The transverse damper system for RHIC

If the beam is injected with a given error with respect to the closed orbit or disturbed by transverse instabilities, it will execute coherent oscillations and will be diluted in betatron phase space within a time interval of about 1/ Delta nu turns (where Delta nu is the tunespread in the beam), even if it is properly matched to the focusing characteristics of the lattice, unless there is an effective damper system to prevent this. For a given damper system the authors consider two modes of operation: (i) the kicker voltage is proportional to the beam position signal, and (ii) the kicker voltage is adjusted to a constant value having a sign which depends on the sign of the signal detected from the beam position. It is shown that the rise and fall times of the damper system should be short enough to allow individual damping of coherent motion of up to 3*57 bunches.<>