Release of FLUKA 4-2.0

Dear FLUKA users,

It is our pleasure to announce that a new major release of the FLUKA code, FLUKA 4-2.0, has been issued and can be downloaded from here.

See the release notes at the bottom of this message for a detailed account of all new features and highlights.

To profit from the new features, please update to the latest version of Flair (3.1.15).

With our kindest regards,

The FLUKA developer team at CERN and collaborating institutes


This release contains several improvements and bug fixes as listed in the following. Among the first ones, the inclusion of low energy deuteron interactions and the availability of state-of-the-art dose equivalent conversion coefficients are of particular significance.

With this release, the embedded DPMJET package is now aligned with the officially distributed DPMJET-III version 19.2.0.

Linux users of gfortran 11 (who should download the gfor9 precompiled package of FLUKA, as indicated in the installation guide), should avoid subversions older than 11.2, which are known to miscompile. Please update to gfortran 11.2.

(All other Linux users with gfortran from 7 to 10 are not affected by this issue).


  • An effective model for nuclear reactions of low energy (< 150 MeV/n) deuterons has been included, accounting for stripping to the continuum, stripping to discrete levels (for a selection of light isotopes), and deuteron elastic break-up. This overcomes a very long-lasting lack that in the past was crudely treated by adding in the input file a PHYSICS card requesting IONSPLIT for deuterons. In order to engage the new model, as recommended, such a PHYSICS/IONSPLIT card has to be removed. Although this new interaction model has been reasonably tested, residual bugs or misbehaviors cannot be excluded: thanks in advance for reporting them on! As a control measure, a PHYSICS card with SDUM=LOWDEU allows to switch off low-energy deuteron nuclear reactions altogether (not recommended). For deuteron-beam interactions on deuterium, tritium, and helium, the model performances are still tentative and the use of a user-customized source routine describing independently the interaction products may remain preferable.
  • A deuteron preformation mechanism is now accounted for in the course of the intranuclear cascade and pre-equilibrium stages of a hadron-nucleus interaction, provided a PHYSICS card is input with SDUM=COALESCE (as recommended for several purposes). This improves the excitation functions of reactions like (p,d)/(p,pn) and (n,d)/(n,np) on light nuclei at low and intermediate energies, as illustrated in Nuclear Data Sheets 120 (2014) 211–214 (Fig. 4).
  • The explicit generation and transport of alpha particles from the decay of radioactive nuclei are now performed.
  • The nuclear reaction cross section of protons has been refined in the near-threshold region for {50,52,53,54}Cr, {54,56,57,58}Fe, {60,61}Ni, {63,65}Co, {92,94,95,96,100}Mo, and 184W.
  • Optical photon generation by local sub-threshold energy deposition events is now accounted for, addressing the behavior reported in
  • Further dose-conversion coefficients are now available (see the manual for more details):
    • Coefficients for effective dose from ICRP Publication 116 for photons, neutrons, electrons, positrons, protons, charged muons, charged pions and alpha particles.
    • Ambient dose from ICRU Report 95 for photons, neutrons, electrons, positrons, protons, charged muons, charged pions and alpha particles.
    • Personal dose from ICRU Report 95 for photons, neutrons, electrons, positrons, protons, charged muons, charged pions and alpha particles for different irradiation geometries.
    • Directional and personal absorbed dose in the lens of the eye from ICRU Report 95 for electrons, positrons, neutrons and photons.
    • Directional and personal absorbed dose in the local skin from ICRU Report 95 for photons, neutrons, electrons and positrons on the slab phantom.


  • Two new cards (MGNCREATe and MGNDATA, see the manual) have been added, allowing for the definition of multiple custom magnetic fields, either analytical for the most common fields (from dipole up to decapole), interpolated in 2D or 3D, or a combination of both (analytic in the so-called core region and interpolated outside), allowing to exploit mirror symmetries if applicable.
  • An unnecessary restriction in regard to the SPECSOUR use was lifted, which was preventing to simulate interactions on a target particle at rest.
  • All post-processing tools (bin/us*, bin/gplevbin, and bin/detsuw) now make use of dynamic memory allocation.
  • A new processing tool (usbscw) is available in order to add USRBINs from different study cases with respective weights. This applies for instance to independent source terms, such as for separate electromagnetic dissociation and nonelastic interaction SPECSOUR runs (to be weighted by the respective cross section), or synchrotron radiation emission from different circular arcs or helical paths.


  • Fixed a crash occurring when ions with high transport threshold were ranged out in a material with low delta-ray production threshold
  • Fixed rare crash in kaon-nucleon elastic and charge-exchange interaction
  • Fixed DETECT card misbehavior reported in this forum post
  • Fixed crashes occurring in the de-excitation of super-heavy systems generated by nucleus-nucleus interactions in rQMD.
  • Fixed a series of rare rQMD crashes, including those reported in this forum post
  • In the aftermath of a nucleus-nucleus nuclear interaction in rQMD, corrected a Lorentz boost loss of precision due to a small transverse momentum component
  • Fixed exponential overflow in the evaporation module occurring in a nuclear inelastic interaction between heavy ions
  • In the crystal module, particles entering the crystal with an angle at the limit of the volume reflection acceptance and approaching the channeling acceptance exhibited a spurious kick. This has now been fixed
  • A temporary treatment is now in place to fix a spurious volume-reflection kick in case of low delta-ray production thresholds in crystal regions
  • Added a protection for activity scoring in regions whose material is changed in the radioactive decay stage