FLUKA: EMFCUT
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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.
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, 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
: no default, it must be set, 0 is an allowed
value but rarely the correct one (see above)
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, or PROMPT, or DELAYED:
|WHAT(1)
| = electron and positron transport energy cutoff in GeV. If
SDUM
= blank, the cutoff refers to all e+/-; if SDUM
= PROMPT,
it concerns only prompt ones; if SDUM
= DELAYED, only electrons
and positrons emitted as decay radiation.
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). If SDUM
= blank, the
cutoff refers to all photons; if SDUM
= PROMPT, it concerns only
prompt ones; if SDUM
= DELAYED, only photons emitted as decay
radiation.
= 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)
("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)
("...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 or = PROMPT, or = DELAYED 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): 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.
3) The minimum threshold energy for transport and production of photons
is 100 eV. For electrons and positrons, it is 1 keV.
4) Different transport cutoffs for prompt and decay e+/e-/gamma can
be set also by WHAT(5)
of command RADDECAY, but only identically
for all regions, while EMFCUT with SDUM
= PROMPT or DELAYED can be
tuned per region.
Example 1 (number-based):
EMFCUT -1.0E-5 1.0E-5 0.0 4.0 8.0 PROD-CUT
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
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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