Control of Multibunch Longitudinal Instabilities and Beam Diagnostics Using a DSP-Based Feedback System

A bunch-by-bunch longitudinal feedback system has been designed and built o control coupled-bunch instabilities in the PEP-I1 machine. A prototype system has been installed at the Advanced Light Source at LBNL. Programmable DSPs allow longitudinal feedback processing in conjunc-tion with data acquisition or instrumentation algorithms. Here we describe techniques developed for different beam and system diagnostics, such as measurements of the modal growth and damping rates and measurements of the bunch-by-bunch currents. Results from the Advanced Light Source are presented to illustrate these techniques. 1 SYSTEM OVERVIEW The multibunch longitudinal feedback system for use by PEP-11, ALS, and DAQNE is designed using a modula