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REFIT (Package NEA-0914)


REFIT carries out fits to measured neutron cross-section data, by adjusting the nuclear parameters used in the multi-level R-matrix formalism as well as experimental parameters. The adjustment of the parameters is continued until the calculated transmission and/or reaction yields from neutron Time Of Flight (TOF) measurements agree with the observed data within the limits of the measured uncertainties. In its present form it can perform simultaneous fits on up to 30 sets of measured data. The data sets can be of different types, refer to different target sample thickness and refer to different sample isotopic composition. The types of measurement include transmission and the reaction types: capture, fission, scattering and self-indication. The output gives details of the analysis and all the fitted parameters with their uncertainties. The code also outputs a new list of resonance parameters in ENDF6 format suitable for putting in an evaluation file.


Default Data Bank license

The NEA Data Bank Computer Program Service offers a standard Data Bank license for REFIT

Supplementary material

Working with experts from the UK, Belgium and Japan, the Data Bank hosts a private GitLab repository for the REFIT source code, which accepts contributions from collaborators. Responsibility for accepting merge requests and any formal releases rests with the code owner and contributor of the package.

If you are interested in contributing to the development repository for REFIT, please contact the NEA for more information and to obtain access.



M.C. Moxon, T.C. Ware, C.J. Dean, "REFIT-2009: A Least-Square Program for Resonance Analysis of Neutron Transmission, Capture, Fission and Scattering Data" Users' Guide for REFIT-2009-2009-10 (April 2010)

Training materials

The NEA Data Bank has not hosted a training course on this software. If you are interested, please contact us.