I. Introduction
The China Accelerator Driven Subcritical System (China-ADS) project, as an ADS demonstration facility, has been proposed and launched. Injector II as one of the parallel injectors of China-ADS is prompted by the Institute of Modern Physics (IMP). In the superconducting section of the injector II, superconducting focusing solenoids and SRF (Superconducting Radiofrequency) cavities are installed in a cryomodule [1].