Multi- Physics analysis of the RFQ for the Injector Scheme II of CADS Driver Linac

A 162.5 MHz, 2.1 MeV Radio Frequency Quadruples (RFQ) structure is being designed for the Injector Scheme II of China Accelerator Driver System (CADS) driver linac. The RFQ will operate at continuous wave (CW) mode as required. For the CW normal conducting machine, the heat management will be one of the most important issues, since the temperature fluctuation may cause cavity deformation and leading to the resonant frequency shift. Therefor a detailed multi-physics analysis is necessary to ensure that the cavity can be stably worked at the required power level. The multi-physics analysis process includes RF Electromagnetic analysis, Thermal analysis, Mechnical analysis, and this process will be iterated for several cycles until the satisfied solution can be found. As one of the widely accepted measures, the cooling water system is used for frequency fine tunning, so the tunning capability of the cooling water system is also studied at different conditions. The results indicate that with the cooling water system, both the temperature rise and the frequency shift can be controlled in an acceptable level.