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The CEPC has two rings, the booster ring and the collider ring. There are 432 superconducting cavities in total. In the booster ring, there are 96 ILC type 1.3 GHz 9-cell superconducting cavities; eight of them will be packaged in one 12-m-long module. There are 12 such modules. In the collider ring, there are 240 650 MHz 2-cell cavities; six of them will be packaged in one 11-m-long module. There are 40 of them. All the cavities will be cooled in a liquid-helium bath at a temperature of 2K to achieve a good cavity quality factor. The cooling benefits from helium II thermo-physical properties of large effective thermal conductivity and heat capacity as well as low viscosity and is a technically safe and economically reasonable choice. The 2K cryostat will be protected against heat radiation by means of two thermal shields cooling with 5-8K helium as well as 40-80K helium from a refrigerator. There are 4 cryo-stations along the 100km circular collider with the physical design of double ring. Generally, each cryo-station is supplied from a common cryogenic plant, with one refrigerator and one distribution box. The cooling capacity of each refrigerator is 18kW @ 4.5K., Proceedings of the 62th ICFA ABDW on High Luminosity Circular e$^+$e$^-$ Colliders, eeFACT2018, Hong Kong, China

Platform of Advanced Photon Source Technology R (PAPS) in the Institute of High Energy Physics (IHEP) is an ongoing project, which aimed to provide a comprehensive research and testing platform for the particle accelerator, X-ray detection and optics. As one of the important parts of the platform, cryogenic vertical test stand for the superconducting cavities is composed of three big vertical test cryostats with 2 different inner diameters, which can provide 4.5K liquid helium, 2K superfluid helium and the lowest 1.5K environments according to the cavities test requirements. The cryogen-ic vertical test stands also focus on current international ¿hot spot¿ fast cool down to the superconducting cavi-ties, maximum liquid helium mass flow rate can be reached to 80g/s. Because of the big size of the cryostats and certain scale, the finished cryogenic vertical test stand can meet several different type cavities test, such as 1.3GHz 9cell, Spoke, elliptical, etc. And also can provide the cavities¿ mass vertical testing for the large scale superconducting accelerators., Proceedings of the 19th International Conference on RF Superconductivity, SRF2019, Dresden, Germany

The Chinese Accelerator Driven Sub-critical system (C-ADS) uses a high energy proton beam to bombard the metal target and generate neutrons to deal with the nuclear waste. The Chinese ADS proton linear has two 0~10 MeV injectors and one 10~1500 MeV superconducting linac. Injector-I is studied by the Institute of High Energy Physics (IHEP) under construction in the Beijing, China. The linear accelerator consists of two accelerating cryomodules operating at the temperature of 2 Kelvin. This paper describes the structure and thermal performances analysis of the cryomodule. The analysis takes into account all the main contributors (support posts, multilayer insulation, current leads, power couplers, and cavities) to the static and dynamic heat load at various cryogenic temperature levels. The thermal simulation analysis of the cryomodule is important theory foundation of optimization and commissioning., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

CEPC is a 100 km circular electron positron collider operating at 90-240 GeV center-of-mass energy of Z, W and Higgs bosons. CEPC and its successor SPPC, a 100 TeV center-of-mass super proton-proton collider, will ensure the elementary particle physics a vibrant field for decades to come. The conceptual design report (CDR) of CEPC will be completed in the end of 2017 as an important step to move the project forward. In this contribution, CEPC SRF system CDR design and challenges will be introduced, including the system layout and parameter choices, configuration at different operation energies, transient beam loading and its compensation, cavity fundamental mode (FM) and higher order mode (HOM) induced coupled bunch instabilities (CBI) and the beam feedback requirement, etc. The SRF technology R&D plan and progress as well as the SRF infrastructure and industrialization plan are discussed at last., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

The Circular Electron Positron Collider (CEPC) is a long-term collider project, which will serve as a Higgs Factory and offer a unique opportunity for direct searches for New Physics in the high-energy range far beyond LHC reach [1]. In the frame of this project, a large 2K cryogenic system will be built to provide coolant for superconducting cavities used in booster ring and collider ring. All the superconducting cavities will be working under 2K. This paper will give a brief introduction to the preliminary considerations of this large cryogenic system, including the general layout, heat load estimation, helium refrigerator, schematic flow diagram as well as the main parameters and working process, Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea