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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"

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

For expert users#

Further control of electromagnetic parameters can be made by parameters displayed below. The values shown are those default found in Geant4 class G4EmParameters. However, different electromagnetic physics modules (start with “g4em-” in the table below) override the default values from G4EmParameters class, thus check the corresponding Geant4 class for further details

# For ionization
b:Ph/Default/ICRU90 = "False"
u:Ph/Default/EMRoverRange = 0.2
d:Ph/Default/EMFinalRange = 1.0 mm
d:Ph/Default/LowestElectronEnergy = 1.0 keV

# For multiple scattering
b:Ph/Default/MottCorrection = "False"
u:Ph/Default/MSCGeometryFactor = 2.5
u:Ph/Default/MSCSkinFactor = 1.0
u:Ph/Default/MSCRangeFactor = 0.04
b:Ph/Default/MSCSafetyFactor = 0.6
s:Ph/Default/MSCStepLimitType = "safety" # "safetyplus" "distancetoboundary"

# For electron solvation
s:Ph/Default/SolvatedElectronThermalizationModel = "meesungnoen" # "ritchie" "terrisol" "meesungnoensolid" "kreipl"

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

tsphotoneutron**

N/A

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_QGSP_FTFP_BERT

HadronPhysicsQGSP_FTFP_BERT

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

** See the publication here .