[Gate-users] Large difference positron source vs BackToBack

[J.J.M. Kouwenberg]

Dear All,

I'm experiencing trouble with my positron source. It produces about 10 times less coincidences than its BackToBack counterpart! The reconstruction of the positron source looks nothing like the original the source, compared to a good reconstruction of the BackToBack source.
Can someone help me with finding whether my GATE scripts is wrong? I suspect the positron are not annihilating correctly.

PHYSICS (6.2):
/gate/physics/addProcess PhotoElectric
/gate/physics/processes/PhotoElectric/setModel StandardModel

/gate/physics/addProcess Compton
/gate/physics/processes/Compton/setModel StandardModel

/gate/physics/addProcess RayleighScattering
/gate/physics/processes/RayleighScattering/setModel PenelopeModel

/gate/physics/addProcess GammaConversion
/gate/physics/processes/GammaConversion/setModel StandardModel

/gate/physics/addProcess ElectronIonisation
/gate/physics/processes/ElectronIonisation/setModel StandardModel e-
/gate/physics/processes/ElectronIonisation/setModel StandardModel e+

/gate/physics/addProcess Bremsstrahlung
/gate/physics/processes/Bremsstrahlung/setModel StandardModel e-
/gate/physics/processes/Bremsstrahlung/setModel StandardModel e+

/gate/physics/addProcess PositronAnnihilation

/gate/physics/addProcess eMultipleScattering e- 
/gate/physics/addProcess eMultipleScattering e+
/gate/physics/processes/eMultipleScattering/setModel Urban95Model 

/gate/physics/processList Enabled
/gate/physics/processList Initialized

POSITRON SOURCE:
/gate/source/addSource 68Ga_Beta
/gate/source/68Ga_Beta/gps/particle e+
/gate/source/68Ga_Beta/gps/energytype Arb
/gate/source/68Ga_Beta/setActivity 1000000 becquerel

/gate/source/68Ga_Beta/gps/histname arb
/gate/source/68Ga_Beta/gps/emin 0.0 MeV
/gate/source/68Ga_Beta/gps/emax 1.921 MeV
#                                       MeV      Yield
/gate/source/68Ga_Beta/gps/histpoint    0.0150    0.0000
/gate/source/68Ga_Beta/gps/histpoint    0.0320    0.0001
/gate/source/68Ga_Beta/gps/histpoint    0.0400    0.0002
/gate/source/68Ga_Beta/gps/histpoint    0.0500    0.0003
/gate/source/68Ga_Beta/gps/histpoint    0.0600    0.0005
/gate/source/68Ga_Beta/gps/histpoint    0.0700    0.0007
/gate/source/68Ga_Beta/gps/histpoint    0.0800    0.0010
/gate/source/68Ga_Beta/gps/histpoint    0.0900    0.0012
/gate/source/68Ga_Beta/gps/histpoint    0.1100    0.0019
/gate/source/68Ga_Beta/gps/histpoint    0.1300    0.0027
/gate/source/68Ga_Beta/gps/histpoint    0.1500    0.0036
/gate/source/68Ga_Beta/gps/histpoint    0.1800    0.0053
/gate/source/68Ga_Beta/gps/histpoint    0.2000    0.0065
/gate/source/68Ga_Beta/gps/histpoint    0.2400    0.0092
/gate/source/68Ga_Beta/gps/histpoint    0.2800    0.0122
/gate/source/68Ga_Beta/gps/histpoint    0.3200    0.0155
/gate/source/68Ga_Beta/gps/histpoint    0.4000    0.0228
/gate/source/68Ga_Beta/gps/histpoint    0.5000    0.0326
/gate/source/68Ga_Beta/gps/histpoint    0.6000    0.0423
/gate/source/68Ga_Beta/gps/histpoint    0.7000    0.0513
/gate/source/68Ga_Beta/gps/histpoint    0.8000    0.0589
/gate/source/68Ga_Beta/gps/histpoint    0.9000    0.0647
/gate/source/68Ga_Beta/gps/histpoint    1.0000    0.0677
/gate/source/68Ga_Beta/gps/histpoint    1.1000    0.0677
/gate/source/68Ga_Beta/gps/histpoint    1.2000    0.0643
/gate/source/68Ga_Beta/gps/histpoint    1.3000    0.0577
/gate/source/68Ga_Beta/gps/histpoint    1.4000    0.0483
/gate/source/68Ga_Beta/gps/histpoint    1.5000    0.0369
/gate/source/68Ga_Beta/gps/histpoint    1.6000    0.0244
/gate/source/68Ga_Beta/gps/histpoint    1.8000    0.0036
/gate/source/68Ga_Beta/gps/arbint Lin

/gate/source/68Ga_Beta/setForcedUnstableFlag false
/gate/source/68Ga_Beta/setForcedHalfLife 100 s
/gate/source/68Ga_Beta/gps/angtype iso

/gate/source/68Ga_Beta/gps/type Volume
/gate/source/68Ga_Beta/gps/shape Sphere
/gate/source/68Ga_Beta/gps/radius 1. cm

The source is located inside the following phantom
/gate/world/daughters/name phantom
/gate/world/daughters/insert cylinder

/gate/phantom/geometry/setRmin 0 cm
/gate/phantom/geometry/setRmax 10 cm
/gate/phantom/geometry/setHeight 20 cm
/gate/phantom/setMaterial Water
/gate/phantom/vis/forceSolid
/gate/phantom/vis/setColor blue

/gate/phantom/attachPhantomSD

Thanks in advance!

Jasper J.M. Kouwenberg
Medical Physics Graduate student
Nuclear Medicine

E-mail j.kouwenberg at erasmusmc.nl | Phone +316 2532 9809

________________________________________
From: gate-users-bounces at lists.opengatecollaboration.org [gate-users-bounces at lists.opengatecollaboration.org] on behalf of Hojjat Mahani [hojjat.mahani at gmail.com]
Sent: 28 February 2015 07:49
To: GATErs
Subject: Re: [Gate-users] problem with gate

Dear Khadidja,

I guess you are using Gate 6.2 (or older versions). The ellipsoid volume is just implemented in Gate 7.0.

Hope this helps!

Hojjat