  We report the development and implementation of an energy feedback system for
the MIT/Bates Linear Accelerator Center. General requirements of the system are
described, as are the specific requirements, features, and components of the
system unique to its implementation at the Bates Laboratory. We demonstrate
that with the system in operation, energy fluctuations correlated with the 60
Hz line voltage and with drifts of thermal origin are reduced by an order of
magnitude.
