Last version:
FLUKA 2020.0.10, April 11th 2021
(last respin )
flair-2.3-0 28-Apr-2017


-- Fluka Release
( 11.04.2021 )

FLUKA 2020.0.10 has been released.

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Release notes for Fluka2020.0-beta -

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

This fully brand new release includes a plethora of improvements and new features, which, while they had been extensively tested and debugged, could still be subject to some residual hidden problem, hence the "beta" appellation. For this reason, for a few weeks both fluka2011.2x.8 and fluka2020.0beta will available on the web site, and assistance will be exceptionally provided for both. Please SPECIFY WHICH VERSION you are using, possibly in the subject, when asking for help at

Please take note of the revised license, which you can find in the LICENSE.2020.0beta file, or printed by the code when it runs.


  • The PEANUT model has been significantly improved in the energy range from a few GeV's on. Comparisons with experimental data for production in the 10-20 GeV range shows noticeable improvements in the predicted distributions, particularly for heavy targets. The introduction of cross section fluctuations now allows better predictions of multiplicity distributions of fast hadrons in the multi-GeV regime, with impact on computed calorimeter resolutions (#)
  • Electro-nuclear reactions are now implemented and can be activated with the PHOTONUC card with sdum=ELECTNUC (see the manual for further details)
  • Muon-nuclear reactions are now extended down to virtual photon energies in the quasi-deuteron and Giant Dipole Resonance regions with significant improvements in the predictions of cosmogenics backgrounds
  • Electro-Magnetic-Dissociation has been inproved introducing also the Electric Quadrupole (E2) contribution, of particular importance at the lowest energies
  • An extended and improved nuclear database allows better treatment of unstable nuclei near the neutron and proton drip lines. Masses, decay channels and branching ratios have been extensively revised. Many more isomers are now included in the database: conventionally FLUKA considers "isomers" all excited states with half-lives in excess of 1 microsecond. Please note that residual nuclei output files from previous versions cannot be processed with the fluka2020.0 auxiliary routines, because of their dependence on the nuclear database.(see below)
  • The inclusion of many more isomers makes the old, crude, 50-50% estimate for isomer vs ground state production rather questionable. That estimate, applied a posteriori and only for activation and residual dose rate purposes, becomes more and more unphysical, particularly for nuclei with more than one isomer (eg a nucleus with 3 isomers would be scored on a 25-25-25-25% basis). An attempt to evaluate isomer production "a priori" during the nuclear model evolution is now implemented. It is still rudimentary, but it should be already better that the old ansatz. Together with the isomer production data now available in the neutron cross section file (see below), it should significantly improve isomer production predictions. It should be noted that now isomers, when produced, are allowed to fly until stopping, since their half-life is such that they will hardly decay before stopping in most practical problems. The new isomer production mechanism can be switched off (strongly discouraged) by setting What(1)=-1 in a PHYSICS card with sdum=ISOMERS (#)
  • A deuteron pre-formation production mechanism by light nuclei has been implemented, resulting in much better predictions of excitation functions of reactions like (p,d)/(p,pn), (n,d)/(n,np) on light nuclei at low and intermediate energies. This mechanism is automatically activated if the user requests COALESCEnce (PHYSICS card) as recommended
  • Direct reactions to IAS (Isobar Analogue State) have ben implemented for a few isotopes of particular importance as neutron producing targets, resulting in major improvements in the prediction of neutron spectra at forward angles at low to medium energy (#)
  • Full account for discrete levels, out of the (IAEA) Ripl-3 library, is now implemented in every nuclear reaction step/generator
  • Heavy fragment evaporation up to Z_max=4, A_max=9, is now automa- tically activated when the PRECISIOn default is selected. For residual nuclei activation and/or dose rates it is recommended to activate heavy fragment evaporation up to the maximum Z and A implemented (eg with what(1)=3.0 in the PHYSICS card with sdum EVAPORATion)
  • A simplified model for angular momentum barriers is now implemented inside the Fermi break-up de-excitation model whenever emission cannot occur with L=0. Major improvements in residual nuclei predictions for virtual or real photons on light nuclei in the GDR region had been observed thanks to this extension
  • Photofission is back working in reasonable shape
  • The high energy fission model has been improved. Further work on this topic is scheduled in the near future
  • Fission fragment yields by low energy neutrons (neutrons below 20 MeV) are now based on the most recent evaluations, Endf/b-VIIIr0, Jeff-3.3, and Jendl-4.0
  • Neutron cross sections for several isotopes had been updated with more recent evaluations, mostly Endf/b-VIIIr0. The Tellurium cross sections have been added (see the manual for further details). As a consequence of the availability in Endf/b-VIIIr0 of some isotopes previously missing (eg 13C, 17O, 18O) the FLUKA identifier for some elements are now different (eg for OXYGEN), please refer to the manual for further details
  • Neutron cross sections now contain the information for production of isomers, out of the European Activation File. Therefore isomer versus ground state production by low energy neutrons is no longer based on the "old", crude, estimate 50-50%, but it is rather calculated according to the evaluated values when available (#)
  • Fully correlated pointwise cross sections are now available for neutrons below 20 MeV for 2-H, 3-He, 4-He and 12-C (in addition to 1-H and 6-Li which were already implemented). They are automatically selected when What(6) of LOW-NEUT is set to a suitable value (see the manual), or by default for some DEFAULTS, if the material name is respectively DEUTERIUM, HELIUM-3, HELIUM-4, CARBON/C-12/12-C/C-NAT/NAT-C (all 5 are recognized for Carbon)
  • (Anti)Neutrino cross sections have been revised and improved, particularly at the higher energies, and for charm production
  • A preequilibrium step, based on the PEANUT one, has been introduced in the rQMD event generator. Together with other improvements this results in significantly better reproduction of ion-ion experimental data, particularly towards the bottom energy range of application of rQMD
  • A preequilibrium step, based on the PEANUT one, has been introduced in the BME event generator when the projectile-target/pre-fragment combination is not one of those pre-calculated in the BME database. This addition results in significant improvements particularly for (very) light projectiles on heavy targets. There are still some weaknesses for intermediate-to-heavy projectiles on intermediate-to-heavy targets, with BME somewhat overpredicting ejectile high energy tails
  • Alpha-Nucleus cross sections for light nuclei have been updated according to the recent exprimental data, bringing better agreement with measured attenuation curves and Bragg peaks
  • A special treatment has been implemented for some exo-energetic, low energy reaction cross sections, in particular p-11B, Alpha-18O, Alpha-17O, Alpha-13C
  • Default damage threshold energies when asking DPA estimates are now available for all elements. The user can still override them by inputting her/his own values. Please note that widely different values are sometimes available in the literature for the same element, hence care must be used when using these default values. Also they apply to elements, for compounds/mixtures no specific default is available
  • Explicit emission of Alpha particles is now included in the radioactive decay part, for isotopes whose alpha decay energies and branchings are known.


  • Dynamic memory allocation for the blank common is now supported in the Gfortran versions. The code allocates a preset memory size and automatically increases it whenever a USRBIN/EVENTBIN or VOXEL card so requires. If the available memory is exhausted somewhere else (i.e. geometry), or anyway is she/he so wishes, the user can ask for a larger preset (blank common) memory by selecting a proper value with What(6) in the GLOBAL card. Max ~4GB.
  • The maximum region number is now set at 100000 for the G77 version, while it is "unlimited" for the Gfortran version thanks to the dynamic memory allocation. For both versions all region number dependent arrays are now allocated in blank common according to the actual number of regions, with the exception of one, dynamically allocated by Gfortran and statically set to 100000 for G77 (#)
  • The SPOTBEAM, SPOTDIR, SPOTPOS, and SPOTTRAN cards allow treatment planning system like multi-energy/position beams to be used (see the manual for further details)
  • The special SPECSOURce sdum BIN-SOUR can be used to create a spatially distributed source out of a USRBIN file (eg a radioactive isotope distribution, see the manual for further details)
  • The Earth magnetic field according to the latest (December 2019) release of the International Geomagnetic Reference Field (Igrf13) has been implemented into the code and it is an option for space and cosmic ray calculations
  • The PYX, PYY, PYZ (PYramid along X, Y, or Z axis) bodies have been added to the geometry (#)
  • Up to two nested roto-translations are now allowed in geometry, both for bodies and lattices (see the manual, in particular the new option LATTSNGL, for details)
  • Parentheses in region definitions are now evaluated run time, if the initialization time expansion results in too many terms
  • The rQMD event initialization has been made significantly faster, resulting in speed-up factors up to x3 for light projectiles
  • Hadron masses and physical constants have been updated to the values reported in the PDG 2018 edition


We would like to stress once more that whenever activation is a concern or, "precise" particle production calculations are required, the PEANUT extended model, as well as heavy particle evaporation/fragmentation and coalescence should be switched on (see below for details)
  • Already starting from Fluka2006.3, a new high energy event generator had been developed, based on the sophisticated nuclear physics of PEANUT coupled with the proved FLUKA Dual Parton Model description for hadron-hadron collisions and a brand new Glauber cascade treatment. Starting from fluka2011.2x release, this model is substituting as default the old one (PEANUT was already the default below 5 GeV). All thin target benchmarks of the code by the development team are run with the new model, the development of the old one being frozen. Only this model should be considered representative of the ultimate FLUKA performances. The PHYSICS card with SDUM PEATHRESH allows to switch back to the old model (highly discouraged) Also the new model potentially provides a fully featured simulation of high energy quasi-elastic events, but this requires cleaning up some FLUKA inconsistencies and therefore is not yet activated.
  • 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. These suggestions are mandatory for residual nuclei calculations. Those options are not on by default because the heavy evaporation carries a big CPU penalty which would be a waste for most problems when residuals are not a issue. Starting from Fluka2020.0, heavy evaporation is on by default (limited to A_max=9, Z_max=4) when the PRECISIOn default is requested
  • 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. They will disappear entirely with the next full release. The same geometrical shapes can be obtained in a safer way using a combination of the other body types and of transformations.
  • !!!! MAJOR WARNING, please read !!!! The use of so-called "expressions" inside the Flair preprocessor, those writing pseudo-comments in the input file like !@what.1=-1.5e-2 has been found to be prone to potentially dangerous situations, where FLUKA runs with parameters different from those intended by the user with no detectable warning. This is particularly true if a Flair generated input is modified by editing it outside Flair or viceversa, or in all cases where inputs using the #include directive together with those kind of expressions or similar operators are modified in Flair. The developer team has identified already a few scenarios where because of these shortcomings of the Flair implementation, FLUKA could run with a setup different from the one shown in the Flair screen. Therefore it is STRONGLY recommended to refrain from using such Flair features until a safer implementation will be available (the developer team is working on it). If you cannot avoid using those features, please ALWAYS CHECK what ended up into the input file (and the corresponding interpretation in the output file), since what will be actually run is what is written in the WHATs fields of the input file (!... comments ignored) and not what the Flair screen can show in case they are different. Warnings have been added in the .err and .out files for this purpose. In order to still use those kind of expressions, the user has to explicitly set SDUM=OLDFLAIR in the GLOBAL card. If by chance, a user needs to use those expressions AND some deprecated body types (see the previous warning) at the same time, the special SDUM=OLDFLBDY is available for this purpose Please note that FLUKA offers the possibility to code expressions *DIRECTLY IN THE INPUT FILE*, through the #define directive.
  • Modifications to user-written source.f routines Due to the new treatment of isomeric states, three new variables have to be initialized in the stack: EEXSTK, TMNSTK, ILVSTK. Users should modify their custom source.f routines accordingly, setting the variables as in the new source.f template. Also, two arrays relative to the (not yet implemented) crystal channeling have changed: was
    To be converted in
    ( see the template in usermvax )
  • Old residual nuclei output files As described above, 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 can do it by keeping their fluka2011.2x distribution. Users who already produced xxx_tab.lis and xxx_sum.lis files are not concerned.


This version of the code should be run on the platforms for which it has been released, that is Linux x86 under g77 (which runs on both 32 and 64 bit machines) and Linux x86_64 under gfortran. The latter requires a recent version of the gfortran compiler, given the incompatibility between different versions of gfortran. A Mac OS version compiled with gfortran is also available. The available gfortran versions are compiled with gfortran 9.2 (Linux) and gfortran 9.2 (Mac). Files compiled with gfortran 8.4 (Linux) and gfortran 8.3 (Mac) are also available. Users running on Windows can install fluka in a virtual machine through the provided dockers scripts (on the website). The code has been reasonably checked and validated for these platforms/compilers only. There is no warranty whatsoever that the code and/or the compilers used are bug free, see the disclaimer in the license file for further details.

The availability of the source code shall not be exploited for tentative builds on other architectures or with different compilers/compiler options than the ones recommended by the development team. Our experience shows that for a code of the complexity of FLUKA the chances of hitting one or more compiler issues are pretty high. Therefore users shall not make use for every serious task, including whichever form of publication or presentation, of code versions built on platforms and/or with compiler options which have not been cleared as safe by the development team.


The gfortran (64 bits) version is for x86_64 machines and cannot be run on 32 bit architectures. The FLUKA scripts recognize which version the user is running according to the following:

  • a) The FLUFOR environmental variable, which can take the values "g77" or "gfortran"
  • b) If FLUFOR is not set, if the directory name contain the "gfor" string gfortran is assumed, g77 otherwise
  • c) If gfortran is selected by means of a) or b), the additional variable GFORFLU can be set to specify the specific version of gfortran to be used if more than one is available. Please note that gfortran >= 6.3 is required. For example, if on your machine "gfortran" points to a version < 6.3, and "gfortran63" points to version 6.3, you can set GFORFLU to "gfortran63" and happily use the FLUKA gfortran (64 bits) version


Use of FLUKA must be compliant with the FLUKA user license, which is not a GPL-like license. Therefore, users shall read carefully the licensing conditions as available in the distribution tar file, on the FLUKA website and in the output files. In case of doubts or need for special authorizations, or anyway for licensing and commercial questions, or questions related to publications or releases, users shall contact the Fluka Scientific Committee (FSC) (


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

  • 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
  • T.T. Bohlen, F. Cerutti, M.P.W. Chin, A. Fasso`, A. Ferrari, P.G. Ortega, A. Mairani, P.R. Sala, G. Smirnov, and V. Vlachoudis,
    "The FLUKA Code: Developments and Challenges for High Energy and Medical Applications",
    Nuclear Data Sheets 120, 211-214 (2014)

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).

In the following part of the release notes of Fluka2011.2x.y previous releases are reported if they are still relevant:

From Fluka2011.2x on:


  • The vastly revised and improved (new) Dpmjet-3 is now included, substituting the previous version and removing the need to distribute Dpmjet-2.5 since the new Dpmjet-3 is able to treat all particles at cosmic ray energies. The upgraded Dpmjet-3 results mostly from the PhD work of Anatoli Fedynitch, and it has been benchmarked against LHC data, showing significantly better reproduction of experimental data at centre-of-mass energy in excess of 2 TeV
  • The default option governing the iterative convergence of the kinematics of nucleon-nucleon scattering in nuclei has been changed providing (marginally) better results in some cases
  • The calculations of the DPA contribution by hadrons below energy cut-off has been improved. Still the treatment is approximate, so one must run with the lowest possible threshold for charged hadrons when looking for DPA's

From Fluka2011.2x.6 on:

  • A special source for synchrotron radiation is now available. It can be activated with the SPECSOUR card, SDUM=SYNC-RAD or SYNC-RDN or SYNC-RAS, or SYNC-RDS. Detailed instructions are available in the ASCII manual (fluka2011.manual) or in Chapter 16bis towards the end of the pdf manual
  • Optical photons can now be input in a user written source routine. They can used in source as any other particle, using the particle id -1 (ILOFLK (NPFLKA)=-1). Fluka then takes care of moving them to the optical photon stack and to track them. Of course, as usual, the optical properties of the various media must be provided by the user with the relevant OPT-PROP option


  • A problem affecting the sampling of the angular distribution of pp scattering at energies around 400-700 MeV has been fixed, the impact is minimal
  • Some dimensions have been increased where user experience showed that limitations could occur
  • Several sanity checks have been backported from the development tree in the hope to catch common input mistakes
  • The #define directive has been improved, now it allows to define a value for a symbolic name, eg
    #define BeamEne 200.0
    and use it in a data card, eg
    BEAM $BeamEne
  • The SDUM=IONSPLIT workaround in the PHYSICS card has been modified in fluka2011.2x, in order to prevent unphysical features in proton/neutron spectra when run with WHAT(6)=0/1. WHAT(6)=0 is now deprecated, and must be avoided if rQMD/DPMJET-3 are not linked. Indeed a protection has been implemented starting from Fluka2011.2x.4. A new, more physically sound, option, WHAT(6)=3, is available in Fluka2011.2x. The best choice, and the recommended setup, is to link rQMD and Dpmjet-3, and set: PHYSICS 1.0 0.005 0.15 2.0 3.0 3.0IONSPLIT Still keep in mind that this is still a rough workaround waiting for a native model for deuteron interactions below 150 MeV/n
  • Separators in FREE format: the "/" separator in free format input has been removed and substituted by the "%" one in order to avoid confusion with the mathematical operator. The other separators, ";", ",", "\", ":" are unchanged
  • Execution script rfluka: the rfluka script used to launch Fluka has been slightly modified since now the code opens the input file through a name exported by the script rather than through a pipe. Old rfluka scripts will no longer work with Fluka2011.2x.4

From Fluka2011.2x.8 on: <\p>

  • A new DAMAGE default for damage (DPA) calculations is now available
  • The TPSSCORE and RAD-BIOL cards for radiobiological linear-quadratic alpha/beta scoring are available (see the ASCII manual for further details)
  • The generalized particles 'RES-NUCL', 'DOSE-H2O', 'ALPHA-D ', 'SQBETA-D', 'LGH-IONS', 'HVY-IONS', 'E+E-GAMM', 'ANNIHRST' have been added
  • The IAZTRK flag in TRACKR allows for tagging products of a given radioisotope
  • AUXSCORE filtering is now available for resnuclei USRBIN's
  • The ability to change into whichever material for decay product transport (limited before to vacuum or blackhole) is now implemented
  • Catching of the TERM interrupt has been implemented in order to stop cleanly the run as soon as possible at the end of the current event
  • Control of the echo input file has been added through the environmental variable FLUKAECHO (see the ASCII manual for details)
  • A protection against "impossible" isotopes requested with the MATERIAL card has been implemented

  • Last updated: 2nd of February, 2020

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