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The 166.6 MHz radio frequency (RF) system with five superconducting HOM damped cavities is adopted to accelerate the 200 mA electron beam in the storage ring of the High Energy Photon Source (HEPS). The 166.6 MHz cavity cryomodules have been designed, constructed and horizontal tested at IHEP since the beginning of 2019. The thermal performances of the cryomodule are analyzed by numerical simulations which take into account the main contributors to the static heat loads at various temperature levels. The experiment investigations including the cool down, operating with RF power and static heat load measurements of the cryomodule are performed in the liquid helium cryogenic system. The calculated static heat loads have been compared with the experimental measurements, and the results show that deviations between the calculated heat loads and available experimental measurements at 4.2 K temperature level are within a small range, which indicates that thermal simulations are accurate. The detailed operating parameters in the cryogenic environment are reported. [ABSTRACT FROM AUTHOR]

• The 325 MHz spoke cavity cryomodules have been designed, fabricated and commissioned. • The bottom-supported cryomodules have been put into operation. • The thermal performances analysis and experimental measurements were compared. • The cryomodules are in a stable operation at 2 K and 31 mbar with beam commissioning. • The accelerating cryomodules successfully reached to 10 MeV in pulse and CW mode. The Chinese Accelerator Driven Sub-critical system (C-ADS) is an important strategic research that is based on a high energy proton beam for nuclear waste transmutation. To meet the requirements of stability and reliability of the lower energy part, two identical Injectors are operated in parallel. The Injector-I is designed and constructed by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) in Beijing, China. The Injector-I linac with two accelerating cryomodules (named CM1 and CM2) successfully accelerated the proton beam to 10.67 MeV with the beam current of 10.11 mA in pulse mode and 10.0 MeV with a beam current of 1.6 mA in CW (continuous wave) mode. The cryomodules have been designed, fabricated, assembled and commissioned at IHEP since the beginning of 2012. The thermal performances of the cryomodules were analyzed with numerical simulations and the empirical calculations take into account all the main contributors (support posts, multilayer insulation, current leads, power couplers and cavities) to the static and dynamic heat loads at various temperature levels. Two designs of current leads are developed and analyzed, and the case 2 current leads are tested and used in the CM2. The estimated static heat loads by analysis have been compared with the available experimental measurements. The operation experiences including the cool down, operating parameters and heat load measurements are reported, and the results were shown that the cryomodules can keep in a stable operation at 2 K and 30 mbar ±10 Pa. [ABSTRACT FROM AUTHOR]