A semi - clmsical treatment of channeling radiation reaction *

A semi-classical formafism is used to calculate the radiation reaction of a relativistic particle in a straight, continuous focusing system. Due to the absence of quantum excitation in such a focusing system, the radiation damping rate of the transverse action obtained using this formafism agrees exactly with the result from the classical Lorentz-Dirac radiation reaction equation. In the fimit where the pitch angle of the particle is much smder than the radiation opening angle, the transverse action damps exponentially with an energy-independent rate that is much faster than the energy decay rate. In the opposite Mmit, both the transverse action and the energy damp with power laws and their relative rates are comparable. The general time-dependence of the transverse action damping and the energy decay are obtained analytica~y from these rate equations.