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.     

Improved nonlinear optimization in the storage ring of the modern synchrotron radiation light source

In the storage ring of the third generation light sources, nonlinear optimization is an indispensable course in order to obtain ample dynamic acceptances and to reach high injection efficiency and long beam lifetime, especially in a low emittance lattice. An improved optimization algorithm based on the single resonance approach, which takes relative weight and initial Harmonic Sextupole Integral Strength （HSIS） as search variables, is discussed in this paper. Applications of the improved method in several test lattices are presented. Detailed analysis of the storage ring of the Shanghai Synchrotron Radiation Facility （SSRF） is particularly emphasized. Furthermore, cancellation of the driving terms is investigated to reveal the physical mechanism of the harmonic sextupole compensation. Sensitivity to the weight and the initial HSIS as well as dependence of the optimum solution on the convergent factor is analyzed.     

Improved nonlinear optimization in the storage ring of the modern synchrotron radiation light source

In the storage ring of the third generation light sources,nonlinear optimization is an indispensable course in order to obtain ample dynamic acceptances and to reach high injection efficiency and long beam lifetime,especially in a low emittance lattice.An improved optimization algorithm based on the single resonance approach,which takes relative weight and initial Harmonic Sextupole Integral Strength (HSIS) as search variables,is discussed in this paper.Applications of the improved method in several test lattices are presented.Detailed analysis of the storage ring of the Shanghai Synchrotron Radiation Facility (SSRF) is particularly emphasized.Furthermore,cancellation of the driving terms is investigated to reveal the physical mechanism of the harmonic sextupole compensation.Sensitivity to the weight and the initial HSIS as well as dependence of the optimum solution on the convergent factor is analyzed.     

On the possibility of synchrotron radiation source modification

The possibility of reconstructing old-generation electron colliders for effective use as synchrotron radiation sources is discussed. Among other positive features related with using the wiggler in the accelerator, the possibility of using lateral petals of the radiation for the division of several experiments on one beam is estimated. An analysis of coherent effects for systems with a large undulator coefficient is presented.     

Special-purpose radiation sources based on the Siberia-2 storage ring

Synchrotron radiation (SR) generated by homogeneous magnetic fields of bending magnets is now employed at the Siberia-2 electron storage ring. It is planned that, in the near future, most of the storage ring’s free straight sections will be equipped with insertion devices (undulators and wigglers). Two projects of specialized radiation sources based on the Siberia-2 stor age ring are discussed. The first source is a vacuum milliundulator intended for generation of extremely bright X-ray beams. An X-ray source with vertically limited diffraction is shown to be feasible when the vertical emittance of an electron beam is equal to the diffraction emittance of photons with an energy of 2 keV. The second source uses edge radiation (ER) generated at the ends of bending magnets of the storage ring. Calculations show that, in the infrared and ultraviolet spectral regions, the ER intensity must exceed the intensity of standard SR formed by the homogeneous field of a bending magnet.     

激光同步辐射光源的辐射条件

激光同步辐射光源是一种新型的X射线光源，它利用高强度激光与相对论电子束发生康普顿散射，从而在电子的运动方向上辐射出X射线．本文在考虑电子的反冲基础上，利用康普顿散射研究了激光同步辐射光源（LSS）辐射光子的精确波长和能量；同时发现，对于背散射情况，只有当种子激光的波长λ1大于电子的物质波波长λm时才能发生LSS辐射；最后给出LSS辐射的极值波长λ2max=h/（m0γv）和极值能量εc2max=βε3.     

Microanalysis station at the Kurchatov synchrotron radiation source

The REFRA station developed, fabricated, and put into operation at the Kurchatov Synchrotron Radiation Center is described. The station is placed on beamline 5.6 of the big storage ring. The station consists of a vertical beam position monitor, an operating shutter, vertical and horizontal slits for the white beam, a monochromator, an alignment stage, an intensity monitor, an EXAFS spectrometer unit, a diffractometer unit, detectors, and a data control and acquisition system. The station operating energy range is 5–30 keV. The station is fully-automated and has been operating with the SR beam since spring 2005. The station units can be reproducibly mounted on the SR beam to provide various research configurations.     

Studying acoustic-wave fields in langasite-family crystals using the BESSY II synchrotron radiation source

The process of the excitation and propagation of pseudosurface acoustic waves in crystals of the langasite family is studied via X-ray diffractometry for the first time. The investigations are carried out using the BESSY II synchrotron radiation source in the double-crystal X-ray diffractometer scheme. The process of pseudosurface acoustic wave propagation is studied based on an analysis of the diffraction spectra of acoustically modulated crystals. Both the velocities of the pseudosurface acoustic waves and the power flow angles of the acoustic energy are measured for the first time. The pseudosurface acoustic wave is shown to be flowing. Surface and pseudosurface acoustic waves generated by an interdigital transducer in the Z cut of a La₃Ga_5.5Ta_0.5O₁₄ crystal are compared.     

Minimizing radial emittance of a beam from a synchrotron radiation source

The feasibility of minimizing the radial emittance of a beam from a synchrotron radiation source (storage ring) is studied. It is shown that the emittance can be diminished by producing nonuniform fields in the magnetic storage ring.     

第三代同步辐射光源X射线相干性测量研究

随着高性能第三代同步辐射光源的建成开放,基于X射线相干特性的实验方法得到了快速发展和广泛应用.作为一个典型的例子,X射线相位衬度成像已经成为常规的X射线实验方法并向用户开放.相干散射、相干衍射成像、光子关联谱等X射线实验方法正日益受到重视,在高空间分辨、时间分辨等研究领域已显示出其独特的优越性.因此,研究和测量第三代同步辐射的空间相干特性对进一步发展这些新的实验方法具有重要意义.基于Talbot自成像原理成功测量了上海光源X射线成像线站发射的X射线的空间相干长度,并进而测得了相应光源的空间尺度.光子能量为33.2 keV时,测得的X射线光束垂直方向空间相干长度为8.84μm,对应的光源尺寸为23μm,测量结果与理论分析相符.     

Development of scattering near-field optical microspectroscopy apparatus using an infrared synchrotron radiation source

We report the status of a scattering near-field microspectroscopy apparatus developed at SPring-8 using an infrared synchrotron radiation (IR-SR) source. It consists of a scattering type scanning near-field optical microscope and a Fourier transform infrared spectrometer. The IR-SR is used as a highly brilliant and broad-band IR source. This apparatus has potential for application in near-field spectroscopy with high spatial resolution beyond the diffraction limit. In order to eliminate background scatterings from the probe shaft and/or sample surface, we used higher harmonic demodulation method. The near-field spectra were observed by 2nd harmonic components using the lock-in detection. The spatial resolution of about 300 nm was achieved at around 1000 cm^? 1 (10 μm wavelength).     

Multi-objective optimization of ring stiffened cylindrical shells using a genetic algorithm

In this paper, the genetic algorithm (GA) method is used for the multi-objective optimization of ring stiffened cylindrical shells. The objective functions seek the maximum fundamental frequency and minimum structural weight of the shell subjected to four constraints including the fundamental frequency, the structural weight, the axial buckling load, and the radial buckling load. The optimization process contains six design variables including the shell thickness, the number of stiffeners, the width and height of stiffeners, the stiffeners eccentricity distribution order, and the stiffeners spacing distribution order. The real coding scheme is used for representing the solution string, while the generation number-based adaptive penalty function is applied for penalizing infeasible solutions. In analytical solution, the Ritz method is applied and the stiffeners are treated as discrete elements. Some examples of simply supported cylindrical shells with nonuniform eccentricity distribution and nonuniform rings spacing distribution are provided to demonstrate the optimality of the solution obtained by the GA technique. The effects of objective weighting coefficients and bounding values of the design variables on the optimum solution are studied for various cases. The results show that the optimal solution can vary with the weighting coefficients significantly. It is also found that extreme reduction and augmentation in turn in the structural weight and fundamental frequency can be simultaneously achieved by selecting suitable stiffeners’ geometrical parameters and distributions. Furthermore, the bounding values of the design variables have great effects on the optimum results.     

第四代同步辐射光源的光束线站及其应用

随着第四代同步辐射光源的兴起,得益于X射线亮度和相干性的大幅度提升,同步辐射实验技术在谱学、散射和成像等方面取得了显著进步。这些技术能够探测复杂非均匀体系和动态变化过程中的物质结构、成分、化学价态、电子态和磁性等关键信息,在基础科学领域和应用基础研究中发挥关键作用。文章旨在介绍第四代同步辐射光源的线站技术优势,并结合具体例子探讨其在若干物理研究中的应用,同时也讨论了当前存在的工程技术挑战。希望人们能够了解第四代同步辐射光源的光束线站的特点和应用潜力,以促进其在各个科研领域的推广。     

基于遗传算法的光学膜系初始结构优化设计

膜系初始结构优化设计是膜系优化设计的关键。针对多膜料设计 ,提出了一种新的膜系初始结构优化设计算法 ,将膜系的初始设计视为组合优化问题 ,采用遗传算法 ,求得组合的最优解。给出了算法的原理 ,并给出了相应的设计实例。结果表明 ,本算法是一种简单、有效、通用性强的膜系初始化设计方法     

Nuclear resonant scattering using synchrotron radiation

A one-dimensional quantum model for nuclear resonant scattering using synchrotron radiation has been developed. This model gives a clear physical interpretation of the most prominent features of the coherent forward scattering process namely, the “speed-up” and “dynamical beat” effects. The form of the solution, for the time-dependent forward scattered intensity of the resonant radiation from the resonant medium after synchrotron radiation excitation, is a finite series. This unique solution can be interpreted in terms of a summation over all multiple forward scattering paths the radiation takes in reaching the detector. The resonant medium is represented by a linear chain of N effective resonant nuclei. The analysis starts from a coupled set of quantum mechanical equations for the relevant amplitudes in frequency space. Transformation to the time domain gives an analytical expression for the forward scattered intensity. The contribution of every order of the multiple scattering processes from the N effective nuclei appears naturally. The expression gives a clear physical understanding of all relevant aspects of resonant forward nuclear scattering. Furthermore, the present formalism allows the consideration of incoherent processes. This permits the study of processes in which there is gamma emission with recoil or emission of internal-conversion electrons. This revised version was published online in August 2006 with corrections to the Cover Date.     

同步辐射软X射线显微成像

软X射线显微成像是同步辐射最主要的应用之一,本文简明介绍软X射线显微成像的衬度机制,光源,成像方法和一些应用结果。     

Determination of the electron beam size at the Kurchatov synchrotron radiation source using an X-ray refractive lens

The electron beam size in the storage ring of the Kurchatov synchrotron radiation source at 2.5 GeV is determined using an x-ray two-dimensional parabolic refractive lens. The vertical size of the electron beam of the storage ring is found to be 270 μm, which exceeds the corresponding design value 140 μm (at a betatron coupling of 1%). The difference is explained by the imperfect geodetic arrangement of ring elements and the incomplete adjustment of the ring.     

第四代同步辐射光源加速器物理与技术

同步辐射光源是20世纪应用最广泛的高性能X射线源,已成为物理、化学、能源环境、生物医学、先进材料等领域前沿研究的重要工具。进入21世纪,基于电子储存环的同步辐射光源的发展前沿是第四代同步辐射光源(4GLS)。其采用紧凑型的多弯铁消色散结构,可以实现接近甚至达到X射线衍射极限的超低束流发射度,将光源亮度在第三代光源基础上进一步提升2—3个数量级。文章将重点介绍第四代同步辐射光源关键的加速器物理与技术,以及国际范围内第四代同步辐射光源装置的发展情况。