Data collection and evaluation
The USAXS instrument is run using software package
called “Spec”. The data collected by Spec
are written into the structured ASCII file. The spec provides programmable
command line environment and automatic data collection.
Standard SAS data collection
Standard small-angle scattering (SAS) data collection is the
most-used mode in which this instrument is used. In this case one collects
triplets of Q, Intensity, error for range of Qs. The absolute calibration is
part of the data collection process. The procedure in short includes:
Samples are mounted into sample holder.
Using radiography the samples are located and their positions
are recorded. For large samples this step can be skipped and positions can be
measured by ruler.
Command file is written.
Command file is executed. Data are collected for each sample.
Depending on the Q range studied, measurement time and number of steps in Q
taken for each sample, the collection of data from one sample takes anywhere
from 15 to 120 minutes. Most used conditions result in about 20 minutes per
sample. Since there is need to collect blank (instrumental curve) for about
each 3 – 6 samples, it is possible to process about 2.5 samples per hour -
assuming the APS storage ring does not have beam dump and everything else works
With improvements in stability of the instrument and added
automatic procedures it is possible now to program large number of samples for