FLUKA: DELTARAY
Previous Index Next
DELTARAY
Activates delta ray production by muons and charged hadrons and controls the
accuracy of the dp/dx tabulations
See also IONFLUCT
WHAT(1)
> 0.0 : kinetic energy threshold (GeV) for delta ray production
(discrete energy transfer). Energy transfers lower than
this energy are assumed to take place as continuous energy
losses
= 0.0 : ignored
< 0.0 : resets the default to infinite threshold, i.e. no delta ray
production
Default
= 0.001 (1 MeV) if option DEFAULTS is not used, or if it
is used with SDUM
= NEW-DEFAults.
If DEFAULTS is used with SDUM
= CALORIMEtry,
HADROTHErapy, ICARUS or PRECISIOn, the default
is 0.0001 (100 keV).
If it is used with any other SDUM
value, the default is
-1.0 (continuous slowing down approximation without
production of delta rays)
WHAT(2)
> 0.0 : number of logarithmic intervals for dp/dx momentum loss
tabulation
= 0.0 : ignored
< 0.0 : resets the default to 50.0
Default
= 50.0 (this is the default if option DEFAULTS is not
used, or is used with anything but SDUM
= CALORIMEtry,
ICARUS or PRECISIOn).
With the latter, the default is 80.
See Note 2 below for more details
WHAT(3)
> 1.0 : logarithmic width of dp/dx momentum loss tabulation
intervals (ratio between upper and lower interval limits).
0.0 =< WHAT(3)
=< 1.0: ignored
< 0.0 : resets the default to 1.15
Default
= 1.15 (this is the default if option DEFAULTS is not
used, or is used with any SDUM
value but HADROTHErapy,
ICARUS or PRECISIOn).
If DEFAULTS is used with SDUM
= ICARUS or PRECISIOn, the
default is 1.04.
With SDUM
= HADROTHErapy the default is 1.03.
See Note 2 below for more details
WHAT(4)
= lower index bound (or corresponding name) of materials where
delta ray production or specified tabulation accuracy are
requested
("From material WHAT(4)
...")
Default
= 3.0
WHAT(5)
= upper index bound (or corresponding name) of materials where
delta ray production or specified tabulation accuracy are
requested
("...to material WHAT(5)
...")
Default
= WHAT(4)
WHAT(6)
= step length in assigning indices
("...in steps of WHAT(6)
")
Default
= 1.0
SDUM
: = PRINT: prints dE/dx tabulations for the given materials on
standard output (see Note 1)
= NOPRINT: resets to no printing a possible previous request for
these materials
= blank: ignored
Default
: NOPRINT
Default
(option DELTARAY not requested): the defaults depend on option
DEFAULTS as explained above. See also Note 9.
Notes:
1) To calculate energy loss by charged particles, FLUKA sets up and
uses internally tables of momentum loss per unit distance (dp/dx)
rather than the more commonly used dE/dx. However, if requested to
print those tables, it outputs them as converted to dE/dx.
2) The upper and lower limit of the dp/dx tabulations are determined by
the options BEAM and PART-THR, or by the corresponding defaults.
Therefore, either the number OR the width of the intervals are
sufficient to define the tabulations completely. If both WHAT(2)
and
WHAT(3)
are specified, or if the value of both is defined implicitly
by the chosen default, the most accurate of the two resulting
tabulations is chosen.
3) The lower tabulation limit is the momentum of the charged particle
which has the lowest transport threshold. The upper limit
corresponds to the maximum primary energy (as set by BEAM) plus an
additional amount which is supposed to account for possible
exoenergetic reactions, Fermi momentum and so on.
4) This option concerns only charged hadrons and muons. Delta rays
produced by electrons and positrons are always generated, provided
their energy is larger than the production threshold defined by
option EMFCUT.
5) Request of delta ray production is not alternative to that
of ionisation fluctuations (see IONFLUCT). The two options, if not
used at the same time, give similar results as far as transport and
energy loss are concerned, but their effect is very different
concerning energy deposition: with the IONFLUCT option the energy
lost is sampled from a distribution but is deposited along the
particle track, while DELTARAY, although leading to similar
fluctuations in energy loss, will deposit the energy along the delta
electron tracks, sometimes rather far from the primary trajectory.
IONFLUCT can be used even without requesting the EMF option, while
when requesting DELTARAY the EMF card must also be present (or
implicitly activated by default) - see option DEFAULTS - if
transport of the generated electrons is desired.
6) Normally, the energy threshold for delta ray production should be
higher than the electron energy transport cutoff specified by
EMFCUT. If it is not, the energy of the delta electron produced is
deposited on the spot. As explained above, this will result in
correct energy loss fluctuations but with the energy deposited along
the particle track, a situation similar to that obtained with
IONFLUCT alone.
7) Note that FLUKA makes sure that the threshold for delta ray
production is not set much smaller than the average ionisation
potential.
8) Presently, DELTARAY can be used together with the IONFLUCT option
with a threshold for delta rays chosen by the user. As a result,
energy losses larger than the threshold result in the production and
transport of delta electrons, while those smaller than the threshold
will be sampled according to the correct fluctuation distribution.
9) Here are the settings for delta ray production and dp/dx tabulations
corresponding to available DEFAULTS options:
- ICARUS, PRECISIOn: threshold for delta ray production 100 keV;
momentum loss tabulation with 80 logarithmic intervals or 1.04
logarithmic width (whichever is more accurate)
- CALORIMEtry: threshold for delta ray production 100 keV;
momentum loss tabulation with 80 logarithmic intervals or 1.15
logarithmic width
- HADROTHErapy: threshold for delta ray production 100 keV;
momentum loss tabulation with 50 logarithmic intervals or 1.03
logarithmic width
- NEW-DEFAults, or DEFAULTS missing: threshold for delta ray
production 1 MeV; momentum loss tabulation with 50 logarithmic
intervals or 1.15 logarithmic width
- Any other SDUM
value: no delta ray production; momentum loss
tabulation with 50 logarithmic intervals or 1.15 logarithmic
width
Example, for a number-based input:
DELTARAY 0.01 30. 0.0 3.0 18.0 PRINT
DELTARAY 0.02 0.0 1.05 4.0 12.0 8.0 NOPRINT
An equivalent example, for a name-based input, is:
DELTARAY 0.01 30. 0.0 HYDROGEN TANTALUM PRINT
DELTARAY 0.02 0.0 1.05 HELIUM COPPER 8.0 NOPRINT
The following is an example where a threshold of 500 keV is set for delta
ray production in ALL materials:
DELTARAY 5.E-4 0.0 0.0 HYDROGEN @LASTMAT PRINT
Previous Index Next
