Physics methods for the simulation of photoionisation

Transcription

1 Physics methods for the simulation of photoionisation T. Basaglia 1, M. Batic 2, M. C. Han 3, G. Hoff 4, C. H. Kim 3, H. S. Kim 3, M. G. Pia 5, P. Saracco 5 1 CERN 2 Sinergise, Ljubljana, Slovenia 3 Hanyang University, Seoul, Korea 4 Pontificia Universidade Catolica do Rio Grande do Sul, Porto Alegre, Brazil 5 INFN Genova, Italy 27 October 2 November 2013 Seoul, Korea

2 Rationale Simulation physics The simulation of photon physics is well-established. à Is there any quantitative validation? New physics New theoretical calculations and parameterisations were released recently. à Are they accurate than old one? New trends Very low energy(~ev scale) & micro/nano dosimetry ex. FLUKA, Geant4-DNA, MOCA, OREC/ NOREC, PARTRAC, Penelope, PTB-code, Trion etc. à How accurate are models? Project to validate a wide set of simulation modeling options against a large collection of experimental data State-of-the-art simulation of photon interactions Elastic scattering : Published Photoelectric effect Compton scattering pair production : first results 2

3 Photoionisation in Monte Carlo codes Cross sections Angular distribution EGS5 PHOTX Sauter EGSnrc Storm-Israel Fit to XCOM EPDL97 (subshell) Sauter FLUKA EPDL97 Sauter Geant4 Revised Biggs-Lighthill (Henke) EPDL97 Sauter-Gavrila Same direction ITS Scofield 1973 Fischer+Sauter MCNP(X) EPDL89, EDPL97 ENDFB/IV+Storm-Israel Penelope EPDL97 Sauter (K shell) 3

4 Photoionisation in Geant4 9.6 G4VDiscreteProcess utils::g4vemprocess -currentmodel utils::g4vemmodel -anglmodel utils:: G4VEmAngularDistribution Em process Photoelectric effect standard:: G4PhotoElectricEffect - isinitialised :G4bool Packages lowenergy polarisation standard utils lowenergy:: G4PhotoElectricAngularGeneratorSimple same as incident γ lowenergy:: G4PhotoElectricAngularGeneratorSauterGavrila Sauter-Gavrila standard:: G4PEEffectFluoModel Biggs-Lighthill Em models lowenergy:: G4PenelopePhotoElectricModel Penelope 2008 EPDL97 lowenergy:: G4PhotoElectricAngularGeneratorPolarized Sauter-Gavrila polarisation:: G4PolarizedPEEffectModel polarized Geant4 9.6 MGP 9/9/2013 reverse engineered lowenergy:: G4LivermorePolarizedPhotoElectricModel -fatomdeexcitation polarized EPDL97 -fatomdeexcitation utils:: G4VAtomDeexcitation -fatomdeexcitation -fatomdeexcitation lowenergy:: G4LivermorePhotoElectricModel Livermore EPDL97 Base class for atomic deexcitation polarisation:: G4VPolarizedCrossSection polarisation:: G4PolarizedPEEffectCrossSection 4

5 Cross section sources Year Compilation Energy Z (sub)shell Method Biggs-Lighthill 10 ev 100 GeV parameterised 1992 Brennan-Cowan 30 ev 700 kev tabulated 2000 Chantler 10 ev 433 kev 1-92 K tabulated 2003 Ebel 1 kev 300 kev 1-92 all parameterised 2002 Elam 100 ev 1 MeV tabulated 1997 EPDL97 (Scofield) 10 ev 100 GeV all tabulated Henke 10 ev 30 kev tabulated McMaster/Shaltout 1 kev 700 kev tabulated 1989 PHOTX (Scofield) 1 kev 100 MeV tabulated ev 30 kev 1-99 all tabulated 1973 Scofield 1 kev 1.5 MeV all tabulated 1970 Storm-Israel 1 kev 100 GeV tabulated 1973 Veigele 100 ev 100 MeV tabulated XCOM (Scofield) 1 kev 100 GeV tabulated Different methods and calculations e.g. Chantler s exchange potential in his DHF calculation is different from Scofield s 5

6 Strategy " Evaluate a large number of available modeling options " Suitable for use in Monte Carlo simulation codes Tabulated theoretical calculations Simple analytical formulations, with documented parameters " All options evaluated in the same computational environment Minimize dependencies on other software parts (not always components) " Quantitative, objective evaluation based on statistical methods " Establish state-of-the-art for the simulation of photoionisation on objective ground " Computational performance measured along with physical accuracy We only focus on the simulation with non-polarised photons case. 6

7 Computational environment Streamlined software design consistent with Geant4 kernel G4VProcess processes-management:: G4VDiscreteProcess Sharp domain decomposition Clearly identified responsibilities No duplication of code nor of functionality G4TPhotoionisation «bind» TCrossSection TFinalState «bind» Policy-based class design (à la Alexandrescu, Modern C++ design, 2001) minimize dependencies lightweight unit tests for validation G4CsTabula G4FsPhotoionisation Strategy pattern G4IPhotoelectronGenerator or G4CsPhotoIoniBiggs, or G4CsPhotoIoniEbel First design iteration MGP January 2013 G4AtomDeexcitation G4PhotoelectronSauter G4PhotelectronSauterGavrila G4PhotoelectronSimple 7

8 Experimental data " Collected from the literature Total cross sections Partial cross sections Angular distributions " Data types > 150 references > 5000 data points ~ 3700 σ total ~ 1400 σ shell Pure experimental cross sections: direct measurements Semi-empirical cross sections: involve theoretical manipulations e.g. subtraction of calculated scattering contribution (Compton and elastic) " Format Tables, text Figures: digitized, digitization error estimated " Evaluation of experimental data Systematic effects: identified whenever possible Outliers 8

9 EPDL E > 1 kev Chantler E > 1 kev Henke E > 1 kev E > 1 kev Systematic effect? Scofield E > 1 kev XCOM E > 1 kev Brennan E > 1 kev Penelope E > 1 kev VeigeleL E > 1 kev Biggs E > 1 kev PHOTX E > 1 kev VeigeleH E > 1 kev McMaster E > 1 kev Storm E > 1 kev Elam E > 1 kev Ebel E > 1 kev Difference between calculated and experimental total cross sections, expressed in terms of number of standard deviations: pure experimental and semi-empirical data Only pure experimental data used in the validation process 9

10 Data analysis method " Two-stage statistical analysis 1. Compatibility of each cross section calculation method with experiment 2. Comparison of compatibility with experiment across modeling categories " Quantitative appraisal of capabilities and differences Compatibility with experiment Difference across categories Goodness-of-fit test χ 2 test α = 1 α 1 α < 1 pass fail efficiency= N pass / N test cases Contingency tables Fisher exact test Barnard test Pearson χ 2 test α = 5 as appropriate 10

11 Results - Total cross sections E>250 ev Cross section (kb) (Kb) " Most calculation methods exhibit similar compatibility with experiment for E>250 ev Chantler, Brennan-Cowan look worse " Degraded accuracy below 250 ev Fe Fe, Z=26 Dachun1992 Murty1998 DelGrande1986 EPDL Chantler Storm Henke Veigele H Elam Brennan Biggs Ebel Cross Cross section (Mb) Analysis of contingency tables EPDL Chantler EPDL Brennan-Cowan Fisher Pearson χ Barnard H H, Z=1 Beynon1965 Beynon1966 Kohl1978 Palenius1976 EPDL Chantler Biggs E (kev) E (kev) E (kev) E (kev) (kev) E (kev) Efficiency Cross section (Mb) Cross section (Mb) preliminary O Cross section model E<250 ev O, Z=8 Cole1978a Angel1988 Cairns1965 Samson1985 EPDL Chantler Henke Brennan Biggs E>250 ev E<250eV EPDL Chantler Henke Scofield Penelope PHOTX Storm XCOM VeigeleL VeigeleH Elam Brennan Sandia McMaster Ebel 11

12 Cross section (Kb) Cross section (b) Results - Shell cross sections kev Arora1981 Karabulut2005 Ertugrul2003 EPDL scaled Chantler Ebel K kev Karabulut2005 Karabulut2002 EPDL scaled Ebel L 3 Z Z Cross section (Mb) Cross section (Mb) O 1 E (kev) Xe, Z=54 Becker1987 EPDL scaled E (kev) M 4 Ba, Z=56 Bizau1989 EPDL Systematic effect observed with shell cross sections (presumably a missing factor in the calculation) Calculated inner shell cross sections compatible with experiment Outer shell cross sections inconsistent with experimental data Beware: small data sample, limited data sources p-value χ 2 test shell EPDL Chantler sc Ebel K <01 15 <01 L1 75 < L2 39 < L3 1 < M1 <01 <01 <01 M4 31 <01 <01 M5 <01 <01 <01 N1 <01 <01 <01 N6 <01 <01 <01 <01 N7 <01 <01 <01 <01 O1 <01 <01 <01 <01 O2 <01 <01 <01 <01 O3 <01 <01 <01 <01 P1 <01 <01 <01 <01 12

13 Results - Angular distribution Option à la GEANT 3 (Sauter) evaluated along with other Geant4 options Qualitative appraisal Limited experimental sample Experimental systematic effects (corrected/uncorrected data) Normarilzed cross section Aluminium K- shell 1170 kev Exp. G4Polar G4Sauter GEANT 3 Normarilzed cross section Gold L2- shell 412 kev Exp. G4Polar G4Sauter GEANT Θ angle (degrees) Θ angle (degrees) Normarilzed cross section Gold L3- shell 412 kev Exp. G4Polar G4Sauter GEANT 3 Normarilzed cross section 0.8 Krypton M1- shell kev Exp. G4Polar G4Sauter GEANT Θ angle (degrees) Θ angle (degrees) 13

14 Conclusion " Large scale effort to evaluate quantitatively physics methods for photoionisation simulation Part of a wider project for quantitative assessment of state-of-the-art simulation of photon interactions " Total cross section Most calculation methods exhibit similar behaviour More recent calculations (Chantler, Brennan-Cowan) do not appear more accurate than old Scofield s 1973 (unrenormalized) " Inner shells EPDL, (corrected) appear equivalent, Ebel s parameterisation inconsistent with experimental K shell data " Outer shells No calculation method appears adequate to reproduce experimental data " Photoelectron angular distribution Scarce data and experimental systematics prevent a quantitative discrimination All results will be documented in detail in a forthcoming publication 14

15 a big THANK YOU to the CERN Library!