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IEEE NSS 2013
IEEE NSS 2013 27 October – 2 November 2013
Seoul, Korea
T. Basaglia1, M. Batic2, M. C. Han3, G. Hoff4, C. H. Kim3, H. S. Kim3, M. G. Pia5, P. Saracco5
1CERN
2Sinergise, Ljubljana, Slovenia 3Hanyang University, Seoul, Korea
4Pontificia Universidade Catolica do Rio Grande do Sul, Porto Alegre, Brazil 5INFN Genova, Italy
Physics methods for the simulation of photoionisation
IEEE NSS 2013
Rationale
2
State-of-the-art simulation of photon interactions
Elastic scattering : Published Photoelectric effect Compton scattering
pair production : first results
New theoretical calculations and parameterisations were
released recently.
à Are they accurate than old one?
New physics 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?
New trends
The simulation of photon physics is
well-established.
à Is there any quantitative validation?
Simulation physics
Project to validate a wide set of simulation modeling options against a large collection of experimental data
IEEE NSS 2013 3
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)
Photoionisation in Monte Carlo codes
IEEE NSS 2013
lowenergy::G4LivermorePhotoElectricModel
utils::G4VEmModel
lowenergy::G4LivermorePolarizedPhotoElectricModel
lowenergy::G4PenelopePhotoElectricModel
standard::G4PEEffectFluoModel
polarisation::G4PolarizedPEEffectModel
polarisation::G4VPolarizedCrossSection
polarisation::G4PolarizedPEEffectCrossSection
lowenergy::G4PhotoElectricAngularGeneratorSauterGavrila
utils::G4VEmAngularDistribution
lowenergy::G4PhotoElectricAngularGeneratorSimple
lowenergy::G4PhotoElectricAngularGeneratorPolarized
Photoelectric effect
Geant4 9.6MGP 9/9/2013 reverse engineered
standard::G4PhotoElectricEffect
- isInitialised :G4bool
G4VDiscreteProcessutils::G4VEmProcess
utils::G4VAtomDeexcitation
-anglModel-currentModel
-fAtomDeexcitation-fAtomDeexcitation
-fAtomDeexcitation
-fAtomDeexcitation
4
Sauter-Gavrila
Sauter-Gavrila
same as incident γ
Base class for atomic deexcitation
Penelope 2008 EPDL97
polarized EPDL97
polarized Livermore EPDL97
Biggs-Lighthill Em models
Em process
Packages • lowenergy • polarisation • standard • utils
Photoionisation in Geant4 9.6
IEEE NSS 2013 5
Year Compilation Energy Z (sub)Shell Method 1967-1988 Biggs-Lighthill 10 eV – 100 GeV 1-100 - parameterised
1992 Brennan-Cowan 30 eV – 700 keV 3-92 - 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 1-98 - tabulated
1997 EPDL97 (Scofield) 10 eV – 100 GeV 1-100 all tabulated
1982-1993 Henke 10 eV – 30 keV 1-92 - tabulated
1970-2006 McMaster/Shaltout 1 keV – 700 keV 1-94 - tabulated
1989 PHOTX (Scofield) 1 keV – 100 MeV 1-100 tabulated
2001 RTAB 10 eV – 30 keV 1-99 all tabulated
1973 Scofield 1 keV – 1.5 MeV 1-100 all tabulated
1970 Storm-Israel 1 keV – 100 GeV 1-100 - tabulated
1973 Veigele 100 eV – 100 MeV 1-94 - tabulated
1987-2010 XCOM (Scofield) 1 keV – 100 GeV 1-100 - tabulated
e.g. Chantler’s exchange potential in his DHF calculation is different from Scofield’s
Different methods and calculations
Cross section sources
IEEE NSS 2013
" 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
6
Strategy
※ We only focus on the simulation with non-polarised photons case.
IEEE NSS 2013
TCrossSectionTFinalState
G4TPhotoionisation
G4CsTabula G4FsPhotoionisation G4IPhotoelectronGenerator
G4PhotoelectronSauter G4PhotelectronSauterGavrila G4PhotoelectronSimple
G4VProcessprocesses-management::G4VDiscreteProcess
G4AtomDeexcitation
Photoionisation
Strategy pattern
First design iterationMGP January 2013
or G4CsPhotoIoniBiggs,or G4CsPhotoIoniEbel
«bind»«bind»
7
Streamlined software design consistent with Geant4 kernel
Policy-based class design (à la Alexandrescu, Modern C++ design, 2001) § minimize dependencies § lightweight unit tests for validation
Sharp domain decomposition Clearly identified responsibilities
No duplication of code nor of functionality
Computational environment
IEEE NSS 2013
" Collected from the literature ‒ Total cross sections ‒ Partial cross sections ‒ Angular distributions
" Data types ‒ 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
> 150 references > 5000 data points ~ 3700 σ total ~ 1400 σ shell
Experimental data
IEEE NSS 2013
Systematic effect?
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0.0
0.1
0.2
0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
EPDL E > 1 keVexp.semiemp.
0.0
0.1
0.2
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Number of standard deviationsFr
actio
n
−10 −7 −4 −1 1 3 5 7 9
Chantler E > 1 keVexp.semiemp.
0.0
0.1
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0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Henke E > 1 keVexp.semiemp.
0.0
0.1
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0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
RTAB E > 1 keVexp.semiemp.
0.0
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0.2
0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Scofield E > 1 keVexp.semiemp.
0.0
0.1
0.2
0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Penelope E > 1 keVexp.semiemp.
0.0
0.1
0.2
0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
PHOTX E > 1 keVexp.semiemp.
0.0
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Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Storm E > 1 keVexp.semiemp.
0.0
0.1
0.2
0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
XCOM E > 1 keVexp.semiemp.
0.0
0.1
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0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
VeigeleL E > 1 keVexp.semiemp.
0.0
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Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
VeigeleH E > 1 keVexp.semiemp.
0.0
0.1
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Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Elam E > 1 keVexp.semiemp.
0.0
0.1
0.2
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Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Brennan E > 1 keVexp.semiemp.
0.0
0.1
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Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Biggs E > 1 keVexp.semiemp.
0.0
0.1
0.2
0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
McMaster E > 1 keVexp.semiemp.
0.0
0.1
0.2
0.3
Number of standard deviations
Frac
tion
−10 −7 −4 −1 1 3 5 7 9
Ebel E > 1 keVexp.semiemp.
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
IEEE NSS 2013
" 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
10
Compatibility with experiment
Goodness-of-fit test χ2 test α = 0.01
α ≥ 0.01 pass α < 0.01 fail
Difference across categories
Contingency tables Fisher exact test
Barnard test Pearson χ2 test
α = 0.05
as appropriate
Data analysis method
𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲= 𝐍↓𝑝𝑎𝑠𝑠 /𝐍↓𝑡𝑒𝑠𝑡 𝑐𝑎𝑠𝑒𝑠
IEEE NSS 2013
" Most calculation methods exhibit similar compatibility with experiment for E>250 eV ‒ Chantler, Brennan-Cowan look worse
" Degraded accuracy below 250 eV
11
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Cross section model
Effic
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EPD
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hant
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keRT
ABSc
ofie
ldPe
nelo
pePH
OTX
Stor
mXC
OM
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eleL
Veig
eleH
Elam
Bren
nan
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iaM
cMas
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Ebel
● E>250 eVE<250eVpreliminary
Analysis of contingency tables EPDL
Chantler EPDL
Brennan-Cowan Fisher 0.044 0.011 Pearson χ2 0.033 0.007 Barnard 0.035 0.007
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0.014 0.016 0.018 0.020
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E (keV)C
ross
sec
tion
(M
b)
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H, Z=1Beynon1965Beynon1966Kohl1978Palenius1976EPDLRTABChantlerBiggs
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O, Z=8Cole1978aAngel1988Cairns1965Samson1985EPDLRTABChantlerHenkeBrennanBiggsH O
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Fe, Z=26Dachun1992Murty1998DelGrande1986EPDLRTABChantlerStormHenkeVeigele HElamBrennanBiggsEbelFe
E<250 eV Results - Total cross sections
E>250 eV
E (keV) E (keV) E (keV)
Cro
ss s
ectio
n (k
b)
Cro
ss s
ectio
n (M
b)
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ss s
ectio
n (M
b)
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59.54 keVArora1981Karabulut2005Ertugrul2003EPDLRTABscaled RTABChantlerEbel
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Xe, Z=54Becker1987EPDLRTABscaled RTAB
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ss s
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Ba, Z=56Bizau1989EPDLRTAB
shell EPDL Chantler RTAB scRTAB Ebel K 0.209 0.350 <0.001 0.315 <0.001 L1 0.075 <0.001 0.069 0.964 L2 0.339 <0.001 0.299 0.154 L3 1 <0.001 1 1 M1 <0.001 <0.001 <0.001 M4 0.031 <0.001 <0.001 M5 <0.001 <0.001 <0.001 N1 <0.001 <0.001 <0.001 N6 <0.001 <0.001 <0.001 <0.001 N7 <0.001 <0.001 <0.001 <0.001 O1 <0.001 <0.001 <0.001 <0.001 O2 <0.001 <0.001 <0.001 <0.001 O3 <0.001 <0.001 <0.001 <0.001 P1 <0.001 <0.001 <0.001 <0.001
p-value χ2 test
Systematic effect observed with RTAB 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
K
L3
M4
O1
Results - Shell cross sections
IEEE NSS 2013 13
0 30 60 90 120 150 180
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Θ ang le (deg rees )
Normarilz
ed cross
sec
tion
E xp. G 4P ola r G 4S auter G E ANT 3
A luminiumK -‐s hell1170 keV
Qualitative appraisal Limited experimental sample
Experimental systematic effects (corrected/uncorrected data)
Option à la GEANT 3 (Sauter) evaluated along with other Geant4 options
Results - Angular distribution
0 30 60 90 120 150 180
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Normarilz
ed cross
sec
tion
E xp. G 4P ola r G 4S auter G E ANT 3
G oldL 2-‐s hell412 keV
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Normarilz
ed cross
sec
tion
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E xp. G 4P ola r G 4S auter G E ANT 3
0 30 60 90 120 150 180
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K ryptonM1-‐s hell1.2536 keV
Θ ang le (deg rees )
Normarilz
ed cross
sec
tion
IEEE NSS 2013
" 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) RTAB 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
14 All results will be documented in detail in a forthcoming publication
Conclusion
IEEE NSS 2013
…a big THANK YOU to the CERN Library!