Modular Physics Lists

The default list we provide is a Modular physics list. It is specified by the parameters described here.

The Geant4 EM physics group recommends against setting EMRangeMin too low:

  • Set to 100. eV or greater when using standard Geant4 EM physics
  • Set to 10. eV or greater when using Geant4-DNA physics

If you want to run with no physics, but only the transportation process (useful for some demos and tests), specify the modules in the following special way:

sv:Ph/Default/Modules = 1 "Transportation_Only"

If you want to simplify physics so that only basic electromagnetic physics is done (useful for making basic geometry tests run faster), specify just the one module:

sv:Ph/Default/Modules = 1 “g4em-standard_opt0”

Below is a List of Available Modules with the corresponding Geant4 class names. Users who are advanced experts in Geant4 physics can also write their own Geant4 physics modules.

The remaining options for the "Geant4_Modular" physics type are:

d:Ph/Default/CutForAllParticles = 0.05 mm # single range cut to use for all particles
d:Ph/Default/CutForGamma = 0.05 mm # overrides CutForAllParticles for Gamma
d:Ph/Default/CutForElectron = 0.05 mm # overrides CutForAllParticles for Electron
d:Ph/Default/CutForPositron = 0.05 mm # overrides CutForAllParticles for Positron
d:Ph/Default/CutForProton = 0.05 mm # overrides CutForAllParticles for Proton
d:Ph/Default/CutForAlpha = 0.05 mm # overrides CutForAllParticles for Alpha
d:Ph/Default/CutForDeuteron = 0.05 mm # overrides CutForAllParticles for Deuteron
d:Ph/Default/CutForTriton = 0.05 mm # overrides CutForAllParticles for Triton
d:Ph/Default/EMRangeMin = 100. eV # minimum for EM tables
d:Ph/Default/EMRangeMax = 500. MeV # maximum for EM tables
i:Ph/Default/EMBins = 77 # number of bins for EM tables
i:Ph/Default/EMBinsPerDecade = 7 # number of bins per decade for EM tables
b:Ph/Default/Fluorescence = "False" # Set to true to turn on Fluorescence
b:Ph/Default/Auger = "False" # Set to true to turn on Auger
b:Ph/Default/AugerCascade = "False" # Set to true to turn on AugerCascade
b:Ph/Default/DeexcitationIgnoreCut = "False" # Set to true to implement DeexcitationIgnoreCut
b:Ph/Default/PIXE = "False" # Set to true to turn on PIXE

Physics Regions

By default, cuts affect the entire world, but you can optionally divide the world into several regions and can specify different cuts in each region. First, specify which components belong to a given region:

s:Ge/MyComponent/AssignToRegionNamed = "MyRegion"
  • All children of this component will also be assigned to that region, unless the child has its own AssignToRegionNamed parameter.
  • There is no requirement that all of the components in a given region be contiguous.

Then assign cuts per region by including the region name in the parameter name as in:

d:Ph/Default/ForRegion/MyRegion/CutForGamma = 0.05 mm
d:Ph/Default/ForRegion/MyRegion/CutForElectron = 0.05 mm
d:Ph/Default/ForRegion/MyRegion/CutForPositron = 0.05 mm
d:Ph/Default/ForRegion/MyRegion/CutForProton = 0.05 mm

Note: CutForAllParticles does not have effect on physics regions. The cuts in physics regions should be specifically assigned to each particle. On the contrary, a cut of 0.05 mm will be assigned for the particles without specified cuts in the named region.

Cuts do not affect all processes, but only those listed below:

  • Energy thresholds for gamma are used in Bremsstrahlung

  • Energy thresholds for electrons are used in ionization and e+e- pair production processes Energy thresholds for positrons are used in e+e- pair production process

  • Energy thresholds for gamma and electrons are used optionally in all discrete processes

    • Photoelectriceffect
    • Compton
    • gamma conversion
  • Energy thresholds for protons are used in processes of elastic scattering for hadrons and ions defining the threshold for kinetic energy of nuclear recoil

List of Available Modules

Users who are advanced experts in Geant4 physics can also write their own Geant4 physics modules and plug these into TOPAS through the Extensions Interface.

TOPAS Module Name Geant4 Class Name
g4h-chargeexchange G4ChargeExchangePhysics
g4decay G4DecayPhysics
g4em-dna G4EmDNAPhysics
g4em-dna_opt1 G4EmDNAPhysics_option1
g4em-dna_opt2 G4EmDNAPhysics_option2
g4em-dna_opt3 G4EmDNAPhysics_option3
g4em-dna_opt4 G4EmDNAPhysics_option4
g4em-dna_opt5 G4EmDNAPhysics_option5
g4em-dna_opt6 G4EmDNAPhysics_option6
g4em-dna_opt7 G4EmDNAPhysics_option7
g4em-dna_opt8 G4EmDNAPhysics_option8
g4em-dna-stationary G4EmDNAPhysics_stationary
g4em-dna-stationary_opt2 G4EmDNAPhysics_stationary_option2
g4em-dna-stationary_opt4 G4EmDNAPhysics_stationary_option4
g4em-dna-stationary_opt6 G4EmDNAPhysics_stationary_option6
g4em-dna-chemistry G4EmDNAChemistry
g4em-standard_GS G4EmStandardPhysicsGS
g4em-standard_SS G4EmStandardPhysicsSS
g4em-standard_WVI G4EmStandardPhysicsWVI
g4h-phy_QGSP_BIC_AllHP G4HadronPhysicsQGSP_BIC_AllHP
g4em-extra G4EmExtraPhysics
g4em-livermore G4EmLivermorePhysics
g4em-polarized G4EmLivermorePolarizedPhysics
g4em-lowep G4EmLowEPPhysics
g4em-penelope G4EmPenelopePhysics
g4em-standard_opt0 G4EmStandardPhysics
g4em-standard_opt1 G4EMStandardPhysics_option1
g4em-standard_opt2 G4EMStandardPhysics_option2
g4em-standard_opt3 G4EMStandardPhysics_option3
g4em-standard_opt4 G4EMStandardPhysics_option4
g4h-elastic_D G4HadronDElasticPhysics
g4h-elastic G4HadronElasticPhysics
g4h-elastic_HP G4HadronElasticPhysicsHP
g4h-elastic_LEND G4HadronElasticPhysicsLEND
g4h-elastic_XS G4HadronElasticPhysicsXS
g4h-elastic_H G4HadronHElasticPhysics
g4h-inelastic_QBBC G4HadronInelasticQBBC
g4h-phy_FTFP_BERT HadronPhysicsFTFP_BERT
g4h-phy_FTFP_BERT_HP HadronPhysicsFTFP_BERT_HP
g4h-phy_FTFP_BERT_TRV HadronPhysicsFTFP_BERT_TRV
g4h-phy_FTF_BIC HadronPhysicsFTF_BIC
g4h-phy_QGSP_BERT HadronPhysicsQGSP_BERT
g4h-phy_QGSP_BERT_HP HadronPhysicsQGSP_BERT_HP
g4h-phy_QGSP_BIC HadronPhysicsQGSP_BIC
g4h-phy_QGSP_BIC_HP HadronPhysicsQGSP_BIC_HP
g4h-phy_QGS_BIC HadronPhysicsQGS_BIC
g4h-phy_Shielding HadronPhysicsShielding
g4ion-binarycascade G4IonBinaryCascadePhysics
g4ion-inclxx G4IonINCLXXPhysics
g4ion G4IonPhysics
g4ion-QMD G4IonQMDPhysics
g4n-trackingcut G4NeutronTrackingCut
g4optical G4OpticalPhysics
g4radioactivedecay G4RadioactiveDecayPhysics
g4stopping G4StoppingPhysics