Provides extra information about materials
(see also MATERIAL, STERNHEIme)
a) can supply extra information about gaseous materials and
materials with fictitious or effective density.
b) can be used to override the default average ionisation potential.
c) allows a rough rescaling of thermal neutron cross sections
if the actual material temperature is different from the one of
the low energy neutron cross section data set.
d) allows to set a flag to call the user routine USRMED every
time a particle is going to be transported in the selected
material(s)
For SDUM whatever except LOWNTEMP, USERDIRE:
WHAT(1) = Gas pressure in atmospheres.
0.0 : ignored
< 0.0 : resets to 1 atm a possible previously input
pressure value
WHAT(2) = RHOR factor : this factor multiplies the density of the
material(s) when calculating the density effect parameters
(e.g. if a reduced density is used to simulate voids, but
of course the density effect parameters must be computed
with the actual local physical density at the microscopic
level).
= 0.0 : ignored
< 0.0 : a possible previously input value is restored to
default = 1.0
Default = 1.0
WHAT(3) > 0: average ionisation potential to be used for dE/dx
calculations (eV)
< 0: a default value of the average ionisation potential
is obtained from the systematics of Ziegler [Zie77]
or Sternheimer, Berger and Seltzer [Ste84]
= 0: ignored
Default: ionisation potential calculated from systematics
WHAT(4) = lower bound of the indices of materials in which gas
pressure, RHOR factor or ionisation potential are set
("From material WHAT(4)...")
Default = 3.0
WHAT(5) = upper bound of the indices of materials in which gas
pressure, RHOR factor or ionisation potential are set
("... to material WHAT(5)...")
Default = WHAT(4)WHAT(6) = step length in assigning indices
("...in steps of WHAT(6)")
Default = 1.
Default (option MAT-PROP not given): if the density of the default
material or that assigned by a MATERIAL card is > 0.01, the
material is not assumed to be a gas. Otherwise it is a gas
at a default pressure of 1 atmosphere. If the material is a
compound, the average ionisation potential is that resulting
from applying Bragg's rule of additivity to stopping power.
For SDUM = LOWNTEMP:
WHAT(1) = Temperature ratio (T_actual/T_xsec) with respect to the
nominal one. The nominal temperature T_xsec (given by
WHAT(3), see below) is the temperature for which the
neutron cross sections of the FLUKA material(s) concerned
have been prepared (see the Table in 10}). See Notes below
for more details and limitations.
= 0.0 : ignored
< 0.0 : a possible previously given value is restored to
default = 1.0
Default = 1.0
WHAT(2) = Number of (thermal) groups to which the temperature
ratio has to be applied. It must be <= N_th, where
N_th is the number of thermal groups in the cross section
library. If WHAT(2) < N_th, the last WHAT(2) groups are
affected (see the LOW-NEUT option for setting the number
of thermal groups).
= 0.0 : ignored
< 0.0 : a possible previously given value is restored to
default = 0.0
Default = 0.0 (i.e., no correction, the whole command is
ignored).
WHAT(3) = Nominal temperature (K) of the indicated FLUKA materials
= 0.0 : ignored
< 0.0 : a possible previously given value is restored to
default (3rd identifier, see below)
Default = the temperature given as 3rd identifier of the
associated low energy neutron data set (see
LOW-MAT and the cross section description in the
associated low energy neutron data set (see
LOW-MAT and the cross section description in 10})
WHAT(4) = lower bound of the indices of materials in which the
temperature rescaling has to be applied
("From material WHAT(4)...")
Default = 3.0
WHAT(5) = upper bound of the indices of materials in which the
temperature rescaling has to be applied
("... to material WHAT(5)...")
Default = WHAT(4)WHAT(6) = step length in assigning indices
("...in steps of WHAT(6)")
Default = 1.
For SDUM = USERDIREctive
WHAT(1) = 0.0 : ignored
> 0.0 : a call to the user routine USRMED will be performed
at run time every time a particle is going to be transported
in the selected materials (spot depositions ARE anyway performed)
< 0.0 : a possible previously given value is restored to
default = no call
Default = no call (-1.0)
WHAT(2) = Not used
WHAT(3) = Not used
WHAT(4) = lower bound of the indices of materials for which the
call to USRMED has to be performed
("From material WHAT(4)...")
Default = 3.0
WHAT(5) = upper bound of the indices of materials for which the
call to USRMED has to be performed
("... to material WHAT(5)...")
Default = WHAT(4)WHAT(6) = step length in assigning indices
("...in steps of WHAT(6)")
Default = 1.
Default (option MAT-PROP not given): no extra information about the
assigned materials is supplied.
Notes:
SDUM = blank (i.e. /= LOWNTEMP, USERDIREctive):
When issuing a MATERIAL definition the gas pressure is set to
1 if the density RHO is < 0.01. If this value is not
acceptable to the user, a MAT-PROP card must be issued AFTER
the MATERIAL card to force a different value of the gas
pressure. Note that this is one of the rare cases (with GLOBAL,
DEFAULTS and PLOTGEOM) where sequential order of input cards is of
importance in FLUKA.
A non-zero value of WHAT(1) must be given only for gases: it
is important when calculating the density effect parameters
of the stopping power (see Note to option STERNHEIme).
If WHAT(1) is set to a value > 0.0, the transport of hadrons will
be calculated according to a density RHO defined at the actual pressure
by the corresponding MATERIAL card, while the density effect
correction to stopping power will be calculated using a density
RHO(NTP) = RHO/WHAT(1) and then re-scaled to the actual density.
When giving a WHAT(2) non-zero value, remember that if RHO (defined
by a MATERIAL card) indicates the "transport (effective) density",
the "physical density" used to calculate the density effect on
stopping power will be RHOR*RHO.
SDUM = LOWNTEMP:
The temperature ratio is used to rescale the thermal group
velocities, absorption probabilities, gamma generation
probabilities, fission probabilities and kermas. For absorption,
fission and gamma generation a 1/v dependence of the corresponding
cross sections is implicitly assumed: IF THIS IS NOT THE CASE THE
WHOLE PROCEDURE IS MEANINGLESS.
No modification is made to the elastic cross section and hence to the
downscattering matrix: THIS CAN BE A VERY BAD APPROXIMATION,
ESPECIALLY FOR LIGHT MATERIALS. No modification is applied for
possible Doppler broadening effects on resonances for thermal and
epithermal neutrons: again, this can be a bad approximation.
The total cross section is rescaled according to the modified
absorption and fission cross sections.
The temperature ratio is used to rescale the thermal group(s)
velocities, absorption probabilities, gamma generation prob-
abilities, fission probabilities and kermas. For absorption,
fission and gamma generation it is implicitly assumed a 1/v
dependence of the corresponding cross section(s): if this is
not the case all the procedure is crazy. No modification is
made to the elastic cross section and hence to the downscat-
tering matrix: this can be a very bad approximation, mostly
for light materials. No modification is applied for
possible Doppler broadening effects on resonances for thermal
and epithermal neutrons: again this can be a bad approxim-
ation. The total cross section is rescaled according to the
modified absorption and fission ones.
Cross section rescaling is applied to the FLUKA materials at
run time, that is if for example two 10-B materials are def-
ined and both point to the same cross section data set, a
possible temperature rescaling will affect only the FLUKA
material indicated by MAT-PROP, while the other one will be
unaffected, although they share the same low energy neutron
cross section data set.
Velocity setting is applied for compounds INDEPENDENT from
cross section rescaling, that is, a (nominal) temperature
input for a compound is fully meaningful and will be used for
velocity computation. However cross section rescaling is
applied on single constituents (of course!) and therefore...
!!!!! IMPORTANT WARNING !!!!
...it cannot be used for compounds unless the corresponding
neutron cross section data sets is a pre-mixed one. Other-
wise a new compound must be created with new elemental
constituents and the correction must be invoked for each
constituent.
SDUM = USERDIREctive:
User routine USRMED is typically used to implement albedo and
refraction, especially in connection with optical photon
transport as defined by OPT-PROP. See 13} for instructions.
Example 1:
* Call USRMED every time a particle is going to be transported in Pb Glass or
* in plexiglas (PMMA)
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MATERIAL 1. 1.00794 8.3748E-5 7. 0.0 1. HYDROGEN
MATERIAL 6. 12.011 2.265 8. 0.0 0. CARBON
MATERIAL 8. 15.9994 0.001429 9. 0.0 0. OXYGEN
MATERIAL 14. 28.0855 2.33 10. 0.0 0. SILICON
MATERIAL 22. 47.88 4.54 11. 0.0 0. TITANIUM
MATERIAL 33. 74.9216 5.73 12. 0.0 0. ARSENIC
MATERIAL 82. 207.2 11.35 13. 0.0 0. LEAD
MATERIAL 0. 0. 6.22 18. 0.0 0. LEADGLAS
COMPOUND -0.156453 9. -0.080866 10. -0.008092 11. LEADGLAS
COMPOUND -0.002651 12. -0.751938 13. 0.0 0. LEADGLAS
MATERIAL 0. 0. 1.19 15. 0.0 0. PMMA
COMPOUND -0.080538 7. -0.599848 8. -0.319614 9. PMMA
MAT-PROP 1.0 0.0 0.0 15. 18. 3. USERDIRE
Example 2:
* Lung tissue with ICRP composition and Sternheimer parameters
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MATERIAL 1. 1.00794 8.3748E-5 3. 0.0 1. HYDROGEN
MATERIAL 6. 12.011 2.265 6. 0.0 0. CARBON
MATERIAL 7. 14.00674 0.0011653 7. 0.0 0. NITROGEN
MATERIAL 8. 15.9994 0.001429 8. 0.0 0. OXYGEN
MATERIAL 11. 22.98977 0.971 9. 0.0 0. SODIUM
MATERIAL 12. 24.305 1.74 10. 0.0 0. MAGNESIU
MATERIAL 15. 30.97376 2.2 11 0.0 0. PHOSPHO
MATERIAL 16. 32.066 2.0 12. 0.0 0. SULFUR
MATERIAL 17. 35.4527 2.9947E-3 13 0.0 0. CHLORINE
MATERIAL 19. 39.0983 0.862 14. 0.0 0. POTASSIU
MATERIAL 20. 40.078 1.55 15. 0.0 0. CALCIUM
MATERIAL 26. 55.847 7.874 16. 0.0 0. IRON
MATERIAL 30. 65.39 7.133 17. 0.0 0. ZINC
* Local density of lung is 1.05 g/cm3
MATERIAL 0.0 0.0 1.05 18. 0.0 0. LUNG
COMPOUND -0.101278 3. -0.10231 6. -0.02865 7. LUNG
COMPOUND -0.757072 8. -0.00184 9. -0.00073 10. LUNG
COMPOUND -0.0008 11. -0.00225 12. -0.00266 13. LUNG
COMPOUND -0.00194 14. -0.00009 15. -0.00037 16. LUNG
COMPOUND -0.00001 30. 0. 0. 0. 0. LUNG
* Average density of lung is 1.05*0.286 = 0.3 g/cm3. Average ionisation
* potential is 75.3 eV (At. Data Nucl. Data Tab. 30, 261 (1984))
MAT-PROP 0.0 0.286 75.3 18. 0. 0.
STERNHEI 3.4708 0.2261 2.8001 0.08588 3.5353 0. 18
Example 3:
* Definition of air at non-standard pressure.
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MATERIAL 6. 12.011 2.265 6. 0.0 0. CARBON
MATERIAL 7. 14.00674 0.0011653 7. 0.0 0. NITROGEN
MATERIAL 8. 15.9994 0.001429 8. 0.0 0. OXYGEN
MATERIAL 18. 39.948 1.662E-3 9. 0.0 0. ARGON
* AIR defined as air with normal NTP density (0.001205)
MATERIAL 0.0 0.0 0.001205 10. 0.0 0. AIR
COMPOUND -0.000124 6. -0.755267 7. -0.231781 8. AIR
COMPOUND -0.012827 9. AIR
* AIR2 defined as air with a density 0.002410, double of that at NTP
MATERIAL 0.0 0.0 0.002410 11. 0.0 0. AIR2
COMPOUND -0.000124 6. -0.755267 7. -0.231781 8. AIR2
COMPOUND -0.012827 9. AIR2
* The pressure of AIR2 is 2 atm. Set also the ionisation potential = 85.7 eV
MAT-PROP 2.0 0.0 85.7 10.
STERNHEI 10.5961 1.7418 4.2759 0.10914 3.3994 0. 11
Example 4:
* The total and capture cross sections of Au have a good 1/v dependence in the
* thermal region. Here we assume Gold to be at a temperature of 300K, while
* the cross sections in the FLUKA library are at 293K.
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MATERIAL 79.0 196.9665 19.32 15. 0.0 0.
* Next card is not strictly necessary, since it doesn't change any default
LOW-MAT 15.0 79.0 197.0 293.0 0.0 0. GOLD
* (300/293 = 1.02389). The present library has only 1 thermal group.
MAT-PROP 1.02389 1.0 293. 15. 0.0 0. LOWNTEMP
