Last version:
FLUKA 2021.2.8, November 20th 2022
(last respin 2021.2.8)
flair-2.3-0c 11-Sep-2022

News:

-- Fluka Release
( 20.11.2022 )

FLUKA 2021.2.8 has been released.


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FLUKAFIX

Sets the size of the step of muons and charged hadrons to a fixed fraction of the kinetic energy in different materials

See also EMFFIX, MULSOPT, STEPSIZE

     WHAT(1) = fraction of the kinetic energy to be lost in a step
               (cannot be > 0.2)
               Default: if option DEFAULTS is used with SDUM = ICARUS, the
                        default is 0.02.
                        With SDUM = HADROTHErapy or PRECISIOn, the default
                        is 0.05.
                        If SDUM = CALORIMEtry, the default is 0.08.
                        With any other SDUM value, or if DEFAULTS is missing,
                        the default is 0.1.

     WHAT(2) = "epsilon" parameter used to check the finite size of the
               nucleus when the nuclear form factor is not invoked by
               the multiple scattering algorithm (see Note 3 below)
               For code development only, do not change!
               Default = 0.15

     WHAT(3) = high-energy limit for the fraction of energy to be lost
               in a step (the fraction is given by WHAT(3) times WHAT(1))
               For code development only, do not change!
               Default = 0.012

     WHAT(4) = lower index bound (or corresponding name) of materials where
               the specified energy loss per step is to be applied
               (From material WHAT(4)...)
               Default = 3

     WHAT(5) = upper index bound (or corresponding name) of materials where
               the specified energy loss per step is to be applied
               (... to material WHAT(5)...)
               Default = WHAT(4)

     WHAT(6) = step length in assigning indices
               (...in steps of WHAT(6))
               Default = 1

     SDUM :   not used

     Default (option FLUKAFIX not given): the defaults listed above apply

Notes:

  • 1) Usually there is no need for changing the default value of 10% (0.1) for WHAT(1)

  • 2) The input value is actually applied as such only at intermediate energies (between about a few tens of MeV and 1 GeV): at low energies it is slowly increased to twice the requested value, while at high energies it decreases to a limit controlled by WHAT(3), usually about one hundredth of the input value.

  • 3) The "epsilon" parameter controls the accuracy of the multiple scattering algorithm by limiting the step. In most cases the length of the step is practically limited anyway by the hadron interaction length, so the "epsilon" default value is of little importance and does not need to be changed. However, in some problems of large dimensions, especially when transporting muons, a small value of epsilon can slow down the calculations without necessity. In such cases, WHAT(2) can be safely set = 1000.0

Example (number based):

 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
 FLUKAFIX        0.03        0.        0.       21.        0.        0.
 *  The maximum fractional energy loss for hadrons and muons is set to
 *  3 percent in material 21.

The same example, name-based:

 FLUKAFIX        0.03        0.        0.   CALCIUM        0.        0.

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