NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROGRAM OR FUNCTION, METHODS, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, RELATED AND AUXILIARY PROGRAMS, STATUS, REFERENCES, HARDWARE REQUIREMENTS, LANGUAGE, SOFTWARE REQUIREMENTS, NAME AND ESTABLISHMENT OF AUTHORS, MATERIAL, CATEGORIES

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Program name | Package id | Status | Status date |
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REFIT-2009 | NEA-0914/08 | Tested | 27-OCT-2011 |

Machines used:

Package ID | Orig. computer | Test computer |
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NEA-0914/08 | PC Windows | PC Windows |

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3. DESCRIPTION OF PROGRAM OR FUNCTION

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.

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.

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4. METHODS

The nuclear cross section for each nucleus is calculated from initial parameters using an R-matrix multi-level formalism. The cross section is then Doppler broadened using either an ideal gas model or Moxon's simple Phonon Model, or Meister's Einstein Crystal Model, or Naberejnev's Harmonic Crystal Model. Some of the parameters associated with the Doppler broadening can be adjusted in the fit e.g. in the gas model the effective temperature. The transmission or reaction yield for a given sample is then calculated from the Doppler broadened cross sections, given abundances of the nuclei and the thickness of the sample in the neutron beam. In the case of reaction data the calculated reaction yield includes the effects of a multiple collision of the neutrons in the sample and the detection of scattered neutrons. The theoretical curves are then folded with the resolution function which can be calculated from parameters that include: - the initial pulse width, the decay of neutrons leaving the source and moderator, etc or from tabulated values. The nuclear parameters are the resonance energies, neutron widths, radiation widths and effective nuclear interaction radii. Provision has also been made to fit experimental parameters such as zero delay, flight path length, background, normalisation, resolution parameters etc. as well as the nuclear parameters.

The nuclear cross section for each nucleus is calculated from initial parameters using an R-matrix multi-level formalism. The cross section is then Doppler broadened using either an ideal gas model or Moxon's simple Phonon Model, or Meister's Einstein Crystal Model, or Naberejnev's Harmonic Crystal Model. Some of the parameters associated with the Doppler broadening can be adjusted in the fit e.g. in the gas model the effective temperature. The transmission or reaction yield for a given sample is then calculated from the Doppler broadened cross sections, given abundances of the nuclei and the thickness of the sample in the neutron beam. In the case of reaction data the calculated reaction yield includes the effects of a multiple collision of the neutrons in the sample and the detection of scattered neutrons. The theoretical curves are then folded with the resolution function which can be calculated from parameters that include: - the initial pulse width, the decay of neutrons leaving the source and moderator, etc or from tabulated values. The nuclear parameters are the resonance energies, neutron widths, radiation widths and effective nuclear interaction radii. Provision has also been made to fit experimental parameters such as zero delay, flight path length, background, normalisation, resolution parameters etc. as well as the nuclear parameters.

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8. RELATED AND AUXILIARY PROGRAMS

A modified version of the Harwell computer library minimising routine VA02A is used to obtain the best fit to the data by varying the required parameters, and outputs the parameters at the minimum value of chi-squared. The modified library routine SV01AS outputs the uncertainties (one standard deviation) together with the correlation coefficients matrix. The source of these routines is present with the main source code.

Also contained in the package is the following auxiliary program:

RESCON-2009 converts ENDF format into REFIT format.

A modified version of the Harwell computer library minimising routine VA02A is used to obtain the best fit to the data by varying the required parameters, and outputs the parameters at the minimum value of chi-squared. The modified library routine SV01AS outputs the uncertainties (one standard deviation) together with the correlation coefficients matrix. The source of these routines is present with the main source code.

Also contained in the package is the following auxiliary program:

RESCON-2009 converts ENDF format into REFIT format.

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NEA-0914/08, included references:

- M. C. Moxon, T. C. Ware, C. J. Dean:REFIT-2009 A Least-Square Fitting Program for Resonance Analysis of Neutron

Transmission, Capture, Fission and Scattering Data

Users' Guide for REFIT-2009-10 (UKNSF(2010)P243, April 2010)

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Package ID | Computer language |
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NEA-0914/08 | FORTRAN-90, FORTRAN-95 |

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NEA-0914/08

/REFIT-2009 The REFIT-2009 directoryREADME.txt Readme file

REFIT-2009-10.exe REFIT executable

RESCON-2009-10.exe RESCON executable

/source Source code directory

REFIT-2009-10.FOR REFIT source

RESCON-2009-10.FOR RESCON source (auxiliary code)

DOPINP-2009-10.FOR Part of REFIT source used to model Doppler Broadening at

low neutron energies

*.REF Common files used by REFIT (72 in total)

/test Directory containing test cases

*.cmm Command files

*.cnt Control files

*.out Formatted output files

*.oux Summary output files

*.plt Formatted output file suitable for plotting with common

data graphing software packages

*.fit0; *.fitx Unformatted output files

/data Directory containing resonance and measurement data for test cases

/doc Directory containing the user manual in Acrobat PDF format

Keywords: Doppler broadening, R matrix, capture, least square fit, multilevel analysis, neutron cross sections, neutron reactions, neutron spectra, resolved region, resonance integrals, transmission.