Diffraction-limited storage rings (DLSRs), with sub-$100\mathrm{pm}\cdot \mathrm{rad}$ electron emittances approaching the diffraction limit for hard X-rays, would provide unprecedented transverse coherence and much higher brightness than currently operational light sources to the synchrotron radiation scientific community. Instead of typical flat beam, some individual synchrotron light users prefer round beam, a beam with equivalent emittances between the horizontal and vertical planes, for the reasons of fully transverse coherent X-ray radiation and better photon–electron phase space match, and so on. To meet the requirements of different experimenters, obtaining a locally-round beam will be a significant subject in DLSR studies. We investigate the approaches of realizing locally-round beam in a storage ring, by means of a local emittance equalization of the transverse planes. In this paper, a novel method is proposed to achieve locally-round beam, performed with a combination of skew quadrupoles in insertion section of the storage ring. Theoretical analysis and application of this method to achieve a locally-round beam at DLSRs, particularly to High Energy Photon Source (HEPS) storage ring, are presented.

衍射极限存储环（DLSR），其中$100\mathrm{下午}\cdot \mathrm{拉德}$电子辐射接近硬X射线的衍射极限，将为同步加速器辐射科学界提供前所未有的横向相干性，并且比当前可操作的光源提供更高的亮度。由于完全横向的相干X射线辐射和更好的光子-电子相空间匹配等原因，某些同步加速器用户不是典型的平光束，而是圆形光束，该光束在水平和垂直平面之间具有相同的发射率。 。为了满足不同实验者的要求，获得局部圆形光束将是DLSR研究中的重要课题。我们研究了通过横向平面的局部发射率均衡在存储环中实现局部圆形光束的方法。在本文中，提出了一种新颖的方法来实现局部圆形光束，该光束是通过在存储环的插入部分中组合使用倾斜四极杆来实现的。提出了该方法在DLSR处实现局域圆形光束的理论分析和应用，特别是在高能光子源（HEPS）存储环上。