First lasing, capabilities, and flexibility of FIREFLY

Abstract FIREFLY is a free electron laser (FEL) designed to produce picosecond pulses of intense light between 10 and 100 μm. It uses an inexpensive electromagnetic wiggler and variable outcoupling to provide maximum flexibility for user experiments. FIREFLY first lased on November 23, 1994, and has now operated successfully from 15 to 65 μm. It has lased in both a traditional undulator configuration and as an optical klystron, and has also operated in the undulator configuration on the third harmonic. During initial tests FIREFLY reached theoretical extraction efficiency for fundamental, third harmonic, and optical klystron operation, and demonstrated wavelength switching between adjacent peaks in the gain spectrum of an optical klystron for the first time.