Experimental study on a Raman free-electron-laser of 3mm wavelength

A novel small-period wiggler was developed and reported here, and based on it, a Raman free-electron-laser of 3mm in wavelength was successfully tested by using a bifilar helical wigger of 1cm in period to reduce the wavelength of the free-electron-laser from 8mm to 3mm but still with the same beam energy. The measured radiation power is of 1MW with efficiency of 0.55%.