FIRST LASING OF THE COMPACT INFRARED FREE-ELECTRON LASER

On 15 May 1996, lasing was achieved at the Compact Infrared Free-Elect ron Laser (CIRFEL) at 14 mu m. The electron beam energy was 11.2 MeV a nd the micropulse charge was 1 nC. The width of the detuning curve was approximately 50 mu m. Since achieving this milestone, we have lased repeatedly from 12.5 to 20 mu m with between 0.25 and 1.5 nC of charge . Saturation is typically reached in less than 1.5 mu s. The measured FEL spectrum is Gaussian in shape with a line width of 56 nm at 13 mu m. Assuming a transform limited pulse, this corresponds to an FEL ligh t pulse of 4.4 ps. The CIRFEL is a photocathode based free-electron la ser with a micropulse width of 4-10 ps and a micropulse separation of 7 ns. The macropulse length is between 4 and 6 mu s and the repetition rate is between 1 and 5 Hz. We present details of the CIRFEL machine as well as experimental measurements of the FEL radiation.