Last version:
FLUKA 2023.3.2, November 21st 2023
(last respin 2023.3.2)
flair-2.3-0d 13-Sep-2023


-- Fluka Release
( 21.11.2023 )

FLUKA 2023.3.2 has been released.

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==== Release notes for Fluka2023.3 ,  ====

==== the 4th generation of the FLUKA ====

==== MC code, authored by A.Fassò,  ====

==== A.Ferrari, J.Ranft, and P.R.Sala   ====

his is a major release with several important physics and technical improvements and additions.

New features are shortly listed below, and described in more detail in the following of these release notes, and in the manual.


  • Photonuclear interactions: both cross sections and models are completely new above ~100 MeV: this is a major improvement which gets rid of many limitations and inaccuracies of the the previous implementation;
  • Photon cross section: upgraded from EPDL97 to EPICS2017;
  • Photon cross sections and bremsstrahlung cross sections: extended up to 1.E21 eV;
  • Updated GDR photonuclear cross sections for a few isotopes;
  • Ortho-Positronium three-gamma annihilation: see the EMFRAY option in the manual, in particular (but not only) the SDUM's ORTHPOSI and ORTPOSTM;
  • Hadronisation model: fully reworked in order to better account for experimental data which somewhat contradict widely accepted assumptions about string hadronization;
  • Hadron-nucleus cross sections are new and extended up to 1.E20 eV, and all of them are now consistently calculated with PEANUT;
  • Coherent elastic scattering of neutrons between 20 and 40 MeV is now treated using ad-hoc Legendre expansions;
  • Updated galactic cosmic ray spectra: now based on AMS02 data, they can be activated by new option in SPECSOUR : sdum = GCR-AMS;
  • Built-in source routines for neutron spectra from Am-Be, Am-B, 252-Cf sources (see the BEAM card);
  • Internal conversion decays (IC) are now modeled as such and no longer as (wrongly) gamma emission;
  • New stopping power in water, according to ICRU90 recommendations
  • The sampling of the example solar flare spectra has been definitively corrected;
  • Default DPMJET: the newest one, 3.19.3.x, the previous version is no longer distributed;
  • Default intranuclear cascade reinteractions in Dpmjet: now treated by the FLUKA hadronic models;
  • Sets of fluence-to-dose conversion coefficients from ICRP116: in particular ambient dose has been added;
  • Interface CORSIKA7/8: completely streamlined and reworked;
  • Dose averaged LET maps (new generalized particle DOSAVLET);
  • Corresponding neutron group-wise cross sections no longer needed if point-wise one are requested for a given material;
  • Interface to Ultra High Energy Cosmic Ray generators: new, at present it supports interfacing to EPOS and Sibyll;
  • Source code reorganization.


  • Completely new cross sections and models for photo-nuclear interactions above 100 MeV have been developed (Fasso` and Ferrari). In the Delta resonance region, an universal cross section curve has been implemented for all nuclei with A>4, extending up to 2-3 GeV: this curve reproduces the experimental data significantly better than the previous parametrization which was 30 years old. Now, photon-nucleus interactions for A>4, and in this energy range, are simulated with PEANUT as such and no longer as pseudo-pi0. In particular, the initial target nucleon is chosen from the nuclear volume using new parametrizations for the photon-nucleon cross sections, accounting for the in-medium broadening of the intermediate Delta resonance, and accounting for the resulting 2 and 3-nucleon absorption channels. MAID07 generated data are now used for the single pion photon-nucleon cross sections and angular distributions. Several other resonant and non resonant photon-nucleon channels have been introduced in order to model multi-pion and strangeness production up to 2-3 GeV. Photon interactions at higher energies are described with PEANUT and no longer with the old interaction model which has been deleted. The procedure is explained the following:
    • a) First the photon is supposed to fluctuate into a vector meson, with probability according to experimental coupling;
    • b) then the selection is made between a (point-like) photon interaction (a volume one with no shadowing), and a vector-meson nucleus like one with shadowing;
    • c) If the interaction is not a point-like one, it is selected whether the interaction proceeds through a diffractive-like coherent pseudo-elastic scattering, or through a non elastic vector meson nucleus one (the latter including the pseudo-quasielastic);
    • d) If the interaction is a point-like one, or a VMD non-elastic one, the vector meson is used as projectile in PEANUT, in the former case with a volume selection of the target nucleon, in the latter with a hadron like (Glauber) interaction. PEANUT can now deal with vector meson resonances as projectiles, and with their (re)interaction and decay inside the nucleus.
    All this machinery is applied to real as well as virtual photon interactions.
  • The Photon cross section had been upgraded from EPDL97 to EPICS2017;
  • The Photon and bremsstrahlung cross sections had been extended up to 1.E21 eV;
  • GDR photonuclear cross sections have been updated for a few isotopes, in particular Lead ones;
  • Ortho-Positronium three-gamma annihilation is now included, including the 3-body matrix-element for the decay. The ratio 3/2 photon annihilation is tunable per element and region/material (default 1/378). The decay time constants are also tunable. See the EMFRAY option in the manual, in particular (but not only) the SDUM's ORTHPOSI and ORTPOSTM;
  • The hadronisation model of the high energy generator has been deeply reworked in order to better account for experimental data which somewhat contradict widely accepted assumptions about string fragmentation. In particular, the surprisingly large yield of hard rho0's measured in pion-nucleon and pion-nucleus experiments, and the evolving rho0/Omega/pi0 ratio with Feynmann X could not be reconciled with some critical assumption of all string hadronization/fragmentation models. Those features are important for very high energy cosmic rays, since they can slow down the increase of the EM fraction in air showers and increase their muon content. They are also important for calorimeters, since they can impact the e/h ratio;
  • All hadron-nucleus cross sections are new and extended up to 1.E20 eV, and all of them are now consistently calculated with PEANUT. The PEANUT Glauber model had been improved and its capability of computing reliable quasi-elastic and absorption cross section extended to very high energies. The computed cross sections had been validated up to the highest cosmic ray data, and by default they substitute the previous FLUKA high-energy hadron-nucleus cross sections which were still based on 1980's extrpolations of available experimental data;
  • Coherent elastic scattering of neutrons between 20 and 40 MeV is now treated using ad-hoc Legendre expansions derived from ENDF/B-VIIIr0;
  • Updated galactic cosmic ray spectra, based on AMS02 data (thanks to Nicola Mazziotta and Pedro de la Torre Luque) are now available: they can be activated by new option in SPECSOUR : sdum = GCR-AMS;
  • Built-in source routines for neutron spectra from Am-Be, Am-B, 252-Cf sources are now available (see the BEAM card);
  • Internal conversion decays (IC) are now modeled as such and no longer as (wrongly) gamma emission, including the explicit transport of the excited nuclei to the decay point;
  • The evaluations of charged particle stopping power in water have been changed to bring it in agreement with the ICRU90 recommendations. In particular, but not only, the water average ionization potential is now set to the new ICRU adopted value, I=78 eV;
  • The sampling of the example solar flare spectra has been definitively corrected;
  • The default DPMJET is now the newest one, 3.19.3.x, the previous version is no longer distributed;
  • By default intranuclear cascade reinteractions in Dpmjet are now treated by the FLUKA hadronic models;
  • The sets of fluence-to-dose conversion coefficients from ICRP116 are now available, in particular ambient dose has been added;
  • A new interface to Ultra High Energy Cosmic Ray generators is now available: at present it supports interfacing to EPOS and Sibyll. The rationale is twofold:
    • a) Despite the FLUKA philosophy of developing/choosing the best model for a given application/energy range and stick with it, above LHC energies there are little or no direct data available, and therefore the possibility to explore a range of predictions with 3-4 models can be important;
    • b) At the same time, this interface allows FLUKA to run at the highest cosmic ray energies, which of course is an added bonus for the code.
    Those interested in understanding how to use this new feature please contact one of the Authors;
  • Dose averaged LET maps are now implemented on-line (generalized particle DOSAVLET): they are computed taking care also of particles below threshold in order to minimize whichever possible bias;
  • When pointwise cross sections are requested for a given material, the code will no longer stop if a corresponding group-wise set is not available;
  • The source code has been deeply reorganised. Among others, the old high energy interaction model (eventv/eventvmvax) has been removed, since it is no longer used by any of the interaction routines;


The usrsuwev.f off-line inventory evolution file is not yet updated to deal with the new isomer calulation capabilities of FLUKA, hence off-line inventory evolution concerning isomers should be avoided. A version properly accounting for the FLUKA isomers prediction capabilities will come with one of the next releases


  • Whenever residual nuclei (and residual dose rates) scoring is of importance, or accurate neutron yields are required, the heavy residual emission ("fragmentation") and the coalescence emission of fast complex particles should be switched on, through the following data cards:
    and (as a consequence of coalescence) it would be wise to link with rQMD-2.4 (and DPMJET) and activate ion transport and interactions, and circumvent the lack of deuteron interactions at low energy with
    PHYSICS 1.0 0.005 0.15 2.0 2.0 2.0IONSPLIT
    These suggestions are mandatory for residual nuclei calculations.
  • Old residual nuclei output files The auxiliary programs (usrsuw and usrsuwev in $FLUPRO/flutil) that sum and process the residual nuclei output files depend on the nuclear database. Users who still need to process files produced with previous fluka versions should contact the fluka developers. Users who already produced xxx_tab.lis and xxx_sum.lis files are not concerned.
  • The ARB, BOX, WED body types, which are deprecated since many years due to their precision problem prone coding, are now accepted only if the user explicitly sets SDUM=DEPRBODY in the GLOBAL card.
  • The use of so-called "expressions" inside the Flair preprocessor, those writing pseudo-comments in the input file like !@what.1=-1.5e-2is deprecated. In order to still use those kind of expressions, the user has to explicitly set SDUM=OLDFLAIR in the GLOBAL card.


The use of the FLUKA code must be acknowledged explicitly by quoting at least the following set of references

  • F. Ballarini, G. Battistoni, N. Belcari, G. Bisogni, M. Campanella, M.P. Carante, G. Dedes, P. Degtiarenko, P. de la Torre Luque, R. dos Santos Augusto, A. Fasso`, A. Fedynitch, Alfredo Ferrari, Anna Ferrari, E. Fiorina, G. Kharashvili, A. Kraan, G. Magro, A. Mairani, I. Mattei, M.N. Mazziotta, M.C. Morone, S. Mueller, S. Muraro, K. Parodi, V. Patera, F. Pennazio, L.S. Pinsky, R. Rachamin, R. Luis Ramos, S. Rollet, P.R. Sala, M.S. Leitner, L. Sarchiapone, T. Tessonnier, K. Smeland Ytre-Hauge, L. Zana, "FLUKA: status and perspectives", Proceedings of the "15th Workshop on Shielding Aspects of Accelerators, Targets, and Irradiation Facilities" (SATIF-15), East Lansing, Michigan, USA, September 20-23, 2022, in press
  • A. Ferrari, P.R. Sala, A. Fasso`, and J. Ranft,
    "FLUKA: a multi-particle transport code",
    CERN 2005-10 (2005), INFN/TC_05/11, SLAC-R-773

Use of Flair must be acknowledged using the following reference:

  • V. Vlachoudis,
    Proc. Int. Conf. on Mathematics, Computational Methods & Reactor Physics (M&C 2009),
    Saratoga Springs, New York, 2009

Additional FLUKA references can be added, provided they are relevant for this FLUKA version.

The use of the neutrino event generator (NUNDIS) must be acknowledged by quoting

  • G. Battistoni, A. Ferrari, M. Lantz, P. R. Sala and G. I. Smirnov,
    "A neutrino-nucleon interaction generator for the FLUKA Monte Carlo code",
    Proceedings of 12th International Conference on Nuclear Reaction Mechanisms,
    Varenna, Italy, 15-19 June 2009,
    CERN-Proceedings-2010-001 pp.387-394.

For medical applcations of FLUKA:

  • G. Battistoni, J. Bauer, T.T. Boehlen, F. Cerutti, M.P.W. Chin, R. Dos Santos Augusto, A. Ferrari, P.G. Ortega, W. Kozlowska, G. Magro, A. Mairani, K. Parodi, P.R. Sala, P. Schoofs, T. Tessonnier, V. Vlachoudis,
    "The FLUKA code: An accurate simulation tool for particle therapy",
    Frontiers in Oncology, Radiation Oncology Section, 00116 (2016)

If FLUKA is used together with rQMD-2.4, DPMJET-2.53, or DPMJET-3 the following references should be quoted:


- H. Sorge, H. Stoecker, and W. Greiner, Annals of Physics 192, 266 (1989)


- J. Ranft. Physical Review D51, 64 (1995)


- S.Roesler, R.Engel, J.Ranft: "The Monte Carlo Event Generator DPMJET-III"
in Proceedings of the Monte Carlo 2000 Conference, Lisbon, October 23-26
2000, A. Kling, F. Barao, M. Nakagawa, L. Tavora, P. Vaz eds.,
Springer-Verlag Berlin, 1033-1038 (2001).



Starting with Fluka2021.2.9 the low energy neutron cross sections for a few extra isotopes are available in both the groupwise and pointwise neutron libraries, specifically, 226Ra, 227Ac, 231Pa, 233Pa, 237Np, 239Np.

Please refer to the manual for further informations about how to access those cross sections data sets


Starting with fluka2021.2.7, the description of hadron-nucleon intranuclear cascade reinteractions in Dpmjet3x (see below) can now optionally be performed with the Fluka hadron-nucleon interaction models, rather than the old hadrin model contained in Dpmjet3x.

This is not yet the default (it will soon become the default): in order to activate this important feature, please include a DPMJET card with

    WHAT(6)=1 or 10 or 11

  • 1 = nonelastic hadron-nucleon reinteractions managed by Fluka routines
  • 10 = elastic hadron-nucleon reinteractions managed by Fluka routines
  • 11 = both elastic and nonelastic hadron-nucleon reinteractions managed by Fluka routines (recommended)

Also starting with fluka2021.2.7 a new version of Dpmjet3, Dpmjet3.19.3, is available (only for the gfortran based releases). This new release (thanks to A.Fedynitch) introduces several improvements, streamlines the interface with Fluka making its maintenance much easier, and it greatly improves the issues with Kaon production in AA collisions below 10-20 GeV/n.

The possibility of using Fluka hadron-nucleon interaction models for reinteractions (described in the first point) applies both to the "old" Dpmjet3.17 and the "new" Dpmjet3.19.3.

In order to link the new Dpmjet version, please use the script flutil/ldpmqmdnw instead of flutil/ldpmqmd, and use the resulting executable which is called by default flukadpmnw.

For the time being both the "old" and "new" Dpmjet versions are available (gfortran releases), in the future only the new one will be distributed.

Release notes for Fluka2021.2 -

This is a major release with several important physics and technical improvements and additions..

New features are shortly listed below, and described in more detail in the following of these release notes, and in the manual.

Some of the features require modifications of the users routines please read carefully if you have any.

If you are using the tar files rather than the rpm's, please note that you have to download two files since now all data libraries, which are common to all compilers/architectures are now provided in a separate file (see below and the README file)


  • Pointwise transport of low energy neutrons with correlated interactions is now available. A separate data file has to be downloaded (see README)
  • Runge-Kutta based transport in electric fields is implemented for vacuum and gas regions
  • Optional Runge-Kutta based transport in magnetic field in vacuum and gas regions
  • New physics model for coherent elastic scattering of hadrons on nuclei
  • New treatment for quasi-elastic scattering of hadrons on nuclei
  • Transport and in-flight decay of excited residual nuclei
  • Improved nuclear mass/decay/deexcitation database
  • Revised hadron-nucleus interaction cross sections
  • Revised cross sections for proton - light ion interactions
  • Non monochromatic scintillation light emission and transport
  • Delta resonance decay in photon+nucleon


  • magfld.f has one more argument: time
  • source.f variables related to in-flight transport have to be initialized
  • mgdraw.f entry USDRAW: pay attention to quasielastic, flags available (see below)
  • mgdraw.f entry USDRAW: new interaction code for ion splitting events
  • new routines for non-monochromatic scintillation light (see manual)
Please always refer to the updated templates in the usermvax directory.


  • Pointwise transport of low energy neutrons. This brand new feature, a major improvement in FLUKA capabilities, includes both the "continuous" transport of neutrons, and the generation of interaction products with a mixed data and model driven treatment fully conserving energy event-by-event. Pointwise transport is available as an option, the group-wise transport is still the default. Hybrid simulations are also possible. Pointwise cross sections are activated through a new card:
    Details are available in the manual.
    When neutron pointwise transport is activated, it is also possible to set-up estimators with equidistant (linear or logarithmic) energy intervals, without the usual groupwise structure. See the description of the relevant scoring card in the manual. IMPORTANT WARNING: to save space and bandwidth, all data libraries for nuclear data, photon data, and neutron and pointwise cross sections are NOT included in the fluka tar files. They have to be downloaded separately, and placed in the same $FLUPRO directory as the rest of the distribution. A consistency check between Fluka version and data file version is automatically performed.
  • Transport in electric field is implemented in vacuum and gas. A new card
    activates it in selected regions, as flagged through the ASSIGNMAT card. A new user routine,
    is available for providing non-uniform fields. Time-varying fields can also be implemented through this user routine. Combined electric and magnetic fields are supported. Transport is performed according to a Runge-Kutta treatment. In case of transport in gas, single scattering is automatically activated. See the manual for details.
  • Transport in non uniform magnetic fields through the same Runge-Kutta algorithm is available as an option for vacuum and gas regions (it is used by default if an electric field is also present) by using
    The Runge-Kutta algorithm is signficantly more accurate than the traditional one for the same CPU time, or it is faster for the same accuracy. See the manual for details.
  • New algorithm for coherent elastic scattering of hadrons on nuclei. A general model from combining black disk scattering and grayness has been derived for FLUKA. Parameters of the model for p and n up to 200 MeV have been fitted to distributions available in ENDF/B-8R0 and JENDL40-HE. Experimental data have been used to set the model parameters above 1 GeV. Scaling and interpolation of parameters are used for combinations where no data is available. The new algorithm is applied to protons and neutrons up to 200 MeV, and to all hadrons from 1 GeV upwards. Only for 4He, 12C, 16O, 208Pb the model is applied for protons and neutron scattering over the whole energy range.
  • Quasi elastic interactions (above few GeV): quasi-elastic are interactions where the projectile scatters elastically on one of the target nucleons. Traditionally, those interactions are considered as nonelastic one at low energies. As energy increases, they are less and less experimentally distinguishable from coherent elastic scattering. In FLUKA, high energy quasielastic was included up to now in the elastic scattering treatment, without production of secondaries. Since Fluka2021, quasielastic has its own treatment, including production of secondary particles from nuclear de-excitation. For users implementing their own scoring of interactions: please be aware of this difference with respect to the past. Quasielastic are now flagged in USDRAW with the same code as inelastic (101). They carry as .true. the flag LELEVT in (EVTFLG) and the flag LQEEVT in (NUCFLG).
  • In-flight decay of excited residual nuclei. Excited nuclei with measurable/known mean life will not de-excite during the nuclear interaction which produced the excited state, but rather will fly until decay according to the level mean life. This has consequences for instance at very high energies, with nuclei potentially decaying far from the production point, and for Doppler broadening of gamma lines. In-flight decay can be activated/deactivated with the
    It is on by default with the PRECISIO and HADROTHE defaults.
  • The nuclear properties database has been upgraded, in particular with the update of nuclear masses to the newest compilation, AME 2020.
  • A full revision of hadron-nucleus cross sections, in particular for nucleons and pions in the 1-20 geV energy range, has been carried out
  • Cross sections for interactions of very light ions, mass 3 and 4 on hydrogen (and for the inverse kinematic reaction) have been greatly improved.
  • The possibility to genarate and transport optical photon from non-monochromatic scintillation lines is now available. New user routines have to be edited to provide spectrum and intensity of scintillation lines: sphspc.f and usfsci.f. They can be activated through the OPT-PROD card (see manual for details)
  • Decay of the Delta(1232) resonance in photon+nucleon is now simulated. The branching ratio (small) depends on the actual Delta mass.

Last updated: 13th of September, 2023

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