Article title: Intra-beam scattering and beam lifetime in a candidate lattice of the soft X-ray diffraction-limited storage ring for the upgraded SSRF

文章标题：束团内部散射和束流寿命在上海光源软X射线衍射极限升级方案中的优化研究

DOI: https://doi.org/10.1007/s41365-021-00913-y

One sentence summary:

一句话概要：

For Shanghai Synchrotron Radiation Facility Upgrade (SSRF-U), a candidate lattice of the storage ring, reaching soft-X ray diffraction limit, was designed, and Intra-beam scattering optimization was completed.

为上海光源升级改造，设计了一个达到软X射线极限的储存环磁铁聚焦结构，并完成了束团内部散射效应的优化。

http://www.nst.sinap.ac.cn/newsDetails/112/17388/en/

The Novelty (What)

创新性（主要内容）

In this study, we design a new lattice of the Shanghai Synchrotron Radiation Facility upgrade (SSRF-U), which is a low-emittance photon source designed with an emittance of 53.2 pm·rad (N-IBS), using 20 seven-bend achromat cells. This small emittance and high electron density will inevitably lead to non-negligible intrabeam scattering (IBS) and Touschek scattering. Therefore, to weaken the effect of IBS and Touschek scattering, emittance growth and beam lifetime in the SSRF-U storage ring were studied by the method of particle simulation within a serious of different configurations of the machine.  After almost all the methods consideration, a best configuration was obtained, which would contribute to the upgrade plan of SSRF storage ring. The method of this paper has important reference significance for the transformation of other light sources or the design and construction of new light sources.

在本报告中我们为上海光源升级改造，设计了一个发射度达到软X射线极限的7BA储存环磁铁聚焦结构。但衍射极限环中，束团内部散射与托歇克散射效应对发射度影响较大。为减弱束团内散射和托歇克散射效应, 对在几乎全部能抑制束团内散射效应的方法，都做了非常详细的分析。全面优化设计完成以后，为上海光源的升级改造建立了最优化的设计方案。文章的分析方法对其他光源的改造或新光源的设计建设都具有重要的借鉴意义。

The Background (Why)

研究背景（主要原因）

The high-performance SSRF has contributed to significant scientific findings related to various research fields, including biomedicine, material science, environmental science, physics, and chemistry. Meanwhile, there is an increasing demand for synchrotron light sources with reduced beam emittance approaching or reaching X-ray diffraction limits. However, the properties (e.g., beam lifetime and brightness) of such light sources are bound to be degraded by IBS and Touschek scattering. While designing a new lattice of storage ring, reaching soft-X ray diffraction limit, to upgrade the SSRF, this study has also run extensive simulations to overcome the adverse effects of IBS and Touschek scattering. By identifying the optimal parameters for yielding a beam with lower emittance and higher brightness. The SSRF-U would become one of the state-of-the-art research assets to facilitate scientists making exceptional scientific contributions.

SSRF高性能的运行对生物医学、材料科学、环境科学、物理学和化学等各个研究领域的重大科学发现做出了贡献。 同时，科学家对束流发射度接近或达到X射线衍射极限的同步加速器光源的需求也在不断增加。由于IBS和Touschek散射，这类光源的性能（例如光束寿命和亮度）必然会降低。所以在为SSRF升级改造设计新的储存环聚焦结构的同时，本研究还进行了广泛的模拟，以克服IBS和Touschek散射的不利影响。 通过确定产生发射度较低、亮度较高的光束的最佳参数。SSRF-U将会成为最先进的研究资产之一，以便利科学家作出卓越的科学贡献。

The SDG impact (Big Why)

SDG影响力（研究意义）

The SSRF is well-known as a necessary light source facility that contributes to multiple subjects of studies. Despite that, continuous upgrading and improving SSRF are essential to enhance its beam properties and performance to keep up with the rapid pace of scientific research. The candidate lattice of the storage ring for SSRF-U, reaching soft-X ray diffraction limit, and Intra-beam scattering optimization. which would contribute to the upgrade plan of SSRF storage ring. Hence, this study is well-aligned with the targets of UNSDG 9: Industries, Innovation & Infrastructure.

SSRF作为一个必要的光源设施，为多个研究课题做出贡献，这是众所周知的。 尽管如此，不断升级和改进SSRF对于提高其束流特性和性能以跟上科学研究的快速步伐是必不可少的。这项研究中设计的软X射线的储存环聚焦结构与束团内部优化方案将为上海光源升级提供坚实的基础。 因此，这项研究与联合国可持续发展目标9（工业、创新和基础设施）的目标完全一致。