Signal Processors

The operation of a longitudinal multi-bunch damping sys-tem using digital signal processing techniques is shown via measurements from the LBL Advanced Light Source. The feedback system (developed for use by PEP-II, ALS and DANE) uses a parallel array of signal processors to im-plement a bunch by bunch feedback system for sampling rates up to 500 MHz. The programmable DSP system al-lows feedback control as well as accelerator diagnostics. A diagnostic technique is illustrated which uses the DSP sys-tem to excite and then damp the beam. The resulting 12 ms time domain transient is Fourier analyzed to provide the si-multaneous measurement of growth rates and damping rates of all unstable coupled-bunch beam modes. 1 SYSTEM DESCRIPTION Figure 1 presents a block diagram of the processing system developed for use at the SLAC PEP-II accelerator.[1