The development of new automatic bunch current sensitive fast attenuator for RF front-end of bunch-by-bunch feedback system at SPring-8

We are currently developing a new bunch current sensitive automatic attenuation system for the RF front-end of the bunch-by-bunch feedback system in the SPring-8 storage ring. It controls the attenuation of the signal from high current bunch to avoid the saturation of RF front-end and for equalization of the feedback gain of hybrid beam filling modes consist of few-mA singlet bunches and sub-mA bunch trains. To achieve more attenuation level and more flexible operation, we are now developing a new attenuation system with a voltage variable and a digital controlled attenuator devices combined a modified DC-outputs of Bunch-by-Bunch Feedback Signal processor. This paper describes the new attenuation system and its test results under developing. (author)