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sansigormacros / ncnrsansigormacros

Reduction software for small-angle neutron scattering used by multiple neutron scattering facilities..
https://www.nist.gov/ncnr/data-reduction-analysis/sans-software
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Large angle correction to detector efficiency #10

Closed krzywon closed 4 years ago

krzywon commented 4 years ago

As described in Annie Brulet's recent paper, at large scattering angles, the detector efficiency changes. This change in efficiency can not be corrected by making detector senstivity measurements at each instrument configuration, because the scattering from pleiglass or water is not flat at high angles, and the scattering is no longer monochromatic, with significant fraction of scattered neutrons having wavelength 1 A to 3 A.

The attached word document describes a simple algebraic fix that can be added to the SANS IGOR data reduction. There are also detector dependent parameters that may need to be added to the raw data headers. Namely, attenuation constant for aluminum and absorption constant for He(3).

From: http://rt.ncnr.nist.gov/Ticket/Display.html?id=760

krzywon commented 4 years ago

[srkline] Done. Added to the DetCorr() function in WorkFileUtils.ipf.

The correction is applied as the data is added to a work file, in 2D form.

As per John's memo, the correction is very small, (=1 most everywhere) but up to a few percent at the very largest angles, and increases the measured value.