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NEA-0914 REFIT-2009.

REFIT, Multilevel Resonance Parameter Least Square Fit of Neutron Transmission, Capture, Fission & Self Indication Data

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1. NAME OR DESIGNATION OF PROGRAM:  REFIT-2009.
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2. COMPUTERS
To submit a request, click below on the link of the version you wish to order. Only liaison officers are authorised to submit online requests. Rules for requesters are available here.
Program name Package id Status Status date
REFIT-2009 NEA-0914/08 Tested 27-OCT-2011

Machines used:

Package ID Orig. computer Test computer
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.
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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.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The program in its present form is set up for a maximum of 30 different samples, 40 different isotopes with a total of only 8000 resonance parameters, 185 variables and a total of 10000 data points.
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6. TYPICAL RUNNING TIME

The running time is variable and case dependent. The test cases run with the following elapsed time on the PC:
Copper test2 takes a few seconds.
Resium theoretical tests 1 and 2 take a few seconds and stop when measurement data are required.
U238 test takes 2.5 hours.
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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.
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9. STATUS
Package ID Status date Status
NEA-0914/08 27-OCT-2011 Tested at NEADB
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10. REFERENCES:
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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11. HARDWARE REQUIREMENTS:  PC Windows.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0914/08 FORTRAN-90, FORTRAN-95
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13. SOFTWARE REQUIREMENTS

Windows XP.
COMPILERS : Compac Visual Fortran 6.6a, GNU Fortran g95, Layhey/Fujitsu Fortran 95 (version 5.50).
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15. NAME AND ESTABLISHMENT OF AUTHORS

M. C. Moxon (lead)
3 Hyde Copse,
Marcham,
Abingdon,
Oxfordshire,
OX13 6PT
United Kingdom
  
T. C. Ware
Contact via C. J. Dean
  
C. J. Dean
Serco
Kimmeridge House,
Dorset Green Technology Park,
Winfrith Newburgh,
Dorchester,
Dorset,
DT2 8ZB
United Kingdom
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16. MATERIAL AVAILABLE
NEA-0914/08
/REFIT-2009          The REFIT-2009 directory
README.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
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17. CATEGORIES
  • M. Data Management
  • O. Experimental Data Processing

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