SLAC National Accelerator Laboratory
BL4-2 Biological Small Angle Scattering/Diffraction

Creating an s-axis File

Detector channels should be converted to s values.  In OTOKO and SAPOKO, the X-axis is stored in a separate file and most of the data processing is performed on Y-axis values (detector counts) only.  The inverse Bragg spacing (in either nm or Å), i.e. "s", can be used in the programs.

Run OTOKO and use ".cur" to read the peak positions (-1st, 1st, 2nd, and 3rd, or as many reflections as are visible) in a data set of cholesterol myristate or silver behenate powder diffraction.  For example the d-spacing ("repeat") of the cholesterol myristate (100) reflection is 50.1Å (± 0.1Å).  Record peak positions with OTOKO.

Screen shot 1

Screen shot 2

Screen shot 3

Use ".xax" in OTOKO to generate an s-axis file. Q-axis can be obtained by setting "multiplier" 2p."

(2p)*(s)*Rg -> 2p*smax*Rg

Screen shot 4