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To meet the fast-growing demands for high-quality low-energy photon beams, a new synchrotron radiation light source conception was brought forward several years ago by National Synchrotron Radiation Laboratory, which was named Hefei Advanced Light Source (HALS). The dominant radiation of HALS will be located in the VUV and soft X-ray region, which will be complementary with that of SSRF and HEPS. Except for high brilliance, high transverse coherence will be another signature feature of HALS. To achieve these goals, a multi-bend achromat based diffraction-limited storage ring was adopted as the main body of HALS. The general description and preliminary design of HALS will be briefly presented in this paper. Under the support of the Chinese Academy of Sciences and local government, the preliminary research and development (R&D) for HALS is undergoing. Several key technologies will be developed in the R&D project, which will lay good foundation for the construction of HALS., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

In this paper, a new multi-bend achromat (MBA) lat-tice concept that we recently proposed for diffraction-limited storage rings is described, where two pairs of interleaved dispersion bumps are created in each cell and also most of the nonlinear effects produced by the sextupoles located in these bumps can be cancelled out within one cell. Following this concept, two 7BA lattices have been designed for the Hefei Advanced Light Source storage ring as the second version lattic-es, one with uniform dipoles and the other with nonu-niform dipoles. The latter has a lower natural emit-tance of 23 pm·rad, in which longitudinal gradient bends and anti-bends are employed. The optimized nonlinear dynamics for these two lattices are rather good, and especially the dynamic momentum aperture can be larger than 8% without off-momentum tunes crossing non-structure half-integer resonance lines., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

An elliptically polarized undulator (EPU) was applied to obtain high-brightness coherent synchrotron radiation at the upgraded Hefei Light Source, HLS-II. However, the EPU has serious dynamic effects on the beam performances including close orbit, emittance and dynamic aperture etc. when installed at the storage ring. In order to understand the effects, a Taylor expanded generating method was adopted to generate a fast and symplectic map for particle tracking. As for the compensation of the EPU, striplines were equipped above and below the vacuum chamber to reduce the nonlinear effects. With the symplectic tracking routine and the surface fitting method, different parameters such as dynamic aperture and the driving terms, could be set as the objective function to accomplish the optimization of the EPU., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The Shanghai Coherent Light Facility (SCLF) is a newly proposed high repetition-rate X-ray FEL facility, based on an 8-GeV CW superconducting RF linac. It will be located at Zhangjiang High-tech Park, close to the SSRF campus in Shanghai, at the depth of ~38m underground and with a total length of 3.1 km. Using 3 phase-I undulators, the SCLF aims at generating X-rays between 0.4 and 25 keV at rates up to 1MHz. This paper describes the design concepts of this hard X-ray user facility., Proceedings of the 38th Int. Free Electron Laser Conf., FEL2017, Santa Fe, NM, USA

An elliptically polarized undulator (EPU) was installed at the upgraded Hefei Light Source, HLS-II, for special users. Due to that the area of good field of the EPU is not large enough, the resulting beam dynamics is serious. At present, the lattice is changed to lower beta functions at the EPU to solve this problem. However, the compensation for the EPU is necessary for better operation of the machine in the future. In this paper, we used the surface fitting method to extract the Hamiltonian of the EPU from the real surface magnetic field data. Thus, we can obtain the effective Hamiltonian of the ring, which can be analyzed using normal form or other techniques. Then the beam dynamics effects resulting from the EPU can be compensated by optimizing the nonlinear quantities with striplines., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark