defines the particle types to be discarded (i.e. not to be transported)
WHAT(1...6) = id-number of particles to be discarded (see particle
numbering in 5}).
Setting one of the WHATs to a negative value will cancel a previous
corresponding DISCARD command (explicit or by default).
When full heavy particle transport is activated (see EVENTYPE), discarding
of heavies can be performed setting the WHATs = (1000 + Kheavy),
with Kheavy = 3....6 (heavy ion particle code:
3 = 2-H, 4 = 3-H, 5 = 3-He, 6 = 4-He, 7-12 = fission fragments.
Undiscarding heavies is obtained by setting WHATs equal to (1000 - Kheavy).
The whole scheme is shown in the following table:
Discard Undiscard
2-H 1003 997
3-H 1004 996
3-He 1005 995
4-He 1006 994
fission fragments 1007-1012 993-988
No default
SDUM: not used
Default (option DISCARD not given): only neutrinos and antineutrinos are
discarded by default. Set the WHATs = -5., -6., -27., -28., -43. or
-44. in order to have them transported.
Notes:
1) There is no limit to the number of DISCARD definitions given.
Discarding a particle means that that type of particle will possibly
be produced but not transported.
2) The user may want to process some particle types with other programs
providing only the production by the FLUKA code. These particles can
be discarded. The results will then not contain the contribution of
the discarded particle types and of their descendants.
3) Neutrinos are always discarded by default, to avoid useless
tracking. To force neutrinos (or other particles) to be NOT
discarded, set their particle number to negative. In that case,
however, remember that:
- no neutrino cross sections are available for transport in FLUKA:
these particles are just tracked through the geometry until they
escape. Boundary crossing and tracklength density can however be
scored if requested
- if neutrinos are not discarded, their transport threshold is set
= 0. by default. This value can be changed (by option PART-THR),
but it must be kept in mind that the energy of any neutrino
produced below the threshold WILL BE DEPOSITED LOCALLY, generating
a likely bias in dose calculations.
4) WARNING: discarding the particles which propagate the hadronic
cascade (neutrons, protons, pions) will lead in general to
unpredictable results.
Example:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
DISCARD 3.0 4.0 7.0 10.0 11.0 23.0
* This example illustrates a typical situation where the use of DISCARD
* can considerably reduce the computing time: for instance in pure
* hadronic or neutron problems (fluence calculations without interest in
* energy deposition). In this case electrons, positrons, photons, muons
* and pi0 do not contribute to the result and can be discarded
