[Gate-users] Para source with cold region

[Judit Lantos]

Dear Gate Users,

I’d like to simulate a rectangular source which contains a cold cylinder.
I’ve tried to use ‘confine’ to define the source shape but a strange (cylindrical) pattern appeared in the source distribution. When I tried to only ‘forbid’ the cold region there were some source positions still appearing in the forbidden area.

To test the problem I’ve defined 5 cases:
1, box phantom, para source
2, box phantom, para source confined to box geometry
3, box phantom with cold cylinder, para source confined to box geometry
4, box phantom with cold cylinder, para source confined to box geometry & with forbidden cold cylinder
5, box phantom with cold cylinder, para source with forbidden cold cylinder

It seems that when there is no confinement there is no artifact. But using only the forbid option I cannot get a clean cold region.

I’ve attached 5 images which depict the 2D density of the x-y source coordinates of the single events (so it’s a projection not a slice). 2 detector heads were used in the simulation aligned with the longer (y axis) side of the phantom.

The code I’ve used (certain parts were commented to create the cases):

####################
#                  #
#  P H A N T O M   #
#                  #
####################

/gate/world/daughters/name tegla
/gate/world/daughters/insert box
/gate/tegla/setMaterial Water
/gate/tegla/placement/setTranslation 0. 0. -1.75 cm
/gate/tegla/geometry/setXLength  6.4 cm
/gate/tegla/geometry/setYLength 12.5 cm
/gate/tegla/geometry/setZLength  6.9 cm
/gate/tegla/vis/forceSolid
/gate/tegla/vis/setColor white

/gate/tegla/daughters/name coldcyl
/gate/tegla/daughters/insert cylinder
/gate/coldcyl/setMaterial Air
/gate/coldcyl/geometry/setRmin 0. cm
/gate/coldcyl/geometry/setRmax 1. cm
/gate/coldcyl/geometry/setHeight 6.9 cm
/gate/coldcyl/placement/setTranslation 0. -3. 0. cm
/gate/coldcyl/vis/forceWireframe
/gate/coldcyl/vis/setColor blue

/gate/tegla/attachPhantomSD
/gate/coldcyl/attachPhantomSD

/gate/geometry/rebuild


#################
#               #
#  S O U R C E  # 
#               #
#################

/gate/source/addSource background
/gate/source/background/setActivity 1000000. becquerel
/gate/source/background/setType backtoback

/gate/source/background/gps/centre 0.0 0.0 -1.75 cm

/gate/source/background/gps/particle gamma
/gate/source/background/gps/energytype Mono
/gate/source/background/gps/monoenergy 0.511 MeV

/gate/source/background/gps/type Volume
/gate/source/background/gps/shape Para
/gate/source/background/gps/halfx  3.2  cm
/gate/source/background/gps/halfy  6.25 cm
/gate/source/background/gps/halfz  3.45 cm
/gate/source/background/gps/angtype iso

/gate/source/background/gps/Forbid coldcyl
/gate/source/background/gps/confine tegla

/gate/source/list


Any help would be greatly appreciated.

Thank you,
   Judit Lantos
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Case_1.png
Type: image/png
Size: 44257 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20150225/c8275b76/attachment-0005.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Case_2.png
Type: image/png
Size: 46479 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20150225/c8275b76/attachment-0006.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Case_3.png
Type: image/png
Size: 44556 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20150225/c8275b76/attachment-0007.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Case_4.png
Type: image/png
Size: 44772 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20150225/c8275b76/attachment-0008.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Case_5.png
Type: image/png
Size: 43203 bytes
Desc: not available
URL: <http://lists.opengatecollaboration.org/mailman/private/gate-users/attachments/20150225/c8275b76/attachment-0009.png>