1. NAME AND TITLE

PEGAS: Pre-Equilibrium-Equilibrium Gamma-and-Spin Code System.

2. CONTRIBUTORS

Institute of Physics, Slovak Academy of Sciences, Bratislava, Czechoslovakia through the NEA Data Bank, Issy-les-Moulineaux, France.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; IBM PC and compatibles.

4. NATURE OF PROBLEM SOLVED

PEGAS is a pre-equilibrium-equilibrium gamma-and-spin code, based on the unified model of nuclear reactions. Therein, the equilibrium (compound-nucleus) emission is treated as an organic part of the pre-equilibrium emission. The code has two important novel features: the angular-momentum couplings are correctly taken into account for all processes (equilibration, particle and gamma emission), and nucleon as well as gamma emissions are calculated with all possible cascades for all possible sequences of the ejectiles. PEGAS addresses the lack of possibilities, with currently existing codes, to trace a complete development of the reaction system including the consistent treatment of cascade emissions (e.g., the pre-equilibrium emission is often limited to the primary particle only). PEGAS also provides a full treatment of angular momentum conservation.

5. METHOD OF SOLUTION

Master equations of the exiton model are solved by the algorithm of Chatterjee and Gupta. Gamma emission is according to Oblozinsky. The general philosophy of the PEGAS code is derived from the nonspin version named PEQAG.

6. RESTRICTIONS OR LIMITATIONS

The present version of PEGAS is designed for reactions induced by nucleons, though other projectiles are allowed as well, leading to the composite system with the excitation energy not exceeding 30 MeV and with nuclear spins limited to < 15h. The limitations in spin, energy, and number of successive nucleons may be shifted by adjusting the dimensions of the array.

7. TYPICAL RUNNING TIME

Sample problem execution time:

(on a Northgate 486/66) 9 minutes 43 seconds

8. COMPUTER HARDWARE REQUIREMENTS

PEGAS runs on an IBM PC or compatible with at least 578K of RAM (recommended) for compilation and linking and at least 520K for execution. Approximately 3.5 MB of free disk space is required for execution because the disk is used for temporary file swapping.

9. COMPUTER SOFTWARE REQUIREMENTS

PEGAS runs under DOS. The MS Fortran 5.0 compiler was used to create the executable included in the package.

10. REFERENCE

E. Betak and P. Oblozinsky, "PEGAS Pre-Equilibrium-Equilibrium Gamma-And-Spin Code (PC version)," Slovak Academy of Sciences unpublished report (October 1992).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and 1 DS/HD 5.25-in. (1.2 MB) diskette which contains the source code, executable, sample input/output, and a README.RSI file which describes the installation and operation of PEGAS.

12. DATE OF ABSTRACT

September 1993.