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RSIC CODE PACKAGE PSR-357

1. NAME AND TITLE

CEM95: Monte Carlo Code System to Calculate Nuclear Reactions in the Framework of the Cascade-Exciton Model.

2. CONTRIBUTORS

Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Moscow; Region, Russian Federation through the NEA Data bank, Issy-les-Moulineaux, France.

3. CODING LANGUAGE AND COMPUTER

FORTRAN 77; VAX and PC (P00357/MNYCP/00).

4. NATURE OF PROBLEM SOLVED

CEM95 is intended for the Monte Carlo calculation of nuclear reactions in the framework of the Cascade-Exciton Model (CEM) of nuclear reactions. CEM95 calculates reaction, elastic, fission and total cross sections; excitation functions; nuclide yields, energy and angular spectra; double differential cross sections; mean multiplicities, i.e., number of ejectiles per incident bombarding particle; ejectile yields; mean energies and production cross sections for neutrons, protons, deuterons, tritons, He3, He4, pions-, pions0, and pions+ emitted in nucleon- and pion-induced reactions using the Cascade-Exciton Model (CEM) of Nuclear Reactions. A detailed description of the CEM may be found in Ref.2. Part of primary version of the code concerning the preequilibrium and equilibrium stages of reactions is published in Ref.3. The Dubna version of the intranuclear cascade model used in the CEM95 is described in detail in the monograph 4. A detailed description of the subroutines used at the cascade stage of reaction may be found in Ref.5. All the models incorporated in the CEM95 for description of the level density parameter are given in Ref.6. All the models incorporated in the CEM95 to take into account competition between particle emission and fission at the compound stage of the reactions are described in Ref.7. Exemplary results obtained with the code CEM95 may be found in Refs 8,9. CEM95 is an extended version of CEM92M.

5. METHOD OF SOLUTION

Monte Carlo simulation method is used. The CEM assumes that reactions occur in three stages. The first stage is the intranuclear cascade. The excited residual nucleus formed after the emission of cascade particles determines the particle-hole configuration that is a starting point for the second preequilibrium stage of the reaction. The subsequent relaxation of the nuclear excitation is treated in terms of the exciton model of preequilibrium decay which includes the description of the equilibrium evaporative stage of the reaction.

6. RESTRICTIONS OR LIMITATIONS

The CEM95 allows us to calculate nucleon- and pion- induced reactions for Carbon and heavier targets for incident energies from 10-15 MeV to several GeV.

7. TYPICAL RUNNING TIME

It depends on the concrete characteristics to be calculated: 5 min may be enough to calculate fission cross section at a given energy; tens of hours may be needed to calculate with a good statistics double differential cross sections at backward angles and high energy of ejectiles.

NEA-DB ran the test cases included in this package on both a DEC/VAX 6000 machine and a PC/80486 (66 MHZ) microcomputer. The following table summarizes the execution times found:

VAX PC

Test 1 26 min 45 min

Test 2 1 hr 45 min 2 hr 40 min

Test 3a 2 min 2 min

Test 3b 4 hr 36 min 7 hr 40 min

8. COMPUTER HARDWARE REQUIREMENTS

The program was installed and run by NEA-DB both on a DEC/VAX 6000-510 computer and a DELL 466/L PC/80486 with 66 MHZ and 12 MBytes of RAM.

9. COMPUTER SOFTWARE REQUIREMENTS

The implementation on VAX was done under VMS V.6.1 and using the VAX FORTRAN compiler version 6.2. The implementation on the PC was done under MS-DOS V.6.20; and the source was compiled with the Microsoft Fortran compiler Version 5.1.

10. REFERENCES

a: Included in document:

S. Mashnick, "User Manual for the Code CEM95" (1995).

K. K. Gudima, S. G. Mashnik, and V. D. Toneev, "Cascade-Exciton Model of Nuclear Reactions," Nucl. Phys. A401, 329-361 (1983).

b: Background information:

S.G. Mashnik, V.D. Toneev, "MODEX - the Program for Calculation of the Energy Spectra of Particles Emitted in the Reactions of Pre-Equilibrium and Equilibrium Statistical Decays," Communications of the Joint Institute for Nuclear Research, P4-8417, Dubna, (1974) (FORTRAN66, text - in Russian).

V.S. Barashenkov, V.D. Toneev, "Interaction of High Energy Particles and Nuclei with Atomic Nuclei," Moscow, 'Atomizdat' (1972) (in Russian).

F.G. Geregi, et al., "Calculation of Cross-Sections for Photonuclear Reactions," Kishinev, Kishinev State University (1990) (in Russian).

S.G. Mashnik, "Statistical Model Calculations of Nuclear Level Density with Different Systematics for the Level Density Parameter," Acta Phys. Slov. 43 (1993), No.2, 86-107.

S.G. Mashnik, "Optimal Systematics of Single-Humped Fission Barriers for Statistical Calculations Acta Phys. Slov. 43 (1993), No.4, 243-270.

S.G. Mashnik, Nucl. Phys. A568(1994)703.

S.G. Mashnik, S.A. Smolyansky, "The Cascade-Exciton Approach to Nuclear Reactions (Foundation and Achievements)," JINR Preprint E2-94-353, Dubna (1994).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents in 10.a and one 3.5-in. (1.44 MB) diskette which includes source, executable, documentation and test case input and output written in self-extracting compressed DOS files.

12. DATE OF ABSTRACT

July 1995.

KEYWORDS: NUCLEAR MODELS; MONTE CARLO; MICROCOMPUTER