Present status of C-band accelerating section development for SuperKEKB

This paper reports on recent R and D status of C-band accelerating section for future upgrade of the KEKB. Four 1-m long accelerating sections have been developed and installed in the KEKB injector linac as two pairs of two sections connected in series. They are driven by a 50-MW klystron through an rf pulse compressor. This C-band accelerator module has been operated for ten months since the summer of 2005. A beam acceleration study shows the module generates an average field gradient of 36.5 MV/m at 42 MW of klystron output power. Also given is a description of recently developed fifth accelerating section which replaces one of the sections in the module. (author)