1. NAME AND TITLE

PREM: Code System for Pre-equilibrium Process with Multiple Nucleon Emission.

2. CONTRIBUTOR

Faculty of Science, Tohoku University, Sendai, Japan, through the NEA Data Bank, Gif-sur-Yvette, Cedex France.

3. CODING LANGUAGE AND COMPUTER

Fortran-4; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

PREM calculates the energy spectra and distribution of excitons at each stage of a multi-nucleon emission process when the initial exciton distribution is given. The time evolution can also be calculated.

5. METHOD OF SOLUTION

PREM solves the master equations for any number of nucleon emissions under the assumption of pre-equilibrium as well as equilibrium processes. The energy spectra of nucleons and the probability of a certain nucleus being left as the residual nucleus are calculated at each stage. Reactions may be induced by nucleons, light ions as well as heavy ions. In the last case, the initial exciton distribution function must be supplied.

All the calculations are based on the following assumptions and limitations: 1) only nucleon emissions are considered, 2) the angular momentum conservation is not taken into account, 3) angular distribution of emitted particle is not calculated, 4) the Erickson's formula is used for level density, 5) simple formulas are used for escape and spreading widths.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

No study has been made by RSIC of typical running times for PREM.

8. COMPUTER HARDWARE REQUIREMENTS

PREM is operable on IBM 360/370 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran-4 compiler is required.

10. REFERENCE

G. Keeni and S. Yosida, "Computer Code for Pre-Equilibrium Process With Multiple Nucleon Emission PREM," NEA 0888/01 (December 1982).

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.

12. DATE OF ABSTRACT

May 1986.