Study on the UV FEL single-shot damage threshold of an Au thin film
What is it about?
We evaluate the damage threshold of an Au coated flat mirror, which is one of the reflective optics installed on FEL-1 beamline of Dalian Coherent Light Source (DCLS), upon far UV free electron laser (FEL) irradiation. The surface of the coating is characterized by profilometer and optical microscope. We present also theoretical approach of the phenomenon by applying conventional single-pulse damage threshold calculation, one-dimensional thermal diffusion model as well as finite element analysis with ANSYS to the case.
Why is it important?
In this paper, we presented the result from an experiment performed at Dalian Coherent Light source, a FEL facility operating in UV wavelength range. We took an Au-coated mirror and bombarded its surface with UV FEL (121.6nm) in normal incidence geometry. As the repetition rate was merely 20Hz, such experiment was considered for single shot. Trend of the damage crater evolving with different pulse energy and time of irradiation (or number of pulses) was presented, together with different theroretical apporaches that shown mismatch. Such mismatch was later discussed and explained by the experimental conditions. The result can be good reference for the community and is worthy of some attention.