THE FREE-ELECTRON-LASER USER FACILITY FELIX

The Free Electron Laser for Infrared eXperiments FELIX presents to its users a versatile source of radiation in the infrared and far-infrare d spectral regions. Presently, the wavelength range of operation exten ds from 5 to 110 mu m (2000-90 cm(-1)). The wavelength is continuously tunable over an octave in a few minutes. The output normally consists of macropulses of 5-10 mu s duration, formed by a train of micropulse s of a few ps length. Average power in the macropulses is of order 10 kW, peak power in the micropulses is in the MW range. The temporal and spectral characteristics of the micropulses can be controlled by vary ing the synchronism between the electron pulses and the optical pulses circulating in the laser cavity. Transform-limited pulse lengths in t he rage 2-20 ps can be generated. Long-range coherence has been induce d by phase-locking successive micropulses, and narrow-band, essentiall y single-mode, radiation has been selected from the output.