SASI - Small-Angle Scattering
Instrument
Instrument Scientist: Jyotsana Lal
Scientific Associate: Ed Lang
Post
Docs:
Markus Bleuel
Post Docs: Dennis Liang
Small-angle scattering is a powerful tool for the microscopic characterisation of materials. Providing information in the size range 10 to 1000 Å, the Small Angle Scattering Instrument (SASI) enables structure determination in diverse systems such as polymers, ceramics, alloys and glasses, macromolecules, colloids, biomolecules, composites and porous systems.
| Q range |
0.007 to 1.45 Å-1 |
| Q resolution (s(Q)/Q) |
0.3 to 0.036 |
| Area detector - active volume |
50 x 50 cm2, 2.5 cm thick |
| Detector resolution |
3 - 5 mm FWHM |
| Beam line |
C1 |
| Source frequency |
30 Hz |
| Moderator |
Decoupled 24K solid methane |
| Wavelength range |
0.9 - 14 Å |
| Moderator-to-sample distance |
7.5 m |
| Moderator-to-beam monitor distance |
6.24 m |
| Moderator-to-transmission monitor distance |
8.44 m |
| Sample-to-area detector distance |
1.44 m |
| Focussing Soller collimators |
0.0034 radians FWHM |
| Beam diameter at moderator |
9.0 cm |
| Beam diameter at area detector |
2.1 cm |
Ancillary Equipment: |
| Sample changer |
0 - 100 C |
| Resistance heater |
20 - 200 C |
| Pressure cell |
1 - 2500 bar |
| Stretcher |
Variable strain (for elastomers) |
| Electromagnet |
.1 and 10 kGauss |
PHASE SEPARATION IN BINARY PARAFFIN MIXTURES STUDIED ON THE SMALL ANGLE SCATTERING INSTRUMENT
SASI is a time-of-flight Small Angle Scattering Instrument at the IPNS facility at Argonne National Laboratory. This instrument, by simultaneously using neutrons with a wide range of wavelengths (0.9 to 14 Å),
produces SANS data in a wide Q range (0.007 to 1.45 Å-1) in a single measurement. At the reactor-based SANS instruments, it will take several repetitive experiments to build up data in a similar Q range. The accessibility of a wide Q range in a single measurement at SASI makes the SANS experiments (time-dependent and conventional) very easy.
As an example, data from an in-situ SANS study of the phase separation in a paraffin mixture 4:1 C30D62:C36H74 doped into the pores of an exfoliated graphite substrate are shown below (Gilbert, Reynolds and White, J. Phys. Chem. 100 (1996) 18201-18213). The figures in the inset to the figure represent the minutes elapsed after quenching the system from 100C (above the melting point of the paraffin mixture) to 27C. A microphase structure is observed to grow in the adsorbed system with aging.
Small Angle Scattering Links
SANS instruments
SAND, IPNS, USA
LOQ, ISIS, UK
NG3, NG5, NG7, NIST, USA
D11, D22, ILL, Grenoble, France
HB-3A,B&C, ORNL, USA
LQD, Los Alamos, USA
PAXY, PAXE, PACE and PAPOL, LLB, Saclay, France
V4, HMI, Berlin, Germany
SANS-U, ULS, ISSP, Tokai, Japan
YUMO, IBR-2, Dubna, Russia
AUSANS, Lucas Heights, Australia
Other links
CanSAS Conference on Small-Angle Data
Small-Angle Special Interest Group, ACA
Commission on SAS, IUCr
SAS Mailing List
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