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DISCARD

defines the particle types to be discarded (i.e. not to be transported)

     WHAT(1...6) = id-number or name of particles to be discarded (see particle
                   numbers and names in (5)).

If one of the WHATs is preceded by a minus sign a previous corresponding DISCARD command (explicit or by default) will be canceled.

When full heavy particle transport is activated (see IONTRANS), 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.

Except for fission fragments, the corresponding names can also be used.

Undiscarding heavies is obtained by setting WHATs equal to (1000 - Kheavy), or by making the corresponding names to be preceded by a minus sign. The whole scheme is shown in the following table:

                                 Discard                Undiscard
        2-H                   1003 or DEUTERON        997 or -DEUTERON
        3-H                   1004 or TRITON          996 or -TRITON
        3-He                  1005 or 3-HELIUM        995 or -3-HELIUM
        4-He                  1006 or 4-HELIUM        994 or -4-HELIUM
        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.,
             -44. or NEUTRIE, ANEUTRIE, NEUTRIM, ANEUTRIM, NEUTRIT, ANEUTRIT
             in order to have them transported.

Notes:

• 1) There is no limit to the number of DISCARD definitions given.

• 2) Discarding a particle means that that type of particle will possibly be produced but not transported.

• 3) 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.

• 4) Neutrinos are always discarded by default, to avoid useless tracking. To force neutrinos (or other particles) to be NOT discarded, make their particle number or name to be preceded by a minus sign. 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 (number-based):

 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
 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

The same example, name-based:

 DISCARD     ELECTRON  POSITRON    PHOTON     MUON+     MUON-    PIZERO