Release of FLUKA 4-5.1

Announcements
1

Dear FLUKA users,

It is our pleasure to announce that a new minor release of the FLUKA code, version 4-5.1, has been issued and can be downloaded from the Official CERN FLUKA website.

See the release notes at the bottom of this message for a detailed account of all novelties.

For consistency, please update to the latest version of Flair, available from the Official Flair website.

With our kindest regards,

The FLUKA developer team at CERN and Collaborating Institutes

=== Fluka-4.5.1 ===

PHYSICS IMPROVEMENTS:

  • Adjusted the sampling of the polar angle of fission neutrons to ensure being
    isotropic in the lab frame, if required by the neutron library. This also
    reduces the resampling occurrence and results in a more accurate reproduction
    of the neutron multiplicity and library neutron spectra.

TECHNICAL IMPROVEMENTS:

  • Updated DPMJET from version 19.3.6 to the latest minor release 19.3.8 (no
    physics change is expected). The DPMJET version is henceforth reported
    explicitly in the fort.19 file.

  • Added dedicated user routines in the new src/coupling directory to enable the
    coupling of FLUKA to the Xsuite code and other tracking codes, as discussed in
    the new chapter 19 of the FLUKA manual.

  • Source packages can now also be compiled with the latest GNU Compiler
    Collection (gcc), version 15.2.

BUG FIXES:

  • Fixed a bug introduced in 4.5.0 whereby all decay products of Cs-137 decay
    except the beta themselves were generated twice, as reported in this forum thread.

  • Fixed a bug whereby, in the aftermath of a Compton scattering event close to a
    UMESH region boundary with the outgoing photon changing region, the
    normal-vector information (needed for path length correction and lateral
    displacement) failed to propagate to the daughter electron.

  • A numerical precision error incurred for grazing particles close (within
    1e-13 cm) to a tetrahedral element surface, led to a large amount of
    microscopic steps. Resolved by an adapted tolerance in boundary detection.

  • Fixed a precision loss bug when combining UMESH with LATTICE having the
    prototype located at a large distance: in some cases, when no boundary
    crossing was found, the combined transformations led to a returned distance
    slightly longer than the physics step, which is now enforced.

  • The verbosity of geometry error messages triggered by extremely problematic
    region boundary crossings has been reduced, so as to not fill up the disk
    before duly crashing.

  • Protection for an out-of-bounds exception triggered by low-energy-neutron
    point-wise inelastic composite channels.

  • Fixed a bug that was inhibiting LE-FISS scoring in case of point-wise neutron
    interactions, as reported in this forum thread.

  • Fixed a rejection of deuteron nuclear interactions on deuterium which led to
    an overestimation of the D(d,n) channel.

  • Fixed an inconsistency in the mass value of 3He which led to a rare crash.

  • Fixed a bug wherein muon-pair production by photons led to a slightly negative
    (within numerical precision) recoil kinetic energy.

  • Fixed a rare crash in the handling of residual nuclei at rest with
    sub-threshold (<1 keV) excitation energy to be transferred into kinetic
    energy.

  • Fixed a bug wherein X and Y Gaussian angular divergence values were
    inadvertently swapped, affecting the source_newgen.f user source routine and
    the BEAMSPOT special-source.