Measurement of characteristics of the infrared free electron laser with the L-band linear accelerator at Osaka University

Characteristics of the free electron laser based on the L-band electron linear accelerator at Osaka University have been studied by measuring the output light with a fast infrared detector. The time resolution of the detector has been measured to be 170 ns with the self-amplified spontaneous emission from the single-bunch electron beam. The time spectrum of the output light from the free electron laser operated at a wavelength of 40 mu m and the output power of 800 mu J/macropulse has been measured with the detector, and the gain of the free electron laser and the loss of the optical cavity in the round trip are derived to be 58 and 6%, respectively. The calculated gain based on a two-dimensional model agrees fairly well with the measured value.