倍频腔法测BEPCⅡ直线加速器的束团长度

 阐述了利用倍频腔束团长度监测器测量北京正负电子对撞机二期工程电子直线加速器束团长度的原理,通过两个月的测试和数据采集,测得的束团长度集中在1.4~2.0 mm之间,与理论值1.5 mm基本相符。根据不同时刻的记录,基频腔峰值电压与束流流强探测器BCT3所测流强值近似成正比关系;当大幅改变预聚束器和聚束器参数而束流流强不变时,反映聚束质量的五倍频腔信号也随之大幅改变,而反映流强信号的基频腔信号则变化不大,这些试验结果与理论分析完全一致。     

A massive-ion beam driver for high-energy-density physics and future inertial fusion

Several heavy ion drivers for heavy ion inertial fusion have been proposed in the US and Europe, based on linear induction accelerator technology [1] and existing RF technology [2], respectively, although they have not been realized on a large scale. Developing accelerator technology may provide an alternative efficient, robust, and relatively cheap massive-ion beam driver for future particle beam inertial fusion. Here, we propose an accelerator complex for accelerating giant cluster ions, instead of lead or bismuth ions, toward 120 GeV by using induction acceleration over the entire energy region. The proposed two-way multiplex induction synchrotron that is the main accelerator for the giant cluster ion beam would be equivalent to 10 synchrotrons of the same size for a single beam.     

BEPCⅡ正电子环真空度随流强的非线性变化

 观察发现负电子环的真空度随流强呈线性变化,正电子环的真空度随流强呈非线性变化,在正电子环的弧区,真空度的非线性变化很明显。讨论了非线性变化的原因,可能是同步光电子在正电子束流横向作用下加速碰壁,发生了二次电子发射,并在一定条件下形成了束流引起的多次碰壁效应,造成了大量放气。改变正电子束流的束团填充方式来观察真空度的非线性变化,得到了与KEK-B低能环一致的实验结果,该非线性变化呈现一定的阈值性,发生非线性的条件是有足够大的单束团流强和每列足够多的连续束团。     

基于积分束流变压器的加速器束团电荷量测量系统

 为满足清华大学加速器实验室光阴极微波电子枪实验平台的发展需求,设计了束团电荷量测量系统,可以实现实时测量加速器束团电荷量的目标。这套测量系统基于积分束流变压器,包括前置放大器、门控积分器、模数转换和数据传输模块。利用信号发生器模拟束流,对整套系统进行了离线测量实验。当前置放大器放大倍数取200和20时,AD转换值和束流电荷的比值分别为2.181 PC-1和0.195 PC-1,与理论值2.070 PC-1和0.207 PC-1基本吻合;其对应的电荷量测量误差分别小于2 PC和15 PC。测量结果和模拟束流电荷量值的拟合曲线线性度好,相关系数的平方均大于0.999 0。该结果验证了系统的可行性。     

改进的合肥光源逐束团流强测量方案

 对于多束团运行的储存环,逐束团流强的测量是研究注入填充和束流不稳定性阈值等的重要内容。介绍了加速器常用的一些逐束团监测手段,在此基础上,利用HLS（Hefei Light Source）现有的逐束团测量设备,并配合相应前端信号处理电路,进行了HLS储存环逐束团流强测量。实验线路方面,在传统的高频频率倍频信号检波的基础上,尝试了新的与同步方波信号检波的方法。分别在多束团和单束团情况下对HLS的束团流强进行了连续检测实验,对实验结果进行线性拟合,得到了定标结果,结果表明系统的1阶线性拟合标准偏差均在1%左右;最后对其中非线性部分的物理本质进行了解释。     

X波段准周期加载微波腔研究

 准周期加载微波腔的基本结构是周期结构，在强引导磁场作用下，强流电子束同微波强作用产生高功率微波；作用过程分为三个阶段：电子俘获、群聚和换能；而周期结构的作用主要在于电子俘获。适当设计的结构，不仅束波转换效率高，而且对电子束质量（如能散）的要求也不高。从微波场对电子运动的影响，研究了电子束在微波腔中的俘获、群聚和换能的束波互作用过程。基于760kV，7kA的环形电子束，采用准周期加载微波腔结构，在模拟上获得了X波段（9.3GHz）峰值功率为1.3GW的微波输出，效率接近24%。     

电子在α-磁铁中的运动描述

 由于α-磁铁具有能量选择和束团脉宽压缩的功能，它是RF-gun注入器中一个非常重要的组成部分。描述了α-磁铁的结构特点，讨论了电子在α-磁铁中运动的归一化方程。采用数值计算的方法给出了与电子运动能量无关的理想轨道运动方程，并导出了α-磁铁的主要性质。     

Starch based Active Packaging Film Reinforced with Empty Fruit Bunch (EFB) Cellulose Nanofiber

Biopolymer active packaging is known to have low mechanical strength and highly brittle. Regardless to its disadvantage, polymers from natural sources have attracted serious attention since the non-renewable sources for example petroleum, the major precursor of plastic manufacturing become depleted. Starch-Chitosan for instance is a hybrid film that entirely green as it produced from a renewable material and totally degradable. The addition of chitosan in film packaging able to kill pathogen hence increases the food shelf life. Through nanotechnology advance, nanomaterial can be used for material reinforcement. Nowadays, greener approach could be applied by incorporating natural cellulose nanofiber into the film matrix. Oil palm empty fruit bunch (OPEFB) fiber that rich of cellulose contents could be treated chemically to purify the cellulose in the fiber. Cellulose fiber obtained was cut to a nano-size using acid hydrolysis. Transmission Electron Microscopy (T.E.M) obtained shown the nanofiber size was ranged between 1-100 nm in diameter. Nanocomposite film formulation, was constructed by varying the cellulose nanofiber incorporation between 2-10% per weight of starch. The strength of the films was measured as well as antimicrobial properties. The addition of 2% cellulose nanofiber into the film matrix exhibits high tensile strength with 5.25 Mpa compared to starch-chitosan hybrid film with 3.96 Mpa. However, no significant improvement in tensile strength was distinguished beyond that ratio. Antimicrobial analysis shows that the addition of cellulose nanofiber could increase the inhibition effect towards gram-positive bacteria but not towards gram-negative bacteria. The addition of 2% cellulose nanofiber increased the inhibition diameter towards gram positive bacteria, Bacillus subtilis up to 33%. However, inhibition towards Bacillus subtilis decreased with the incorporation of more cellulose nanofiber. In gram-negative bacteria Escherichia coli, the addition of cellulose nanofiber does not give significant effect to bacterial. In General, the addition of the unique structure of cellulose nanofiber in the starch based polymer system could enhance the mechanical strength of the film and increase the inhibition of the gram positive bacteria.     

同轴电缆头和转接头HPM击穿现象初步分析

介绍了同轴电缆头和转接头的HPM击穿实验研究方法,给出了几种电缆头和转接头微波击穿功率随微波频率、脉冲宽度、重复频率和脉冲持续时间变化规律的实验研究结果。结果表明:微波击穿发生在同轴电缆头连接处,是电缆接头沿面滑闪,且击穿功率随同轴电缆及转接头尺寸的减小而降低;击穿功率也随微波脉冲宽度（30 ns～1 μs）的增大而减小,并且在100 ns附近有一拐点;在低重复频率（1～1000 Hz）下,重频对击穿功率的影响不大;微波频率在2.856～9.37 GHz变化时,微波频率对击穿功率的影响不明显;微波脉冲宽度较窄时（几十ns以下）,击穿功率随持续时间变化不大,脉冲宽度较宽时（百ns以上）,击穿阈值随持续时间的增大而下降。     

Measurement of bunch length evolution in electron beam macropulse of S-band linac using coherent edge radiation

Intense coherent edge radiation (CER) with a power of 0.10 mW was observed in a straight line with an undulator of Kyoto University Free Electron Laser (KU-FEL). To investigate the evolution of a bunch length in a macropulse of an electron beam, a technique was developed using the CER beam. The measured air-extracted CER beam profile has a hollow structure resembling the first-order Laguerre–Gaussian mode with asymmetric intensity in horizontal direction. It roughly agrees with the profile calculated considering the effective area of a deflection mirror employed to extract the beam from the FEL optical cavity into air. The root-mean-squared (RMS) bunch length determined from a measured spectrum of the CER beam is 60 μm for an electron-beam macropulse. Changes in the CER intensity in the electron-beam macropulse were measured by diode detectors with short time constants at two frequencies. The evolution of the RMS bunch length was determined using the ratio of the CER intensity at the two frequencies. It could be concluded that the evolution correlated with the macropulse structure of the FEL power. Therefore, measuring the evolution of the CER intensity at multiple frequencies proved useful to control FEL macropulses.