Maria Grazia Pia, INFN Genova Geant4 Electromagnetic Geant4 Electromagnetic Validation Validation (mostly electromagnetic, but also a bit of (mostly electromagnetic, but also a bit of hadronic…) hadronic…) K. Amako, G.A.P. Cirrone, G. Cuttone, F. Di Rosa, S. Guatelli, V. Ivanchenko, M. Maire, B. Mascialino, K. Murakami, P. Nieminen, L. Pandola, S. Parlati, M.G. Pia, G. Russo, T. Sasaki, L. Urban et al. Geant4 Workshop Bordeaux, 7-10 November 2005
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Maria Grazia Pia, INFN Genova Geant4 Electromagnetic Validation (mostly electromagnetic, but also a bit of hadronic…) K. Amako, G.A.P. Cirrone, G. Cuttone,
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(mostly electromagnetic, but also a bit of hadronic…)(mostly electromagnetic, but also a bit of hadronic…)
K. Amako, G.A.P. Cirrone, G. Cuttone, F. Di Rosa, S. Guatelli, V. Ivanchenko, M. Maire, B. Mascialino, K. Murakami, P. Nieminen, L. Pandola, S. Parlati,
Hadronic physics– in some experimental cases EM and hadronic physics cannot be separated
Geant4 Physics BookGeant4 Physics Book– on-going project to document the performance of Geant4 physics against
experimental data and in relevant experimental application domains
Maria Grazia Pia, INFN Genova
Validation processValidation process
Geant4 test process– Physics packages are subject to unit and system testing– Verification, validation of single processes/models performed by Working Groups
Validation process– systematicsystematic: cover all models of a given process– comparison to experimental dataexperimental data and established reference databases– rigorous software processrigorous software process to guarantee quality and reliability
Goals– evaluate quantitatively the accuracy of Geant4 physics models– document their respective strength– provide guidance to users to select appropriate models in their
applications
Maria Grazia Pia, INFN Genova
Scope of this talkScope of this talk
Common project for Geant4 Electromagnetic Physics validation– systematicsystematic– spanning all all existing electromagnetic models– rigorous software processrigorous software process– performed in a transparenttransparent way (agreed methods & tools, code in CVS)– quantitative results through rigorous statistical analysisstatistical analysis– goal: produce publication-qualitypublication-quality results
Other on-going “private” activities not covered in this talk– no time to present everything…– but also don’t know what is going on…
Maria Grazia Pia, INFN Genova
Overview of recent validation Overview of recent validation activitiesactivities
Geant4 Physics Book: Electromagnetic Volume– comparison against the NIST databases– K. Amako, S. Guatelli, V. N. Ivanchenko, M. Maire, B. Mascialino, K. Murakami, P. Nieminen,
L. Pandola, S. Parlati, M. G. Pia, M. Piergentili, T. Sasaki, L. Urban
Comparison of Geant4 electromagnetic physics models against the NIST reference dataIEEE Trans. Nucl. Sci., Vol. 52, Issue 4, Aug. 2005, 910-918
Current Physics Book projects (preliminary results)– Bremsstrahlung final state– Atomic relaxation and PIXE + Radioactivity from composite materials– Bragg peak (EM + hadronic)
Other Geant4 validation activities– Validation of specific physics models done by each Geant4 Working Groups– LCG Simulation Validation Project: focus on hadronic physics– User own projects
Maria Grazia Pia, INFN Genova
NIST TestNIST TestPhoton Mass Attenuation Coefficient
Photon Partial Interaction Coefficient – related to the cross section of a specific photon
Low Energy ICRU49Low Energy Ziegler 1977Low Energy Ziegler 1985Low Energy Ziegler 2000(Low Energy: free electron gas + parameterisations + Bethe-Bloch)
Simulation configuration reproducing NIST conditions (ionisation potential, fluctuations, production of secondaries etc.)
Maria Grazia Pia, INFN Genova
G.A.P Cirrone, S. Donadio, S. Guatelli, A. Mantero, B. Mascialino, S. Parlati, M.G. Pia, A. Pfeiffer, A. Ribon, P. Viarengo
Statistical analysisStatistical analysis Goodness-of-Fit test (Statistical Toolkit)
GoF test(χ2 test)
Distance between Geant4 simulation
and NIST reference data
Test resultp-value
Geant4 simulation
results+
ReferenceData
The p-value represents the probability that the test statistics has a value at leastat least as extreme as the one observed, assuming the null hypothesis is true
0 0 ≤ p ≤ 1≤ p ≤ 1
p < 0.05p < 0.05 Geant4 simulation and NIST data differ significantly p > 0.05p > 0.05 Geant4 simulation and NIST data do not differ significantly
Alternative hypotheses under test:
Maria Grazia Pia, INFN Genova
Photon mass attenuation coefficientPhoton mass attenuation coefficientGeant4 models:
• Standard• Low Energy – EPDL• Low Energy – Penelope
ResultsResultsThe Geant4 Low Energy models look in disagreement with the reference data for some materials
Geant4 LowE Penelope Geant4 LowE EPDLNIST - XCOM
Rayleigh interaction coefficient in Be
rr )(
AVN
A
Be 0.99 1
Al 0.32 <0.05
Si 0.77 <0.05
Fe 1 <0.05
Ge <0.05 0.39
Ag 0.36 0.08
Cs <0.05 <0.05
Au <0.05 <0.05
Pb <0.05 <0.05
U <0.05 <0.05
EPDLXCOM
PenelopeXCOM
Geant4 models:• Low Energy – EPDL• Low Energy – Penelope• (no standard Rayleigh process)
Reference data: NIST - XCOM
Maria Grazia Pia, INFN Genova
Zaidi H., 2000, Comparative evaluation of photon cross section libraries for materials of interest in PET Monte Carlo simulation IEEE Transaction on Nuclear Science 47 2722-35
The disagreement is evident between 1 keV and 1 MeV photon energies
For what concerns the Geant4 Low Energy EPDL model, the effect observed derives from an intrinsic inconsistency between Rayleigh
cross section data in NIST-XCOM and the cross sections of EPDL97, on which the model
is based
Differences between EPDL97 and NIST-XCOM have already been highlighted in a paper by Zaidi,
which recommends the Livermore photon and electron data libraries as the most up-to-date and
accurate databases available for Monte Carlo modeling.
The complex physics modeling of ion interactions in the low energy range is addressed by the Geant4 Low Energy package and it represented one of the main motivations for the developing of this package.
The complex physics modeling of ion interactions in the low energy range is addressed by the Geant4 Low Energy package and it represented one of the
main motivations for developing this package
Maria Grazia Pia, INFN Genova
Quantitative process evaluationQuantitative process evaluation2 conference presentations with preliminary results (CHEP, NSS 2003)Final results presented at NSS 2004, October 2004
~ 10 months to put test infrastructure in place and get first results~ 1 year to get publication-quality results~ 3 months to write paper and produce final plots
Publication – submitted to IEEE TNS March 2005– accepted April 2005– published August 2005
Workers/authors– 13 authors– Barbara, Koichi, Sandra, Susanna + unnamed person did all the work – other people provided significant support to the project (funds, management,
infrastructure etc.)
Maria Grazia Pia, INFN Genova
BremsstrahlunBremsstrahlungg
3 sets of models availableStandard: G4eBremsstrahlungLow Energy EEDL: G4LowEnergyBremsstrahlungLow Energy Penelope: G4PenelopeBremsstrahlung
3 angular distributions: Tsai, 2BS, 2BN
Angular distribution of photons is strongly model-dependent
Penelope
Standard
Low Energy EEDL (default)
PenelopeLowE-EEDL TSAI (def)
LOWE-EEDL 2BSLOWE-EEDL 2BN
Angle (deg) Angle (deg)
Susanna GuatelliBarbara Mascialino
Luciano PandolaMG Pia
Maria Grazia Pia, INFN Genova
Reference dataReference data
The absolute Bremsstrahlung cross section can be tested
Transmitted energy spectrum at two different
emission angles for four materials (Al, Pb, W,
Ag)
Absolute yields are reported (=
photons/primary), though with an “odd” normalization
R. Ambrose et al., Nucl. Instr. Meth. B 56/57 (1991)
327
Maria Grazia Pia, INFN Genova
Relative comparison...Relative comparison...
Relative comparison (45 degree direction)Shapes of the spectra are in good agreement
Work in progress, will be published
Inte
nsi
ty/Z
(eV
/sr
keV
)
Photon energy (keV)
Photon energy (keV)
LowE-Penelope
Low E EEDL - TSAI
Inte
nsi
ty/Z
(eV
/sr
keV
)
Maria Grazia Pia, INFN Genova
Proton Bragg PeakProton Bragg Peak
Geant4 models: electromagneticGeant4 models: electromagneticStandardLow Energy ICRU 49Low Energy Ziegler 1977Low Energy Ziegler 1985Low Energy Ziegler 2000
Angle of incidence (withrespect to the normal to the sample surface) = 0°
Maria Grazia Pia, INFN Genova
CommentsComments
Feedback from users is a helpful contribution to Geant4 validation– but the systematicsystematic work needed to document Geant4 validity
quantitatively can only come from the Geant4 Collaboration
Better communication and collaboration is desirable– internal competition in the Geant4 Collaboration is not constructive– competition against Geant4 students and post-docs is not constructive– slow progress is due to limited womanpower
Dedicated validation workshops are necessary and fruitfulfruitful– not easy to organize (and expensive to attend)
Regular VRVS Validation meetings will be organized in 2006
The key to success for publication-quality results is a The key to success for publication-quality results is a rigorous software processrigorous software process
Maria Grazia Pia, INFN Genova
Geant4 Physics Validation Workshop, Genova, July 2005http://www.ge.infn.it/geant4/events/july2005/
Maria Grazia Pia, INFN Genova
ConclusionConclusion
More results available, no time to show them all…– multiple scattering?– atomic relaxation (A. Mantero, B. Mascialino, M.G. Pia, V. Zampichelli)– validation for specific use cases – etc.
Systematic, quantitative validation of Geant4 EM physics in progress– all available models– rigorous statistical analysis
A lot of work!– first paper published– several on-going projects– limited resources available
The validation work provides valuable feedback for the improvement of Geant4 physics models
Maria Grazia Pia, INFN Genova
Geant4 validation is not an easy Geant4 validation is not an easy job…job…
experimental data often exhibit large differences!
Maria Grazia Pia, INFN Genova
PublicationsPublications
It would be desirable to agree a publication plan for Geant4 physics validation
– electromagnetic + hadronic
IEEE Trans. Nucl. Sci.– major scientific journal about nuclear technologies and instrumentation– many Geant4-related papers published or currently in the review process– please consider publishing your results concerning Geant4– copyright compatible with Geant4 Physics Book