Precision Validation of Geant4 Electromagnetic

Physics

Precision Validation of Geant4 Electromagnetic

Physics

Geant4 DNA Project Meeting

26 July 2004, CERN

http://www.ge.infn.it/geant4/analysis/test

Michela PiergentiliINFN Genova, Italy

S. Guatelli (INFN Genova), V. Ivanchenko (Budker), M. Maire (LAPP), A. Mantero (INFN Genova), B. Mascialino (INFN Genova), P. Nieminen (ESA), L. Pandola (INFN LNGS), S. Parlati (INFN LNGS), A.

Pfeiffer (CERN), M.G. Pia (INFN Genova), M. Piergentili (INFN Genova), L. Urban (Budapest)

Geant4 Electromagnetic

Physics

Geant4 Electromagnetic

Physics

Alternative models for the same physics processAlternative models for the same physics process

High energy modelsHigh energy models– fundamental for LHC experiments, cosmic ray experiments etc.

Low energy modelsLow energy models– fundamental for space and medical applications, neutrino

experiments, antimatter spectroscopy etc.

It handles electrons and positrons gamma, X-ray and optical

photons muons charged hadrons ionsmultiple scattering

Bremsstrahlung

ionisation

annihilation

photoelectric effect

Compton scattering

Rayleigh effect

gamma conversion

e+e- pair production

synchrotron radiation

transition radiation

Cherenkov

refraction

reflection

absorption

scintillation

fluorescence

Auger

Geant4 e.m. package

Standard Package

LowEnergy Package

Muon Package

Optical photon Package

Standard electromagnetic processesStandard electromagnetic processes

PhotonsPhotons– Compton scattering

conversion– photoelectric effect

Electrons and positronsElectrons and positrons– Bremsstrahlung– Ionisation

ray production– positron annihilation– synchrotron radiation

Charged hadronsCharged hadrons

Variety of modelsVariety of models for ionisation and energy loss

1 keV up to 100 TeV1 keV up to 100 TeV

Shower shapes

Courtesy of D. Wright (Babar)

Geant4 Low Energy Package Geant4 Low Energy Package

Geant4 Low Energy Package is fundamental for– Biomedical applications– Space Science– Neutrino and dark matter experiments

Geant4 Low Energy Package describes the interactions of photons, electrons, positrons, hadrons and ions with matter down to low energies.

Extensions of the physics models– down to 250 eV / 100 eV250 eV / 100 eV for electrons and photons– down to < 1 keV< 1 keV for protons, antiprotons, ions

Two models available: – based on evaluated data libraries – based on Penelope analytical models

Low energy Low energy e.m. e.m.

extensionsextensions

Low energy Low energy e.m. e.m.

extensionsextensions

Fundamental for neutrino/dark matter

experiments, space and medical applications,

antimatter spectroscopy etc.

e,down to 250 eV

0.01 0.1 1 100.01

0.1

1

10

100

1000

Geant4 LowEn NIST

/

(cm

2 /g

) in

iron

Photon Energy (MeV)

Based on EPDL97, EEDL and EADL evaluated data libraries

shell effects

Photon attenuation

Hadron and ion models based on Ziegler and ICRU data and parameterisations

Bragg peak

ions

antiprotons

protons

Processes à la PenelopeProcesses à la PenelopeThe whole physics content of the Penelope Monte Carlo code has been re-engineered into Geant4 (except for multiple scattering)

– for photons, electrons, positrons

Physics models by F. SalvatF. Salvat (University of Barcelona, Spain),

J.M. Fernandez-VareaJ.M. Fernandez-Varea (University of Barcelona, Spain), E. Acosta

(University of Cordoba, Argentina), J. SempauJ. Sempau (University of Catalonia, Spain)

Power of the OO technology:Power of the OO technology:– extending the software system

is easy– all processes obey to the same

abstract interfaces– using new implementations in

application code is simple

x-ray attenuation coeff in Al

Att

enuati

on c

oeff

. (c

m2/g

)

NIST data

Penelope

E.M. Physics Validation E.M. Physics Validation

Validation is fundamental in Geant4Validation is fundamental in Geant4

Validations at different levelsValidations at different levels

Comparisons to experimental measurements and Comparisons to experimental measurements and recognised standard referencesrecognised standard references

• Unit, integration, system testing• Microscopic physics validation• Macroscopic validation experimental use cases

Microscopic validationMicroscopic validation

Validation of Geant4 electromagnetic physics models

Attenuation coefficients, CSDA ranges, Stopping Power, distributions of physics quantities

Quantitative comparisons to experimental data and recognised standard references

G4Standard

G4 LowE

NIST

Photon mass attenuation coefficient

Photon mass attenuation coefficient

Photon beam (Io)

Transmitted photons (I)

0

ln1

I

I

d

2N-L=13.1 – =20 - p=0.87

2N-S=23.2 – =15 - p=0.08

x-ray attenuation coeff in U

NIST data

Penelope2=19.3

=22

p=0.63Absorber MaterialsAbsorber Materials:

Be, Al, Si, Ge, Fe, Cs, Au, Pb, U

Electron stopping power

and CSDA range Electron stopping power

and CSDA range G4 StandardG4 LowE-EPDL

NIST

CSDA range: particle range without energyloss fluctuations and multiple scattering

centre

Experimental set-up

Absorber MaterialsAbsorber Materials: Be, Al, Si, Ge, Fe, Cs, Au, Pb, U

2N-S=0.267 =28 p=1

2N-L=1.315 =28 p=1

G4 StandardG4 LowE-EPDL

NIST

Transmission tests

Transmission tests

e-

beam

Experimental set-up

Backscattering coefficient – E=100keV Backscattering coefficient – E=100keV

Angle of incidence (withrespect to the normal to the sample surface) = 0°

G4 LowE

Lockwood et al. (1981)

Incident e-

beam

Experimental set-up

Backscattered e-

The problem of validation: finding reliable dataThe problem of validation: finding reliable data

Note: Geant4 validation Note: Geant4 validation is not always easyis not always easy

experimental data often exhibit large differences!Backscattering low energies -

Au

ConclusionsConclusions

Geant4 electromagnetic package encompasses an ample set of physics models, specialised for particle type, energy range and detector applications

Exploitation of OO technology and sound architectural design make it possible to extend the Geant4 physics capabilities

– LowE / Livermore extensions– LowE / Penelope– LowE/ hadrons and ions

Geant4 e.m. physics is subject to a rigorous testing and validation process

Geant4 e.m. physics validation is in progress with Geant4 6.2 – IEEE TNS paper to be submitted in October

Geant4 Physics BookGeant4 Physics Book

A project has been launched for a Geant4 Physics Book

To have a solid and comprehensive reference on Geant4 physics

Wide effort involving Geant4 Collaboration

Main focus of the project is Geant4 physics models validation