Last version:
FLUKA 2021.2.1, July 26th 2021
(last respin )
flair-2.3-0b 30-Jul-2021


-- Fluka Release
( 30.07.2021 )

FLUKA 2021.2.1 has been released.
Fluka Major Release 18.05.2021 FLUKA 2021.2.0 has been released.
Congratulations from INFN: ,
Dear Paola,
I wish to congratulate you and all the authors and collaborators for this new Fluka release, which looks at the future and confirms the support of INFN in the development and continuous improvement of this code.
best regards
Diego Bettoni
INFN Executive Committee

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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.


  • 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

  • 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).

Last updated: 18th of May, 2021

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