上海同步光源定时系统物理设计

正在建造中的上海光源(SSRF)设计为一台能量为3.5GeV的第三代同步辐射光源,其定时系统的物理设计使其能够满足储存环的不同运行模式,如单束团模式、多束团模式、混合模式及Top-up运行模式,定时系统具有高的稳定性和低的时间晃动.基于EPICS控制系统的定时系统可提供精确的可编程序事件驱动信号序列,根据不同需求提供电子枪、调制器、增强器和储存环高频,注入引出及束测等设备的触发信号.     

HLS储存环束流发射度研究

 研究了合肥光源(HLS)储存环束流发射度与其长直线节消色散条件之间的关系；在考虑到H函数的匹配时，计算了储存环最低束流发射度；为光源多种运行模式提供了理论依据。     

北京同步辐射装置3B3光束线传输效率及输出特性的计算

从北京正负电子对撞机储存环弯转磁铁光源的辐射特性入手, 分析了BSRF-3B3光源及其光束线光学系统的输出特性, 分别给出各光学元件的传输效率和采用不同单色器晶体在样品处的计算结果. 为光束线设计、调试及诊断提供了理论依据. 同时也为弯转磁铁光源光束线的输出特性的计算, 提供了一个模式.     

上海光源储存环工作点测量系统

报道了工作点测量技术的研究现状,对束流频谱分析用于工作点测量的方法进行了详细说明。介绍了上海光源储存环工作点测量系统的物理需求、方案设计、硬件结构及关键设备选型。采用束流实验的方法对系统配置参数进行优化,对系统测量误差及分辨力进行测试评估,讨论了测量系统不同工作模式的优缺点,并给出加速器不同运行阶段应该采用的运行模式。优化后的上海光源工作点测量系统,其系统测量误差小于0.000 1,测量分辨力好于0.000 05,测量过程对束流轨道及等效束斑尺寸的扰动控制在μm量级,现已在上海光源运行及机器研究中投入实用。     

基于嵌入式EPICS的合肥光源储存环束流损失监测系统

针对合肥光源储存环恒流运行(Top-off)改造等性能提升的需要,研制了新型的基于嵌入式EPICS架构的储存环束流损失监测(BLM)系统,用于监测储存环中束流损失发生的位置和大小。新BLM处理器获取储存环各处双PIN型光电二极管传感器所采集的簇射电子的信号,分析处理后通过各个处理器内部的嵌入式系统所运行的EPICS程序将数据实时发布到加速器控制网络,使中控室能够实时获取束损的数据。新BLM系统能够实时对双PIN型传感器进行自检操作,排查故障隐患,提高了系统运行的效率和可靠性,经过试运行表明,新BLM系统可完全满足合肥光源恒流的运行需要。     

利用直流辅助凸轨设计HLS注入系统研究

合肥同步光源的现有注入凸轨由3块冲击磁铁产生,不同的运行模式具有不同的凸轨.为了改变这种凸轨参数与储存环参数的相互依赖,提出采用集中布局的方案,即在注入长直线节形成注入局部凸轨.由于HLS的注入长直线节很短,需要冲击磁铁为束流提供较大的偏转角度.为此,本文研究了采用辅助直流凸轨的方案,以减小对冲击磁铁强度的要求,并分析该注入系统对储存环动力学孔径的改善.     

上海光源工作点在线监测系统

上海光源储存环运行在恒流注入(top-up)模式下每10min注入一次,注入引起的β振荡为测量工作点提供了有利条件。通过数字束流位置处理器采集储存环注入时的逐圈数据,对数据进行快速傅里叶变换计算获得工作点,以此搭建了刷新间隔为10min的工作点在线监测系统。2014年上半年的运行结果表明,该系统能够有效检测工作点变化并评估加速器工作点可达到的最优性能。利用该系统能够及时发现加速器运行异常,并结合各设备运行状态可有效定位异常原因。     

合肥光源注入系统建造与调试

介绍了HLS(合肥光源)储存环注入系统建造与调试情况. 重点讨论了各种公差、公差判断及抑制措施, 经过改进与及仔细调整, 得到了平均累积速率2—6mA/s的日常运行水平, 最高累积流强400mA, 该系统已经稳定使用近两年, 在光源的运行中起到了重要作用.     

合肥光源高亮度模式Lattice设计

介绍了一组合肥光源新高亮度模式的Lattice. 新的设计维持了储存环上所有元件和光束线位置不变,也没有加入新的元件. 取得了较低发射度. 所有直线节处的垂直方向β函数值都很小，适合插入件的运行. 跟踪计算表明新Lattice具有足够大的动力学孔径用于注入和储存粒子.     

用于HLS单束团运行模式的高频剔除系统

 介绍了主要用于实现合肥光源单束团运行模式的高频剔除（RFKO）系统。该系统完全基于仪器设备(分频器、波形发生器、宽带放大器和具有I/Q调制功能的矢量信号发生器)，无任何专门设计的电子线路。高频剔除的原理是激励粒子横向振荡而丢失。激励信号产生的过程是：将取自储存环高频系统的信号进行分频，得到束团同步信号；用束团同步信号触发波形发生器，生成窄脉冲；该窄脉冲调制信号发生器，输出高频剔除信号，放大后加在条带电极上，进行束团剔除。目前获得了18 mA的单束团最高流强。改变分频数和脉冲长度，可得到其它一些周期性填充模式，其中3串6束团以及非均匀填充模式得到了实验验证。     

储存环高频剔除系统

 介绍了用于电子储存环部分填充和非均匀填充的一种实验装置,它利用储存环中电子运动所具有的横向自由振荡和束团脉冲的时间结构这一特性,采用外加激励的方法使其产生共振,从而使得储存环中部分束团中的电子丢失,形成储存环的部分填充和非均匀填充。还扼要介绍了用高频剔除系统在储存环上实现不同填充方式时的束流积累结果。     

The nuclear-resonance-scattering station at the PETRA II undulator beamline

PETRA II, a 12 GeV accelerator at DESY, Hamburg, is used to produce synchrotron radiation (SR) for experiments in the hard X-ray regime when it is not running as injector for HERA. The beam from an undulator is split by a diamond crystal in Laue geometry to feed two experimental stations, one of which is now dedicated for nuclear resonance experiments. The X-ray energy may be chosen in the range from 5 to 55 keV covering all isotopes already observed with SR and many interesting candidates for new resonances. Tuning may be performed by optimising the magnetic gap and the storage ring energy. In particular, the opportunities for timing experiments are unique due to a very flexible filling mode of the storage ring. The flux at the sample position is comparable to undulator beams at ESRF. The second beamline covers higher energies up to some 300 keV and may also be used for nuclear resonance experiments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spin-charge separation in Aharonov-Bohm rings of interacting electrons

We investigate the properties of strongly correlated electronic models on a flux-threaded ring connected to semi-infinite free-electron leads. The interference pattern of such an Aharonov-Bohm ring shows sharp dips at certain flux values, determined by the filling, which are a consequence of spin-charge separation in a nanoscopic system.     

Beam lifetime measurement and analysis in Indus-2 electron storage ring

In this paper, the beam lifetime measurement and its theoretical analysis are presented using measured vacuum pressure and applied radio frequency (RF) cavity voltage in Indus-2 electron storage ring at 2 GeV beam energy. Experimental studies of the effect of RF cavity voltage and bunched beam filling pattern on beam lifetime are also presented. An equation of stable beam current decay is evolved and this equation closely follows the observed beam current decay pattern. It shows that the beam is stable and the beam current decay is due to the beam–residual gas interaction (vacuum lifetime) and electron–electron interaction within a bunch (Touschek lifetime). The estimated vacuum, Touschek and total beam lifetimes from analytical formulations are also compared with the measured beam lifetime.     

An experimental study of a new multi-bunch damping mechanism in PETRA

A new damping mechanism of multi-bunch oscillations in a storage ring with help of a narrow-band feedback system has been experimentally tested in PETRA. The oscillations of a multi-bunch filling were sucessfully damped. The bandwidth of the active loop was 1.5 kHz instead of 5 MHz needed for standard damper systems.     

Anomalous hollow electron beams in a storage ring

This Letter reports the first observations of an anomalous hollow electron beam in the Duke storage ring. Created by exciting the single-bunch beam in a lattice with a negative chromaticity, the hollow beam consists of a solid core inside and a large ring outside. We report the detailed measurements of the hollow beam phenomenon, including its distinct image pattern, spectrum signature, and its evolution with time. By capturing the postinstability bursting beam, the hollow beam is a unique model system for studying the transverse instabilities, in particular, the interplay of the wakefield and the lattice nonlinearity. In addition, the hollow beam can be used as a powerful tool to study the linear and nonlinear particle dynamics in the storage ring.     

数字束流位置信号处理算法优化

在已有束流位置信号下变频算法的设计与实现的基础上,优化了算法时序,设计实现了数字自动增益控制、慢应用信号处理等模块功能,能获得逐圈、快应用及闭轨数据。上海光源储存环上的束流测试结果显示,处理器可正确获取包含束流真实运动的多速率位置数据。在174 mA储存环流强、500个束团的填充模式时,逐圈位置数据分辨力达到0.84 m,快应用位置数据分辨力达到0.44 m,闭轨位置数据分辨力达到0.23 m,性能满足设计要求。     

Influence of timing jitter on nonlinear dynamics of a photonic crystal fiber ring cavity

We demonstrate that timing jitter has a strong influence on supercontinua generated in a photonic crystal fiber ring cavity synchronously pumped by 140?fs pulses. The global dynamics with respect to cavity detuning is analyzed both numerically and experimentally by tracking the cavity pulse energy. The results show that low-frequency timing jitter, induced by both the pump oscillator and the external cavity, masks the fine underlying bifurcation structure of the system. Numerical simulations in the absence of timing jitter reveal that the system dynamics fall into four qualitatively different regimes. The existence of these regimes is experimentally observed in first-return diagrams.     

Injection performance evaluation for SSRF storage ring

The injection performance of the storage ring is one of the most important factors to consider at a synchrotron radiation facility, especially in the top-up mode. To evaluate the injection performance of the storage ring at the Shanghai Synchrotron Radiation Facility, we have built a bunch-by-bunch position measuring system based on an oscilloscope Input/Output Controller. Accurate assessment of energy mismatching, distribution of residual oscillation, and angle error of injection kickers can be achieved by this system.