Theoretical study of medium emittance lattice at HLS

In order to improve the performance of Hefei Light Source (HLS), two medium emittance lattices of HLS storage ring are calculated. Lattices are designed with the HLS hardware constraints and no new hardware is used. Emittance of the lattice "w3" is 64.2 nmrad, and the "w3u" is 37.5 nmrad. The "w3u" is a non-achromatic lattice with non-zero dispersion function at long straight section. Coefficients of quadrupoles of "w3u" is designed to be similar with the "w3" in order for that "w3u" can be smoothly transited from "w3". This can avoid the beam dynamics problem of the "w3u" lattices.