聚束系统设计与计算程序

LMOVE程序是一个模拟粒子纵向运动的FORTRAN语言程序。它可以计算由三电极双间隙聚束器(或这种聚束器的组合)、单狭缝谐波聚束器、静电加速管和自由飘浮空间组成的束流脉冲化系统。程序采用大量粒子模拟束团在纵向相空间内的运动,并用Monte-Carlo方法随机产生相空间内各代表点的初始条件。因此,较为适合模拟粒子在配有聚束器件的静电加速器中的纵向运动。本程序不考虑粒子的空间电荷效应。     

兰州重离子加速器冷却储存环射频堆积过程模拟

考虑了重离子冷却储存环中粒子纵向相振荡的运动特性及电子冷却的作用,模拟兰州重离子加速器冷却储存环（HIRFL－CSR）主环中的射频堆积过程,给出了高频参数在射频堆积过程中随时间的变化曲线,为高频腔的设计及机器运行时的参数预置了理论依据。     

脉冲束在三维均匀倾斜场中的传输

本文通过求解六维相空间里的粒子相点运动方程式,给出了脉冲束中任意粒子在三维均匀倾斜场中的非线性传输方程,并通过相对于中心粒子展开,给出了相对运动的线性传输方程及脉冲束的一阶六维传输矩阵,并进而概括地讨论了脉冲束团的传输。从而,完善了静电均匀场的传输理论。     

CSR ns级重离子束动力学研究

采用束团在纵向相空间快速旋转的非绝热压缩方法研究了在兰州重离子加速器冷却储存环(HIRFL-CSR)上获取高能ns量级短脉冲重离子束的可行性,利用K-V包络方程对能量为250MeV/u、初始纵向束团长度为200ns、初始动量分散为5×10-4的238U72+离子束团的非绝热压缩过程进行了束流动力学模拟,给出了在束团压缩过程中束流相关参数的变化。结果表明,在CSR上可取得最短为16ns长度的238U72+离子束团,可满足用于高能量密度物理研究的50ns束团长度的要求。     

面对称磁场中粒子的六维传输特性

导出了（ｘ，ｘ＇，ｙ，ｙ＇，ｔ，ｔ＇）相空间中粒子的一般六维运动方程。对于面对称磁场，还导出了（ｘ，ｘ＇，ｙ，ｙ＇，τ，τ＇）相空间粒子运动的二阶运动方程及其严格的一阶和二阶形式解。最后，给出了偏转磁铁具体的一阶及二阶传输解。     

偏转磁铁的六维传输矩阵

本文给出在实空间为平面曲线坐标和相空间为六维循环坐标的情况下,离子束团在静磁光学元件的六维相点运动方程组,从此方程出发导出了偏转磁铁的六维线性传输矩阵,并进而给出了由于横向对纵向的耦合效应所引起的脉冲宽度修正公式。     

同步辐射散射图像中心定位算法研究

介绍了一种基于相空间重构和主分量分析的样品在同步辐射SAXS\WAXS各向同性图像中散射环的中心定位算法。该算法在水平和垂直方向上分别扫描散射图像,并提取图像部分行和列的主分量以提高散射环中心定位的准确性,再根据圆的垂线定理确定圆心。通过实验计算的结果和fit2d软件的比较,验证了该算法的有效性。     

数字束流位置处理器在合肥光源束流诊断中的应用

数字束流位置处理器Libera可直接用于测量宽带束流位置信号,在束流参数测量与诊断中得到广泛应用。本工作利用Libera在合肥光源储存环上完成了工作点、相空间和横向振荡阻尼时间常数等的测量,并给出测量结果。     

核微孔滤膜辐照模拟

在辐照粒子膜向高斯分布、纵向均匀分布的情况下，模拟计算核微孔滤膜的辐照，并给出 模拟计算和实测结果。     

HIAF-CRing俘获方式研究

在研究强流重离子加速器装置(HIAF)纵向运动特性的基础上,对压缩环(CRing)内重离子的俘获方式进行了模拟研究。选取由增强器(BRing)注入的能量为800 MeV/u、动量散度为±5×10~(-4)的~(238) U~(34+)典型离子,利用纵向动力学方向的粒子追踪软件ESME,分别模拟了不同俘获电压曲线下的俘获过程。通过对俘获结果的比较,选取了其中最为高效的俘获方式作为HIAF-CRing的工作方式。     

An automatic phase-matching technique of CYCIAE-100 cyclotron

The RF system of CYCIAE-100 cyclotron has two cavities,which are driven separately by two identical 100-kW RF amplifiers.Due to the power on sequence issue of the three DDSs in the LLRF systems,each time when the system is individually switched on,the phase relationship may not satisfy the requirements of beam acceleration.Instead of adding an extra reset logic to the system,a search and validation algorithm based on the decision tree has been carried out to make sure the phase of the two cavities is correct right after applying power to the cavities,taking advantage of existing hardware resources.In the first year of operation,there are more than 20 times of scheduled shutdown of the cyclotron system.For each time when the cyclotron RF system is completely shutdown and powered on again,the operator confirmed that the phase matching of the two cavities can be done automatically within 30 s.The related work,including the optimization of the phase detector and the development and validation of the algorithm,is reported in this paper.     

Simulation studies on two-frequency RF gun

Photocathode RF gun is widely used for particle accelerators as an electron source.When driving an RF electron gun at the fundamental frequency and a higher harmonic frequency simultaneously with proper field ratio and relative phase,it generates electron beams of ultralow emittance and a linear longitudinal phase space distribution.Such a gun provides high quality electron beam with low energy spread,small traverse emittance and high brightness.In this paper,the RF design of a 1.5 cell cavity is presented.Simulation results of beam dynamics for the two-frequency gun and a standard single-frequency RF gun are also shown in this paper.In addition,bunch compression with a two-frequency gun is explored.     

驻波电子直线加速器中的RF相位聚焦

分析了驻波电子直线加速器中电子受ＲＦ场的横向作用与其所处相位的关系,探讨了驻波直线加速器中的ＲＦ相位聚焦以及不对称场幅值分布对粒子横向动力学的影响,并给出利用相位聚焦和不对称场幅值分布技术设计的两只加速管实例。     

Advanced topics on RF amplitude and phase detection for low-level RF systems

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 Swiss FEL measurements, but the algorithms introduced are general for RF signal detection in particle accelerators.     

用于回旋加速器射频低电平系统的通用DSP固件程序设计

针对回旋加速器射频系统幅度、相位、启动逻辑、联锁保护、在线参数修改等控制需求,编写了一种基于有限状态机的通用DSP固件程序。该固件程序将射频系统启动过程划分为5个状态:封锁RF信号、搜索腔体谐振点、提升射频功率、匹配相位、幅相闭环控制。该固件程序通过串口与本地上位机和远程控制机进行实时通信,支持在线修改射频系统启动参数;采用异步事件驱动方式,实现对打火和反射功率过大等异常情况快速响应。该固件程序成功应用于CYCIAE-100回旋加速器射频低电平系统中,在CYCIAE-100回旋加速器调束过程中,完成了射频系统的启动控制和设备保护,满足加速器控制系统的需求。     

Beam dynamics,RF measurement,and commissioning of a CW heavy ion IH-DTL

A 53.667 MHz CW(continuous-wave) heavy ion IH-DTL has been designed for the SSC-LINAC injector of HIRFL-CSR(Heavy Ions Research Facility at Lanzhou-Cooling Storage Ring). It accelerates ions with maximum mass-to-charge ratio of 7.0 from 143 to 295 ke V/u. Low-power RF measurement of the IH-DTL1 has been taken to investigate the RF performance and the quality of the electric field distribution on the beam axis.The measured Q_0 value and the shunt impedance are 10,400 and 198 MX/m, respectively. The electric field distributions on and around the beam axis were evaluated and compared with the design value. By a new approach,the dipole field component is also estimated. The beam dynamics simulation using measured field distribution was presented in this paper. Based on the dynamics analysis in both transverse and longitudinal phase space, the field distribution can meet the design requirement. Finally, the RF conditioning and very first beam commissioning on the IH-DTL1 were finished. The beam test results agree well with the simulation results; what's more, the property of the variable output beam energy about the separated functions DTL was verified.     

Beam trip diagnostic system at SSRF

In this paper we report the design and realization of beam trip diagnostic system at Shanghai Synchrotron Radiation Facility (SSRF).The system can find out the first fault signal in the key operation signals related to the RF system by analyzing the time sequence,also it can decide which trips occurs first among the three superconducting RF stations.All the states of monitored signals in a time period ahead and behind beam trip are recorded.The results are compared with those from other diagnostic tools at SSRF.The work is of help in improving reliability of the superconducting RF system and stability of the storage ring operation.     

合肥光源的新高频腔阻抗谱计算

用电磁场计算软件MAFIA，在时域和频域两种情况下，对高频腔的耦合阻抗及电子束在此结构中产生的尾场进行了计算。结果表明，新高频腔里存在较强的高次模，需要采取措施加以抑制。     

SHINE腔式BPM系统射频信号调理前端研制

基于低温超导直线加速器的上海硬X射线自由电子激光装置（SHINE）需1个分辨率可达200 nm的束流位置测量系统,以实现电子束与光子束在波荡器中的紧密相互作用和能量交换。现已研制的束流位置测量系统不能完全满足上述要求,为此,基于对关键技术指标的分配,设计研制了一个由C波段腔式探头、低噪声系数的单路下变频至低中频的射频信号调理前端以及专用数字信号束流位置处理器构成的CBPM系统样机。而作为连接腔式探头和数字信号采集电子学之间的桥梁,射频信号调理前端（radio frequency front end, RF前端）的结构和性能也直接决定了CBPM系统的性能。本文从SHINE对CBPM系统的整体需求为出发点,分析了系统对射频信号调理前端的指标分配,提出了一种放大器开关切换型RF前端的方案设计,并成功搭建了1套可模拟束流条件的离线全锁相采样测试平台。此外,在上海软X射线自由电子激光装置（SXFEL）中搭建了测试平台并完成了射频信号调理前端的带束性能评估,束流实验结果表明,在束团电荷量为100 pC、系统动态范围在±100 μm的条件下,采用腔式探头射频信号一分二的评估方法,位置分辨率可达71 nm,优于设计指标需求。