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Question Forced Collision in daughter volumes 

Forum: Biasing and Scoring
Date: 01 Mar, 2018
From: Youming Yang <Youming Yang>

Hello Geant4 community,

I could not find much documentation on forced collisions, so I would just like to inquire here:

I am attempting to perform a reweighting of a photon as it flies through a geometry that contains daughter volumes, and utilize the forced collision class to properly calculate the reweighting given interactions that could have occurred.

If I apply forced collisions to the mother volume, the particle will: 1. clone when entering biasing volume (one particle will free-flight, other will force collide) 2. Exit biasing when entering daughter volume (do whatever it needs to do in this volume) 3. Clone when re-entering mother volume, again one particle will free-fly and other will collide

In the above, ray-tracing cannot be gauranteed in daughter volume at step 2.

If I apply forced collision to just the daughter volume, then ray-tracing cannot be gauranteed in the mother volume itself.

When I try to apply forced collisions to the mother _and_ daughter volume, I see this warning message:

 >  *********************************************************************************************************
 >  * G4Track Information:   Particle = gamma,   Track ID = 2,   Parent ID = 1
 >  *********************************************************************************************************
 >  
 >  Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
 >      0        0        0      -10         1        0        0       490    >  test.phys initStep
 >  Proposing biasing operation SharedForceInteraction
 >  Proposing biasing operation SharedForceInteraction
 >  Operation applied SharedForceInteraction
 >  Operation applied SharedForceInteraction
 >      1        0        0     -9.9         1        0      0.1       490  test1.phys Transportation
 >  Proposing biasing operation SharedForceInteraction
 >  Proposing biasing operation SharedForceInteraction
 >  Proposing nonphysics biasing operation Cloning
 >  Operation applied Cloning
 >  Operation applied SharedForceInteraction
 >  Operation applied SharedForceInteraction
 >      2        0        0     -9.9         1        0        0       490  test1.phys biasWrapper(0)
 >      3        0        0      9.9         1        0     19.8       510   test.phys Transportation
 >  Proposing nonphysics biasing operation Cloning
 >  Operation applied Cloning
 >      4        0        0      9.9         1        0        0       510   test.phys biasWrapper(0)
 >  Proposing biasing operation FreeFlight-compt
 >  Proposing biasing operation FreeFlight-phot
 >  
 >  -------- WWWW ------- G4Exception-START -------- WWWW -------
 >  *** G4Exception : BIAS.GEN.05
 >        issued by :  G4BOptnForceFreeFlight::ApplyFinalStateBiasing(...)
 >   Initial track weight is null !
 >  
 >  *** This is just a warning message. ***
 >  -------- WWWW -------- G4Exception-END --------- WWWW -------
 >  
 >  Operation applied FreeFlight-phot
 >  
 >  -------- WWWW ------- G4Exception-START -------- WWWW -------
 >  *** G4Exception : BIAS.GEN.05
 >        issued by :  G4BOptnForceFreeFlight::ApplyFinalStateBiasing(...)
 >   Initial track weight is null !
 >  
 >  *** This is just a warning message. ***
 >  -------- WWWW -------- G4Exception-END --------- WWWW -------
 >  
 >  Operation applied FreeFlight-compt
 >      5        0        0       10         1        0      0.1       510       World Transportation
 >  Exiting Biasing.
 >  Exiting Biasing.
 >  Exiting Biasing.
 >  Exiting Biasing.
 >  Exiting Biasing.
 >      6        0        0    1e+04         1        0 9.99e+03  1.05e+04  OutOfWorld Transportation
 >  
 >  *********************************************************************************************************
 >  * G4Track Information:   Particle = gamma,   Track ID = 16,   Parent ID = 2
 >  *********************************************************************************************************

I am wondering if this behavior is known/intended?

thank you in advance. Ming

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1 None: Re: Forced Collision in daughter volumes   (Marc Verderi - 01 Mar, 2018)
(_ None: Re: Forced Collision in daughter volumes   (Youming Yang - 02 Mar, 2018)
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