Operating Performance of the Lowgroup Delaywoofer Channel in PEP-II

In PEP-II collider a dedicated low group-delay processing channel has been developed in order to provide high damping rates necessary to control the fast-growing longitudinal eigenmodes driven by the fundamental impedances of the RF cavities. A description of the digital processing channel operating at 9.81 MHz and capable of supporting finite impulse response (FIR) controllers with up to 32 taps will be presented. A prototype system has been successfully commissioned in the High-Energy Ring (HER) in May 2004. Operating experiences with the prototype and the newly determined limits on achievable longitudinal damping will be discussed and illustrated with experimental data.