合肥光源逐束团测量系统研制

逐束团测量装置属于宽带和实时测量,足以分辨重复频率为204 MHz的相邻束团的信号,设计功能包括横向水平和垂直Beta振荡,纵向同步相位振荡,束团填充等信息的实时检测。对信号频谱分析,系统参数设计,前端射频检测,锁相环信号合成,高速数据采集以及基于PXI的整个系统作了详细介绍,分析了若干调试和实验结果,并讨论了合肥光源储存环目前存在的不稳定性及该测试手段在诊断中的应用。     

合肥光源逐束团测量系统研制

 逐束团测量装置属于宽带和实时测量,足以分辨重复频率为204 MHz的相邻束团的信号,设计功能包括横向水平和垂直Beta振荡,纵向同步相位振荡,束团填充等信息的实时检测。对信号频谱分析,系统参数设计,前端射频检测,锁相环信号合成,高速数据采集以及基于PXI的整个系统作了详细介绍,分析了若干调试和实验结果,并讨论了合肥光源储存环目前存在的不稳定性及该测试手段在诊断中的应用。     

合肥光源单束团下束团长度和能散的测量

根据同步光与储存环中的束流信号具有相同的时间结构的原理,测量同步光脉冲的半高全宽值可以计算出束团的长度。根据合肥光源的特点和实际需要,选择快速光电接收器搭配高速高带宽示波器作为在线测量束团长度和纵向分布等的主要手段。对单束团模式下束团长度随流强和高频腔腔压的变化趋势进行了测量。测量结果表明:束团长度与腔压的0.3次方成反比,比理论值0.5小;而束团长度随流强的增长率为2.0 ps/mA。通过测量纵向量子寿命进行了能散随流强变化的间接测量,结果表明,束团的拉伸是能散变化和势阱效应共同作用的结果。     

合肥光源单束团下束团长度和能散的测量

根据同步光与储存环中的束流信号具有相同的时间结构的原理,测量同步光脉冲的半高全宽值可以计算出束团的长度。根据合肥光源的特点和实际需要,选择快速光电接收器搭配高速高带宽示波器作为在线测量束团长度和纵向分布等的主要手段。对单束团模式下束团长度随流强和高频腔腔压的变化趋势进行了测量。测量结果表明：束团长度与腔压的0.3次方成反比,比理论值0.5小;而束团长度随流强的增长率为2.0 ps/mA。通过测量纵向量子寿命进行了能散随流强变化的间接测量,结果表明,束团的拉伸是能散变化和势阱效应共同作用的结果。     

直线加速器中双向高斯密度分布电荷束团发射度增长的比率关系

采用直线加速器中的空间电荷束团的有限圆柱模型，并假设该有限圆柱体电荷密度分布在横向ｒ和纵向ｚ都满足高期分布，推导得到了该电荷束团的自场能与发射度增长公式；通过数值模拟计算，给出了束流发射度增长随束团参数和加速器系统参数变化的图表曲线，讨论了该双向高期密度分布电荷束团发射度增长的比率关系．     

小波分析方法在合肥光源逐束团测量系统中的应用

介绍了小波分析方法在逐束团束流位置测量系统中的应用。小波分析方法在高频处频率窗口较宽,具有较高的时间分辨力,使用小波分析可分离并提取信号的振荡成分及基线漂移成分,各成分在时间轴上的位置与原信号相同,原有的线性关系保持不变,在处理非平稳信号时不会造成信号明显劣化,如幅度失真和相位偏差。基于小波分解和重构的时间序列多分辨力滤波处理非平稳信号时不会造成信号明显劣化,保证了追踪束团振荡强度、相位、频率和振荡模式随时间变化的结果更真实可信。在合肥光源中,小波分析方法成功用于横向振荡振幅包络的提取及增长率、阻尼率的计算,也可用于提取横向振荡振幅包络及计算增长率和阻尼率,为机器研究、束流诊断和逐束团反馈系统调试提供了准确的依据。     

基于Hilbert变换的相空间重建方法在HLS逐束团测量系统中的应用

引入基于Hilbert变换的相空间重建手段, 对合肥光源(HLS)逐束团测量系统采集的数据进行了全面的分析, 其中包括单个束流位置监测器(BPM)数据的相空间重建, 逐圈逐束团振荡相位信息、束团振荡模式信息、逐束团横向工作点(tune值)变换. 提出了新的分析束团tune值的手段, 提供传统方法无可比拟的更高的时间和频率分辨率. 还对不同模式的阻尼率进行了计算, 这为衡量逐束团反馈系统的效果提供了确实可靠的方法.     

直线加速器中双向高斯密度分布电荷束团发射度增长的比率关系

采用直线加速器中的空间电荷束团的有限圆柱模型,并假设该有限圆柱体电荷密度分布在横向r和纵向z都满足高期分布,推导得到了该电荷束团的自场能与发射度增长公式;通过数值模拟计算,给出了束流发射度增长随束团参数和加速器系统参数变化的图表曲线,讨论了该双向高期密度分布电荷束团发射度增长的比率关系.     

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。     

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。     

HLS bunch current measurement system

Bunch current is an important parameter for studying the injection fill-pattern in the storage ring and the instability threshold of the bunch, and the bunch current monitor also is an indispensable tool for the top-up injection. A bunch current measurement (BCM) system has been developed to meet the needs of the upgrade project of Hefei Light Source (HLS). This paper presents the layout of the BCM system. The system based on a high-speed digital oscilloscope can be used to measure the bunch current and synchronous phase shift. To obtain the absolute value of bunch-by-bunch current, the calibration coefficient is measured and analyzed. Error analysis shows that the RMS of bunch current is less than 0.01 mA when bunch current is about 5 mA, which can meet project requirement.

     

A study of pickup and signal processing for HLS- bunch current measurement system

For the HLS-bunch current measurement system,in order to obtain the absolute value of bunch current,the calibration factor should be determined by using DCCT.At the HLS storage ring,the stretch efect of bunch length is observed and the change rate is about 19% when the bunch current decays over time and this will afect the performance of bunch current detection.To overcome the bunch stretch influence in the HLS-bunch current measurement,an evaluation about pickup type and signal processing is carried out.Strip-line pickup and button pickup are selectable,and the theoretical analysis and demonstration experiment are performed to find out an acceptable solution for the bunch current measurement system at HLS-.The experimental data analysis shows that the normalized calibration factor will change by about 27% when the bunch length changes by about 19% if using the button pickup and processing by peak value of bunch signal;the influence will be reduced to 2% less if adopting the strip-line pickup and integral.     

A prototype silicon detector system for space cosmic-ray charge measurement

A readout electronics system used for space cosmic-ray charge measurement for multi-channel silicon detectors is introduced in this paper, including performance measurements. A 64-channel charge sensitive ASIC (VA140) from the IDEAS company is used. With its features of low power consumption, low noise, large dynamic range, and high integration, it can be used in future particle detecting experiments based on silicon detectors.     

A prototype silicon detector system for space cosmic-ray charge measurement

A readout electronics system used for space cosmic-ray charge measurement for multi-channel silicon detectors is introduced in this paper, including performance measurements. A 64-channel charge sensitive ASIC （VA140） from the IDEAS company is used. With its features of low power consumption, low noise, large dynamic range, and high integration, it can be used in future particle detecting experiments based on silicon detectors.     

BEPCII次谐波聚束系统物理公差要求的研究

 为了进一步提高束流品质并逐步采用双束加速技术, BEPCII直线加速器准备采用带有两个次谐波聚束器的双次谐波聚束系统。目前, 该次谐波聚束系统的物理设计和优化已经基本完成。由于新设计的双次谐波聚束系统很不同于BEPCII现有的聚束系统, 因此, 就要求对聚束系统中存在的各种抖动(jitter)效应重新进行研究。 使用多粒子模拟计算程序PARMELA对电子枪的高压抖动和定时抖动、次谐波聚束器的相位抖动以及功率抖动、聚束器中加速电场相位以及A0加速管(俘获加速节)中加速电场相位的抖动等效应进行了研究, 并最终确定了聚束系统中各部件的物理公差要求。     

BEPCII横向束流反馈系统前端电子学

 选择了一台商业化的前端电子学RFTF（radio frequency front-end for transverse feedback system）用于BEPCII横向束流反馈系统, 这是跟进世界先进加速器技术的具体实施。在BEPC同步运行模式下对RFTF的性能进行了测试实验，结果表明使用RFTF可以得到理想的波形，能够满足BEPCII横向反馈系统的需要，但是，当储存环出现不稳性时，系统无法正常工作，这就要求BEPCII纵向不稳定很小或者用纵向反馈系统来抑制存在的纵向不稳定。     

BEPCII横向束流反馈系统前端电子学

选择了一台商业化的前端电子学RFTF（radio frequency front-end for transverse feedback system）用于BEPCII横向束流反馈系统, 这是跟进世界先进加速器技术的具体实施。在BEPC同步运行模式下对RFTF的性能进行了测试实验,结果表明使用RFTF可以得到理想的波形,能够满足BEPCII横向反馈系统的需要,但是,当储存环出现不稳性时,系统无法正常工作,这就要求BEPCII纵向不稳定很小或者用纵向反馈系统来抑制存在的纵向不稳定。     

BEPCII次谐波聚束系统物理公差要求的研究

为了进一步提高束流品质并逐步采用双束加速技术, BEPCII直线加速器准备采用带有两个次谐波聚束器的双次谐波聚束系统。目前, 该次谐波聚束系统的物理设计和优化已经基本完成。由于新设计的双次谐波聚束系统很不同于BEPCII现有的聚束系统, 因此, 就要求对聚束系统中存在的各种抖动(jitter)效应重新进行研究。 使用多粒子模拟计算程序PARMELA对电子枪的高压抖动和定时抖动、次谐波聚束器的相位抖动以及功率抖动、聚束器中加速电场相位以及A0加速管(俘获加速节)中加速电场相位的抖动等效应进行了研究, 并最终确定了聚束系统中各部件的物理公差要求。     

A device for aerosol charge measurement and sampling

In this work, a device for aerosol charge measurement and dust sampling is presented. The device is basically an open-ended Faraday pail with a filter to collect the sample. It can be attached to a pneumatic transfer line or it can be used with hose, depending on the situation. When the system was developed, special emphasis was put on the ease of use and reliability. The device can be assembled and disassembled with one twist. The reliability and the operation of the device was tested using two different powder materials, test dust and polystyrene pellets, and four different hose materials. By combining these materials, different extents and polarities of tribo-charge were obtained. The device proved to be easily operated and the test results showed good reproducibility.     

A method of charge measurement for contact electrification

A method for studying contact electrification charge between different materials was developed. Physical models for the contact electrification measurement system of metal/metal, metal/insulator and insulator/insulator were proposed, where the relationships between charge and measuring potential were developed. According to the models, an electrification charge measurement system was built. As an example of using the method, contact electrification experiment between polytetrafluoroethylene (PTFE) and carbon steel plates was conducted. Comparison of the charge results by this method and Faraday cup method was made, which suggested that the current method reduced the error resulted from the charge dissipation.