1. NAME AND TITLE

SIOB: Calculation of Least-Squares Shape Fitting Several Neutron Transmission Measurements Using the Breit-Wigner Multilevel Formula.

2. CONTRIBUTOR

Computer Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

SIOB was developed to least-square fit the shape of neutron transmission curves. It was designed for the simultaneous analysis of transmissions on the same energy scale through several thicknesses. It was also successfully applied to the analysis of transmission data through samples composed of medium and lightweight nuclei.

5. METHOD OF SOLUTION

Any number of measurements on a common energy scale for different sample thicknesses can be simultaneously fitted. The computed transmission curves can be broadened with either a Gaussian or a rectangular resolution function, or both, with the resolution width a function of energy. The total cross section is expressed as a sum of single-level or multilevel Breit-Wigner terms and Doppler broadened using a fast interpolation routine.

6. RESTRICTIONS OR LIMITATIONS

The number of data points, resonance levels and variables which can be handled simultaneously is limited only by the overall dimensions of two arrays in the program and by the stability of the matrix inversion.

7. TYPICAL RUNNING TIME

In a test problem, seven transmissions with 3750 data points each were simultaneously fitted using 74 resonances and 110 variable parameters. On an IBM 360/91 computer, this problem took 47 min of CPU time for 3 iterations.

8. COMPUTER HARDWARE REQUIREMENTS

SIOB is operable on the IBM 360/370 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCE

G. de Saussure, D. K. Olsen, and R. B. Perez, "SIOB: A Fortran Code for Least-Squares Shape Fitting Several Neutron Transmission Measurements Using the Breit-Wigner Multilevel Formula," ORNL/TM-6286 (ENDF-261) (May 1978).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (1.2MB) DOS diskette which contains the source code and sample problem input and output.

12. DATE OF ABSTRACT

March 1984.