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Geant4 Physics Validation

Geant4 Physics Validation. Pablo Cirrone Giacomo Cuttone Francesco Di Rosa Susanna Guatelli Alfonso Mantero Barbara Mascialino Luciano Pandola Andreas Pfeiffer MG Pia Pedro Rodrigues Giorgio Russo Andreia Trindade Valentina Zampichelli. M.G. Pia On behalf of the

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Geant4 Physics Validation

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  1. Geant4 Physics Validation Pablo Cirrone Giacomo Cuttone Francesco Di Rosa Susanna Guatelli Alfonso Mantero Barbara Mascialino Luciano Pandola Andreas Pfeiffer MG Pia Pedro Rodrigues Giorgio Russo Andreia Trindade Valentina Zampichelli M.G. Pia On behalf of the LowE EM and Advanced Examples Working Groups http://www.ge.infn.it/geant4/lowE Geant4 Space User Workshop Pasadena, 6-10 November 2006

  2. Geant4 Toolkit Wide set of physics processes and models Versatility of configuration according to use cases Provide objective criteria to evaluate Geant4 physics models • Document their precisionagainst experimental data • Test allGeant4 physics models systematically • Quantitative testswith rigorous statistical methods How accurate is Geant4 physics modelling? Which is the most appropriate model for my simulation?

  3. Verification and Validationof Geant4 physics • Verification • = compliance of the software results with the specifications (the underlying physics model) • Unit tests (at the level of individual Geant4 classes) • Validation • = comparison against experimental data • Quantitative estimate of the agreement between Geant4 simulation and reference data through statistical methods (Goodness-of-Fit) A systematic, quantitative validation of Geant4 physics models against reference experimental data is essential to establish the reliability of Geant4-based applications

  4. K. Amako et al., Comparison of Geant4 electromagnetic physics models against the NIST reference dataIEEE Trans. Nucl. Sci., Vol. 52, Issue 4, Aug. 2005, pp. 910-918 • Strategy • Rigorous methods • Systematic, quantitative comparisons • Address all modeling options • Statistical analysis of compatibility with experimental data • Adopt the same method also for hadronic physics validation • Start from the bottom (low energy) • Progress towards higher energy based on previous sound assessments • Guidance to users based on objective ground • not only “educated-guess” PhysicsLists Statistical Toolkit Goodness-of-Fit test Quantitatitative comparison of experimental - simulated distributions

  5. IEEE Trans. Nucl. Sci., December 2006 25 July 2006. Statistical Toolkit • Launched as an ESA project • 2nd development cycle • Released April 2006 • Goodness-of-fit tests • Binned distributions • Unbinned distributions • Performance analysis • Power analysis The most complete software tool for 2-sample GoF tests

  6. Recent validation activities • Atomic relaxation • Fluorescence and Auger transition energies • Bremsstrahlung • Angular distributions • Proton Bragg peak • Electromagnetic interactions • Elastic scattering • Pre-equilibrium • Nuclear de-excitation + other validation activities in Advanced Examples More details: see talks at IEEE NSS 2006

  7. Geant4 Atomic Relaxation models Fluorescence Auger electron emission It is used by Geant4 packages: Low Energy Electromagnetic Photoelectric effect Low Energy electron ionisation Low Energy proton ionisation (PIXE) Penelope Compton scattering Hadronic Physics Nuclear de-excitation Radioactive decay Geant4 Atomic Relaxation • Geant4 Low Energy Electromagnetic package takes into account the detailed atomic structure of matter and the related physics processes • It includes a package for Atomic Relaxation • Simulation of atomic de-excitation resulting from the creation of a vacancy in an atom by a primary process These physics models are relevant to many diverse experimental applications

  8. Geant4 fluorescence Original motivation from astrophysics requirements Cosmic rays, jovian electrons X-Ray Surveys ofAsteroids and Moons Solar X-rays, e, p Geant3.21 ITS3.0, EGS4 Courtesy SOHO EIT Geant4 Induced X-ray line emission: indicator of target composition (~100 mm surface layer) 250 keV C, N, O line emissions included Wide field of applications beyond astrophysics Courtesy ESA Space Environment & Effects Analysis Section

  9. Atomic Relaxation in Geant4 Two steps: • Identification of the atomic shell where a vacancy is created by a primary process(photoelectric, Compton, ionisation) • The creation of the vacancy is based on the calculation of the primary process cross sections relative to the shells of the target atom • Cross section modeling and calculation specific to each process • Generation of the de-excitation chain and its products • Common package, used by all vacancy-creating processes • Geant4 Atomic Relaxation • Generation of fluorescence photons and Auger electrons • Determination of the energy of the secondary particles produced

  10. Modelling foundationin Geant4 Low Energy Electromagnetic Package • Calculation of shell cross sections • Based on the EPDL97 Livermore Library for photoelectric effect • Based on the EEDLLivermore Library for electron ionisation • Based on Penelope model for Compton scattering • Detailed atom description and calculation of the energy of generated photons/electrons • Based on the EADL Livermore Library

  11. Validation of Geant4 Atomic Relaxation • Previous partial validation studies (collaboration with ESA Advanced Concepts Division) • Pure materials: limited number of elements examined • Complex materials: complex experimental set-up, large uncertainties on the target material composition • Systematic validation project: NIST database as reference Authoritative, systematic collection of experimental data

  12. Method and tools • Geant4 test code to generate fluorescence and Auger transitions from all elements • Geant4 Atomic Relaxation handles 6 ≤ Z ≤ 100 • Selection of experimental data subsets from NIST database • The NIST database also contains data from theoretical calculations • Comparison of simulated/NIST data with Goodness-of-Fit test • Data grouped for the comparison as a function of Z according to the initial vacancy and transition type • Statistical Toolkit (http://www.ge.infn.it/statisticaltoolkit) • Kolmogorov-Smirnov test • The result of the agreement is expressed through the p-value of the test

  13. Fluorescence – Shell vacancy K E (keV)  Geant4 ○ NIST Z

  14. Fluorescence – Shell vacancy L1  Geant4 ○ NIST

  15. Fluorescence – Shell vacancy L2  Geant4 ○ NIST

  16. Fluorescence – Shell vacancy L3  Geant4 ○ NIST

  17. Auger electron emission • Scarce experimental data in the NIST database • Often multiple data for the same Auger transition: ambiguous reference • Analysis in progress: comparison of Geant4 simulation data against the NIST subset of experimental data • Preliminary results: good qualitative agreement as in the case of X-ray fluorescence • Rigorous statistical analysis to be completed, will be included in publication

  18. Geant4 electron Bremsstrahlung 2 electromagnetic physics packages Standard Low Energy 3 Bremsstrahlung processes G4eLowEnergyBremsstrahlung G4eBremsstrahlung Tsai Tsai 2BN 2BS angular distribution angular distributions G4PenelopeBremsstrahlung

  19. Validation of Geant4 EM physics Ongoing large-scale project NIST Photon mass attenuation coefficient Range, Stopping power (e, p, a) K. Amako et al., IEEE Trans. Nucl. Sci. 52 (2005) 910 Atomic relaxation (fluorescence, Auger effect) Proton Bragg peak Electron Bremsstrahlung NSS 2006 Bremsstrahlung Difficult to find reference data Thin/thick target experiments Difficult to disentangle effects (because of the continuous part) 1st validation cycle: focus on low energy

  20. Low Energy Package Penelope Standard Low Energy (TSAI) Penelope TSAI 2BS 2BN Angle (deg) Angle (deg) 70 keV Angular distributions Angular distribution of photons is strongly model-dependent

  21. θ The experimental set-up e- beam(70 keV-10 MeV) incident on a slab of material Photon (energy, θ) Electrons andd-rays are absorbed Bremsstrahlung photons can be transmitted electrons Z axis Yield,EnergyandPolar Angleof the emittedphotons Secondary production threshold = 0.5 mm Statistical Toolkit Goodness-of-Fit test in progress Quantitatitative comparison of experimental - simulated distributions

  22. Preliminary results Work in progress! Simulation production: still running Statistical analysis: still preliminary, to be completed Data sets N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Thin target: Be, Al, Au - 2.7, 4.5, 9.7 MeV Double differential cross sections W.E. Dance et al., Journal of Appl. Phys. 39 (1968) 2881 Thick target: Al, Fe – 0.5, 1 MeV Double differential cross sections Integrated g yield R. Ambrose et al., NIM B 56/57 (1991) 327 Absolute and relative yield

  23. data data + + simulation simulation Double differentialsat 2.7 MeV on thin (2.63 mg/cm2) Be target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  24. data data + + simulation simulation Double differential s at 4.5 MeV on thin (2.63 mg/cm2) Be target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  25. data data + + simulation simulation Double differential s at 9.7 MeV on thin (2.63 mg/cm2) Be target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  26. data data + + simulation simulation Double differential s at 2.7 MeV on thin (0.878 mg/cm2) Al target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  27. data data + + simulation simulation Double differential s at 2.7 MeV on thin (0.878 mg/cm2) Al target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  28. data data + + simulation simulation Double differential s at 4.5 MeV on thin (0.878 mg/cm2) Al target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  29. data data + + simulation simulation Double differential s at 9.7 MeV on thin (0.878 mg/cm2) Al target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  30. data data + + simulation simulation Double differential s at 2.7 MeV on thin (0.209 mg/cm2) Au target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  31. data data + + simulation simulation Double differential s at 4.5 MeV on thin (0.209 mg/cm2) Au target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  32. data data + + simulation simulation Double differential sat 9.7 MeV on thin (0.209 mg/cm2) Au target N. Starfelt et al., Phys. Rev. 102 (1956) 1598 Energy (MeV) Energy (MeV)

  33. 500 keV Angular distribution W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 500 keV electrons on Al (0.548 g/cm2)and Fe (0.257 g/cm2) Thick target experiment Preliminary 2 test p-value = 0.10 Standard package Red = data Black = simulation o  Al   Fe Absolute comparison

  34. 500 keV Angular distribution W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 Preliminary 2 test p-value = 0.68 Preliminary 2 test p-value = 0.03 precise agreement!

  35. 500 keV Angular distribution W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 Preliminary 2 test p-value = 0.33 Preliminary 2 test p-value not meaningful

  36. 1 MeV Angular distribution Preliminary Fe 2 test p-value not meaningful Same test for 1 MeV primary electrons (threshold: 50 keV) W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 Targets: Al (0.548 g/cm2) and Fe (0.613 g/cm2) Red = data Black = simulation o  Al   Fe Absolute comparison

  37. 1 MeV Angular distribution W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 Preliminary Fe 2 test p-value = 0.68 Preliminary Fe 2 test p-value = 0.06 precise agreement! Good agreement for Al - Reasonable also for Fe (2BN)

  38. 1 MeV Angular distribution W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 Preliminary Fe 2 test p-value = 0.36 Preliminary Fe 2 test p-value not meaningful 2BS: good for Al and Fe (except in the backward direction)

  39. Integral g yield Total g yield on Al integrated on  (0  p) and on energy (Eth  Emax) Also available for other flavours of Geant4 Bremsstrahlung models W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 o  dat a   simul. Preliminary Preliminary Further investigation in progress

  40. Energy distribution at 70 keV Penelope Low Energy - TSAI R. Ambrose et al., Nucl. Instr. Meth. B 56/57 (1991) 327 Intensity/Z (eV/sr keV) photon direction 70 keV e- 45 deg Photon energy (keV) 70 keV electrons impinging on Al (25.4 mg/cm2)

  41. Relative comparison at 70 keV Low Energy - TSAI Penelope Intensity/Z (eV/sr keV) Intensity/Z (eV/sr keV) Photon energy (keV) Photon energy (keV) Relative comparison (45° direction) Shapes of the spectra are in good agreement

  42. Medical Physics High Energy Physics Space Science Astronauts’ radiation protection LHC Radiation Monitors Oncological radiotherapy Proton Bragg peak • Compare various Geant4 electromagnetic models • Assess lowest energy range of hadronic interactions • elastic scattering • pre-equilibrium + nuclear deexcitation • to build further validation tests on solid ground • Results directly relevant to various experimental use cases

  43. Standard Low Energy – ICRU 49 Low Energy – Ziegler 1977 Low Energy – Ziegler 1985 Low Energy – Ziegler 2000 New “very low energy” models Parameterized (à la GHEISHA) Nuclear Deexcitation Default evaporation GEM evaporation Fermi break-up Pre-equilibrium Precompound model Bertini model Elastic scattering Parameterized models Bertini Intra-nuclear cascade Bertini cascade Binary cascade Relevant Geant4 physics models Hadronic Electromagnetic Subset of results shown here Full set of results in publication coming shortly

  44. Resolution 100 m 2 mm Markus Chamber Sensitive Volume = 0.05 cm3 Experimental data CATANA hadrontherapy facility in Catania, Italy • high precision experimental data satisfying rigorous medical physics protocols • Geant4 Collaboration members Validation measurements Markus Ionization chamber

  45. Geant4 simulation Accurate reproduction of the experimental set-up This is the most difficult part to achieve a quantitative Geant4 physics validation Geometry and beam characteristics must be known in detail and with high precision Ad hoc beam line set-up for Geant4 validation to enhance peculiar effects of physics processes Eproton = 63.5 MeV sE = 300 keV

  46. Electromagnetic processes Electromagnetic options • Standard EM • Low Energy EM – ICRU 49 • Low Energy EM – Ziegler 1977 • Low Energy EM – Ziegler 1985 • Low Energy EM – Ziegler 2000

  47. Standard EM Electromagnetic processes • Standard EM: p, ions, g, e- e+ 1 M events Geant4 Experimental data CvM Cramer-von Mises test KS Kolmogorov-Smirnov test AD Anderson-Darling test mm

  48. LowE EM – ICRU49 Electromagnetic processes • Low Energy EM – ICRU49: p, ions • Low Energy EM – Livermore: g, e- • Standard EM : e+ 1 M events Geant4 Experimental data CvM Cramer-von Mises test KS Kolmogorov-Smirnov test AD Anderson-Darling test mm

  49. LowE EM – Ziegler 1977 Electromagnetic processes • Low Energy EM – Ziegler 1977: p, ions • Low Energy EM – Livermore: g, e- • Standard EM : e+ 1 M events Geant4 Experimental data CvM Cramer-von Mises test KS Kolmogorov-Smirnov test AD Anderson-Darling test mm

  50. LowE EM – Ziegler 1985 Electromagnetic processes • Low Energy EM – Ziegler 1985: p, ions • Low Energy EM – Livermore: g, e- • Standard EM : e+ 1 M events Subject to further investigation Geant4 Experimental data mm

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