Digital Signal Processing for the APS Transverse and Longitudinal Damping System

The Advanced Photon Source (APS) at Argonne National Laboratory will be a 7-GeV machine. It is anticipated that for beam operations beyond the baseline design of 100 mA stored beam current, a transverse and longitudinal damping system is needed to damp instabilities. A key part of this digital damping system is digital signal processing. This digital system will be used to process samples taken from the beam and determine appropriate correction values to be applied to the beam. The processing will take the form of a transversal digital filter with adaptable filter weights. Sampling will be done at 176 MHz with a possible correction bandwidth of 88 MHz. This paper concentrates on the digital processing involved in this system, and especially on the adaptive algorithms used for determining the digital filter weights. I. INTRODUCTION If there are no interactions between circulating bunches of a synchrotron, the motion of each bunch can be described by three harmonic oscillators corresp..