Low power commissioning of an innovative laser beam circulator for inverse Compton scattering γ-ray source

We report on the optical commissioning of the high power laser beam circulator for the high brightness Compton γ-ray source Extreme Light Infrastructure for Nuclear Physics. Tests aiming at demonstrating the optical performances of the laser beam circulator have been realized with a low-power pulsed laser-beam system and without electron beam. We show that, with the developed alignment and synchronization methods coming from the laser beam circulator design study presented in the Dupraz et al. paper [Phys. Rev. Accel. Beams 17, 033501 (2014)], the laser beam circulator enhances the laser-beam power available at the interaction point by a factor in excess of 25. This corresponds to a potential of bringing the average laser-beam power in excess of 1 kW when the laser beam circulator is injected with the interaction point laser-beam pulse energy of 400 mJ at 100 Hz.