Hi everyone,
I am new to TOPAS simulation and have encountered an issue with generating a parallel beam from a ring source. Here’s how I defined the source:
Source Geometry
s:Ge/RingSourceVolume/Type = "G4Torus"
s:Ge/RingSourceVolume/Parent = "World"
s:Ge/RingSourceVolume/Material = "Vacuum"
b:Ge/RingSourceVolume/IsActiveSource = "True"
d:Ge/RingSourceVolume/RTor = 8 um
d:Ge/RingSourceVolume/RMax = 0.01 um
d:Ge/RingSourceVolume/TransZ = 10 um
Source
s:So/RingGammaSource/Type = "Volumetric"
s:So/RingGammaSource/Component = "RingSourceVolume"
sc:So/RingGammaSource/ActiveMaterial = "Vacuum"
s:So/RingGammaSource/BeamParticle = "gamma"
d:So/RingGammaSource/BeamEnergy = 1.25 MeV
s:So/RingGammaSource/BeamPositionDistribution = "Flat"
s:So/RingGammaSource/BeamAngularDistribution = "None"
s:So/RingGammaSource/BeamDirectionType = "FixedDirection"
u:So/RingGammaSource/BeamDirectionX = 0
u:So/RingGammaSource/BeamDirectionY = 0
u:So/RingGammaSource/BeamDirectionZ = -1
i:So/RingGammaSource/NumberOfHistoriesInRun = 1000
However, when I executed the code, the beam irradiated in all directions instead of being parallel.
Could you please help me resolve this issue? I’d greatly appreciate any suggestions.
Looking forward to your response.
Thanks!