Charge stripping accumulation of light heavy ions in HIRFL-CSR main ring

The charge stripping injection method has been adopted for the accumulation of light heavy ions in HIRFL-CSR.This method has some special requirements for the accelerating particles,and at the same time the structure of the injection orbit has to be changed.In this paper,the design of the orbit has been presented,as well as the calculation of the beam line matching.According to the result of commissioning,stripping injection can accumulate the beam to a higher current.     

HITFiL同步加速器剥离注入

一台新的治癌专用加速器HITFiL正在设计和建造中,其中一台同步加速器为其主加速器,以高紧凑性、高可靠性和低成本为设计目标。同步加速器的注入系统采用剥离注入方式,剥离注入与单圈注入方式相比能达到较高的注入效率,而其造价明显低于多圈注入加电子冷却的注入方式。治癌采用碳粒子束,从ECR离子源产生的C5+离子经过回旋加速器预加速后在同步加速器注入点处剥离成为C6+注入到环里。详细阐述了该注入系统的设计方案,并对整个注入过程进行了计算机模拟。在模拟过程中,对束流的注入效率、束流损失机制和粒子数增益进行了研究,得到了实空间和相空间的粒子分布和发射度增长趋势,得到了满足要求的束流流强。     

Stripping extraction calculation and simulation for CYCIAE-100

A 100 MeV H- compact cyclotron is under construction at China Institute of Atomic Energy (CYCIAE-100). The proton beams of 75 MeV-100 MeV at an intensity of 200 μA will be extracted in dual opposite directions by charge exchange stripping devices. The crossing point at the switching magnet center is fixed inside the magnet yoke and the stripping points for various extraction energies are calculated by the code CYCTRS. With the code GOBLIN, we can calculate the transfer matrix including the dispersion effects from the stripping point to the switch magnet. The beam distribution just after stripping foil can be obtained from the multi-particle tracking code COMA and the extracted beam parameters after the switch magnet such as emittance, envelope, dispersion, energy spread, bunch length, etc. are given by the extraction orbit simulations.     

BEPCⅡ直线加速器的误差和抖动效应

为达到BEPCⅡ 直线加速器的设计指标，系统地研究了误差和抖动(Jitter)效应对束流性能的影响。误差效应包括束流的初始偏轴和聚焦透镜偏轴导致的色差效应；束流的初始偏轴和加速结构偏轴导致的尾场效应等。主要的抖动效应包括相位漂移抖动和高频功率源中调制器电压的抖动影响等。确定了在BEPCⅡ直线加速器上对误差和抖动的限制，如来自电子枪的束流的初始偏轴应小于等于0.3 mm，加速结构和聚焦磁铁的安装误差应小于等于0.2 mm，相位漂移抖动误差应小于等于2°，调制器的电压抖动误差应小于等于0.1%。并进一步确认了必须采用相位控制系统和束流轨道校正系统，以抑制这些误差效应的影响，达到正、负电子束流能散度小于等于0.5% 和电子束束流发射度小于等于0.25 mm·mrad，正电子束束流发射度小于等于1.60 mm·mrad 的设计目标。     

HIRFL-CSR commissioning in 2006 and 2007

HIRFL-CSR, a new heavy ion cooler-storage-ring system at IMP, had been in commissioning since the beginning of 2006. In the two years of 2006 and 2007 the CSR commissioning was finished, including the stripping injection (STI), electron-cooling with hollow electron beam, C-beam stacking with the combination of STI and e-cooling, the wide energy-range synchrotron ramping from 7 MeV/u to 1000 MeV/u by changing the RF harmonic-number at mid-energy, the multiple multi-turn injection (MMI), the beam accumulation with MMI and e-cooling for heavy-ion beams of Ar, Kr and Xe, the fast extraction from CSRm and single-turn injection to CSRe, beam stacking in CSRe and the RIBs mass-spectrometer test with the isochronous mode in CSRe by using the time-of-flight method.     

Preliminary study of residual orbit oscillation in BEPC Ⅱ

BEPCⅡ has two rings each with an injection system.The injection system of each ring consists of two kicker magnets and a septum magnet.The injection layout of two rings is the same.Both two kickers would kick the beam in horizontal plane.The betatron phase advance in the horizontal plane between two kickers is designed exactly 180° in order to reduce the perturbation to the circulating beams during injection.In fact,the residual orbit oscillation will originate because of the existence of a variety of errors.The Librea Electron BPM processor is used to acquire the beam position data in turn-by-turn mode and to analyze the residual orbit oscillation.According to the measurement results,minimization of the residual orbit oscillation can be done by adjusting the peak field strength and trigger timing delay of two kickers.With very small residual orbit oscillation the two beams can keep collision condition during the injection.     

7MeV注入剥离膜系统设计

设计了一台注入能量为7 MeV的快循环同步加速器剥离膜装置，介绍了主体结构设计及高精度换膜运动结构，实现膜片精确定位及在线换膜功能。针对注入参数对膜片开展分析计算，分析了7 MeV的负氢离子束注入时相应的碳膜材料的反应截面及不同厚度的剥离效率，给出了膜片厚度的参数选择。对所设计膜片的温升和寿命进行分析，膜片的温升最高点达到755 K，远小于同类的加速器的剥离膜温度，具有更高的寿命和可靠性。     

氢原子束在大气长程传输中的剥离效应

考虑到中性粒子束对近地轨道太空垃圾的清理作用以及在太空探索中的潜在应用前景，研究了中性粒子束在亚轨道空间长程传输过程中影响束流能量和密度损失的主要物理机制，重点分析了剥离效应对束流损耗的影响。中性束剥离效应包括束流粒子之间碰撞导致的自剥离效应和其与大气粒子碰撞导致的剥离效应。以束密度随传播距离变化的方程为基础，通过引用几何因子来表征束流的自剥离效应强度，建立了剥离效应机制下束流的传输模型，由此评估了束流自剥离效应在中性束长程传输中对传输距离的影响关系。研究结果表明，在固定的高度，当中性束密度大于空气粒子密度时，自剥离效应的影响将非常突出，随着传输高度的升高，即使束密度和空气密度同时降低维持量级一致，自剥离效应对传输距离的影响在大几何因子的情况下仍会增强。     

Analysis and correction of linear optics errors,and operational improvements in the Indus-2 storage ring

Estimation and correction of the optics errors in an operational storage ring is always vital to achieve the design performance. To achieve this task, the most suitable and widely used technique, called linear optics from closed orbit(LOCO) is used in almost all storage ring based synchrotron radiation sources. In this technique, based on the response matrix fit, errors in the quadrupole strengths, beam position monitor(BPM) gains, orbit corrector calibration factors etc. can be obtained. For correction of the optics, suitable changes in the quadrupole strengths can be applied through the driving currents of the quadrupole power supplies to achieve the desired optics. The LOCO code has been used at the Indus-2 storage ring for the first time. The estimation of linear beam optics errors and their correction to minimize the distortion of linear beam dynamical parameters by using the installed number of quadrupole power supplies is discussed. After the optics correction, the performance of the storage ring is improved in terms of better beam injection/accumulation, reduced beam loss during energy ramping, and improvement in beam lifetime. It is also useful in controlling the leakage in the orbit bump required for machine studies or for commissioning of new beamlines.     

HIRFL-CSR commissioning in 2006 and 2007

HIRFL-CSR, a new heavy ion cooler-storage-ring system at IMP, had been in commissioning since the beginning of 2006. In the two years of 2006 and 2007 the CSR commissioning was finished, including the stripping injection (STI), electron-cooling with hollow electron beam, C-beam stacking with the combination of STI and e-cooling, the wide energy-range synchrotron ramping from 7 MeV/u to 1000 MeV/u by changing the RF harmonic-number at mid-energy, the multiple multi-turn injection (MMI), the beam accumulation with MMI and e-cooling for heavy-ion beams of Ar, Kr and Xe, the fast extraction from CSRm and single-turn injection to CSRe, beam stacking in CSRe and the RIBs mass-spectrometer test with the isochronous mode in CSRe by using the time-of-flight method.     

HLS注入段束流位置探头定标电场的拟合和误差计算

 描述了束流位置探测器(BPM)探头定标、定标电场的拟合和误差计算。该定标系统采用了具有调节精度为10μm垂直放置真空管道的天线模拟定标装置和分辨率高达1μm外差式、窄带频域信号处理电子学线路。并推导出针对合肥光源（HLS）定标系统条件下的电场拟合函数及相关的BPM-Mapping图和误差计算结果,较精确地计算出该高精度定标系统误差。     

上海光源储存环轨道噪声分析

利用上海光源束流位置测量系统Libera电子学对储存环轨道数据进行了测量,分析了Libera对束流位置测量系统探头信号的处理过程,应用MATLAB软件对数据进行了处理,采用Welch方法对轨道噪声数据进行了功率谱和积分功率谱分析,获得了主要噪声源的相关信息,为消除噪声、提高轨道稳定性提供了依据。实验结果表明:在储存环的不同位置,噪声功率谱的结构具有相似性;尽管不同频段噪声对功率谱影响不同,但是噪声源主要来自于低频段的地基振动、支架共振和磁铁电源。     

TOPOPIC对强流束流在周期FODO结构中的传输研究

粒子云网格(Particle In cell,PIC) 方法是研究带电粒子在加速器中运动的关键工具之一。基于PIC 算法,开发了模拟强流条件下的束流动力学模拟程序TOPOPIC(Trace of Particle Orbit with PIC method),并且利用TOPOPIC,研究了束流在四极铁周期结构(FODO) 中的传输问题。结果表明,在强流条件下空间电荷效应显著地影响了束流的整体行为和单粒子的运动轨迹。最后比较了TOPOPIC 程序和通用的BEAMPATH 程序在相同条件下的计算结果,可以看到两个程序给出的模拟结果吻合得非常好,这表明TOPOPIC程序的计算结果是合理、可靠的。The Particle in cell (PIC) method is one of the key techniques in the research of charged particles in accelerators. Based on the PIC method, a new beam simulation code for high intensity beam named TOPOPIC (Trace of particle orbit with PIC method) has been developed. With the code TOPOPIC,the beam behavior during passing through the periodic quadrupole (FODO) structure has been studied. The results show that the nonlinear space charge affects the single particle behavior and beam envelope a lot. At last, the PIC code BEAMPATH is used for benchmark, the results given by TOPOPIC and BEAMPATH show good agreements,which means the code TOPOPIC is reliable.     

Physics design of CYCAIE-100

The design and construction of Beijing Radioactive Ion-beam Facility (BRIF) was started at China Institute of Atomic Energy -CIAE) in 2004. In this project, a 100 MeV high intensity cyclotron, CYCIAE100, is selected as a driving accelerator for radioactive ion beam production. It will provide a proton beam of 75—100 MeV with an intensity of 200—500 μA. The scheme adopted in this design, i.e., stripping the accelerated H-, makes the structure more compact and construction cost much lower. At present, the design for each system has been accomplished. This paper depicts the basic physics design of the machine, including its major structure and parameters, beam dynamics and each relevant system, e.g. basic structure of the main magnet, numerical simulation of the RF resonant cavity, axial injection system, central region, and study on crucial physics problems concerning the extraction and beam lines. The major problems encountered during the design of CYCIAE-100 are also summarized in this paper.     

CYCIAE型回旋加速器负离子剥离引出的光学行为研究

为了CYCIAE型回旋加速器的剥离靶轴线及旋转角的概念设计,必须对负离子剥离后的光学特性进行研究,基于根据CYCIAE型回旋加速器剥离引出特点编制的程序CYCRS,计算了CYCIAE30加速器不同能量束流引出剥离点的位置,并与实际位置进行比较,证明计算所用的理论及方法是正确的,同时,考察了剥离后的束流空间运动的光学特性.在此基础上,确定了CYCIAE70回旋加速器能量为35—70MeV的束流引出剥离点位置.     

合肥光源电子储存环束流闭轨的局部校正

在合肥同步辐射装置运行过程中，发生储存环的束流轨道偏移。利用现有设备对束流闭轨的位置进行了多次测量和分析，利用测量数据计算得到校正铁强度与束流位置之间移动的响应矩阵，并利用最小二乘法计算得到三个校正铁凸轨系数，用于束流闭轨的局部凸轨校正，取得了预期的效果。     

Stripping voltammetry of Pb and Cu using a microcantilever electrode

Microfabricated silicon microcantilevers coated with gold on one side have been used as working electrode in a three-electrode electrochemical arrangement. In addition to electrochemical current, cantilever bending has been used as a signal for monitoring electrode reactions on the cantilever surface. The microcantilever bending was measured by an optical beam deflection method as the surface potential was scanned and electrochemical reactions occurred on the surface. The microcantilever bending due to differential surface stress was used to sense Pb and Cu using cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV).     

Measurement, analysis and correction of the closed orbit distortion in Indus-2 synchrotron radiation source

The paper presents the measurement, analysis and correction of closed orbit distortion (COD) in Indus-2 at 550 MeV injection energy and 2 GeV synchrotron radiation user run energy. The measured COD was analysed and fitted to understand major sources of errors in terms of the effective quadrupole misalignments. The rms COD was corrected down to less than 0.6 mm in both horizontal and vertical planes. A golden orbit was set for the operating synchrotron radiation beamlines. With COD correction, the injection efficiency at 550 MeV was improved by ~50% and the beam lifetime at 2 GeV was increased by ~8 h. In this paper, the method of global COD correction based on singular value decomposition (SVD) of the orbit response matrix is described. Results for the COD correction in both horizontal and vertical planes at 550 MeV injection energy and at 2 GeV synchrotron radiation user run energy are discussed.     

Progress of the Injector Linac Upgrade for the BEPCⅡ Project

BEPCⅡ—an upgrade project of Beijing Electron Positron Collider (BEPC) is a factory type of e+e- collider. It requires its injector linac to have a higher beam energy (1.89 GeV) for on-energy injection and a higher beam current (40 mA e+ beam) for a higher injection rate ( 50 mA/min). The low beam emittance (1.6π mm·mrad for e+ beam, and 0.2πmm·mrad for 300 mA e- beam) and the low beam energy spread (±0.5%) are also required to meet the storage ring acceptance. Thus the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and will be installed in their final positions in this spring and summer, which are described in this paper.     

Enhancing the accelerated beam current in the booster synchrotron by optimizing the transport line beam propagation

In this paper, we present the results of transverse beam emittance and twiss parameter measurement of an electron beam, delivered by a 20 MeV microtron which is used as a pre-injector system for a booster synchrotron in the Indus Accelerator Facility at RRCAT Indore. Based on these measured beam parameters, beam optics of a transport line was optimized and its results are also discussed in this paper. This beam transport line is used to transport the electron beam from the 20 MeV microtron to the booster synchrotron. The booster synchrotron works as a main injector for Indus-1 and Indus-2 synchrotron radiation facilities. To optimize the beam optics of a transport line for proper beam transmission through the line as well as to match the beam twiss parameters at the beam injection point of another accelerator, it is necessary to know the transverse beam emittance and twiss parameters of the beam coming from the first one. A MATLAB-based GUI program has been developed to calculate the beam emittance and twiss parameters, using quadrupole scan method. The measured parameters have been used for beam transport line optimization and twiss parameters matching at booster injection point. After this optimization, an enhancement of ～50% beam current has been observed in the booster synchrotron.