[Gate-users] using source "confine" option

[Ravindranath, Bosky]

To Giovanni Santin and Gate users,
 
I have  a couple of questions about the "confine" option when defining a source in GATE.  I am trying to define a warm background with a hot spot in the center and I want to keep these two sources independent of one another, i.e have no overlap in the source emission points. 
I tried using the "confine" command in the following way:
 
#Phantom 1: Warm background phantom
/gate/world/daughters/name phantom
/gate/world/daughters/insert cylinder
/gate/phantom/setMaterial Water  
/gate/phantom/vis/forceWireframe
/gate/phantom/vis/setColor white
/gate/phantom/geometry/setRmax   72.65923 mm 
/gate/phantom/geometry/setRmin   0. mm  
/gate/phantom/geometry/setHeight 96.46 mm #array only. increase for OFOV
/gate/phantom/attachPhantomSD

#Phantom 2: Hot Spot Phantom 
/gate/phantom/daughters/name phantom_sp1
/gate/phantom/daughters/insert sphere
/gate/phantom_sp1/setMaterial Water
/gate/phantom_sp1/vis/forceWireframe
/gate/phantom_sp1/vis/setColor blue
/gate/phantom_sp1/geometry/setRmax   7.5 mm  
/gate/phantom_sp1/geometry/setRmin   0. mm  
/gate/phantom_sp1/placement/setTranslation 0. 0. 0. mm  
 
Followed by my Source definition:
# background Source
/gate/source/addSource background
/gate/source/background/setActivity  3851374  becquerel
/gate/source/background/setType backtoback
/gate/source/background/gps/particle gamma
/gate/source/background/gps/energytype Mono
/gate/source/background/gps/monoenergy 0.511 MeV
/gate/source/background/setForcedUnstableFlag true
/gate/source/background/setForcedHalfLife 6586 s
/gate/source/background/gps/type Volume
/gate/source/background/gps/shape Cylinder
/gate/source/background/gps/radius 72.65923 mm 
/gate/source/background/gps/halfz 48.23 mm
/gate/source/background/gps/centre 0. 0. 0. cm
/gate/source/background/gps/confine phantom
/gate/source/background/gps/angtype iso
 
# hotspot Source
/gate/source/addSource twogamma
/gate/source/twogamma/setActivity 35958.45 becquerel 
/gate/source/twogamma/setType backtoback
/gate/source/twogamma/gps/particle gamma
/gate/source/twogamma/gps/energytype Mono
/gate/source/twogamma/gps/monoenergy 0.511 MeV
/gate/source/twogamma/setForcedUnstableFlag true
/gate/source/twogamma/setForcedHalfLife 6586 s
/gate/source/twogamma/gps/type Volume
/gate/source/twogamma/gps/shape Sphere
/gate/source/twogamma/gps/radius 20 mm  
/gate/source/twogamma/gps/centre 0. 0. 0. mm
/gate/source/twogamma/gps/confine phantom_sp1
/gate/source/twogamma/gps/angtype iso
 
The hot spot source gets confined to its confinement volume(phantom_sp1), however the background source is uniformly distributed over the regions of "phantom" as well as "phantom_sp1". I expected that the background source will be confined to the area of (phantom-phantom_sp1)..which in this case should be a cylinder with a hole in the center. I also tried defining the two phantoms as the daughters of the world, but that did not confine the background activity either.
 
 
Any suggestions appreciated.
 
Thanks.
Bosky