[ <--- prev -- ]  [ HOME ]  [ -- next ---> ]

[ full index ]

EMFCUT

Sets the energy thresholds for electron and photon production in different materials, and electron and photon transport cutoffs in selected regions. This command can also request leading particle biasing, but EMF-BIAS must be preferred. It also allows to set an arbitrary energy threshold for all electron and photon interactions managed by EMF on a material basis. This is of course non-physical and it is provided primarily for particular studies where the user wants to switch off selectively a physical process. Only meaningful when the EMF option is chosen (explicitly or implicitly via option DEFAULTS)

See also EMF, EMF-BIAS, BIASING, PART-THR, MATERIAL For SDUM = PROD-CUT:

    |WHAT(1)| = energy threshold for electron and positron production in GeV:
             > 0.0 : energy threshold for electron and positron production is
                     expressed as total energy (kinetic plus rest mass)
             < 0.0 : energy threshold for electron and positron production is
                     expressed as kinetic energy
             = 0.0 : ignored
             Default: equal to the lowest electron transport cutoff in all
                       regions made of this material (see Note 1)

     WHAT(2) > 0.0 : energy threshold for photon production in GeV
             = 0.0 : ignored
               Default: equal to the lowest photon transport cutoff in all
                        regions made of this material (see Note 1)

     WHAT(3) = FUDGEM parameter. This parameter takes into account the
               contribution of atomic electrons to multiple scattering. For
               production and transport cutoffs larger than 100 keV it must be
               set = 1.0, while in the keV region it must be set = 0.0
               Default: 0.0

     WHAT(4) = lower bound (or corresponding name) of the FLUKA material number
               where electron/positron and photon production thresholds
               respectively equal to |WHAT(1)| and WHAT(2) apply. The material
               numbers or names are those pre-defined or assigned using a
               MATERIAL card.
               ("From material WHAT(4)...")
               Default: 3.0

     WHAT(5) = upper bound (or corresponding name) of the FLUKA material number
               where electron/positron and photon production thresholds
               respectively equal to |WHAT(1)| and WHAT(2) apply. The material
               numbers or names are those pre-defined or assigned using a
               MATERIAL card.
               ("...to material WHAT(5)...")
               Default: = WHAT(4)

     WHAT(6) = step length in assigning the material number.
               ("...in steps of WHAT(6)")
               Default: 1.0.

     Default (option EMFCUT with SDUM = PROD-CUT not requested): production
              cutoffs in a material are set equal to the lowest transport
              cutoffs in the regions with that material.

For SDUM = blank:

    |WHAT(1)| = electron and positron transport energy cutoff in GeV.
     WHAT(1) > 0.0 : electron and positron cutoff is expressed as total
                     energy (kinetic plus rest mass)
             < 0.0 : electron and positron transport cutoff is expressed as
                     kinetic energy
             = 0.0 : ignored
             This value can be overridden in user routine UBSSET by assigning
             a value to variable ELECUT.
             Default: the e+e- transport cutoff is set equal to the production
                      threshold for discrete electron interactions

     WHAT(2) > 0.0 : photon transport energy cutoff (GeV)
             = 0.0 : ignored
             This value can be overridden in the user routine UBSSET by
             assigning a value to variable GAMCUT.
             Default: the photon transport cutoff is set equal to threshold for
                      photon production by electron bremsstrahlung

     WHAT(3) > 0.0 : leading particle biasing is activated for electrons,
                     positrons and photons. Which combination of leading
                     particle biasing is actually set up depends on the bit
                     pattern of WHAT(3)

                     Let WHAT(3) be represented as:
                         2^0xb0 + 2^1xb1 + 2^2xb2 + 2^3xb3 + 2^4xb4 +
                         2^5Xb5 + 2^6xb6 + 2^7xb7 + 2^8xb8 + 2^9xb9
                     where the meaning of the ten bits is the following:
                     b0 = 1 --> LPB activated for bremsstrahlung and pair
                                production (old default)
                     b1 = 1 --> LPB activated for bremsstrahlung
                     b2 = 1 --> LPB activated for pair production
                     b3 = 1 --> LPB activated for positron annihilation at rest
                     b4 = 1 --> LPB activated for Compton scattering
                     b5 = 1 --> LPB activated for Bhabha & Moller scattering
                     b6 = 1 --> LPB activated for photoelectric effect
                     b7 = 1 --> LPB activated for positron annihilation in flight
                     b8 = 1 --> not used
                     b9 = 1 --> not used
                     Note that WHAT(1) = 1022 activates LPB for all physical
                     effects (values larger than 1022 are converted to 1022)

             < 0.0 : no leading particle biasing for electrons, positrons and
                     photons
             = 0.0 : ignored (previous definitions hold, if any; otherwise
                     default, i.e. no leading particle biasing)
               This value can be overridden in the user UBSSET routine by
               assigning a value to variable LPEMF.

     WHAT(4) = lower bound (or corresponding name) of the region indices with
               electron cutoff equal to |WHAT(1)| and/or photon cutoff equal
               to WHAT(2) and/or leading particle biasing
               ("From region WHAT(4)...")
               Default: = 2.0.

     WHAT(5) = upper bound (or corresponding name) of the region indices with
               electron cutoff equal to |WHAT(1)| and/or photon cutoff equal
               to WHAT(2) and/or leading particle biasing
               ("...to region WHAT(5)...")
               Default: = WHAT(4)

     WHAT(6) = step length in assigning indices
               ("...in steps of WHAT(6)")
               Default: 1.0.

     Default (option EMFCUT with SDUM = blank not requested): transport
              cutoffs in a region are set equal to the production cutoffs
              in the material of that region.

For SDUM = ELPO-THR:

     WHAT(1) > 0.0 : kinetic energy threshold (GeV) for e+/e- bremsstrahlung
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(2) > 0.0 : kinetic energy threshold (GeV) for Bhabha/Moller scattering
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(3) > 0.0 : kinetic energy threshold (GeV) for e+/e- photonuclear
               interactions
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(4) - WHAT(6): see below

For SDUM = ANNH-THR:

     WHAT(1) > 0.0 : kinetic energy threshold (GeV) for e+ annihilation
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(2) - WHAT(3) : not used

     WHAT(4) - WHAT(6): see below

For SDUM = PHOT-THR:

     WHAT(1) > 0.0 : energy threshold (GeV) for Compton scattering
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(2) > 0.0 : energy threshold (GeV) for photoelectric
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(3) > 0.0 : energy threshold (GeV) for gamma pair production
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(4) - WHAT(6): see below

For SDUM = PHO2-THR:

     WHAT(1) > 0.0 : energy threshold (GeV) for Rayleigh scattering
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(2) > 0.0 : energy threshold (GeV) for photonuclear interactions
             = 0.0 : ignored
             < 0.0 : resets to default
               Default: 0.

     WHAT(3) : not used

     WHAT(4) - WHAT(6): see below

For SDUM equal to ELPO-THR, ANNH-THR, PHOT-THR, PHO2-THR:

     WHAT(4) = lower bound (or corresponding name) of the material indices in
               which the respective thresholds apply
               ("From material WHAT(4)...")
               Default = 3.

     WHAT(5) = upper bound (or corresponding name) of the material indices in
               which the respective thresholds apply
               ("... to material WHAT(5)...")
               Default  = WHAT(4)

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

     Default (option EMFCUT not requested): no leading particle biasing, unless
              requested by the alternative option EMF-BIAS.
              Transport cutoffs are set equal to production thresholds for discrete
              electron interactions and for discrete photon production.

Notes:

• 1) Default values are available for the electron and photon production thresholds in electromagnetic interactions, but they are generated by a complex logic based on possible other settings (transport cutoffs, delta-ray production thresholds, DEFAULTS card, other defaults). It is not always guaranteed that the resulting values be appropriate to the problem of interest. Therefore, in order to have good control of the physics, the user is recommended to provide explicit threshold values, or at least to check them on the main output.

• 2) Transport cutoffs set by EMFCUT override the production thresholds (set with SDUM = PROD-CUT) for discrete interactions, but only if higher than them. If lower, the production thresholds apply, of course. The production thresholds are overridden only for transport purposes, that is, particles with energy higher than production thresholds and lower than transport cutoffs are not transported but are still generated (their energy is deposited at the point of production). It is suggested to avoid such a situation unless it is really necessary, as particle generation demands a considerable computer time and partially offsets the gain due to a higher transport cutoff.

• 3) If WHAT(3) is set > 0, Leading Particle Biasing (LPB) is applied at photon and/or electron interactions, in a manner similar to that provided by option EMF-BIAS (see the Note 9 to that option for a description of the technique and guidance to its use). However, EMF-BIAS offers more flexibility, since it allows to set also an energy threshold for LPB, and to select a number of generations to which it can be applied.

• 4) The minimum threshold energy for transport and production is 1 keV.

Example 1 (number-based):

 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
 EMFCUT       -1.0E-5    1.0E-5       0.0       4.0       8.0          PROD-CUT
 *   A production threshold of 10 keV is set for electrons, positrons and
 *   photons in all materials from 4 to 8.

The same example, name-based:

 EMFCUT       -1.0E-5    1.0E-5       0.0    HELIUM    OXYGEN          PROD-CUT

Example 2 (number-based):

 EMFCUT        -0.002     2.E-4       1.0       1.0      15.0
 EMFCUT       -1.0E-4     1.E-5      -1.0       7.0      11.0       2.0
 *   A kinetic energy transport cutoff for electrons and positrons is set
 *   at 100 keV in regions 7, 9 and 11 and at 2 MeV in all other regions from 1
 *   to 15. Photon transport cutoff is set equal to 10 keV in regions 7, 9, 11
 *   and to 200 keV in the other regions.

The same example, name-based, assuming that the 15 regions are all the regions of the problem:

 EMFCUT        -0.002     2.E-4       1.0  FirstReg  @LASTREG
 EMFCUT       -1.0E-4     1.E-5      -1.0   Seventh  Eleventh       2.0