A Systematic Study of a Transverse Feedback System with a Two-tap Fir Filter

Performance of a transverse feedback system with a simple 2-tap FIR filter was experimentally studied in TRISTAN AR. The 2-tap FIR filter eliminates DC components and change the amount of necessary phase shift by the tapposition. An ADC, a 2-tap FIR filter logic and a DAC are packaged in a single-width CAMAC module, which is also equipped with large-size memory, where the bunch oscillations over thousands of turns are recorded. In the experiments, we kicked the beam transversely to create a large amplitude oscillation and then turn on the feedback system to damp this oscillation. By analysing the data stored in the memory we investigated the relation between the tapposition and the damping rate, with various tap-positions for a given tune and with various tunes for a given tapposition. The results agreed with a calculation.