The Hefei Advanced Light Facility (HALF) is a diffraction limited storage ring (DLSR).The extracted light of HALF has higher brightness resulting in higher heat load to the storage ring. The redundant synchrotron radiation is absorbed by the photon absorber located in the front-end to protect the ultrahigh vacuum system of DLSR. A special design of the photon absorber is required due to the compact physical design. Considering the toothed surface profile, cooling channel, and installation, we propose a photon absorber made of CuCrZr without additional positioning on the basis of the two-piece vertical absorber. The spot size and power of the radiation from the bending magnet with a bending angle of 2.74° are calculated. The thermal-mechanical simulations based on the finite element analysis method show acceptable results. The maximum thermal deformation, temperature, and stress are 0.05 mm, 80 ℃, and 20.8 MPa, respectively, indicating that the new absorber works in a safe range. The present study provides a critical theoretical basis for the design of the photon absorber in the front-end of HALF.

Driven by the demand of science and technology, synchrotron radiation (SR) facilities continue to develop. At present, the development of SR has gone through three generations, and is in the vigorous development stage of the fourth generation (4th). SR based on diffraction-limited storage ring is one of the typical representative of the 4th synchrotron light sources. The mainstream of the 4th SR is to further reduce the electron beam emittance, so that the light source from the 4th SR exhibits excellent transversal coherence and is able to produce circular cross-section radiation. If the beam emittance drops to the optical diffraction limited “radiation wavelength/4π”, its brightness enhances to 2-3 orders of magnitude higher than that of the third generation SR light source. The qualitative leap in the performance of this SR light source will bring a substantive breakthrough to the SR-based experimental techniques, and bring new opportunities to the cutting-edge scientific and technological research, as well as the development of modern industry. Starting with the development trend of worldwide SR facilities, this review first introduces the characteristics and performance of low-energy diffraction limited storage ring (DLSR) light source, then introduces the progress of experimental techniques brought by DLSR, and illustrates the application of low-energy DLSR light source in material science, energy science, life science and environmental science, as well as its industrial opportunities. Finally, the technical breakthrough and potential application prospect of low energy DLSR light source are summarized and prospected.

Hefei Advanced Light Facility (HALF) is aimed to be a world-class diffraction limited storage ring (DLSR) in the soft X-ray & VUV regime. The characteristics and law of beam emittance evolution due to intra-beam scattering (IBS) in HALF storage ring was studied based on equations of equilibrium emittance. The results show that, it is necessary to comprehensively optimize the key parameters to obtain excellent beam performance in physical design of middle to low-energy DLSR. Applying the key parameters optimization strategy and taking methods to release the emittance growth due to IBS into consideration, the new version of HALF lattice can meet the needs of soft X-ray diffraction limit.

Over the past decade, the fourth-generation synchrotron light sources based on diffraction-limited storage rings (DLSRs) have been extensively designed and developed around the world. In China, two fourth-generation synchrotron light sources, the High Energy Photon Source and the Hefei Advanced Light Facility, are being or will be constructed. This paper will report the main issues and progresses in physics design and optimization of DLSRs, including lattice design and optimization, beam injection and collective effects, and will also introduce the current design and construction status of DLSR facilities around the world.

The Hefei Advanced Light Facility (HALF) is a soft X-ray and VUV diffraction-limited storage ring light source, and the construction of HALF has just been approved by the Chinese government. The electron beam energy of the HALF storage ring is 2.2 GeV; the circumference is 480 m; the natural beam emittance is 86 pm·rad; and there are 20 long and 20 short straight sections in total. This paper will report the physics design progress of the HALF storage ring, including lattice design and optimization, simulation and calculation of beam injection and collective effects.

The ultralow emittance storage ring light source based on multi-bend achromats is an important development direction of the new generation of synchrotron radiation light source. As the first fourth generation synchrotron radiation light source in China, High Energy Photon Source (HEPS) is under construction. The physics and engineering design has been finished for HEPS. The beam energy is 6 GeV, the beam current is 200 mA, and the horizontal natural emittance is less than 60 pm∙rad, promising radiation brightness of up to 1×1022phs·s-1·mm-2·mrad-2·(0.1%bw)-1 at typical hard X-ray regime. HEPS will be an important platform to support original and innovative research in the fields of basic science and engineering science. This paper will introduce the overall and physics design of the HEPS project.