Evaluation of Synchrotron Damping Time with Storage Ring Free Electron Lasers

Abstract

We measured the bunch length of an electron beam in the macropulse mode of a storage ring free electron laser (SRFEL) with the compact storage ring NIJI-IV. The energy spread was evaluated from measured data of the bunch length. The synchrotron damping time of the electron bunch was evaluated by applying the evolution of the energy spread to an expression based on the one-dimensional theory of bunch heating. The synchrotron damping time evaluated at five electron-beam currents was in accord with that calculated by computer simulation. This finding suggests that the synchrotron damping time can be measured by the new evaluation method in the SRFEL macropulse mode. It was clarified that the synchrotron damping time measured in a Q-switching operation is shorter than that measured in the macropulse mode. This difference would suggest that the peak intensity of the SRFEL micropulse affects the synchrotron damping time.