INFN homepage
FLUKA: 10.5.3} Photon emission with pointwise cross sections Previous Index Next

10.5.3} Photon emission with pointwise cross sections


 For reaction involving particle emissions, often the final, ground state
 or excited, level ofthe residual nucleus is not provided in the evaluated
 data files. The FLUKA implementation tries to guess as best as possible
 the final excitation on the basis of the inclusive spectra of the
 emitted particles and physics consideration. The following de-excitation
 is performed using the standard FLUKA de-excitation models, which
 heavily rely on experimental data when within the range of known levels.

 For (n,gamma) reactions in the thermal region, the capture photons emission
 schemes are as much as possible based on experimental data of primary
 de-excitation from the capture level as available in the ENSDF database.
 For many light and medium isotopes the available data are more or less
 complete. For  medium to heavy nuclei, the available data, when present,
 often cover only a fraction of the possible schemes. The missing informations
 are generated as usual by the FLUKA de-excitation models.
 Therefore the agreement with experimental secondary lines can be very good
 when primary ones are almost completely known, questionable otherwise.
 It should be noted that even evaluated data files often contain model
 calculated capture gamma spectra, in some cases not even in agreement
 with experimentally known primary lines.

 For capture reactions in the resonance region, the same de-excitation schemes
 of the thermal range are applied. This is obviously not correct since
 the spin and parity of the given resonance could be different from
 those of thermal capture, however the experimental data about gamma
 spectra in the resonance region are very scarce.

 As a consequence of all the above consideration, production of a specific
 isomer can be very accurate in some cases, eg for (n,n') specifically
 ending up on that level, or much less accurate in others. If accurate
 predictions os isomers are of importance, it is better to rely on the
 group-wise cross sections which contain their (uncorrelated) production
 branchings as derived from available evaluated activation files.

Previous Index Next