Fast Digital Feedback System for Energy and Beam Position Stabilization

A digital fast feedback system for beam energy and position stabilization at the target of the CEBAF accelerator is capable of suppressing beam motion in the frequency band from 0 to 80 Hz and also performs narrow band suppression at the first twelve power line harmonics. The system utilizes two VME computers and runs at a 2.4 kHz sampling rate. The numerical algorithm is based on a recursive digital filter with an additional feedforward loop for suppression of high power line harmonics. The system suppresses beam motion by a factor greater than ten, thus achieving the stabilization of relative beam energy fluctuations to better than 10 and stabilization of beam position on the target to better than 20 μm.