MODIFIED FEEDFORWARD CONTROL-SYSTEM AT THE ACCELERATOR-TEST-FACILITY

A modified feed-forward control system has been operated at the Brookh aven Accelerator Test Facility to control the phase and amplitude of t wo high power klystron rf systems used to power a photocathode rf gun and a traveling wave electron linac. The changes to the control algori thm include an improved handling of cross coupling between the amplitu de and the phase channels, an improved calibration routine that allows for changes in the matrix elements due to the variable base-line and improved filtering. The modifications to the software include modulari ty, portability; and user-friendliness. Improvements to the hardware i nclude a linearized phase and amplitude controller with de biasing for an improved dynamic range. The feed-forward system can handle nonline ar and noninstantaneous systems. With simultaneous regulation of two c hannels, the phase and the amplitude fluctuations over a time span of more than 3 mu S were reduced to less than +/- 0.2 degrees and +/- 0.2 %, from the initial +/- 2.7 degrees and +/- 1.8%, respectively. (C) 19 97 American Institute of Physics.