X-ray parametric scattering by a diamond crystal.

Spontaneous X-ray parametric scattering from a diamond single crystal has been observed at the Photon Factory. The high perfection of the diamond single crystal and the small angular divergence of synchrotron radiation has enabled down-converted X-ray photon pairs to scatter into two small solid angles which satisfy the phase-matching condition. High-efficiency noise reduction was performed using avalanche photodiode detectors with good time resolution.