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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 : not allowed
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 : not allowed
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 : not allowed 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 : not allowed 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)
: not used
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) Electron and positron transport cutoffs (indicated in the main output with Ecut) and photon transport cutoffs (Pcut) are assigned by region, while electron/positron production cutoffs (Ae) and photon production cutoffs (Ap) are assigned by material. When the transport cutoffs in a given region are larger than those of production for discrete interactions in the corresponding material, 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. When instead the transport cutoffs are lower than the production ones, they are increased to be equal to them. 4) The minimum threshold energy for transport and production of photons is 100 eV. For electrons and positrons, it is 1 keV. Example 1 (number-based):
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7...
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

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