Controllable X-Ray Pulse Trains from Enhanced Self-Amplified Spontaneous Emission
Joseph Duris, James MacArthur, James M. Glownia, Siqi Li, Sharon Vetter, Alan Miahnahri, Ryan Coffee, Ph. Hering, Alan Fry, Marc Welch, Alberto Lutman, Franz-Josef Decker, Dorian Bohler, J. Mock, Chengcheng Xu, Karl Gumerlock, Justin May, Antonio Cedillos, Eugene Kraft, Manuel Carrasco, Brian E. Smith, Logan R. Chieffo, Joseph Xu, James Cryan, Zhirong Huang, A. Zholents, Agostino Marinelli
Abstract
We report the demonstration of optical compression of an electron beam and the production of controllable trains of femtosecond, soft x-ray pulses with the Linac Coherent Light Source (LCLS) free-electron laser (FEL). This is achieved by enhanced self-amplified spontaneous emission with a 2 μm laser and a dechirper device. Optical compression was achieved by modulating the energy of an electron beam with the laser and then compressing with a chicane, resulting in high current spikes on the beam which we observe to lase. A dechirper was then used to selectively control the lasing region of the electron beam. Field autocorrelation measurements indicate a train of pulses, and we find that the number of pulses within the train can be controlled (from 1 to 5 pulses) by varying the dechirper position and undulator taper. These results are a step toward attosecond spectroscopy with x-ray FELs as well as future FEL schemes relying on optical compression of an electron beam.