[Gate-users] Detection of optical photons

[Paweł Kowalski]

Hello,

I have some questions connected with detection of optical photons. In my
simulations I need to use information about optical photons from Hits tree
because in OpticalData tree there is no information about time (I need this
information).

I simulate single scintillator with two photomultipliers attached at its
ends. Beam of gamma particles is directed perpendiculary to the
scintillator.

I detect optical photons using perfect_apd surfaces between my scintillator
and photomultipliers. Part of hits in the end of scintillator is reflected
and part of it is transported through metal.

My 5 questions:

1) Hits which have processName equal to 'Transportation' should be treated
as optical photons absorbed by the surface?

2) If these photons should be treated as absorbed in metal, why position of
hits with 'Transportation' is not always equal to position of surface? It
is visible on attached picture: phenomenon_in_function_of_location.jpg.
Value 1 means OpticalAbsorption, 2 - Transportation, 3 - Scintillation.
Transportation should be located just at -250 and at 250 but locations of
transportation hits are blurred.

3) After 'Transportation' photon may be reflected from surface? Or it is
rather like photon is either reflected or transported?

4) Accoding to
http://geant4.web.cern.ch/geant4/G4UsersDocuments/UsersGuides/PhysicsReferenceManual/html/node66.html
part
of photons is reflected from surfaces (crystal_last_hit_pos_z_A.png,
crystal_last_hit_pos_z_B.png). Why they are reflected if in surfaces.xml
file reflectivity is set to 0?

Partt of surfaces.xml file:
  <surface name="perfect_apd" type="dielectric_metal" sigmaalpha="0.0"
finish="polished">
    <propertiestable>
      <propertyvector name="SPECULARLOBECONSTANT" energyunit="eV">
<ve energy="1.0" value="0.0"/>
 <ve energy="2.34" value="0.0"/>
<ve energy="4.13" value="0.0"/>
      </propertyvector>
      <propertyvector name="SPECULARSPIKECONSTANT" energyunit="eV">
<ve energy="1.0" value="0.0"/>
 <ve energy="2.34" value="0.0"/>
        <ve energy="4.13" value="0.0"/>
      </propertyvector>
      <propertyvector name="BACKSCATTERCONSTANT" energyunit="eV">
<ve energy="1.0" value="0.0"/>
 <ve energy="2.34" value="0.0"/>
        <ve energy="4.13" value="0.0"/>
      </propertyvector>
      <propertyvector name="REFLECTIVITY" energyunit="eV">
<ve energy="1.0" value="0.0"/>
<ve energy="2.34" value="0.0"/>
        <ve energy="4.13" value="0.0"/>
      </propertyvector>
      <propertyvector name="EFFICIENCY" energyunit="eV">
<ve energy="1.0" value="1.0"/>
 <ve energy="2.34" value="1.0"/>
<ve energy="4.13" value="1.0"/>
      </propertyvector>
    </propertiestable>
  </surface>

5) Is there any way to connect information from Hits and OpticalData trees?
Something like hitID?

I am using Gate v. 6.2.
Thank you in advance for your help.

Best regards,
Paweł Kowalski,
Świerk Computing Centre
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