合肥国家同步辐射实验室电子储存环束流损失监测系统中的几个物理问题

电子储存环中损失的束流电子，在撞击真空室壁时，引起“电子-γ-电子”簇射，在撞击点的下游，真空室的外表面形成次级电子（shower电子）的分布。通过探测这些shower电子，可以知道上游某处的束流损失状况。“合肥国家同步辐射实验室加速器二期工程”中的电子储存环束流损失监测系统，就是利用这个原理。在分析了原有加速器束流损失监测系统的缺陷并对国际上各大型加速器进行了调研的基础上，对该系统中的探测器选型、探测器安装位置的选择以及系统的整体结构等物理问题作了阐述。     

NSRL电子储存环束流损失过程的Monte—Carlo计算

高能电子和物质相互作用是一个级联簇射（shower)物理过程,NSRL电子储存环（HLS）束流损失监测系统利用这一原理,通过探测束流损失电子在储存环真空室外表面产生的shower电子,给出束流损失的有关信息,本文利用Monte-Carlo方法,采用EGS4软件包,对束流损失电子与真空室壁相互作用的过程进行模拟,给出了真空室外表面shower电子的分布特点：（1）shower电子在真空室外表面是前冲性很强的粒子;（2）在垂直方向的分布是比较窄的对称分布,对束流损失探测器的安装有一定的要求;（3）打在真空室内侧壁上的电子及其产生的shower电子有机会反射到外侧壁,并进一步发生shower过程,但其影响会低两个量级以上;（4）shower电子在真空室外表面上的分布,外侧峰位要比内侧峰位位置在束流方向上后移。     

基于示波器嵌入式IOC技术的逐束团位置监测系统研制

为研究尾场引起的束团不稳定性,本工作开发了基于高速宽带示波器嵌入式IOC的逐束团位置测量系统。该系统通过直接获取加速器储存环中钮扣型电极的原始束流信号,进行在线计算独立的水平和垂直方向的逐束团位置。介绍了此系统的需求分析、硬件结构以及嵌入式IOC软件结构。利用在上海光源储存环上获取的逐束团位置数据,对系统性能进行了评估。实验显示,不同束团感应到的工作点及横向振荡振幅与束团编号间的依赖关系,结果证明该系统是一个有效的机器研究工具。     

北京正负电子对撞机(BEPCⅡ)束流注入区辐射场研究

北京正负电子对撞机(BEPCⅡ)正负电子束流注入阶段的束流损失,影响储存环束流注入区及防护区辐射场。本文利用束流损失监测系统(BLM系统)分析了束流注入阶段注入区束流损失的位置和束流损失率,并结合FLUKA软件模拟计算对撞实验模式下束流注入阶段注入区的辐射场。结果表明:注入阶段注入区及其下游束流损失明显;辐射场内粒子能谱情况是中子为宽能谱且各向同性,切割磁铁 (铁靶)出射蒸发谱峰窄,峰值约为0.9 MeV,直接发射谱不显著;真空管(铝靶)出射蒸发谱峰宽且直接发射谱显著,峰值分别为4 MeV和20 MeV;光子能谱峰窄且前向性明显,能量在5 MeV以下分布集中;中子与光子剂量率水平相当;注入阶段比非注入阶段剂量率高约2个数量级;对撞实验模式下,实验测量整个运行阶段储存环光子剂量率平均水平约为1 000 μSv/h,中子剂量率比光子剂量率低1个数量级。     

Study of orbit stability in the SSRF storage ring

In this paper, analysis of the beam orbit stability and conceptual study of the dynamic orbit feedback in the SSRF storage ring are presented. It is shown that beam orbit position movement at the photon source points is smaller than the orbit stability requirements in horizontal plane, but exceeds the orbit stability requirements in vertical plane. A dynamic global orbit feedback system, which consists of 38 high-bandwidth air-coil correctors and 40 high-precise BPMs, is proposed to suppress the vertical beam orbit position movement. Numerical simulations show that this dynamic orbit feedback system can stabilize the vertical beam orbit position movement in the frequency range up to 100 Hz.     

Turn-by-turn system and its primary experiment at HLS

During the Phase II project of NSRL, a turn by turn BPM (Beam Position Monitor) system is proposed for storage ring diagnostics which engages log-ratio electronics circuit to measure machine properties of the HLS (Hefei Light Source) storage ring. The log-ratio processor works at 408 MHz, twice the RF frequency of HLS. Modern logarithmic amplifiers with wide dynamic range, great bandwidth, good logarithmic conformance, and low cost are attractive for beam position measurements. Injection kicker and the stripline-electrode resonant exciting methods are used to excite beam for nonlinear beam dynamics and phase space studies of stored beam. Up to 2 seconds of data acquisition is ensured. In this paper we present the performance of each component and preliminary test results of the turn-by-turn BPM system.     

NSRL储存环真空系统的改进

为了达到储存环能量８００ＭｅＶ时储存流强３００ｍＡ时的束流寿命６００ｍｉｎ以上，详细分析了ＮＳＲＬ真空系统的现状和对真空系统改进设计。     

基于软件无线电的新型数字束流位置处理器

研究了基于软件无线电架构的新型数字束流位置处理器,介绍了处理器样机的射频、模数转换和数字处理模块的硬件架构和主要参数。针对处理器多通道的不对称性,提出了校准方案。测试结果表明,处理器逐圈位置电子学分辨率在输入大于–30 dBm时,优于1.5μm;输入大于–27 dBm时,电子学分辨率达到亚微米量级。处理器在上海光源储存环流强为150 mA条件下测试,逐圈位置分辨率优于2μm,并能够准确获取包含束流实时信息的逐圈位置信号。     

Filling patterns in the SSRF storage ring

<正>There are various filling patterns in a storage ring for the users' requirements and consideration of the machine performances,such as beam lifetime,instability and chamber heating.These effects have been experimentally studied in the SSRF storage ring for typical filling patterns.Some experiment results and general trends of observations discussed in this paper.The explanations of the results are given.     

CCD型束流截面探测器

CCD型束流截面探测器的主要特点是使用电荷耦合器件做传感器,用束流同步光中的可见光成份做为信号源。该探测器同时具有模拟量和数字量两种输出,工作周期短,速度高,不影响束团粒子寿命,在电子储存环物理运行中,是一种有效的探测设备。     

Development of a tune knob for lattice adjustment in the HLS-II storage ring

The betatron tune is an important parameter in a storage ring to enable stable operation. A tune adjustment tool with a small impact on the beam dynamics is useful for user operation and machine studies. Therefore, a tune knob is developed for the Hefei light source-II(HLS-II) storage ring. Owing to the compactness of the storage ring, a global adjustment mechanism is adopted. To reduce the impact on beam injection, only quadrupole families outside the injection section are used by the tune knob, and the b functions of the injection section remain unchanged. A code is developed based on the accelerator simulation software, MAD-X, to calculate the adjustment of the quadrupole strengths. The accelerator toolbox is used to double check the accuracy of the tune knob. Online measurement of the tune knob is also performed. The result shows that the tune knob works well when the tune is adjusted in a specific range. Betatron coupling measurement is also carried out, showing an application of the tune knob on machine studies. In this paper, the development of the tune knob and its experimental results in the HLS-II storage ring are reported in detail.     

Numerical Simulation of the Effect of the Beam Space Charge on the Acceptance of a Storage Ring

A model based on the assumption that there exists a stationary particle distribution in the space of invariants is used to investigate numerically the effect of the space charge of a beam in storage rings. The model is used to develop a computer code that makes it possible to use a personal computer to investigate the dependence of the acceptance on the beam current, betatron frequency, and other machine parameters. The structure of the code and the results obtained using it for the ACR storage ring (RIKEN, Japan) and the accelerator-storage system at the Institute of Theoretical and Experimental Physics are described. The computational results show that this computer code is an effective tool for calculating and optimizing the parameters of high-current storage rings.     

A modeling GUI for accelerator physics of the storage ring at SSRF

In this paper, we report a MATLAB-based GUI tool, bodgui, which integrates functions of lattice editor,linear match, and nonlinear optimization, and visualized tracking functions for beam optics design. A user can switch his/ber design procedures one to another. Flexibilities are provided for adjusting or optimizing the lattice settings in commissioning or operation of the accelerators. The algorithm of the linear match and nonlinear optimization, and the GUI windows including the main functions and running status, are presented. The SSRF storage ring was employed as a test lattice. Several optics modes designed and optimized by the GUI tools were used for commissioning the storage ring. Functions of bodgui tool are machine-independent, and it can be well applied to modern light sources being built in other parts of the world.     

高能同步辐射光源中的耦合阻抗及束流集体效应研究

在高能同步辐射光源（HEPS）的储存环中，由于真空盒尺寸较小、束团中电子密度较大，全环耦合阻抗将显著增加，束流集体效应成为限制机器性能的重要因素。本文基于解析理论和数值模拟程序对HEPS储存环耦合阻抗进行了逐元件建模，并对环中可能发生的束流集体效应进行了系统评估。建立了合理的阻抗模型，给出了不稳定性阈值和增长时间，并对关键的不稳定性问题提出有效的抑制措施。     

锁相法测量BEPC储存环自由振荡频率

BEPC储存环自由振荡频率测量系统包括前端电子学系统，测量系统和激励系统。介绍了采用锁相法的BEPC储存环自由振荡频率测量系统。     

Therapeutic techniques applied in the heavy-ion therapy at IMP

Superficially-placed tumors have been treated with carbon ions at the Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS), since November 2006. Up to now, 103 patients have been irradiated in the therapy terminal of the heavy ion research facility in Lanzhou (HIRFL) at IMP, where carbon-ion beams with energies up to 100 MeV/u can be supplied and a passive beam delivery system has been developed and commissioned. A number of therapeutic and clinical experiences concerning heavy-ion therapy have been acquired at IMP. To extend the heavy-ion therapy project to deep-seated tumor treatment, a horizontal beam line dedicated to this has been constructed in the cooling storage ring (CSR), which is a synchrotron connected to the HIRFL as an injector, and is now in operation. Therapeutic high-energy carbon-ion beams, extracted from the HIRFL-CSR through slow extraction techniques, have been supplied in the deep-seated tumor therapy terminal. After the beam delivery, shaping and monitoring devices installed in the therapy terminal at HIRFL-CSR were validated through therapeutic beam tests, deep-seated tumor treatment with high-energy carbon ions started in March 2009. The therapeutic techniques in terms of beam delivery system, conformal irradiation method and treatment planning used at IMP are introduced in this paper.     

RF front-end for digital beam position monitor signal processor

RF circuit board has a significant impact on performance of the Digital Beam Position Monitor (DBPM) in storage ring of a synchrotron radiation facility.In this paper,a front-end RF board is designed for DBPM,and schematics of the RF board and the test results are given.In view of the inevitable inconsistency in the multi-channel circuit,a calibration circuit is designed to reduce such an influence.The test results show that the calibration method is useful for beam current dependence which is sensitive to channels inconsistency.     

合肥光源储存环控制系统

合肥光源储存环控制系统是一个基于EPICS(Experiment Physics and Industrial Control System)的分布式控制系统,本文首先描述其硬件结构、软件设计,然后重点介绍束流慢加速、束流闭轨校正、机器状态在线查询、数据存档及历史数据查询等应用软件的开发。运行结果表明,合肥光源储存环控制系统很好地满足了机器运行和机器研究的需要。     

Magnet lattice design of the SSRF electron-beam transfer lines

Under three-dimensional plane geometrical constraints （ X, Y, θ ）, with two asymmetric achromatic sections, the combined three-section structural FODO-like magnet lattice design is adopted and finely optimized in the SSRF electron-beam transfer lines. The magnet lattice has high flexibility and robustness, and the Courant-Snyder parameters can be easily adjusted within a wide range to meet the requirements of transmission and injection for different operation modes of the linear accelerator, booster synchrotron, and storage ring. In this article, the main parameters of the linear optics design of the SSRF electron-beam transfer lines are described, involving the physical design criteria, the total geometrical layout, the magnet lattice, and the beam Courant-Snyder parameters matching. The studies of the variant beam dynamic simulation program calculations show that the design purpose of the efficient beam transmission and injection will be basically achieved.     

Beam instrumentation and diagnostics for HLS

The beam diagnostic instrumentation for the Heifei Light Source(HLS) is described ,It provides sufficient parameters for machine study during the commisioning and common operation.The measured results are presented.