Level densities represent one of key ingredients of nuclear reaction cross section
calculations. Present directory, responding to practical formalisms of nuclear level
densities and their parameterization, is subdivided into three parts.
For any applications of the statistical theory of nuclear reactions it is very important to obtain the parameters of the level density description from the reliable experimental data. The cumulative numbers of low-lying levels and the average spacings between neutron resonances are usually used as such data. The level density parameters fitted to such data are compiled in the RIPL Starter File for the tree models most frequently used in practical calculations:
The directory is comprised of the subdirectories RECOMMENDED and OTHER_FILES:
RECOMMENDED
Filename | Contents |
beijing.readme | Readme for beijing_bs.dat and beijing_gc.dat |
Parameters for back-shifted model |
|
beijing_gc.dat | Parameters for Gilbert-Cameron |
obninsk.readme | Readme for obninsk_bcs.dat |
obninsk_bcs.dat | Parameters for superfluid (BCS) model |
OTHER_FILES
Filename | Contents |
beijing.readme | Readme for beijing_bcs.dat |
beijing_bcs.dat | Parameters for superfluid (BCS) model |
bombay.readme | Readme for bombay_bs.dat and bombay_gc.dat |
bombay_bs.dat | Parameters for back-shifted model |
bombay_gc.dat | Parameters for Gilbert-Cameron model |
iljinov.readme | Readme for iljinov_gc.dat |
iljinov_gc.dat | Parameters for Gilbert-Cameron, by Iljinov |
jaeri.readme | Readme for jaeri_gc.dat |
jaeri_gc.dat | Parameters for Gilbert-Cameron, by JAERI |
mengoni.readme | Readme for mengoni_gc.dat |
mengoni_gc.dat | Parameters for Gilbert-Cameron, by Mengoni |
moller.readme | Readme for moller_levels.gz and moller_levels.for |
moller_levels.gz | Single-particle levels by Moller, compressed (14.5 Mbytes) |
moller_levels.for | Utility code for moller_levels.gz |
obninsk_bcs.readme | Readme for obninsk_bcs.for |
obninsk_bcs.for | Code to calculate BCS level densities |
obninsk_gc_bs.readme | Readme for obninsk_gc.dat and obninsk_bs.dat |
obninsk_gc.dat | Parameters for Gilbert-Cameron model |
obninsk_bs.dat | Parameters for back-shifted model |
obninsk_micro.readme | Readme for obninsk_micro.for |
obninsk_micro.for | Code for microscopic total level densities |
2. Fission
Level Densities
Fission level densities (or fissioning nucleus level densities at fission saddle
deformations) are required for statistical model calculations of actinide fission cross
sections. Back-shifted Fermi-Gas Model, Constant Temperature Model, and Generalized
Superfluid Model (GSM) are widely used for the description of level densities at ground
state deformations. These models provide approximately identical level density description
at excitations close to the neutron binding energy. It is low excitation energies where
they are discrepant, while this energy region is crucial for fission cross section
calculations. A drawback of the back-shifted Fermi gas model and traditional
constant temperature model approaches is that it is difficult to include in a consistent
way pair correlations, collective effects, and shell effects. The pairing, shell and
collective properties of nucleus do not reduce just to the renormalization of level
density parameter a, but influence the energy dependence of level densities.
These effects turn out to be important because they depend upon deformation of either
equilibrium or saddle-point. These effects are easily introduced within the GSM approach.
Fission barriers are another key ingredients involved in the fission cross section
calculations. Fission level density and barrier parameters are strongly interdependent.
This is the reason for including fission barrier parameters along with the fission level
densities in the Starter File.
The recommended file is maslov.dat --- fission barrier parameters. Recent version of actinide fission barrier data obtained in Obninsk obninsk.dat should only be considered as a guide for selection of initial parameters. These data are included in the Starter File, together with the fission barrier parameters recommended by CNDC (beijing.dat), for completeness.
The directory is comprised of the subdirectories RECOMMENDED and OTHER_FILES:
RECOMMENDED
Filename | Contents |
maslov.readme | Readme for maslov.dat |
Fission barriers provided by Maslov |
OTHER_FILES
Filename | Contents |
beijing.readme | Readme for beijing.dat |
beijing.dat | Three tables of fission barriers compiled in Beijing |
obninsk.readme | Readme for obninsk.dat |
obninsk.dat | Fission barriers provided by Obninsk |
The RIPL Starter File includes a Fortran code avrigeanu.for by M. Avrigeanu for using various equidistant and Fermi-gas single-particle models, including models that incorporate pairing and shell effects within the closed-form treatments and a Fortran code capote_micro.for by R. Capote, which performs combinatorial counting of p-h configurations in a realisitic shell-model space including pairing interaction.
The directory is comprised of the subdirectories RECOMMENDED and OTHER_FILES:
RECOMMENDED
Filename | Contents |
avrigeanu.readme | Readme for avrigeanu.for |
Code with analytical formulas by M. Avrigeanu |
OTHER_FILES
Filename | Contents |
capote_micro.readme | Readme for capote_micro.for |
capote_micro.for | FORTRAN code to calculate p-h state densities using microscopic theory, by Capote et al. |
Readme for single-particle levels, by P. Moller (LANL, Los Alamos, USA) |