Modified double-double bend achromat lattice for an ultra-low emittance design of the HLS

Abstract

Abstract The storage ring of the present Hefei Light Source (HLS) consists of four double-bend achromat lattice cells, each with two straight sections. In this paper, a modified double-double bend achromat (DDBA) lattice is proposed for an ultra-low emittance design of HLS, where the circumference of the storage ring and the lengths of all straight sections remain the same. Compared to the typical DDBA lattice, this modified lattice can obtain both lower emittance and lower dispersion in the mid-straight section, thus providing higher brightness of insertion device radiation. The natural emittance of the HLS designed with the modified DDBA lattice is 3.9 nm·rad, about one order of magnitude lower than that of the present HLS.