Stimulatd Radiation Spectra in Raman Regime

Raman regime free electron laser experiments for the wiggler pitches of 2cm and 3cm, were carried out. The radiation output pulse has a peak at the flat portion of the diode voltage pulse which is in the decreasing phase of the voltage. The beam energy and the time duration of the flat portion are 0.44 Me V and about lons, respectively. It is considered in the present experiments that the beam energy spread less than a few percent necessary for Raman regime operation, is attained at the flat portion. As a result, with wiggler field of 461 G and 2 cm pitch and axial guiding field of 13.7kG, it is observed that the total output power is 120 kW and the stimulated radiation spectrum has a maximum peak at 63 GHz. From the spectral spread and the width of frequency resolved radiation waveform, the beam energy spread Δγ11 γ11 is estimated as 3.8 %.