Radiation and Radiation Reaction in Continuous Focusing Channels*

We show that the radiation damping rate of the transverse action of a particle in a straight, continuous focusing system is independent of the particle energy, and that no quantum excitation is induced. This absolute damping effect leads to the existence of a transverse ground state which the particle inevitably decays to, and yields the minimum beam emittance that one can ever attain, YE,;, = h/2mc, limited only by the uncertainty principle. Due to adiabatic invariance, the particle can be accelerated along the focusing channel in its ground state without any radiation energy loss. These findings may apply to bent systems provided that the focusing field dominates over the bending field. Presented at the 6th Workshop on Advanced Accelerator Concepts, Lake Geneva, WI, June 12-l&1994. Work supported by Department of Energy contract DE-AC03-76SF00515.