Experimental Study and Simulation of the Damage Induced to Various Multilayer Interferential Mirrors by Soft X-Ray Plasma-Laser Sources

The damage induced to various multilayer interferential mirrors (MIMs) by intense soft X-ray plasma-laser sources are studied both experimentally and theoretically. The mirrors consist of periodic bilayers made up with C/W, Si/Mo, Si/W\. One set of Si/W MIMs is coated with a 100 nm Si film devised to protect the multilayer structure. In the experiment, one resolves in time the evolution of the diffraction pattern of a MIM illuminated by the radiation of a NaCl probing laser-plasma and exposed to the heating radiation emitted by a gold laser-plasma. One measures the damage threshold time and the damage threshold fluence. Simulations are performed by combining an optical code with a Lagrangian thermomechanical code giving at each time the density and the thickness of each layer in the MIM.