Radiation Damping and Quantum Excitation in a Focusing-dominated Storage Ring

In this paper we calculate the eeects of a linearly varying focusing eld on radiation damping and quantum excitation to the transverse emittances in an electron storage ring by using a quantum mechanical perturbation approach. This method allows for arbitrarily strong focusing environment and correctly predicts the limits of both pure bending and pure focusing. We nd that transverse excitation can be exponentially suppressed by the focusing eld when the radiation formation length is comparable to the transverse oscillation wavelengths. Applications to the design of a focusing-dominated damping ring is also explored.