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NCNR Reflectometry Software

NCNR has a number of programs to aid in reflectometry.

Experiment Design

Given your sample structure you can calculate what sort of reflectivity curve you expect to see. To do this you need to compute the scattering length densities in your sample from basic principles using the atomic properties of your sample, or you can calculate them from the chemical formula. Similar calculations are available in the excel spreadsheet nbcu.xls. Given the scattering length densities, you can generate a layer profile from which you can calculate the expected reflectivity. The reflectivity can be calculated with a java applet, or using the data analysis software mentioned below.

Collecting data

Instruments are controlled using ICP. With the appropriate choice of parameters, you can generate specular, background and rocking curves. While you are collecting data you will need xpeek to view the data. This is available on all the instrument computers.

Reflpak

Reflpak provides support for data reduction and simple fitting of ncnr data. Reduction is driven by reflred, which allows you to view raw X-Ray, NG-1 and NG-7 data files and reduce them to a reflectivity curve. For simple analysis there is the layer-based reflfit and reflpol programs. Limited help is available within the programs via the F1 key or online (reflred help and reflfit/reflpol help). Support for linux and OS/X were available in much older versions. Source is available on github.

To run reflred, you will need to download Octave from the link above and install it. Before starting reflred, start Octave, and type the following at the command prompt:

    listen(1515,'nofork')
This sets up the octave server to provide computational support for the reduction program.

Refl1D

Refl1D is a more powerful fitting program which adds capabilities for simultaneaous fitting and uncertainty analysis. See the DANSE/Reflectometry website for more details.

Citing reflfit, reflpol, reflred

Acknowledging use of reflpak in publications may be done by making a reference to this site. For example:
The programs from the reflpak suite were used for elements of the data reduction and analysis.[1]
[1] P.A. Kienzle, K.V. O'Donovan, J.F. Ankner, N.F. Berk, C.F. Majkrzak; http://www.ncnr.nist.gov/reflpak. 2000-2006

Disclaimer

This software was developed at the National Institute of Standards and Technology at the NIST Center for Neutron Research by employees of the Federal Government in the course of their official duties. Pursuant to title 17 section 105* of the United States Code this software is not subject to copyright protection and is in the public domain. NIST does not assume any responsibility whatsoever for the use of this software, and makes no guarantees, expressed or implied, about its quality, reliability, or any other characteristic. The use of certain trade names or commercial products does not imply any endorsement of a particular product, nor does it imply that the named product is necessarily the best product for the stated purpose. We would appreciate acknowledgment if the software is used.

*Subject matter of copyright: United States Government works

Copyright protection under this title is not available for any work of the United States Government, but the United States Government is not precluded from receiving and holding copyrights transferred to it by assignment, bequest, or otherwise.

Acknowledgments

Portions of this work are based upon activities supported by the National Science Foundation under Agreement No. DMR-0412074.

References

Calculating polarized neutron reflectometry
C.F. Majrkzak, K.V. O'Donovan, N.F. Berk (2006); Polarized neutron reflectometry. In Neutron Scattering from Magnetic Materials, T. Chatterji, editor. Elsevier.
Polarization corrections
C.F. Majkrzak (1996); Neutron scattering studies of magnetic thin films and multilayers, Physica B 221, 342-356.
Modelling interfaces with slabs
J.F. Ankner, C.F. Majkrzak (1992); Subsurface profile refinement for neutron specular reflectivity. In S.P.I.E. Conference Proceedings, Vol. 1738. C.F. Majkrzak and J.L. Wood, editors. S.P.I.E., Bellingham, WA.

Last modified 15-July-2014 by website owner: NCNR (attn: Brian Kirby)