北京正负电子对撞机束团拉伸效应研究

本文叙述了在北京正负电子对撞机(BEPC)上,用条纹相机和频谱分析方法对束团拉伸效应的研究.由测量结果归纳出BEPC束团拉伸效应的标度规律,这一规律与理论分析有相当好的一致关系.     

加速器与我

一、芝加哥,回旋加速器我与加速器结缘,始于1947年。那年,我来到美国,进入芝加哥大学物理系研究所。为了维持生计,并且吸收到更多的知识,我在物理系承担各种短期工作。记忆最深的工作首先是在费米教授为期一学年的量子力学课程中担任助教,其后我获得那时正在核研究所(后来改名为费米核研究所)建造的450MeV质子同步回旋加速器(Synchrocyclotron)项目的助理奖学金。项目主管安德森(H.Anderson)教授要我研究加速后质子束流引出的办法。当时束流引出没有任何好办法,唯一的方法是在束流引出的轨道上插入一个散射靶,将部分束流以弹性散射的方法…     

Study of radiation background at the north crossing point of the BEPC in collision mode

Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiati...     

Measurement and correction of coupling in BEPCⅡ

The existing linear coupling theory and representation method are introduced briefly. The so-called local and global coupling is discussed in more detail. The vertical orbit distortion excited by a horizontal corrector is represented with the coupling parameters at the corrector and the observation point. The formula is used to measure the coupling in BEPCⅡ. In order to correct the coupling, vertical correctors are used to change the vertical orbit through sextupoles by a least square method. We also introduce and review other frequently used coupling measurement/tuning methods used in our machine.     

RF trapping and acceleration in CSNS/RCS

In this paper, two injection scenarios with different chopping rate are discussed. The waveforms of the RF voltage are studied and optimized, respectively. Some suggestions are made, concerning chopping and momentum painting of the injected beam. Furthermore, the momentum spread and transverse tune shift are calculated so that the beam aperture and the beam loss can be estimated. Finally, the beam loss with magnet field error is analyzed.     

A scenario for high accuracy τ mass measurement at BEPC-Ⅱ

Scenarios for the τ mass measurement at the upgraded Beijing Electron-Positron Collider (BEPC-Ⅱ) are studied. A nested minimization procedure is used to optimize the data taking plan. It is found that by using five energy points with the total integrated luminosity of 100 pb^-1, the τ mass can be determined with a statistical error of 50 keV.     

MIA analysis of FPGA BPMs and beam optics at APS

Model independent analysis, which was developed for high precision and fast beam dynamics analysis, is a promising diagnostic tool for modern accelerators. We implemented a series of methods to analyze the turn-by-turn BPM data. Green's functions corresponding to the local transfer matrix elements R₁₂ or R₃₄ are extracted from BPM data and fitted with the model lattice using least-square fitting. Here, we report experimental results obtained from analyzing the transverse motion of a beam in the storage ring at the Advanced Photon Source. BPM gains and uncoupled optics parameters are successfully determined. Quadrupole strengths are adjusted for fitting but can not be uniquely determined in general due to an insufficient number of BPMs.     

BEPCII储存环加速器物理问题研究

北京正负电子对撞机改进工程—BEPCⅡ, 已经完成其设计阶段, 并处于建造过程中. 系统回顾了BEPCⅡ储存环的设计, 系统总结了设计中的加速器物理问题.     

北京散裂中子源快循环同步环磁聚焦结构设计

快循环同步环(RCS)是北京散裂中子源(BSNS)的一个重要组成部分, 其物理设计对加速器的性能和造价起到决定性作用. 文章研究了能满足北京散裂中子源~RCS~要求的几种磁聚焦结构, 给出了一个三折结构的详细设计, 并比较分析了其他可供选择的磁聚焦结构.     

τ–粲能区物理及对加速器和探测器设计的要求

基于τ粲能区的物理目标和各物理过程的截面,估计了该能区新一代加速器典型亮度下的事例率和每年运行取得的事例数.指出加速器亮度应优化在ψ″和ψ(4160)之间,峰值亮度决定于探测器触发判选系统、电子学系统及数据获取系统等能处理的最高事例率.