Measured performance of the free electron lasers and electron beam in the compact storage ring NIJI-IV

The temporal performance of the free electron lasers and the electron-beam qualities have been measured with the compact storage ring NIJI-IV at the electron-beam energy of 310 MeV. It was found that the pulse width and spectral width kept decreasing after the peak of the FEL macropulse intensity. It was confirmed that the bunch length and the energy spread increased due to the FEL oscillations. The ratio of the FEL gain to the cavity loss estimated from the beam qualities on and off FEL oscillations was almost in accord with the ratio evaluated directly with the measured data of the FEL gain and the cavity loss.