Input Coupler For The Kekb Normal Conducting Cavity

INTRODUCTION The reliability of the input coupler is usually the critical technical issue for the development of the cavity system. At present stage the cavity for KEK B-factory requires about 400KW (CW) RF-power per cavity (the RF frequency is 508.8 MHz) [1]. In order to keep the stable operation at 400 kW, the coupler should be able to transmit RF-power significantly higher than 400 kW. Thus we have set the target value of the transmitted RF power on 800 kW (CW) that is twice as high as the required power. Since the reliability of the coupler strongly depends on that of the ceramic window in the coupler, we recognize that the choice of the window structure is most important for the design of the coupler. In order to transmit the 800 kW RF power we have chosen a disk-type ceramic for the coupler window. The rational for this choice is described in the next section. Other mechanical structures of the coupler are decided by boundary conditions of the coupler: (1) RF power i