Ultra-Small-Angle, Small-Angle, and Wide-Angle (Diffraction) X-ray Scattering  

The USAXS/SAXS/WAXS facility offers world-unique capabilities to users in physics, chemistry, materials science, polymers, food science, biology, and many others unique capabilities: 

• >5 decades in sizes 
            6 micron to <1 Angstrom in standard resolution (higher sensitivity)
          20 micron to <1 Angstrom in high resolution (lower sensitivity)

• Intensity range of up to 12 decades

• ~2 minutes data collection time

This is achieved by combination of Bonse-Hart USAXS/SAXS scanning device, 500mm long pinhole SAXS, and 300mm long 2D detector based powder diffraction (WAXS) device. See example data below on this page.  Instrument is currently located in 12-ID-E station and operated by CMS group. Instrument scientist: Jan Ilavsky, 630-252-0866. 

Current instrument paper: Ilavsky, J., Zhang, F., et al. (2018). "Development of combined microstructure and structure characterization facility for in situ and operando studies at the Advanced Photon Source." Journal Of Applied Crystallography 51, 867-882. https://doi.org/10.1107/S160057671800643X

Access

1. General User (GU) program (~ 80% of beamtime, see "All about proposals here").  
2. Mail in program: We make available about 2-3 days of beamtime per cycle to users, who have smaller sets of samples (typically less than 20 samples). Typical use is exploratory research (before applying for beamtime) or when project requires only imited number of samples. No beamtime proposal is necessary and users cannot come for experiments to the APS. Samples will be handled by staff and reduced data will be sent back to users. For details see dedicated page.
3. Proprietary (industrial) research is available as part of GU program. Contact staff and APS users office, start here.
4. We also support SAXS-SANS collaboration mail-in program. Contact staff.

Considering applying for beamtime? Read following pages:  What is USAXS instrument , Data collection strategy, Data import to Igor, Igor data, and Sample plates setup. These pages will be helpful for understanding instrument specifics.  This device sensitivity is limited by Bonse-Hart crystal surface background and we cannot measure very weak signals, such as common in bioSAXS (proteins) or very dilute systems. We have modeling tool (link to Youtube) where we can calculate expected signal from your sample. If needed, TALK TO STAFF. 

Important APS user information page

Technical details :

Data are collected sequentially using one or more available instruments. Use of the USAXS instrument is required for access to this station; users who only need conventional SAXS/WAXS should apply to other APS beamlines dedicated to those techniques.

For USAXS measurements, the typical beam size is 1 × 1 mm, with an adjustable range down to 0.2 × 0.2 mm. Smaller beam sizes reduce flux and therefore require more strongly scattering samples or longer collection times.

For standard SAXS/WAXS measurements, the typical beam size is 0.8 × 0.2 mm and can also be reduced to 0.2 × 0.2 mm. As with USAXS, smaller beams generally require longer exposure times.

Typical combined USAXS/SAXS/WAXS data collection takes less than 2 minutes. Standard USAXS scans require 30–120 s (typically about 90 s), while high-resolution scans take 3–6 minutes. SAXS and WAXS exposures are much shorter, typically 1–5 s each, with common values of about 2 s for SAXS and 5 s for WAXS.

The instrument shares the 12-ID-E hutch with the 10 m SAXS instrument and is therefore scheduled for approximately 50% of APS allocated beamtime, or about 2250 hours per year.

Typical parameters:

Standard USAXS configuration (Si 220 crystals, slit smeared) - default

• Energy range ............    10 - 28 keV, typical 21keV
• Q range combined ....    8*10^-5 to 6 [A^-1]
• Q resolution USAXS ..   8*10^-5 [A^-1] in the USAXS range (up to ~0.1 [A^-1])
• Size range combined .    6 micron - 1 Angstrom
• Collection time comb..    <2 minutes
• Intensity range ...........   up to 12 decades (depends on sample), desmeared
• SAXS Q range ...........  ~ 0.03 to 1.3 [A^-1]
• WAXS Q range ..........  ~ 0.8   to  6 [A^-1]

High resolution USAXS configuration (Si 440 crystals, slit smeared) - on request 
(NOTE: this is low sensitivity setup, needs strongly scattering samples). 

• Energy .......................   20 and 24 keV
• Q range combined ....    3*10^-5 to 6 [A^-1]
• Q resolution USAXS...   3*10^-5 [A^-1] in the USAXS range (up to ~0.1 [A^-1])
• Size range combined .    20 micron - 1 Angstrom
• Collection time comb..    ~3 minutes
• Intensity range ...........    up to 12 decades (depends on sample), desmeared
• SAXS Q range ...........   ~ 0.03 to 1.3 [A^-1]
• WAXS Q range ..........   ~ 0.8   to  6 [A^-1]
• Step scanning only, data collection time around 3 minutes. 

USAXS Imaging - not available until after APS upgrade and beamline improvements (~2027?)

Data 

The USAXS instrument produces data that are fully normalized and calibrated. In practice, this means the data are corrected for sample transmission and, when a meaningful sample thickness is available at the time of measurement, placed on an absolute intensity scale with units of [cm²/cm³] = [1/cm]. Absolute calibration also requires background subtraction.

Although the instrument uses slit collimation (and therefore produces slit-smeared data), our standard reduction workflow includes desmearing using the Lake method. As a result, the data delivered to users are typically desmeared, equivalent to standard pinhole-collimation data, and suitable for direct modeling with most common analysis tools.

The standard reduced data set includes:

• Scattering vector, q [1/Å]
• Intensity (absolutely calibrated when applicable*)
• Intensity uncertainty (“error”)
• dQ (q-resolution for each point, units [1/Å]; values vary by point)

Original slit-smeared data are also available in the HDF5 files or can be provided on request in other formats. In those cases, the slit length is included as well (units [1/Å], constant for all points).

Data are available in several formats, including:

• Combined raw and calibrated HDF5 files (see the movie below and consult the manual for details)
• Igor Pro experiment files
• ASCII text formats on request (such as .txt, .dat, and similar)

For users of Irena, pyIrena, SasView, or other applications that can read HDF5 files and support the NXcanSAS format, the HDF5 files alone are often sufficient and no additional data export may be needed.

Here are some resources: YouTube movie,  Indra manual, Nexus Format, NXsas definition, NXcanSAS definition. 

Absolute calibration is performed under the assumption that the sample thickness is both meaningful (for example, not loose powders) and known before measurement. In most cases, thickness is measured and provided by the user prior to data collection. If no thickness value is supplied, the system uses a default sample thickness of 1 mm.

More advanced or specialized absolute calibration procedures can also be performed when arranged with instrument staff in advance and properly configured for the experiment.

Schematics & examples of data:

Schematics of the USAXS - SAXS - WAXS instrument (top view) with three devices. Data are collected sequentially using any sequence of devices, one, two, or three as needed. Changeover time between any two devices is about 5 seconds. USAXS is scanning technique which rotates the analyzer crystal for each measured position (typical scan time 90sec), SAXS/WAXS use area detectors with 1-5 seconds exposure times. 

Data ranges collected with different devices. Note, that USAXS data range is about 3.5 decades (0.0001 - 0.3 [1/A] in normal mode and 4 decades (0.00003 - 0.3[1/A]) in high resolution (low sensitivity) mode. SAXS range is about 0.04 - 1.1 [1/A] and WAXS range is about 1 - 6 [1/A]. SAXS and WAXS ranges depend also on X-ray energy while USAXS range is about the same for all X-ray energies and configurations we offer users. 

Examples of USAXS results :

Review Papers : Review of USAXS in hard materials, Review of USAXS in protein systems 

2018 additive manufacturing USAXS science highlight. 

2019 Story about USAXS in chocolate science (APS version) (Confectionerynews version)

2020 APS Scientific highlight (Pickering Emulsions)

2021 APS Scientific highlight (Colloidal gels)

An in-situ USAXS-SAXS-WAXS study of precipitate dissolution and size evolution in a model gamma-gamma Prime ternary Ni-based alloy (collaboration with Dr. G. Muralidharan, ORNL). A 0.1 mm thick sample was heated from RT to 1100C at 4.5C/min while undergoing repeated USAXS-SAXS-WAXS (24 keV) at 5 minute intervals. Research sponsored by the U.S. Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, as part of the Propulsion Materials Program.

USAXS/SAXS/WAXS data : In situ data collected at 226 °C over about 16 hours represent microstructure evolution of AA2024 aluminum alloy (Allen, Levine, and Zhang, NIST). USAXS data enable quantification of second phase formation (size and volume), WAXS enables phase identification.

Scattering of 1 micron SiO2 spheres in aqueous solution.

USAXS/SAXS/WAXS in situ data : Data collected by LLNL (Trevor Willey et.al.) on high-explosives. The material is composite of two high-explosives and plastic binder. The WAXS clearly shows phase changes while USAXS/SAXS data show microstructure change as function of heating.

Scattering of 1 micron Polystyrene spheres in solution.