High-energy ultra-small-angle X-ray scattering instrument at the Advanced Photon Source

This paper reports recent tests performed on the Bonse–Hart-type ultra-small-angle X-ray scattering (USAXS) instrument at the Advanced Photon Source with higher-order reflection optics – Si(440) instead of Si(220) – and with X-ray energies greater than 20 keV. The results obtained demonstrate the feasibility of high-energy operation with narrower crystal reflectivity curves, which provides access to a scattering q range from ∼2 × 10⁻⁵ to 1.8 Å⁻¹ and up to 12 decades in the associated sample-dependent scattering intensity range. The corresponding size range of the scattering features spans about five decades – from less than 10 Å to ∼15 µm. These tests have indicated that mechanical upgrades are required to ensure the alignment capability and operational stability of this instrument for general user operations because of the tighter angular-resolution constraints of the higher-order crystal optics.