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Superconducting rf cavities have been chosen for High Energy Photon Source, a 6 GeV diffraction-limited synchrotron light source under construction in Beijing. The main accelerating cavity adopted a quarter-wave β=1 structure operating at 166 MHz while the third harmonic cavity utilized the single-cell elliptical geometry at 500 MHz for the storage ring. The high beam current (200 mA) requires a strong damping of higher order modes (HOMs) excited in the superconducting cavities. To meet the beam stability requirements, enlarged beam pipes with a diameter of 505 mm for the 166 MHz cavity and 300 mm for the 500 MHz cavity were chosen to allow all HOMs to propagate along the beam tubes and to be damped by beam-line absorbers. This paper presents the HOM damping scheme and the cavity impedance analysis results. In addition, power losses due to HOMs were also evaluated for various operation modes (high charge and high luminosity) of the HEPS., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

High Energy Photon Source (HEPS) is under construction in Beijing, China. The relatively complete impedance model has been built up based on the element-by-element impedance calculation. However, Coherent Synchrotron Radiation (CSR) impedance, which might affect the longitudinal performance of the beam, was not included in the impedance model of the HEPS storage ring in the preliminary design stage. For completeness, we would like to take the CSR impedance into consideration. The most important contributions to the total CSR impedance come from the bending magnets and insertion devices. We therefore calculate the CSR impedance from both above mentioned elements in HEPS storage ring. The influence of the CSR impedance on the microwave instability threshold is studied and presented., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The High Energy Photon Source (HEPS) is a 34-pm, 1360-m storage ring light source being built in the suburb of Beijing, China. The HEPS construction started in mid-2019. While the physics design has been basically determined, modifications on the HEPS accelerator physics design have been made since 2019, in order to deal with challenges emerging from the technical and engineering designs. In this paper, we will introduce the new storage ring lattice and injector design, and also present updated results of related physics issues, including impedance and collective effects, lattice calibration, insertion device effects, injection design studies, etc., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

he High Energy Photon Source (HEPS), a kilometre-scale storage ring based light source, with emittance less than 60 pm.rad, will be constructed in Beijing, China. It con-sists of a 500 MeV linac, a 500 MeV low energy transport line, a full energy booster synchrotron, two 6- GeV transport lines, a 6 GeV ultra-low emittance storage ring, and the beam line experimental stations. The low energy transport line connecting the linac and the booster. Based on the construction layout restrictions, the beam enve-lopes of the linac and the booster should be matched, and the beam produced by the linac is high efficiently trans-mitted to the booster injection point. HEPS low energy transport line has three functional sections, the achromat injection matching section, the optics matching section and the output matching section. In order to correct the error effects on the beam, 8 BPM are set in the low energy transport line. There are also 6 horizontal correctors and 6vertical correctors for beam trajectory correction. This paper will show the detailed design of HEPS low energy transport line., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The High Energy Photon Source (HEPS) is an ul-tralow-emittance, kilometer-scale storage ring light source to be built in China. In this paper we will introduce the progress of the physics design and related studies of HEPS over the past year, covering issues in storage ring lattice design, injection and injector design, insertion device effects, error study and lattice calibration, collective effects, etc., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

A "charge recovery in booster" scheme* was proposed to deliver the full charge bunches for the swap-out injection of the High Energy Photon Source. In this scheme, the booster is employed also as a full energy accumulator ring to capture the high charge bunch extracted from the storage ring via merging with the small charge bunch accelerated in the booster, after enough damping in the booster for about 20 ms, the recovered full charge bunch is re-injected into the storage ring. This scheme avoids the challenges to accelerate a bunch charge of ~ 15 nC, and is cost effective compared to building a dedicated 6 GeV accumulator ring. However, there will be a period of time during injection that one bunch is missing in the storage ring, which inevitably introduces some injection transients. Since "transparency" to the user experiments is a desired feature of injection schemes for next generation diffraction-limited storage rings, the injection transient effects are simulated for the proposed injection scheme, and how it would affect the user experiments are carefully evaluated., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The High Energy Photon Source (HEPS) is a 6-GeV, ul-tralow-emittance storage ring light source to be built in Huairou District, Beijing, China. The beam energy ramps from 500 MeV to 6 GeV in 400 ms, during which the RF voltage increases accordingly to keep the momentum acceptance large enough. The booster is designed to operate at 1 Hz repetition frequency. In this paper the energy ramping curve, RF choice, beam parameters changing curves and eddy current effect in HEPS booster will be presented., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

High vacuum has always been mandatory in particle accelerators. This is especially true for circular machines, where the beam makes thousands or millions turns, and beam lifetime is heavily affected by the residual gas scattering. At the beginning of storage ring operation the lifetime was very short mostly dominated by residual gas scattering. The residual gas lifetime is comprised of the elastic and inelastic scattering on electrons and elastic and inelastic scattering on nuclei. One usually calculates only the elastic scattering on nuclei (single Coulomb scattering) and inelastic scattering on nuclei (bremsstrahlung) of the residual gas scattering lifetime component. The analytic calculation the residual gas scattering lifetime and simulations of the beam interaction with the residual gas with code will be shown in this presentation, Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia