Effects of radiation damping on beam quality in the inverse free-electron laser accelerator

The effect of synchrotron radiation damping on the transverse beam emittance for an inverse free-electron laser (IFEL) accelerator is studied. A beam envelope equation is derived and solved for an arbitrarily wiggler field. The expression for the evolution of the normalized transverse beam emittance is derived and found to decrease exponentially with distance, due to radiation damping, until it is limited by quantum excitation. Our results show that for acceleration distances comparable to the radiation damping e-folding length, substantial improvements in the beam quality can be realized. (author)