Multiple Pulse Thermal Damage Thresholds Of Materials For X-ray Free Electron Laser Optics Investigated With An Ultraviolet Laser

摘要

Optical elements to be used for x-ray free electron lasers (XFELs) must withstand multiple high-fluence pulses. We have used an ultraviolet laser to study the damage of two candidate materials, crystalline Si and B_4C-coated Si, emulating the temperature profile expected to occur in optics exposed to XFEL pulses. We found that the damage threshold for 10~5 pulses is ～20% to 70% lower than the melting threshold.