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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:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
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
* In this example, delta rays with energies higher than 20 MeV (0.02 GeV)
* will be produced in materials 4 and 12; for the same materials,
* logarithmic intervals with a ratio of 1.05 between the upper and the
* lower limit of each interval are requested for the dp/dx tabulation. For
* all other materials with number between 3 and 18, delta rays are
* produced above 10 MeV and 30 intervals are used in the dp/dx tabulation.
* Tabulations of dE/dx are printed for all materials except 4 and 12.
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

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