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NEA-0648 CERBERO.

CERBERO, Cross-Sections by Optical, Statistical Model for Spin 0, Spin 1/2 Particles

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1. NAME OR DESIGNATION OF PROGRAM:  CERBERO.
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2. COMPUTERS
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Program name Package id Status Status date
CERBERO NEA-0648/01 Tested 22-SEP-1981

Machines used:

Package ID Orig. computer Test computer
NEA-0648/01 IBM 3033 IBM 3033
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3. DESCRIPTION OF PROBLEM OR FUNCTION

The CERBERO-3 code calculates a complete consistent set of binary cross sections, on the basis of the nuclear optical model and of the nuclear statistical model, for incident particles with spin 0 and 1/2. Neutron, proton, alpha particle and gamma-ray competitions can be considered. The present program is designed for use in the incident particle energy region where it may be assumed that shape elastic scattering and compound nucleus absorption are predominant, so that compound nucleus trans-  mission coefficients are those of the optical model and the absorp-  tion cross section is equivalent to the compound nucleus cross section. The program outputs are the total and compound nucleus cross sections, the shape elastic differential and integrated cross  sections, the differential and integrated fluctuation cross sections for the excitation of discrete levels, the differential and inte- grated elastic cross sections, the continuum level excitation func-  tions, the total inelastic scattering cross section and the capture  cross section.
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4. METHOD OF SOLUTION

Only spherical local potentials are allowed.
The scattering amplitudes and the other optical model quantities as well as the shape elastic and compound nucleus cross sections are calculated in accordance with the above described optical model  potentials, by the usual methods.

The total cross section is given as the sum of the shape elastic and compound nucleus cross sections.

The integrated and differential cross sections for compound nucleus  processes may be given according to the three following approxi- mations:

1.  The Hauser-Feshbach theory.

2. The Hauser-Feshbach theory corrected by the width fluctuation     effect.

3.  The Moldauer theory.

Integrated capture cross sections are given according to the various approximations 1, 2, 3 as a difference between the total compound nucleus cross section and the sum of the cross sections for compound elastic and all possible inelastic processes. Therefore for the purpose of capture cross section calculations, the program should be used only as long as the ratio of the total radiative width to the capture width is roughly unity.

Whenever direct processes may be considered unimportant, the CERBERO program can work up to the threshold for the second particle emis- sion.

All cross sections are calculated in the c.m.s. and are given in barns.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maximum number of different incident energies:  100.
Maximum number of two body reactions = 4; maximum number of angles for which each differential cross sections is calculated = 37;
maximum number of discrete levels admitted on the whole = 100.
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6. TYPICAL RUNNING TIME

Running time depends from energy, from number of reactions and from number of levels; possible range is from 5" to 3'.
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7. UNUSUAL FEATURES OF THE PROGRAM

a. Optical model particle transmission coefficients are calculated     according to a spherical optical model.

Optical model parameter sets can be given in input or selected  by means of acronyms out of a library available internally to     the code.



b. The correction for the width fluctuations has been introduced  into channels leading both to discrete and to continuum level     excitation.



c. Composite level density like Gilbert-Cameron is used but with  constant in spin distribution K = .146, when not given in input.  For low lying levels between Ecut and U(x), sigma(E)**2 is auto-  matically interpolated between sigma(LEVELS)**2 and     sigma(U(x))**2 = K.SQRT(aU(x)).exp(A,2/3).  The value

sigma(LEVELS)**2 is obtained by maximum likelihood method to fit     known discrete levels distribution.

Sigma(LEVELS)**2 is calculated by the code on the basis of adop-  ted level for each nucleus involved. Alternatively  sigma(LEVELS)**2 can also be given in input, in those particu-  lar nuclei where additional information is known above Ecut, as     far as spin attribution is concerned.



d. Optionally a parity distribution p(pi)=exp(AE+B) according to     ref. 1 can also be assumed provided A and B are given in input.


e. Gamma-ray transmission coefficients are calculated according to  one or two Lorentzian curves for the E1 photoabsorption cross  sections. Peak energy, half maximum width, peak cross section     must be given in input for the E1 giant resonance.

The resulting total radiative width is spin and parity depen-  dent. In principle it should not be normalized because the  model proved to work satisfactorily. For the purpose of evalua-  tion a normalization constant N (J and pi independent) can be     given in input.



f. Q values are calculated from recent mass excess tables (internal   to the code) provided by Wapstra in 1978 as a private communica-     tion.



g. i) The output are average resonance parameters like strength  functions (from adopted optical model), radiative width          and mean observed level spacing.

ii) Angular distributions are given for compound, shape and  total elastic. Total cross section and primary spectra  are given for all involved particle and gamma-ray emis-          sions.

Compound nucleus and total cross section from optical model  are given at the end together with the percentual differ-  ence between compound nucleus cross section and the sum of  the contribution of all channels via compound nucleus re-          action mechanism.
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8. RELATED AND AUXILIARY PROGRAMS:
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9. STATUS
Package ID Status date Status
NEA-0648/01 22-SEP-1981 Tested at NEADB
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10. REFERENCES

- G. Reffo:
"Theory and Application of Moment Methods in Many Fermion Systems"    p. 167, edited by B.J. Dalton, S.M. Grimes, J.P. Vary, S.A.
  Williams - Plenum 1980.
- G. Reffo, F. Fabbri:
  N.S.E. 66, 251 (1978).
- For Optical Model Potential Calculations see for example D.T.
  Goldmann and C. L. Lubitz
  KAPL-2163 (1961).
NEA-0648/01, included references:
- A. Prince, G. Reffo, E. Sartori:
  "Report on the International Nuclear Model Code Intercomparison,
   Spherical Optical and Statistical Model Study", October 1983
  NEANDC/INDC(NEA)4
- F. Fabbri, G. Fratamico, G. Reffo:
  CERBERO 2: Improved version of the CERBERO computer code for
  calculation of nuclear reaction cross sections
  CNEN - RT/FI(77)6 (April 1977)
- F. Fabbri, G. Reffo:
  CERBERO - A FORTRAN programme for the calculation of nuclear
  reaction cross sections
  CNEN - RT/FI(74)36 (August 1974)
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11. MACHINE REQUIREMENTS

High speed memory used is 240 kbyte, tape 18  is used if the program uses a library for energy levels.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0648/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

The
code is composed of 27 subroutines with an overlay structure.
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15. NAME AND ESTABLISHMENT OF AUTHOR

          F. Fabbri and G. Reffo
          Centro di Calcolo del CNEN
          Bologna, Italy.
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16. MATERIAL AVAILABLE
NEA-0648/01
File name File description Records
NEA0648_01.001 CERBERO SOURCE F4 3375
NEA0648_01.002 TODAY DUMMY ROUTINE 9
NEA0648_01.003 CERBERO SAMPLE PROBLEM INPUT 53
NEA0648_01.004 CERBERO SAMPLE PROBLEM OUTPUT 795
NEA0648_01.005 JCL AND INFORMATION 56
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17. CATEGORIES
  • A. Cross Section and Resonance Integral Calculations

Keywords: Hauser-Feshbach theory, absorption, capture, cross sections, elastic scattering, fluctuations, optical models, statistical models.