Thermal performance analysis and cryogenic experiment of the 650 MHz cavity prototype cryomodule for the circular electron-positron collider

•The 650 MHz cavity prototype cryomodule has been designed, constructed and commissioned.•The thermal performances analysis based on the thermo-electrical analogy are performed.•The theoretical calculations and experimental measurements were compared.•The thermal calculation model of the gas-cooling coupler is developed and verified by experiments in the SHCS. The 650 MHz RF system with 240 cavities will be adopted for the collider ring of the Circular Electron-Positron Collider (CEPC). The prototype test cryomodule (TCM) has been designed, constructed and commissioned at IHEP since the beginning of 2017. The thermal performances of the cryomodule are analyzed based on the thermo-electrical analogy, and the experimental investigations of the cryomodule are performed in the superfluid helium cryogenic system, meanwhile, the theoretical calculations and experimental measurements are compared. The results are shown that the calculation of the gas-cooling power coupler are in good agreement with experimental measurements, which indicates that thermal calculation models are more accurate, moreover, the deviations of static heat load of the cryomodule at 2 K temperature level between the theoretical calculations and experimental measurements are analyzed in the paper.