RSIC COMPUTER CODE PSR-023
1. NAME AND TITLE
SPECTER: Calculation of Energy Distribution of Nuclear Reaction Products.
Brown Engineering Company, Inc., Huntsville, Alabama.
3. CODING LANGUAGE AND COMPUTER
Fortran IV; IBM 360/65/75/91.
4. NATURE OF PROBLEM SOLVED
SPECTER calculates the energy spectra of particles emerging from reactions of the types (y,n),
(y,p), (y,alpha), (y,2n), (y,np), (y,pn), and (y,2p) where the incident particle y may be either n, p, or
alpha. In addition, the code calculates the cross section for each of these reactions.
5. METHOD OF SOLUTION
SPECTER is an outgrowth of PSR-6/EDISN. Whereas EDISN is capable of handling only (n,n') and (n,2n) reactions, SPECTER can treat all the reactions specified above. SPECTER makes use of the Weisskopf-Ewing formula to calculate the energy distributions and reaction cross sections. The cross sections for compound-nucleus formation that are needed in evaluating this formula are calculated by the continuum theory of nuclear reactions. Data required as input are the bombarding energy, the masses of all nuclear species taking part in the reaction, and certain parameters that specify the level density of participating nuclei.
For completeness, a subroutine for calculating the nuclear level density has been included. This
subroutine makes use of the commonly adopted level density formula
derived from the Fermi gas model. U is obtained by adjusting the excitation energy to account for the pairing energy. The user may wish to employ some other analytic expression for rho or a table of values. In this event, the subroutine may be suitably modified or replaced.
A table of cross sections for compound nucleus formation as a function of bombarding energy and
target mass number is generated during the first run and written on magnetic tape for use in all
subsequent runs. These cross sections are calculated by the continuum theory. Optionally, the user
could perform a more sophisticated treatment by replacing this table with a similar one generated from
optical model calculations.
6. RESTRICTIONS OR LIMITATIONS
Ideally, the code is suited to reactions which proceed through the formation of a compound nucleus
(CN). In cases, however, in which the direct interaction mechanism (DI) is also operative, the code
is useful in estimating the relative contribution from direct effects, provided the entire cross section for
the process, sigmaCN+DI, be known, e.g., from experiment. In addition, it is required that the level
structures for all residual nuclei be adequately described by continuous level densities.
7. TYPICAL RUNNING TIME
Running time is highly dependent upon the number of energy increments used in the numerical
integrations. The maximum degree of accuracy is attained with 50 increments. In this case, a typical
calculation on 56Fe at 14 MeV which takes into consideration the reactions (n,n'), (n,2n), and (n,p)
takes about three minutes on the IBM 7094 computer.
8. COMPUTER HARDWARE REQUIREMENTS
SPECTER is operable on the IBM 360/65/75/91 computer. 29 K of memory is required.
However, with some sacrifice in accuracy, this requirement may be relaxed considerably by the
reduction of certain array dimensions.
9. COMPUTER SOFTWARE REQUIREMENTS
A Fortran H-level compiler is required. The Standard Monitor system is used.
R. Snow and M. C. George, "A Computer Code for Calculating the Energy Distribution of
Nuclear Reaction Products," SMSD-SSL-1100 (February 1970).
11. CONTENTS OF CODE PACKAGE
Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code and data input and output.
12. DATE OF ABSTRACT
November 1972; revised November 1983.
KEYWORD: NUCLEAR MODELS