Measurements of Gain Larger than105at12μmin a Self-Amplified Spontaneous-Emission Free-Electron Laser

Abstract

We report measurements of very large output intensities corresponding to a gain larger than ${10}^5$ for a single pass free-electron laser operating in the self-amplified spontaneous emission (SASE) mode at $12\mu \mathrm{m}$. We also report the observation and analysis of intensity fluctuations of the SASE radiation intensity in the high-gain regime. The results are compared with theoretical predictions and simulations.