[Gate-users] Biasing -> variance reduction technique

[Daniel]

Hello to all,


I try to understand the 'setSecBiasing' command.

I am simulating an X-ray tube and use

/process/em/setSecBiasing eBrem anode_target 3 100 MeV

for testing with visualization and a small number of particles.


In the visualization I can see that if a bremsstrahlung interaction 
occurs three photons are generated:

1363 88    0.268   -0.346     89.3    0.0244  0.00129 0.000384      89.3 
anode_target_phys eBrem
1364 :----- List of 2ndaries - #SpawnInStep=  3(Rest= 0,Along= 0,Post= 
3), #SpawnTotal= 78 ---------------
1365 :     0.268    -0.346      89.3   0.00589 gamma
1366 :     0.268    -0.346      89.3   0.00785 gamma
1367 :     0.268    -0.346      89.3  0.000462 gamma

1368 :----------------------------------------------------------------- 
EndOf2ndaries Info ---------------
1369 89    0.268   -0.346     89.3    0.0241 0.000215 7.4e-05      89.3 
anode_target_phys eIoni
1370 90    0.268   -0.346     89.3    0.0228 0.000317 9.4e-05      89.3 
anode_target_phys eIoni
1371 :----- List of 2ndaries - #SpawnInStep=  1(Rest= 0,Along= 0,Post= 
1), #SpawnTotal= 79 ---------------
1372 :     0.268    -0.346      89.3   0.00107


But I don't understand how they can have different energies because 
there is only one electron leaving this interaction (i.e. the 
bremsstrahlung is not complete), see attached screenshot.


My questions are the following:

- What is the energy of the outgoing electron and how is it calculated?

- What is a good strategy to find this outgoing electron energy in the 
very long list created with 'tracking/verbose 2'? I guessed it is the 
one at step 89, but it has 0.0241 MeV energy while the ingoing electron 
had 0.0244 MeV (step 88). The energy sum of the outgoing e- and the 3 
gammas does not match the ingoing e-.


Thanks in advance,

Daniel

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