Gabriele Cosmo
49 lines
2.2 KiB
Plaintext
49 lines
2.2 KiB
Plaintext
Example GB02 : force collision biasing
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This example illustrates how to make a force collision biasing in a way
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that is essentially the same than the MCNP one.
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Generally speaking, the scheme consists of a G4VBiasingOperator that takes
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decisions on what sort of biasing is to be applied. The operator makes these
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decision on requests of the G4BiasingProcessInterface process. This process
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wraps an actual physics process and asks to the operator about what sort of
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biasing it should apply. This operator selects G4VBiasingOperation objects that
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implement the actual biasing content.
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In the present case, we make use of the biasing operator
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G4BOptrForceCollision
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that implements an "a la MCNP" force collision scheme for one particle type.
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This operator is defined in processes/biasing/generic. It is a non-trivial
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operator.
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It starts by "splitting" the track at the volume entrance. Then this
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track is forced to fly through the volume with no interaction. The
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G4OptnForceFreeFlight biasing operation is used for that.
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The second copy is then forced to interact within the volume, which is
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handled by the G4BOptnForceCommonTruncatedExp operation : it is common as it
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takes care of several processes by itself, and it applies a truncated
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exponential law : ie and exponential law limited to the [0,L] range, L being
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the volume width along the track flight.
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To allow several particle types to undergo this force interaction scheme,
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an other operator is defined
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GB02BOptrMultiParticleForceCollision
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which holds one G4BOptrForceCollision per particle type, and which
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delegates then everything to it.
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The geometry is simple : a single volume to which an instance of
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GB02BOptrMultiParticleForceCollision is attached to.
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The wrapping of physics processes by G4BiasingProcessInterface processes
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is simply handled by the G4GenericBiasingPhysics physics constructor, as shown
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in the main program.
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Then, at whatever level (stepping action, or sensitive detector) the
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statistical weight of the track can be obtained as:
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w = track->GetWeight() ; |