常温直线加速器RF系统的建模

为了研究针对RF系统的新的控制方法,用Matlab软件为常温直线加速器的RF系统建立了一个数学模型。模型包括了速调管、SLED和行波加速管等一些典型的微波器件。RF系统模型被用于研究系统在不同输入信号下的输出情况,并用于确定SLED的相位翻转时间和RF系统的工作点。一种新的控制算法,自适应前馈控制算法,也在RF系统模型上得到了验证,并取得了良好的结果。这些都证明所建立的RF系统模型是有效的。     

Error and jitter effect studies on the SLED for the BEPC Ⅱ-linac

An RF pulse compressor is a device used to convert a long RF pulse to a short one with a much higher peak RF magnitude. SLED can be regarded as the earliest RF pulse compressor to be used in large-scale linear accelerators. It has been widely studied around the world and applied in the BEPC and BEPC linac for many years. During routine operation, error and jitter effects will deteriorate the performance of SLED, either on the output electromagnetic wave amplitude or phase. The error effects mainly include the frequency drift induced by cooling water temperature variation and the frequency/Q 0 /β unbalances between the two energy storage cavities caused by mechanical fabrication or microwave tuning. The jitter effects refer to the PSK switching phase and time jitters. In this paper, we re-derive the generalized formulae for the conventional SLED used in the BEPC linac, and the error and jitter effects on SLED performance are also investigated.     

用于长脉冲多束团直线加速器的SLED系统

根据长脉冲多束团直线加速器对输入微波波形的要求,系统研究了带有SLED的微波系统,由SLED基本理论推导了输出RAMP波形和平顶波形脉冲时SLED所需的输入波形,给出SLED的参数优化方法.用冷测实验对所发展的理论进行了验证,第一次用SLED产生了RAMP波形和平顶波形的RF脉冲.     

3 dB桥误差对能量倍增器性能的影响

根据能量倍增器的工作原理,对3 dB桥误差引起的能量倍增器性能变化进行了理论分析,并对BEPC和BEPCⅡ直线加速器所使用能量倍增器的3 dB桥误差进行了讨论,为判断焊接后3 dB桥桥臂波导变形提供了理论参考。结果表明:无论是功率分配不平衡,还是相位关系偏离,都会使部分功率反射回速调管。功率分配不平衡和微波相位关系偏离值越大,则功率倍增因子下降得越多。     

一种新型的能量倍增器解调谐系统

在北京正负电子对撞机(BEPC)直线加速器工程中,参考美国SLAC微波脉冲压缩技术,成功地研制了能量倍增器(SLED).该装置自1988年运行以来,一直存在一个隐患,解调谐系统设计有问题,不能随便解谐.BEPCⅡ经常需要长脉冲束流,这就要求能量倍增器能够方便地进行解调谐.为此,参考日本KEK的资料,对目前能量倍增器解调谐系统进行了彻底的改进,完成了新的SLED解调谐系统的研制任务,并在加速器上成功地进行了高功率试运行.     

A New Type of Detuning System of RF Compressors (SLED)

In our SLAC type of RF pulse compressor (SLED), the detuning device works not as well as expected. It happend that the detuning needles sticked to the sleeves when working at detuning mode. Due to this reason, we can not measure its energy multiplication factor. To solve the sticking problem of SLED needles, a prototype of the new SLED detuning system has been developed and it has been operated with high power successfully on BEPC Linac.     

能量倍增器法微波脉冲压缩

为了开展S波段能量倍增器脉冲压缩实验,对能量倍增器进行了冷测和热测工作,主要包括对能量倍增器的指标、参数的测量以及在高功率下对能量倍增器的输出功率、功率增益等参数的测量。实验中,完成了微波固态源系统的改造,研制了同步信号控制器,研究了输入输出脉冲宽度对输出峰值功率的影响,并对实验中可能的射频击穿问题进行了研究。在输入功率5 MW时,得到了功率增益7.122,输出脉宽260 ns,输出峰值功率35.35 MW。     

Modeling and analysis of SLED

SLED(SLAC Energy Doubler) is a crucial component for the C-band microwave acceleration unit of a soft X-ray Free Electron Laser(SXFEL). To study the behavior of SLED, a mathematical model is commonly built and analyzed. In this paper, a new method is proposed to build the model of SLED at the Shanghai Institute of Applied Physics. With this method, the parameters of the two cavities can be analyzed separately. Also it is suitable to study parameter optimization of SLED and analyze the effect from the parameters variations. Simulation results of our method are also presented.     

C波段能量倍增器的研制

C波段(5712 MHz)能量倍增器——SLED是我国研制的首台C波段能量倍增器。简述了利用三维电磁场仿真软件HFSS和CST对C波段能量倍增器的高品质因数储能腔、耦合孔、3 dB桥等进行优化设计的情况,对加工的能量倍增器做了射频低功率测试,实验测试和理论计算的一致性很好,测试结果表明所有技术参数指标均达到了设计要求。     

Microwave System for BEPCⅡ-Linac

Specifications of microwave system for BEPCⅡ-Linac were enhanced by a wide margin in comparison with those of the microwave system for BEPC-Linac. For this reason many RF components must be developed and improved. This paper introduces the developments of SLED detuning system, accelerating section, high power waveguide valve, high power dummy-load, and medium & high power waveguide attenuator/phase shifters. High power operation of the microwave system has been carried out.     

基于FPGA的能量倍增器相位翻转系统的研制

介绍了基于可编程逻辑门阵列(FPGA)的能量倍增器(SLED)相位翻转系统。该系统主要由微波IQ调制器、FPGA和高速DAC组成。在FPGA的控制下,DAC输出两路双极性脉冲电平信号,加载于调制器的IQ端,将微波连续波输入信号转变为4μs脉冲输出信号,并且在3μs时刻微波相位发生180°跳变。经测试,相位翻转精度为180°±2°,翻转相位的长期稳定度优于±0.5°;相位翻转系统驱动的6台SLED的输出功率增益均超过7dB,最高达到7.54dB,增益的长期稳定度达到±0.1dB。     

光阴极注入器超导加速腔集成实验研究

 光阴极超导加速器实验系统由四倍频Nd：YAG锁模激光器、Cs₂Te光阴极、2+1/2微波电子枪、L波段3.5MW脉冲微波源,1.3GHz单腔超导铌腔,500W连续微波源,超导腔束管耦合器,4.2K低温恒温容器,液氦制冷系统,同步控制系统,束流参数诊断,真空系统等构成。2001年6月在中物院进行了光阴极超导加速器原理性实验,测得超导加速段能量增益0.58MeV,微脉冲束流强度0.1A,取得了预期的实验结果。     

Design and simulation of a C-band SLED with mode converter

The transient response analysis of the SLED based on the equivalent circuit is described. Then, a C-band SLED using TE0,1,15 mode cylindrical cavity with TE10-TE01 mode converter has been designed. According to the main RF parameters of the accelerator, the coupling coefficient is optimized to obtain the maximum multiplication factor. The key components of the pulse compressor include a 3 dB directional coupler, a TE10-TE01 mode converter,and a cylindrical cavity, which are simulated and optimized using 3D electromagnetic field simulation software. In addition, the function defining the relation between the coupling factor and aperture size is derived by a mathematical fitting method.     

High speed integrated RF–VLC data communication system: Performance constraints and capacity considerations

In this research paper, we propose a two-hop integrated radio frequency–visible light communication (RF–VLC) system which may provide a better option to transceive between the hospitals and some laboratory to transfer patient’s information. In the proposed system model, the data (such as patient’s lab test reports) is transmitted towards the amplify and forward (AF) relay mounted on the top of the hospital building via the RF channel. Further, the AF relay amplifies and converts the received information into corresponding optical signal using light emitting diodes (LED) and supporting circuitry. This optical signal is then forwarded towards the destination device (equipped with VLC transceiver), via the VLC channel. To analyse the performance of the system, we first derive the closed form analytical expressions for the cumulative distribution function (CDF) of the end-to-end (e2e) signal to noise ratio (SNR) of the system by using the moment generating function (MGF) of the SNR of the individual RF and VLC channels. Further, we use these statistical expressions to obtain the outage probability, average bit error rate (BER) and the average capacity of the system. Moreover, the asymptotic performance of the proposed system is also analysed to study the system’s behaviour at high SNR regimes. Finally, we studied the impact of the variations in channel parameters on the proposed system model performance through numerically simulated plots.     

Tuning of RF amplitude and phase for the drift tube linac in J-PARC

The J-PARC linac has three DTL tanks to accelerate the negative hydrogen ions from 3 MeV to 50 MeV. The RF phase and amplitude are adjusted for each cavity with a phase scan method within the accuracy of 1°in phase and 1% in amplitude. The experimental results show a remarkable agreement with the numerical model within a sufficient margin in the tuning of the last two DTL tanks. However, a notable discrepancy between the experiment and the numerical model is seen in the tuning of the first DTL tank. After studying with a three-dimensional multi-particle simulation, the generation of the low energy component and the pronounced filamentation are identified as the main causes of the discrepancy. The optimization of the tuning scheme is also discussed to attain the tuning goal accuracy for the first DTL tank.     

CRRFA-30L波段射频加速器

 主要介绍CRRFA-30L波段射频加速器结构和性能，论述了热阴极射频腔注入器、束流加速系统、微波功率源和控制等结构中主要技术及其研究进展，给出了加速器输出束流参数测量与测量结果分析，达到设计应用要求。     

漂移管直线加速器高功率波导窗的物理设计

为了研发中国散裂中子源(CSNS)漂移管直线加速器(DTL)的功率耦合器,在对常规波导窗结构进行改进的基础上,设计了一种新型高功率波导窗。利用微波仿真软件CST优化了波导窗的高频传输特性,并采用ANSYS分析了波导窗在通功率时的温升及热应力以防止陶瓷片破裂,结果表明,波导窗能传输的最大平均功率达到了800 kW。校核了波导窗抽真空时的机械强度,并对陶瓷窗高频打火进行初步讨论,结果表明,漂移管直线加速器入腔功率为2 MW,小于波导窗的临界输入功率2.355 MW,窗内打火的机率很小。     

Emittance coupling driven by space charge in the CSNS linac

In the conventional design of RF linacs, the bunched beams are not in thermal equilibrium. The space charge forces couple the particle motions between the transverse and the longitudinal directions. Fur-thermore it will cause the equipartitioning process which leads to emittance growth and halo formation. In the design of the China Spallation Neutron Source (CSNS) linac, three cases are investigated using the Hofmann stability charts. In this paper, we present the equipartitioning beam study of the CSNS Alvarez DTL linac.     

中物院远红外自由电子激光实验研究

中国工程物理研究院基于射频直线加速器技术的远红外自由电子激光(FIR-FEL)实验取得阶段性进展,于2005年3月24晚8时30分首次出光, 并多次重复. 中心波长115μm, 谱宽1%.介绍了实验系统的主要组成部分和主要实验结果.     

弹性管束换热器动态特性分析及仿真系统设计

在对弹性管束换热器进行合理简化和分析的基础上得到了描述其工作物理过程的数学模型,对其动态特性进行 了理论分析和数值求解,确定了当进水流量和蒸汽压力发生扰动时,弹性管束换热器出水温度的动态响应规律。为该类型 换热器控制系统的设计提供了依据。本文开发的仿真环境也可用于其它换热设备的动态特性模拟。