EXPERIMENTS OF RAMAN FREE ELECTRON LASER WITHOUT AXIAL GUIDING MAGNETIC FIELD

An electron beam, generated by the concave focusing cathode of EAP-74 pulseline accelerator, is injected into the bifilar helical wiggler with a matching thin solenoidal lens. The wiggler length L_w= 1.5m, with period λ_w = 3.45cm. 130A electron beam are obtained at the end of the wiggler exit under the wiggler magnitude of 1.25kG.The growth rate of 130dB/m is obtained by measuring the output power as a function of the wiggler interaction length. Saturation phenomenon and saturation power of 7.6 MW are observed and measured also at L_w≥ 0.9m, and an efficiency of 5% has been achieved. Spectral diagnosing of 35-38 GHz is performed with a waveguied dispersive line. The tolal output energy of 41-48mJ is measured with the calorimeter. The waveguide mode in the interaction region is TE₁₁ Mode.