[Gate-users] Scintillating Materials

[Amy Meldrum]

Gate users,

I have been running a simple simulation with a scintillating square and an
alpha or beta source, which was running quite well. By turning verbosity =
2 and tracking some of the particles' lives, I could confirm that the only
events named "Scintillation" in my Hits.dat file were being generated in my
scintillator volume. An example of the expected screen output is below:

*********************************************************************************************************
* G4Track Information:   Particle = e-,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng
 NextVolume ProcName
    0     1.29    0.386    0.589       0.6        0        0         0
Waterbox_phys initStep
    1     1.29    0.386    0.585       0.6 0.000371  0.00364   0.00364
ScinLayer_phys Transportation
    2     1.29    0.386    0.129     0.475    0.125    0.456      0.46
ScinLayer_phys ElectronIonisation
    :----- List of 2ndaries - #SpawnInStep= 22(Rest= 0,Along= 0,Post=22),
#SpawnTotal= 22 ---------------
    :      1.29     0.386     0.201  2.93e-06      opticalphoton
    :      1.29     0.386     0.303  2.93e-06      opticalphoton
    :      1.29     0.386     0.544  2.93e-06      opticalphoton
(and so on...)

However, I slowly modified this simulation to simulate scintillating
spheres in a cylinder of water, and now the entries marked "scintillation"
in my Hits.dat file no longer make sense. For many particles, the end of
their life is marked "scintillation," but in a non-scintillating volume.
Also I no longer see "Scintillation" in my scintillating spheres before the
generation of optical photons. Now, the optical photons just kind of
happen, and seem to come from my 'water' volume. Below are two screen
output segments showing this odd behavior:

*********************************************************************************************************
* G4Track Information:   Particle = e-,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng
 NextVolume ProcName
    2   -0.421     0.49   0.0672      0.45        0        0     0.219
Waterbox_phys initStep
    3   -0.421     0.49        0     0.439   0.0109   0.0672     0.286
 pmt_phys Transportation
    4   -0.421     0.49   -0.288     0.344   0.0949    0.288     0.574
 pmt_phys ElectronIonisation
    5   -0.421     0.49    -0.53      0.23    0.114    0.242     0.816
 pmt_phys ElectronIonisation
    6   -0.421     0.49   -0.713     0.123    0.107    0.183         1
 pmt_phys ElectronIonisation
    7   -0.421     0.49    -0.81         0    0.123   0.0969       1.1
 pmt_phys ElectronIonisation
    8   -0.421     0.49    -0.81         0        0        0       1.1
 pmt_phys Scintillation

*********************************************************************************************************
* G4Track Information:   Particle = e-,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng
 NextVolume ProcName
    0   -0.466   -0.138    0.267       0.6        0        0         0
Waterbox_phys initStep
    1   -0.466   -0.138    0.214     0.589   0.0113   0.0531    0.0531
ScinLayer_phys Transportation
    2   -0.466   -0.138   0.0864     0.562   0.0269    0.127      0.18
Waterbox_phys Transportation
    :----- List of 2ndaries - #SpawnInStep=  4(Rest= 0,Along= 0,Post= 4),
#SpawnTotal=  4 ---------------
    :    -0.466    -0.138     0.146  2.93e-06      opticalphoton
    :    -0.466    -0.138    0.0994  2.93e-06      opticalphoton
    :    -0.466    -0.138     0.105  2.93e-06      opticalphoton
    :    -0.466    -0.138     0.133  2.93e-06      opticalphoton
    :-----------------------------------------------------------------
EndOf2ndaries Info ---------------


Any thoughts on why this is happening? Why would "Scintillation" come up in
a volume that does not contain a material whose definition includes
scintillation properties? And why are the optical photons appearing to be
generated in my 'Waterbox' volume instead of my scintillating volume
"ScinLayer"? This is output from the same basic file that only had a few
minor geometrical changes made to it.

-Amy
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20140816/e2f10d52/attachment.html>