Beam Line Design and Beam Physics Study of Energy Recovery Linac Free Electron Laser at Peking University

Energy recovering linac (ERL) offers an attractive alternative for generating intense beams of charged particles by approaching the operational efficiency of a storage ring while maintaining the superior beam quality typical of a linear accelerator. In ERLs, the decelerated beam cancels the beam loading effects of the accelerated beam with high repetition rate. Therefore, ERLs can, in principle, accelerate very high average currents with only modest amounts of RF power. So the efficiency of RF power to beam is much higher. Furthermore, the energy of beam to dump is lower, so it will reduce dump radiation. With the successful experiments in large maximum-to-injection energy ratio up to 51:1 and high power FEL up to 14kW, the use of ERL, especially combining with superconducting RF technology, provides a potentially powerful new paradigm for generation of the charged particle beams used in MW FEL, synchrotron radiation sources, high-energy electron cooling devices and so on. The 3+1/2 DC-SC photo injector and two 9cell TESLA superconducting cavity for IR SASE FEL in PKU provides a good platform to achieve high average FEL with Energy Recovery. The work of this thesis is on Beam line design and Beam dynamics study of Energy Recovery Linac Free Electron Laser for Peking University. It is the upgrade of PKU facility, which is under construction. With ERL, this facility can work in CW mode, so it can operate high average beam current without RF power constraint in main linac and generate high average FEL power. Moreover, it provides a test facility to study the key technology in ERL. System parameters are optimized for PKU ERL-FEL. The oscillation FEL output power is studied with different bunch charge, transverse emittance, bunch length and energy spread. The theory of optimal RF power and Q{sub ext} with ERL and without ERL is analyzed and applied to PKU injector and linac including microphonic effect. pace charge effect in the injector and merger is studied for beam energy at ~5MeV. Simulation shows that in the 3+1/2 DC- C injector, there is a region the beam could be over focused by RF electromagnetic field and the transverse emittance in the transport line up to linac will increase instantly due to over focusing. In order to eliminate this effect on beam emittance, several solutions are investigated to avoid over focusing. This result is very important for beam loading experiment for low bunch charge operation. Meanwhile, different merger structures are compared in terms of error sensitivity and emittance increase with space charge effect. In recirculation beam line, a new symmetric 180{degree} arc structure is designed. It fulfills the achromatic condition and adjustable bunch compression. These two parameters are controlled by different Quads knob. With this novel structure, the recirculation lattice can achieve path length adjustment, bunch compression and decompression in a large range. With beamline error, the beam central orbit will deviate from the designed trajectory. An orbit correction system is optimized, which balances between cost and performance of orbit after correction at design level. Different methods are used to estimate its robustness. The BBU instability, especially multi-pass BBU imposed a potentially severe limitation to the average current that can be accelerated in an ERL. Simulation gives the harmful HOMs and predicts that the threshold average current in this machine is much higher than the possible operation current. This work is based on the existing facility in PKU, so it provides guidelines for the facility operation and upgrade in the future. The theoretical analysis of ERL requirement and FEL requirement on beam transport line and beam property paves the way for future ERL research

基于P2P技术的CSRe冷却装置控制系统设计；Design of Control System for CSRe Cooling Equipment Based on P2P Technology

HIRFL-CSR工程对CSRe冷却装置电子冷却部分的控制系统在实时性和可靠性方面提出了非常高的要求。电子冷却工作环境复杂,各种干扰难以预测。从电子冷却的控制系统改进出发,以实现电子冷却的自动调束为目标,以高端FPGA和ARM嵌入式系统为基础,采用P2P通讯技术和神经元网络算法来实现对电子冷却的自动控制。该控制系统对电子冷却控制的完善提供了先进的硬件平台和软件实现方案

HIRFL-CSR主环电子冷却装置控制系统

介绍了HIRFL-CSR中主环电子冷却装置控制系统的整体设计、硬件结构和软件设计。实现了对主环电子冷却装置的计算机控制和网络界面操作,使主环电子冷却装置的运行更加方便、稳定和可靠

Electron Motion and its Collection in Electron Cooling Device

电子冷却能够提高储存环中离子的相空间密度、改善离子束流品质，获得高品质的离子束。快速、有效的电子冷却要求电子冷却装置产生高流强、高准直性、低温的电子束，而得到这样的电子束受电子冷却装置内电、磁场空间分布的影响。另一方面，长期、稳定、低能耗地运行，要求电子冷却装置具有高效率的电子束收集系统。本文从电子冷却原理以及提高电子冷却效果的途径出发，阐述了日子冷却对电子冷却装置内电、磁场空间分布的设计要求，初步设计了HIRFL-CSR两个环的电子准却装置。电子横向温度由电子枪阴极温度、高压电源的不稳定度、电极度几何结构以及磁场分布决定，具体反映在空间电荷场、电子枪及加速区的径向电场、磁场的不均匀性等方面。采用数值模拟方法着重研究了磁场误差对电子横向温度的影响；电子束的绝热展开，电子束通过弯曲螺线管后温度的变化规律以及电子束在收集器区域的运动规律。通过数值模拟计算，获得了允许的磁场误差、弯曲螺线管工作磁场与电子束能量的依赖关系、电子束绝热展开与磁场组态的关系以及达到最侍收集效果时收集器的电、磁参数，为CSR电子冷却装置的设计及运行提供了依据。用电子冷却模拟程序计算了冷却时间随冷却段长度、冷却段磁感应强度、磁场平行度、电子束半径、电子温度的变化规律，并分析了影响冷却时间的因素，获得了电子冷却装置最优参数

CSR电子冷却段磁场造成闭轨畸变及校正

电子冷却的应用提高了重离子储存环的束流品质,也为重离子储存环的运行带来了新的课题．电子冷却段的横向磁场在引导约束强流电子束的同时也不可避免影响了多次经过的离子轨道．为了保证束流的安全运行,必须将离子轨道的畸变部分限制在局部范围,并保证轨道畸变量对储存环接收度的影响可以容忍．讨论在建的兰州重离子储存环HIRFL-CSR电子冷却段磁场及其造成闭轨畸变和校正方案

HIRFL-CSR实验环电子冷却装置参数优化

以 4 0 0 Me V/u的 2 38U91 +为例 ,用电子冷却模拟程序计算了冷却时间随冷却段长度、冷却段磁感应强度、磁场平行度、电子密度、电子束半径、电子温度的变化规律 ,并分析了影响冷却时间的因素 ,获得了电子冷却装置最优参数

电子冷却

本文概述电子冷却原理及其国际现状

HIRFL-CSR电子冷却束流位置测量系统；A Beam Position Monitor System for Electron Cooler in HIRFL-CSR

高效率的电子冷却过程,要求电子束与离子束位置平行且重叠。为了同时测量电子束与离子束的位置,在HIRFL-CSR电子冷却装置上研发了以容性圆筒形极板为感应电极的束流位置探测系统。系统测量束流通过探针时产生的脉冲感应信号,并进行傅里叶变换得到频谱信号,分析4个不同电极上频谱信号强度获取束流的位置信息。测量结果表明,该束流位置探测系统测量准确,为定量研究储存环离子累积和电子冷却过程与两种束流相对位置及角度的依赖关系提供了条件

HIRFL-CSR重离子束内散射效应(英文)

电子冷却本质上是电子冷却作用与重离子束内散射作用的动态平衡过程.在Bjorken和Mtingwa束内散射理论的基础上,应用对称椭圆积分的方法做束内散射增长率的数值模拟,并应用于HIRFL-CSR的磁铁聚焦结构.计算结果表明,束内散射不会成为CSR磁聚焦结构设计的障碍,并且CSR可以达到冷却设计指标

CSR实验环电子冷却装置的纵向电子束温度

电子冷却装置中,电子束纵向温度是计算冷却力的主要参量之一．当电子与被冷却离子的相对速度很小时,纵向冷却力与离子速度呈线性关系,并且线性区域的宽度与电子束纵向温度有关．通过分析影响电子束纵向温度的主要因素,得到了兰州重离子冷却储存环实验环(CSRe)电子冷却装置中电子束纵向温度的大小