BL35XU is a high resolution inelastic scattering beamline for measuring atomic dynamics of materials using X-rays. Typical beam size for inelastic X-ray scattering experiments at BL35XU is 60 to 100 µm diameter using a bent-cylindrical mirror. BL35XU sometimes operates with a smaller beam for measurements of small samples such as samples installed in diamond anvil cells. KB mirrors have been used for such experiments since 2007. However, since ~2012, the time required for KB installation has increased, sometimes to as much as 2 days. In order to reduce the time for installation of the KB mirrors and clarify the problems during the installation, we investigated and resolved the problems related to installation of the KB mirrors.
The purpose at this beamtime was to observe coherent resonant second harmonic generation (SHG) in Gallium Arsenide (GaAs) around the Ga K-edge. The experiment followed a previous measurement of SHG far above resonances in diamond preformed at the SACLA x-ray free electron laser [1]. However, as opposed to the case of far above resonance SHG, the description of resonant SHG requires a full quantum model. We did not measure nonlinear second harmonic generation in GaAs during that beamtime. We could only estimate an upper limit for the magnitude of the effect.