nowadays, we are witnessing an era marked by the autonomy of wireless devices and sensor networks without the aid of batteries. RF energy harvesting therefore becomes a promising alternative for battery dependence. This work presents the design of an RF energy harvesting system consisting mainly of a rectenna (antenna and rectification circuit) and an adaptation circuit. First of all, we designed two dipole type antennas. One operates in the GSM 900 MHz band and the other in the GSM 1800 MHz band. The performances of the proposed antennas are provided by the ANSYS HFSS software. Secondly, we proposed two rectification circuits in order to obtain conversion efficiencies at 0 dBm of 64% for the system operating at the frequency of 900 MHz and 37% for the system at the frequency of 1800 MHz RF-DC. The rectifiers used are based on Schottky diodes. For maximum transfer of power between the antenna and the rectification circuit, L-type matching circuits have been proposed. This rectifier offers DC voltage values of 806 mV for the circuit at the frequency of 900 MHz and 616 mV for the circuit at the frequency of 1800 MHz. The adaptation circuits are obtained by carrying out simulations on the ADS (Advanced Design System) software.展开更多
In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source ...In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source UAV transmits data to a relay UAV using the FSO technique.In the second hop,the relay UAV forwards data to a destination Mobile Station(MS)via an RF channel,with the RIS enhancing coverage and performance.The relay UAV operates in a Decode-and-Forward(DF)mode.As the main contribution,we provide a mathematical performance analysis of the RIS-assisted FSO-RF mixed dual-hop UAV system,evaluating outage probability,Bit-Error Rate(BER),and average capacity.The analysis accounts for factors such as atmospheric attenuation,turbulence,geometric losses,and link interruptions caused by UAV hovering behaviors.To the best of our knowledge,this is the first theoretical investigation of RIS-assisted FSO-RF mixed dual-hop UAV communication systems.Our analytical results show strong agreement with Monte Carlo simulation outcomes.Furthermore,simulation results demonstrate that RIS significantly enhances the performance of UAV-aided mixed RF/FSO systems,although performance saturation is observed due to uncertainties stemming from UAV hovering behavior.展开更多
Most synchrotron light storage rings are equipped with a higher harmonic cavity(HHC)and are currently predominantly used to increase beam life.With the enhancement of the beam current intensity,it is necessary to cons...Most synchrotron light storage rings are equipped with a higher harmonic cavity(HHC)and are currently predominantly used to increase beam life.With the enhancement of the beam current intensity,it is necessary to consider instability problems that may be caused by heavy beam loading effects.In this study,we incorporated a HHC into the small-signal Pedersen mathematical model and used system signal analysis to investigate the mode-zero Robinson instability driven by the passive superconducting harmonic cavity and active superconducting harmonic cavity fundamental modes.To further study and alleviate this instability,we introduced direct radio-frequency feedback,an automatic voltage control loop,and a phase-lock loop into the model,discussed the impact of the feedback loop parameter settings on the stability margin,and provided suggestions for parameter settings.展开更多
数据清洗、特征选择和预测模型建立是基于数据采集与监视控制系统(supervisory control and data acquisition,SCADA)数据,实现风电机组异常状态预警不可缺少的重要环节。先结合孤立森林(isolation forest,iForest)和基于密度的空间聚类...数据清洗、特征选择和预测模型建立是基于数据采集与监视控制系统(supervisory control and data acquisition,SCADA)数据,实现风电机组异常状态预警不可缺少的重要环节。先结合孤立森林(isolation forest,iForest)和基于密度的空间聚类(density-based spatial clustering of applications with noise,DBSCAN)算法对SCADA数据异常点进行有效清洗,并采用随机森林算法(random forests,RF)与Person相关系数法优选模型输入参数;再进而基于Optuna优化的类别提升树(categorical boosting,CATBoost)算法,建立风电机组正常工况齿轮箱油池温度的预测模型;然后采用滑动窗方法,构建状态评价指标,并使用区间估计理论确定油温异常状态判别的临界阈值;实现油温异常预警;最后,采用某风电机组SCADA系统油温异常的真实历史故障数据进行检验,验证了该方法的有效性。展开更多
基金This work was supported by funds from the National Natural Science Foundation of China(Nos.11875270,U1832210,12205317)Youth Innovation Promotion Association CAS(No.2018015)Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120046).
文摘The China Spallation Neutron Source(CSNS) upgrade project(CSNS-Ⅱ) aims to enhance the beam power from 100 to 500 kW. A dual-harmonic accelerating method has been adopted to alleviate the stronger space-charge effect in rapid-cycling synchrotrons owing to the increased beam intensity. To satisfy the requirements of dual-harmonic acceleration, a new radiofrequency(RF) system based on a magnetic alloy-loaded cavity is proposed. This paper presents design considerations and experimental results regarding the performance evaluation of the proposed RF system through high-power tests and beam commissioning. The test results demonstrate that the RF system satisfies the desired specifications and affords significant benefits for CSNS-Ⅱ.
文摘Low-level radio frequency(LLRF)systems stabilize the electromagnetic field in the RF cavities used for beam acceleration in particle accelerators.Reliable,accurate,and precise detection of RF amplitude and phase is particularly important to achieve high field stability for pulsed accelerators of free-electron lasers(FEL).The digital LLRF systems employ analog-to-digital converters to sample the frequency down-converted RF signal and use digital demodulation algorithms to calculate the RF amplitude and phase.Different sampling strategies and demodulation algorithms have been developed for these purposes and are introduced in this paper.This article focuses on advanced topics concerning RF detection,including accurate RF transient measurement,wideband RF detection,and RF detection with an asynchronous trigger,local oscillator,or clock.The analysis is based on the SwissFEL measurements,but the algorithms introduced are general for RF signal detection in particle accelerators.
文摘A longitudinal accumulation scheme based on a triple-frequency RF system,in which the static radio frequency(RF)bucket is lengthened to be compatible with the realizable raise time of a fast pulse kicker,is proposed in this paper.With this technique,the bunch from a booster can be captured by the longitudinal acceptance without any disturbance to the stored bunch,which remains at the center.This composite RF system consists of three different frequencies,which can be regarded as the conventional bunch lengthening RF system(usually containing fundamental and third harmonic cavities)extended by an additional second harmonic RF cavity.In this paper,we discuss the RF jitter and the transverse mode-coupling instability(TMCI)when using this special RF system.Considering several different bunch profiles,we discuss the beam stability with regard to the RF jitter.However,for the TMCI we assume an ideal bunch profile,where the bunch is exactly lengthened to the maximum extent.While macroparticle simulation is the main method used to study the impact of the RF jitter,numerical analysis and simulations for the TMCI while using a triple-frequency RF system are also presented in this paper.An approximation formula,based on the existing model,is also derived to estimate the impact of the TMCI on the single bunch current threshold when using harmonic cavities.
文摘The RF system for TESLA requires a comprehensive interlock system.Usually interlock systems are organized in a hierarchical way,In order to react to different fault conditions in a fast and flexible manner a nonhierarchical organization seems to be the better solution ,At the TESLA Test Facility (TTF) at DESY we will install a nonhierarchical interlock system that is based on user desgned reprogrammable gate-arrays (FPGA's) which incorporate an embedded microcontroller system.This system could beused later for the TESLA linear collider replacing a strictly hierarchical design.
文摘Nowadays, we are witnessing an era marked by the autonomy of wireless devices and sensor networks without the aid of batteries. RF energy harvesting therefore becomes a promising alternative for battery dependence. This work presents the design of an RF energy harvesting system consisting mainly of a rectenna (antenna and rectification circuit) and an adaptation circuit. First of all, we designed two dipole type antennas. One operates in the GSM 900 MHz band and the other in the GSM 1800 MHz band. The performances of the proposed antennas are provided by the ANSYS HFSS software. Secondly, we proposed two rectification circuits in order to obtain conversion efficiencies at 0 dBm of 64% for the system operating at the frequency of 900 MHz and 37% for the system at the frequency of 1800 MHz RF-DC. The rectifiers used are based on Schottky diodes. For maximum transfer of power between the antenna and the rectification circuit, L-type matching circuits have been proposed. This rectifier offers DC voltage values of 806 mV for the circuit at the frequency of 900 MHz and 616 mV for the circuit at the frequency of 1800 MHz. The adaptation circuits are obtained by carrying out simulations on the ADS (Advanced Design System) software.
基金supported in part by the National Research Foundation of Korea(NRF)funded by the Korea government(MSIT)under Grant NRF-2022R1I1A3073740in part by the MSIT(Ministry of Science and ICT),Korea,under the ITRC(Information Technology Research Center)support program(IITP-2024-RS-2024-00436406)supervised by the IITP(Institute for Information&Communications Technology Planning&Evaluation)+1 种基金in part by the Institute for Information and Communications Technology Promotion(IITP)Grant funded by the Korea Government(MSIP,Development of Cube Satellites Based on Core Technologies in Low Earth Orbit Satellite Communications)under Grant RS-2024-00396992in part by the Korea Research Institute for Defense Technology planning and advancement(KRIT)grant,funded by the Korea government(DAPA(Defense Acquisition Program Administration))(21-106-A00-007,Space-Layer Intelligent Communication Network Laboratory,2022).
文摘In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source UAV transmits data to a relay UAV using the FSO technique.In the second hop,the relay UAV forwards data to a destination Mobile Station(MS)via an RF channel,with the RIS enhancing coverage and performance.The relay UAV operates in a Decode-and-Forward(DF)mode.As the main contribution,we provide a mathematical performance analysis of the RIS-assisted FSO-RF mixed dual-hop UAV system,evaluating outage probability,Bit-Error Rate(BER),and average capacity.The analysis accounts for factors such as atmospheric attenuation,turbulence,geometric losses,and link interruptions caused by UAV hovering behaviors.To the best of our knowledge,this is the first theoretical investigation of RIS-assisted FSO-RF mixed dual-hop UAV communication systems.Our analytical results show strong agreement with Monte Carlo simulation outcomes.Furthermore,simulation results demonstrate that RIS significantly enhances the performance of UAV-aided mixed RF/FSO systems,although performance saturation is observed due to uncertainties stemming from UAV hovering behavior.
文摘Most synchrotron light storage rings are equipped with a higher harmonic cavity(HHC)and are currently predominantly used to increase beam life.With the enhancement of the beam current intensity,it is necessary to consider instability problems that may be caused by heavy beam loading effects.In this study,we incorporated a HHC into the small-signal Pedersen mathematical model and used system signal analysis to investigate the mode-zero Robinson instability driven by the passive superconducting harmonic cavity and active superconducting harmonic cavity fundamental modes.To further study and alleviate this instability,we introduced direct radio-frequency feedback,an automatic voltage control loop,and a phase-lock loop into the model,discussed the impact of the feedback loop parameter settings on the stability margin,and provided suggestions for parameter settings.
文摘数据清洗、特征选择和预测模型建立是基于数据采集与监视控制系统(supervisory control and data acquisition,SCADA)数据,实现风电机组异常状态预警不可缺少的重要环节。先结合孤立森林(isolation forest,iForest)和基于密度的空间聚类(density-based spatial clustering of applications with noise,DBSCAN)算法对SCADA数据异常点进行有效清洗,并采用随机森林算法(random forests,RF)与Person相关系数法优选模型输入参数;再进而基于Optuna优化的类别提升树(categorical boosting,CATBoost)算法,建立风电机组正常工况齿轮箱油池温度的预测模型;然后采用滑动窗方法,构建状态评价指标,并使用区间估计理论确定油温异常状态判别的临界阈值;实现油温异常预警;最后,采用某风电机组SCADA系统油温异常的真实历史故障数据进行检验,验证了该方法的有效性。
