Fabrication and evaluation of Si beam splitter used in autocorrelator for hard x-ray free electron laser

Abstract

XFEL (X-ray Free Electron Laser) sources provide ultrashort radiation pulses with unprecedented peak brilliance and high transverse coherence. Great efforts are expected to apply such sources for the investigation of fundamental questions about ultrafast dynamical processes in biological, chemical and physical systems. An autocorrelator has used to provide jitter-free replica pulses for x-ray pump / x-ray probe experiments. We have fabricated a single crystalline Si beam splitter used in an autocorrelator with PCVM (Plasma Chemical Vaporization Machining) which can remove lattice strain and fabricate with high removal rate. As the result of evaluation of the beam splitter using multiple crystal arrangements at SPring-8 BL29XUL, it was found that the Si beam splitter whose thickness was less than 20 μm hardly has lattice strain.