3 GHz Single Cell Cavity Optimization Design

Abstract : In order to develop a high gradient S-band accelerating structure, an optimized travelling wave (TW) single-cell cavity operating at the frequency of 2998.55 MHz at 30 C with 2pi/3 phase advance, is proposed. Starting from the well-known accelerating cells design developed by LAL and SLAC for linear accelerators; it is possible to improve the main RF parameters, such as quality factor, shunt impedance and group velocity, by choosing a suitable shape of the inner surface. Despite the surface electric field being considered as the only main quantity limiting the accelerating gradient; the importance of power flow has resulted from high-gradient experimental data. In this context, the modified Poynting vector quantity can be considered as a new RF breakdown constraint depending on an iris shape. RF simulations have been carried out with HFSS and CST MWS. Simulations results have shown an optimal RF characteristics.