1. NAME AND TITLE

CRYSTAL BALL: Code System for Determining Neutron Spectra from Activation Measurements.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

CRYSTAL BALL is designed to unfold a neutron energy spectrum from measurements using a set of monitors irradiated in a reactor environment.

5. METHOD OF SOLUTION

CRYSTAL BALL uses a new method for the determination of neutron spectra from activation measurements. The method is based on direct approximation of Dirac's delta operator by linear combination of integral operators. Test cases using experimental data have demonstrated that the method is highly stable unless unrealistically low convergence criteria are imposed. Numerical games indicated that the solution is relatively insensitive to the choice of the initial guessed spectrum except where the energy ranges are poorly covered by the cross sections.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

CRYSTAL BALL requires approximately 5 seconds per iteration for a set of 20 monitors.

8. COMPUTER HARDWARE REQUIREMENTS

CRYSTAL BALL is operable on the IBM 360/370 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required.

10. REFERENCE

F. B. K. Kam and F. W. Stallmann, "CRYSTAL BALL, A Computer Program for Determining Neutron Spectra from Activation Measurements," ORNL-TM-4601 (June 1974).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

October 1975; revised November 1982.

KEYWORDS: UNFOLDING; ACTIVATION DETECTOR; NEUTRON