USAXS/SAXS/WAXS INSTRUMENT FOR MATERIALS RESEARCH

J. Ilavský¹, A. J. Allen², F. Zhang², G. G. Long², P. R. Jemian¹, L. E. Levine²

¹Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA

²National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
ilavsky@aps.anl.gov

Practical engineering materials typically exhibit complex microstructures spanning many decades in size. These are often responsible for the in-service properties. Advances and developments for new or improved materials require a detailed understanding of these microstructures over their entire operative size range. Complete characterization over the size range is usually complicated by the need to combine multiple techniques such as SAXS, SANS, electron or optical microscopy, tomography, etc. In this context, the Bonse-Hart type USAXS instrument at APS [Ilavsky et al., 2009] with its wide range of length scales characterized during one measurement was already a unique tool for the quantitative, statistically representative, characterization of material microstructures relevant to a wide range of scientific applications. To address the needs of the user community, we have recently upgraded the USAXS instrument through increases in the measurable ranges of both scattering vector (q) and scattering intensity [Ilavsky et al., 2013]. At large q values, the combination with He-filled pinhole SAXS (pinSAXS) and in-air WAXS cameras improves the data quality by increasing sampling statistics and signal-to-noise sensitivity. More importantly, it extends the contiguous scattering vector q range coverage up to 6 Å^-1 (energy dependent). The need for environmental chambers to simulate in-operando measurements requires higher energy X-rays that minimize window absorption and reduce the exit angles. To reach X-ray energies between 20 keV and 30 keV, the USAXS instrument uses higher order Si(440) instead of Si(220) optics. The narrower Si(440) rocking curves also reduce qmin to ≈ 3 x10^-5 A^-1. Currently, the combined USAXS/SAXS/WAXS instrument at the ChemMatCARS facility at APS, comprising USAXS with Si(440) crystals, pinSAXS, and WAXS, can span about five decades in q, characterizing structures from ≈ 30 micrometers down to ≈ 1 Angstrom during one measurement of typically less than 8 minutes. The talk will present the technical design and capabilities of this instrument, as well as scientific examples taking advantage of this unique instrumentation.

ChemMatCARS Sector 15 is principally supported by the National Science Foundation/Department of Energy under grant number NSF/CHE-0822838. Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Ilavsky, J., Jemian, P.R., Allen, A.J., Zhang, F., Levine, L.E. and Long, G.G. Journal of Applied Crystallography, 42, 2009, 469-479.

Ilavsky, J., Zhang, F., Allen, A.J., Levine, L.E. Jemian, P.R., and Long, G.G. Metallurgical and Materials Transactions A, Metallurgical and Materials Transactions A, 44, 2013,68-76.