衍射极限储存环束流注入物理方案的设计及模拟

衍射极限储存环（DLSR）作为第四代同步辐射光源，正得到世界各国的大力发展和建设。如何在尽量减小对存储束流扰动情况下，高效率地将束流注入到储存环中，是衍射极限储存环设计与运行中的重要课题之一。传统的局部凸轨注入法有着很长的历史，应用广泛且技术成熟，但是传统凸轨注入法会对存储束流造成扰动，且衍射极限储存环的动力学孔径较小，这给传统凸轨注入法的应用带来了困难。为了解决这些问题，改进了一些传统的离轴注入法，提出并发展了一些在轴的注入方法。合肥先进光源（HALF）是规划建设中的衍射极限储存环光源，基于HALF储存环的物理设计方案，设计并应用了几种离轴或在轴的注入方案，通过粒子跟踪和模拟的方法验证了它们的可行性并研究了注入效率等物理问题，并对模拟结果进行了讨论和总结。     

衍射极限储存环物理设计研究进展

总结了国内外在衍射极限储存环(DLSR)物理设计方面的研究进展。为了在合理的周长范围内实现超低束流发射度,DLSR线性束流光学设计普遍采用紧凑型多二极铁消色散结构。在非线性动力学优化中,通常采用相移控制技术、解析和数值优化技术减小由色品六极铁导致的强非线性效应。DLSR束流接受度较小,主要考虑脉冲多极铁偏轴注入和快速冲击磁铁在轴注入两种注入方案。束流集体效应(尤其是束流内部散射和托歇克散射效应)随发射度降低而增强,需要采用束长拉伸、横向反馈等方法提高DLSR中束流的稳定性。     

合肥先进光源储存环初步物理设计

我国最近立项建设的合肥先进光源将是一台软X射线与真空紫外衍射极限储存环光源,其电子束能量为2.2 GeV,周长为480 m,束流自然发射度为86 pm·rad,共有20个长直线节和20个短直线节。介绍了目前合肥先进光源储存环物理设计的进展情况,包括磁聚焦结构设计与优化,束流注入和集体效应的模拟与计算。     

合肥先进光源前端光子吸收器的设计及热分析

合肥先进光源（HALF）将建设成为1台第四代衍射极限储存环光源。HALF的引出光具有更高亮度,能给储存环带来更高的热负载。引光段需设置光子吸收器,以限定引出光的尺寸和吸收其余未使用的同步光,同时减少同步光热负载对储存环超高真空系统的影响。紧凑的衍射极限储存环的物理设计及光子吸收器与真空室连接方式的选择给光子吸收器的设计带来了一系列挑战。在插入式双片型吸收器结构的基础上,综合考虑吸收面形状、水冷结构、安装定位等因素,设计了一种基于CuCrZr材料、与真空室一体、无需单独定位的光子吸收器,并计算其位于弯转角2.74°的弯转磁铁下游光引出段处,被同步光照射的光斑尺寸和辐射功率;采用有限元分析方法对光子吸收器进行热力学模拟,得到辐照后的最高温度约为80 ℃,最大应力为20.8 MPa,最大热变形为0.05 mm。结合制作材料CuCrZr在高热负载下的许用准则,确定了光子吸收器结构的合理性。此研究为合肥先进光源中前端区光子吸收器的设计提供了重要的理论依据。     

低能区衍射限储存环同步辐射的应用浅析

在科学技术新需求的推动下,同步辐射光源持续往前发展。目前,同步辐射装置发展已历经三代,正处于第四代同步辐射光源蓬勃发展阶段。基于衍射极限储存环的同步辐射装置是第四代同步辐射光源的典型代表之一。第四代同步辐射光源主要发展趋势是进一步减小电子束流发射度,使光源具有极好的横向相干性,以及产生圆截面辐射的能力。如果束流发射度降至光学衍射极限“辐射波长/4π”,其亮度比第三代同步辐射光源高2个数量级。这种同步辐射光源在性能上发生的质的飞跃,将给同步辐射实验技术带来实质性的突破,从而给前沿科学技术研究和现代产业发展带来全新的机遇。从国际同步辐射发展趋势入手,首先介绍低能区衍射限储存环光源的特色和性能,然后介绍其带来的同步辐射实验技术的进步,并浅析低能区衍射限储存环光源在材料科学、能源科学、生命科学和环境科学上的应用,以及其带来的产业机遇。最后,总结和展望了低能区衍射限储存环光源带来的技术突破和潜在的应用前景。     

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。     

第四代同步辐射光源物理设计与优化

近十年来,世界上开始大力发展第四代同步辐射光源——衍射极限储存环光源。目前我国正在建设或立项建设两台第四代同步辐射光源:高能同步辐射光源和合肥先进光源。从储存环磁聚焦结构设计与优化、束流注入与集体效应等方面,对第四代同步辐射光源的物理设计与优化进行了介绍;对国际范围内第四代储存环光源装置的研制情况进行了介绍。     

KB镜束流截面测量系统研制

为了对衍射极限储存环的束流横向截面尺寸及发射度进行测量,设计了一套Kirkpatrick-Baez(KB)反射镜聚焦成像系统,并在上海光源(SSRF)储存环进行预制研究。该系统主体由两面垂直放置的KB反射镜组成,分别在水平及垂直方向对弯转磁铁光源点进行成像,系统工作在硬X射线波段,聚焦光斑被闪烁体X射线相机采集。对影响系统成像质量的像差和点扩散函数进行了计算。目前,实现了对束流的实时成像,可精确测量束流横向截面尺寸为75.9 μm(水平方向)和20.2 μm(垂直方向),系统稳定性(RMS)小于0.1 μm。     

合肥储存环电子束流寿命分析

 电子束流寿命是个很重要的指标，直接影响合肥光源的正常运行，为此研究了影响束流寿命的因素，测量了高频腔压、耦合度以及束团长度对电子束流寿命的影响，研究显示合肥储存环的电子束流真空寿命和托歇克寿命相当；并且利用束损系统测量了因托歇克寿命的变化而造成束流损失的相对变化；通过增加耦合度增加束流的垂直发射度，有效地提高了束流的寿命，保证了合肥光源的正常运行。     

电子储存环中离子俘获不稳定性的强-强模型模拟

 电子储存环中,由于被束流势阱俘获的离子会引起束流不稳定性。研究这种不稳定性的产生机制和抑制方法对提高机器的性能有重要理论和现实意义。介绍了用强-强模型对合肥光源（HLS）电子储存环中离子俘获不稳定性产生机制进行的模拟研究。模拟结果可用于理解在合肥光源（HLS）储存环上观察到的离子俘获现象。     

PEPX-type lattice design and optimization for the High Energy Photon Source

A new generation of storage ring-based light sources, called diffraction-limited storage rings(DLSR), with emittance approaching the diffraction limit for multi-ke V photons by using multi-bend achromat lattice, has attracted worldwide and extensive studies of several laboratories, and been seriously considered as a means of upgrading existing facilities in the imminent future. Among various DLSR proposals, the PEPX design demonstrated that it is feasible to achieve sufficient ring acceptance for off-axis injection in a DLSR, by designing the lattice based on the ‘thirdorder achromat' concept and with a special high-beta injection section. For the High Energy Photon Source(HEPS)planned to be built in Beijing, a PEPX-type lattice has been designed and continuously improved. In this paper, we report the evolution of the PEPX-type design for HEPS, and discuss the main issues relevant to the linear optics design and nonlinear optimization.     

Bunch length manipulation in a diffraction-limited storage ring

In an electron storage ring,the bunch length can be increased or decreased by using harmonic cavities.Taking the High Energy Photon Source as an example,we test the bunch length manipulation with harmonic cavities in a diffraction-limited storage ring(DLSR).The most important collective effects in a DLSR,intra-beam scattering and Touschek effects,are evaluated for different bunch-length patterns.Our study shows that it is feasible to produce long and short bunches simultaneously in a DLSR,without causing severe emittance growth and reduction in lifetime.     

ESRF-type lattice design and optimization for the High Energy Photon Source

A new generation of storage ring-based light sources,called diffraction-limited storage rings(DLSRs),with emittance approaching the diffraction limit for multi-keV photons by means of multi-bend achromat lattices,has attracted extensive studies worldwide.Among various DLSR proposals,the hybrid multi-bend achromat concept developed at the European Synchrotron Radiation Facility(ESRF) predicts an effective way of minimizing the emittance while keeping the required chromatic sextupole strengths to an achievable level.For the High Energy Photon Source planned to be built in Beijing,an ESRF-type lattice design consisting of 48 hybrid seven-bend achromats is proposed to reach emittance as low as 60 pm-rad with a circumference of about 1296 m.Sufficient dynamic aperture,allowing vertical on-axis injection,and moderate momentum acceptance are achieved simultaneously for a promising ring performance.     

Optics for the lattice of the compact storage ring for a Compton X-ray source

We present two types of optics for the lattice of a compact storage ring for a Compton X-ray source. The optics design for different operation modes of the storage ring are discussed in detail. For the pulse mode optics, an IBS-suppression scheme is applied to optimize the optics for lower IBS emittance growth rate; as for the steady mode, the method to control momentum compact factor is adopted [Gladkikh P, Phys. Rev. ST Accel. Beams 8, 050702] to obtain stability of the electron beam.     

Optics for the lattice of the compact storage ring for a Compton X-ray source

We present two types of optics for the lattice of a compact storage ring for a Compton X-ray source. The optics design for different operation modes of the storage ring are discussed in detail. For the pulse mode optics, an IBS-suppression scheme is applied to optimize the optics for lower IBS emittance growth rate; as for the steady mode, the method to control momentum compact factor is adopted [Gladkikh P, Phys. Rev. ST Accel. Beams 8, 050702] to     

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.