Different source definitions

mahmoodeid · April 28, 2024, 1:17am

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_Geant4 Version: 11.2
_Operating System: Windows 10
_Compiler/Version: MSVC/14.29.30133
_CMake Version: 3.22.1.0

I’m trying to define the same source by different definitions to compare the results. For example, a point source of Co-60:

Define a point source and decay process:

# specify a physics list
/physics_lists/select Shielding
## initialize geometry and physics
/run/initialize
/process/list Decay
/process/had/rdm/thresholdForVeryLongDecayTime 1.0e+60 year
# Source position and structure
# Co-60
/gps/particle ion
/gps/ion 27 60 0 0
/gps/energy 0
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm

Define a point source and energy histogram:

# specify a physics list
/physics_lists/select Shielding
## initialize geometry and physics
/run/initialize
# Source position and structure
# Co-60
/gps/particle gamma
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm
/gps/ang/type iso
/gps/ene/type User
/gps/hist/type energy
/gps/hist/point 0.34693 0.000076
/gps/hist/point 0.82606 0.000076     
/gps/hist/point 1.173237 0.999736
/gps/hist/point 1.332501 0.999856
/gps/hist/point 2.15857 0.0000111
/gps/hist/point 2.505 2.0E-8

Define a point source of gammas with different intensities:

# specify a physics list
/physics_lists/select Shielding
## initialize geometry and physics
/run/initialize
# Source position and structure
# Co-60
# Gamma 1
/gps/source/intensity 0.000076 # 0.0076%
/gps/particle gamma
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm
/gps/ang/type iso
/gps/ene/type Mono
/gps/ene/mono 346.93 keV
# Gamma 2
/gps/source/add 0.000076 # 0.0076%
/gps/particle gamma
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm
/gps/ang/type iso
/gps/ene/type Mono
/gps/ene/mono 826.06 keV
# Gamma 3
/gps/source/add 0.999736 # 99.9736%
/gps/particle gamma
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm
/gps/ang/type iso
/gps/ene/type Mono
/gps/ene/mono 1173.237 keV
# Gamma 4
/gps/source/add 0.999856 # 99.9856%
/gps/particle gamma
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm
/gps/ang/type iso
/gps/ene/type Mono
/gps/ene/mono 1332.501 keV
# Gamma 5
/gps/source/add 0.0000111 # 0.00111%
/gps/particle gamma
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm
/gps/ang/type iso
/gps/ene/type Mono
/gps/ene/mono 2158.57 keV
# Gamma 6
/gps/source/add 2.0E-8 # 2.0E-6%
/gps/particle gamma
/gps/pos/type Point
/gps/pos/centre 0 0 0 cm
/gps/ang/type iso
/gps/ene/type Mono
/gps/ene/mono 2505 keV

When scoring dose deposition in a probe at a 30 cm distance from the source, i’m getting different results for each source definition. Around 30% difference between 2 and 3. And 300% between1 and 2.

Can anyone explain to me what could be the difference in each case? Excuse my limited background in Geant-4.

Thanks

japost · April 30, 2024, 11:24am

Hello. I don’t have much familiarity with the GSP module.
Previous questions about the General Particle Source were discussed in the “Particles, Run, Track and Event” channel.
I think that it would be a better location for you question.

mahmoodeid · May 10, 2024, 4:43am

Can anyone help with explanation about the difference in the source definition in each case?

mahmoodeid · May 28, 2024, 7:23pm

This is an example of comparing Co-60 source in front of 2.5 cm G4_Fe in different source definitions:

First:

# Co-60
/gps/particle ion
/gps/ion 27 60 0 0
/gps/energy 0
/gps/pos/type Point
/gps/ang/type iso

Second:

# Co-60
/gps/particle gamma
/gps/pos/type Point
/gps/ang/type iso
/gps/ene/type User
/gps/hist/type energy
/gps/hist/point 0.34693 0.000076
/gps/hist/point 0.82606 0.000076     
/gps/hist/point 1.173237 0.999736
/gps/hist/point 1.332501 0.999856
/gps/hist/point 2.15857 0.0000111
/gps/hist/point 2.505 2.0E-8

The plot is showing the gamma flux in a cell 1 m from the source (the iron slab is in between. The total[value] in the first case is 234.29 and in the second case is 468.58.

/score/quantity/cellFlux bin10
/score/filter/particleWithKineticEnergy bin10 0.800 1.00 MeV gamma
/score/quantity/cellFlux bin11
/score/filter/particleWithKineticEnergy bin11 1.00 1.117 MeV gamma
/score/quantity/cellFlux bin12
/score/filter/particleWithKineticEnergy bin12 1.117 1.33 MeV gamma
/score/quantity/cellFlux bin13
/score/filter/particleWithKineticEnergy bin13 1.33 1.5 MeV gamma

In the second source definition (histogram), should the total[value] be multiplyed by 2 to account for the yield to be comparable to the output from the first source definition (Decay)?

Can anyone explains the differnece in the energy bins [ 1 - 1.117 MeV] and [1.33 - 1.5 MeV]? I’m using Shielding physics list:

/physics_lists/select Shielding

Is it related to physics?