Sets the energy thresholds for electron and photon production in different
materials, and electron and photon transport cut-offs 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 cut-off in all
regions made of this material (see Note 1 below)
WHAT(2) > 0.0 : energy threshold for photon production in GeV
= 0.0 : ignored
Default: equal to the lowest photon transport cut-off in all
regions made of this material (see Note 1 below)
WHAT(3) = FUDGEM parameter. This parameter takes into account the
contribution of atomic electrons to multiple scattering. For
production and transport cut-offs 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 of the FLUKA material number where electron/positron
and photon production thresholds respectively equal to |WHAT(1)|
and WHAT(2) apply. The material numbers are those pre-defined or
assigned using a MATERIAL card.
("From material WHAT(4)...")
Default: 3.0
WHAT(5) = upper bound of the FLUKA material number where electron/positron
and photon production thresholds respectively equal to |WHAT(1)|
and WHAT(2) apply. The material numbers 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.
For SDUM = blank:
|WHAT(1)| = electron and positron transport energy cut-off in GeV.
WHAT(1) > 0.0 : electron and positron cut-off is expressed as total
energy (kinetic plus rest mass)
< 0.0 : electron and positron transport cut-off 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 cut-off is set equal to the production
threshold for discrete electron interactions
WHAT(2) > 0.0 : photon transport energy cut-off (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 cut-off 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 of the region indices with electron cut-off equal to
|WHAT(1)| and/or photon cut-off equal to WHAT(2) and/or leading
particle biasing
("From region WHAT(4)...")
Default: = 2.0.
WHAT(5) = upper bound of the region indices with electron cut-off equal to
|WHAT(1)| and/or photon cut-off 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.
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 of the material indices in which the respective thresholds
apply
("From material WHAT(4)...")
Default = 3.
WHAT(5) = upper bound 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.
Cut-offs 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
cut-offs, 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 cut-offs 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 cut-offs 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 cut-off.
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.
Example 1:
*...+....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.
Example 2:
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 cut-off 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 cut-off is set equal to 10 keV in regions 7, 9, 11
* and to 200 keV in the other regions.
