Thermal analysis and water-cooling design of the CSNS MEBT 324 MHz buncher cavity

At least two bunchers are needed in the 3 MeV H~- Medium Energy Beam Transport (MEBT) line located between RFQ and DTL for the CSNS (China Spallation Neutron Source).A nose-cone geometry has been adopted as the type of buncher cavity for its simplicity,higher impedance and lower risk of multipacting. By making use of the results got from the simulations on the buncher with two-dimension code SUPERFISH, the thermal and structural analyses have been carried out,the process and results to determine the resulting frequency shift due to thermal and structural distortion of the cavity are presented,the water-cooling channel position and the optimum cooling water temperature as well as the tuning method by adjusting the cooling water temperature when the cavity is out of resonance are also determined through the analyses.