[Gate-users] LYSO surfaces painted with reflective ink

[Pedro Correia]

Dear Gate users

I’m trying to simulate a PET system, with some LYSO crystals as scintillators. In our experimental setup, we paint the LYSO lateral faces, with reflective ink, in order to reduce the optical photon escape. 

At this point, I’m reproducing this at GATE using rough reflective surfaces in the Surfaces.xml file, between the faces of the LYSO crystal and the external volume. But I only want to paint the lateral faces, and when I use the code bellow, all the faces of the LYSO became reflective, and I’m not able to collect the photons in the electronic photomultipliers located at the tops of the LYSO.

Do you have any suggestion to solve this?

The code that I’m using is:

#       C R Y S T A L
/gate/box2/daughters/name box3
/gate/box2/daughters/insert box
/gate/box3/geometry/setXLength 21. mm
/gate/box3/geometry/setYLength 1.5 mm
/gate/box3/geometry/setZLength 1.5 mm
/gate/box3/setMaterial Air
/gate/box3/vis/forceWireframe


#       L A Y E R LYSO
/gate/box3/daughters/name LYSO
/gate/box3/daughters/insert box
/gate/LYSO/geometry/setXLength 20. mm
/gate/LYSO/geometry/setYLength 1.5 mm
/gate/LYSO/geometry/setZLength 1.5 mm
/gate/LYSO/placement/setTranslation -0.5 0 0 mm
/gate/LYSO/setMaterial LYSO
/gate/LYSO/vis/setColor green
/gate/LYSO/vis/forceWireframe
#/gate/LSO/vis/forceSolid

#       L A Y E R MPPC for photon collection
/gate/box3/daughters/name mppc
/gate/box3/daughters/insert box
/gate/mppc/geometry/setXLength  1. mm
/gate/mppc/geometry/setYLength  1.5 mm
/gate/mppc/geometry/setZLength  1.5 mm
/gate/mppc/placement/setTranslation 10. 0 0 mm
/gate/mppc/setMaterial Air
/gate/mppc/vis/setColor cyan
/gate/mppc/vis/forceWireframe

#Surface conditions 
/gate/LYSO/surfaces/name   cristal_surf1
/gate/LYSO/surfaces/insert box3
/gate/LYSO/surfaces/cristal_surf1/setSurface rough_reflector

and in the Surfaces.xml file, the rough_reflector is defined as

  <surface name="rough_reflector" type="dielectric_dielectric" sigmaalpha="6.0"\
 finish="groundbackpainted">
    <propertiestable>
      <propertyvector name="SPECULARLOBECONSTANT" energyunit="eV">
        <ve energy="1.84" value="1"/>
        <ve energy="4.08" value="1"/>
      </propertyvector>
      <propertyvector name="SPECULARSPIKECONSTANT" energyunit="eV">
        <ve energy="1.84" value="0"/>
        <ve energy="4.08" value="0"/>
      </propertyvector>
      <propertyvector name="BACKSCATTERCONSTANT" energyunit="eV">
        <ve energy="1.84" value="0"/>
        <ve energy="4.08" value="0"/>
      </propertyvector>
      <propertyvector name="EFFICIENCY" energyunit="eV">
        <ve energy="1.84" value="0"/>
        <ve energy="4.08" value="0"/>
      </propertyvector>
    <propertyvector name="REFLECTIVITY" energyunit="eV">
        <ve energy="1.84" value="0.99"/>
        <ve energy="4.08" value="0.99"/>
      </propertyvector>
      <propertyvector name="RINDEX" energyunit="eV">
        <ve energy="1.84" value="1.55"/>
        <ve energy="4.08" value="1.55"/>
      </propertyvector>
    </propertiestable>
  </surface>

Many thanks.

Best regards, Pedro Correia
PhD Student at University of Aveiro