  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.
