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flair-2.3-0e 06-May-2024


-- New Fluka Major Release
( 06.05.2024 )

FLUKA 2024.1.0 is available.
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Defines the energy threshold for star density scoring Sets thresholds for elastic and inelastic hadron reactions


     WHAT(1), WHAT(2) : not used

     WHAT(3) = threshold kinetic energy for hadron elastic scattering
               Default: same as for particle transport (set by option
               PART-THR or by default (i.e. the minimum one for which
               the present physics can work, typically 0.02/0.05 GeV
               depending on the hadron)

     WHAT(4) = threshold kinetic energy for hadron inelastic reactions
               Default: same as for particle transport, as defined by option
               PART-THR or by default. The default thresholds are: 0.0 for
               protons and pions, 0.02 GeV for high energy neutrons, 0.0 for
               particles which annihilate at rest - but the latter will not
               undergo any inelastic interaction between the interaction threshold
               (in the range 0 and 0.050 GeV depending on the hadron),
               and 0.0 - and between 0 and 0.050 GeV for all other hadrons)

     WHAT(5) : not used

     WHAT(6) = threshold kinetic energy for star scoring
               Default: the same values as set for inelastic reactions
               (see WHAT(4) above)

     SDUM :    not used

     Default (option THRESHOLd not given): the threshold for star scoring
              is set at 20 MeV for protons and neutrons, and at 50 MeV for
              all other hadrons


  • 1) The possibility to change the threshold for elastic scattering or inelastic collisions (WHAT(3) and WHAT(4)) is not to be used in normal transport problems, but is made available to investigate the relative importance of different processes on the studied problem.

  • 2) For reasons explained in Note
  • 4) to command SCORE, it is recommended to set the threshold for star scoring (WHAT6)) equal to 0.050 GeV overriding the default of 0.020 GeV. A 0.050 GeV cutoff was used in the past to establish so-called omega factors which are still currently used to estimate induced activity (see [Ran70b,Hof75a,Hof75b]). Stars defined in this way do not include those produced by annihilating particles.

  • 3) The threshold for star scoring requested by option THRESHOLd applies ONLY to the output related to options SCORE and USRBIN. The number of stars reported in the summary statistics at the end of the standard output is always based on the actual energy thresholds for nonelastic interactions (except for neutrons for which stars are reported above 20 MeV).

Example 1:

 THRESHOLd        0.0       0.0       2.0       0.0       0.0       0.0
 *  Switch off elastic scattering of hadrons below 2 GeV

Example 2:

 THRESHOLd        0.0       0.0       0.0       0.0       0.0      0.05
 *  Score stars only above 50 MeV

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