Conceptual design of Hefei advanced light source

The conceptual of Hefei Advanced Light Source, which is an advanced VUV and Soft X-ray source, was developed at NSRL of USTC. According to the synchrotron radiation user requirements and the trends of SR source development, some accelerator-based schemes were considered and compared; furthermore storage ring with ultra low emittance was adopted as the baseline scheme of HALS. To achieve ultra low emittance, some focusing structures were studied and optimized in the lattice design. Compromising of emittance, onmomentum and off-momentum dynamic aperture and ring scale, five bend acromat (FBA) was employed. In the preliminary design of HALS, the emittance was reduced to sub nm·rad, thus the radiation up to water window has full lateral coherence. The brilliance of undulator radiation covering several eVs to keVs range is higher than that of HLS by several orders. The HALS should be one of the most advanced synchrotron radiation light sources in the world.     

Low emittance lattice optimization using a multi-objective evolutionary algorithm

A low emittance lattice design and optimization procedure are systematically studied with a non-dominated sorting-based multi-objective evolutionary algorithm which not only globally searches the low emittance lattice, but also optimizes some beam quantities such as betatron tunes, momentum compaction factor and dispersion function simultaneously. In this paper the detailed algorithm and lattice design procedure are presented. The Hefei light source upgrade project storage ring lattice, with fixed magnet layout, is designed to illustrate this optimization procedure.     

Minimum emittance in TBA and MBA lattices

For reaching a small emittance in a modern light source, triple bend achromats(TBA), theoretical minimum emittance(TME) and even multiple bend achromats(MBA) have been considered. This paper derived the necessary condition for achieving minimum emittance in TBA and MBA theoretically, where the bending angle of inner dipoles has a factor of 3~(1/3) bigger than that of the outer dipoles. Here, we also calculated the conditions attaining the minimum emittance of TBA related to phase advance in some special cases with a pure mathematics method. These results may give some directions on lattice design.     

Measurement of optics for the SSRF storage ring in commissioning

The Shanghai Synchrotron Radiation Facility (SSRF) is a low emittance third-generation synchrotron radiation light source. Some optics parameters of the storage ring were measured when commissioning. This report presents the common methods for measuring some optics parameters of the storage ring, including the betatron tune, beta function, chromaticity, natural chromaticity and dispersion. The results and analysis of measurement for the optics parameters are given here, which are indispensable for the orbit correction of the accelerator and the nonlinear optimization.     

Commissioning experience with insertion devices at PETRA III

PETRA III is a new hard X-ray synchrotron radiation source, operating at 6 GeV with a beam current of up to 100 mA and extremely low horizontal emittance of 1 nm rad. Such low emittance is achieved by using two 100 m long damping wiggler sections which reduce the emittance by a factor of 4. Altogether the damping sections contain 20 wigglers of 4m length each. The emitted synchrotron radiation power produced by wigglers amounts to 420 kW at 100 mA beam current in total. In the new octant of PETRA III, there are 14 undulator beamlines, with a brilliance up to 10²¹ (s mrad² mm² 0.1% BW)⁻¹ which cover an energy range from 0.3 keV to more than 100 keV. The low emittance raises very high requirements to the field quality of the insertion devices. At first, it should not affect the positron beam trajectory. Secondly, the spectral properties of the radiation created, like the intensity of higher harmonics, should not be limited by the undulator field quality, but by the beam emittance effects in order to have some reserve for future machine upgrades or possible radiation demagnetization. This paper presents the current status of PETRA III insertion devices and describes intermediate commissioning results like impact of IDs on the positron beam orbit or photon beam and radiation problems.     

Transfer matrices of dipoles with bending radius variation

With the increasing demand of high brightness in light source, the uniform dipole can not meet the needs of low emittance, and thus the dipole with bending radius variation is introduced in this paper. The transfer matrix of a non-uniform dipole whose bending radius is linearly changed is chosen as an example and a very simple calculation formula of non-uniform dipole transfer matrices is given. The transfer matrices of some common profile non-uniform dipoles are also listed. The comparison of these transfer matrices and the matrices calculated with slices method verifies the numerical accuracy of this formula. This method can make the non-uniform beam dynamic problem simpler, very helpful for emittance research and lattice design with non-uniform dipoles.     

Emittance measurement & optimization for the photocathode RF gun with laser profile shaping

The Laser Undulator Compact X-ray source(LUCX) is a test bench for a compact high brightness X-ray generator,based on inverse Compton Scattering at KEK,which requires high intensity multi-bunch trains with low transverse emittance.A photocathode RF gun with emittance compensation solenoid is used as an electron source.Much endeavor has been made to increase the beam intensity in the multi-bunch trains.The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects,so that ...     

Measurement of optics for the SSRF storage ring in commissioning

The Shanghai Synchrotron Radiation Facility (SSRF) is a low emittance third-generation synchrotron radiation light source. Some optics parameters of the storage ring were measured when commissioning. This report presents the common methods for measuring some optics parameters of the storage ring, including the betatron tune, beta function, chromaticity, natural chromaticity and dispersion. The results and analysis of measurement for the optics parameters are given here, which are indispensable for the orbit correction of the accelerator and the nonlinear optimization.     

ECR离子源束流发射度的实验研究

利用最新自行研制的电扫描发射度探测系统, 在ECR离子源上进行了一系列关于ECR离子源引出束流发射度的研究. 这套电扫描发射度探测系统安装在中国科学院近代物理研究所(兰州)的LECR3试验平台的束运线上. 试验中, 通过测量相关参数, 研究了磁场、微波、掺气效应及负偏压效应等对引出束流发射度的影响. 利用实验所得的结果与关于ECR等离子体和离子源束流发射度的半经验理论, 分析推导了离子源各可调参数与ECR等离子体的直接关系, 这为分析探索ECR离子源的工作机制提供了一定的参考依据.     

强流RFQ加速器的匹配设计方法研究

模拟计算和束流实验证明不匹配是直线加速器中强流束产生束晕的直接原因. 束晕的产生将导致束流品质下降和束流丢失, 也使得不匹配成为引起束流丢失的主要原因. 为了提高强流RFQ加速器中束流的传输品质和提高传输效率, 在分析了RFQ加速器中束流不匹配的原因之后, 提出了基于常规四部曲方法的匹配动力学设计方法. 该设计方法可以有效地抑制发射度增长和提高束流的传输效率.     

Emittance measurement & optimization for the photocathode RF gun with laser profile shaping

The Laser Undulator Compact X-ray source(LUCX) is a test bench for a compact high brightness X-ray generator,based on inverse Compton Scattering at KEK,which requires high intensity multi-bunch trains with low transverse emittance.A photocathode RF gun with emittance compensation solenoid is used as an electron source.Much endeavor has been made to increase the beam intensity in the multi-bunch trains.The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects,so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough.A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform.In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance.With the uniform driving laser and the unbalanced RF gun,the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm.mrad.     

Resonant transition radiation in the X-ray region from a low emittance 855 MeV electron beam

The interference of transition radiation coherently produced from a periodic stack of four polyimide foils of 7.2 μm thickness and a separation of 162 μm was investigated. This stack has been brought into the low emittance (3 π nm rad) electron beam of the 855 MeV Mainz Microtron MAMI. Transition radiation was observed in the energy range from 2 to 15 keV with a LN₂-cooled pin photodiode. A good energy resolution of 0.8 keV and angular resolution of 0.15 mrad was achieved simultaneously allowing for the first time to quantitatively study the interference pattern. Good agreement with theoretical calculations is found. Prospects to exploit transition radiation in the x-ray region from a low emittance electron beam as a high brilliant radiation source are discussed.     

Low emittance lattice for the storage ring of the Turkish Light Source Facility TURKAY

The TAC(Turkish Accelerator Center) project aims to build an accelerator center in Turkey. The first stage of the project is to construct an Infra-Red Free Electron Laser(IR-FEL) facility. The second stage is to build a synchrotron radiation facility named TURKAY, which is a third generation synchrotron radiation light source that aims to achieve a high brilliance photon beam from a low emittance electron beam at 3 Ge V. The electron beam parameters are highly dependent on the magnetic lattice of the storage ring. In this paper a low emittance storage ring for TURKAY is proposed and the beam dynamic properties of the magnetic lattice are investigated.     

9MeV,小于0.1mm微焦点X射线源验证实验

密度高、成像分辨率高、成像速度快的X射线数字成像检测需要高能微焦点大剂量X射线源,高品质电子源是实现这一X射线源的关键手段。基于中国工程物理研究院太赫兹自由电子激光的主加速器,验证了低发射度、低能散度的高亮度电子束实现高能微焦点的可行性,得到电子束半高全宽尺寸小于70μm的9 MeV微焦点,并初步开展成像实验,双丝像质计焦斑清晰分辨9D号丝,丝直径0.13 mm。     

HLS储存环束流发射度研究

 研究了合肥光源(HLS)储存环束流发射度与其长直线节消色散条件之间的关系；在考虑到H函数的匹配时，计算了储存环最低束流发射度；为光源多种运行模式提供了理论依据。     

Single-bunch emittance dilution in the perfect ILC main linac

In the ILC (International Linear Collider) main linac, low emittance preservation is the most important issue for beam dynamics study. As the main sources of emittance dilution, the dispersive and wakefield effects were studied in this paper. The theoretical calculations and numerical simulations of these two effects on single-bunch emittance dilution, without any misalignment errors, are presented in detail.     

胡椒孔法在强流脉冲离子束中的发射度测量

真空弧离子源的引出束流具有低能、强流等特点,当离子源工作在单脉冲模式时,被广泛采用的缝-杯式和Alison式发射度测量方法不再适用。采用基于成像板的胡椒孔法测量了真空弧离子源的发射度。初步研制了胡椒孔法发射度测量装置,利用该装置测量了引出电压为64 kV时脉冲束流的发射度和发射相图。在x方向和y方向,测得归一化均方根发射度分别为6.41,4.61 mmmrad。测量结果表明该真空弧离子源在64 kV时的归一化发射度远大于其他类型的离子源的发射度。     

影响X光源特性的参数研究

针对高能电子束撞击重金属靶产生轫致辐射光子, 利用蒙特卡罗方法详细研究了电子束半径与发射度以及靶的厚度对X光源特性的影响. 结果表明：电子束半径与发射度不仅是影响照射量的主要因素, 也是造成照射量分布不均匀的主要原因; 给定电子束, 存在一个靶厚度使得靶前1 m处的照射量最大. 因此, 在X射线成像系统的设计和模拟过程中, 应综合考虑电子束半径与发射度和靶厚的影响.