Validation of the Bremsstrahlung models

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Validation of theBremsstrahlung models

• Susanna Guatelli, Barbara Mascialino, Luciano
  Pandola, Maria Grazia Pia, Pedro Rodrigues,
  Andreia Trindade

INFN Genova INFN Gran Sasso Laboratory - LIP
IEEE Nuclear Science Symposium San Diego, 30
October 4 November 2006
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Geant4 electron Bremsstrahlung
2 electromagnetic physics packages
Standard
Low Energy
3 Bremsstrahlung processes
G4eLowEnergyBremsstrahlung
G4eBremsstrahlung
Tsai
Tsai
2BN
2BS
angular distribution
angular distributions
G4PenelopeBremsstrahlung
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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
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The experimental set-up
e- beam(70 keV-10 MeV) incident on a slab of
material
Photon (energy, ?)
Electrons and d-rays are absorbed Bremsstrahlung
photons can be transmitted
electrons
Z axis
Yield, Energy and Polar Angle of the emitted
photons
Secondary production threshold 0.5 mm
Statistical Toolkit Goodness-of-Fit test
Quantitatitative comparison of experimental -
simulated distributions
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Data sets
Preliminary results Work in progress!
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
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Double differential s at 2.7 MeV on thin (2.63
mg/cm2) Be target
N. Starfelt et al., Phys. Rev. 102 (1956) 1598
Energy (MeV)
Energy (MeV)
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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)
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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)
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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)
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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)
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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)
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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)
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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)
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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)
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Double differential s at 9.7 MeV on thin (0.209
mg/cm2) Au target
N. Starfelt et al., Phys. Rev. 102 (1956) 1598
Energy (MeV)
Energy (MeV)
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Angular distribution
500 keV
W.E. Dance et al., Journal of Applied Physics 39
(1968) 2881
Ethr 46 keV
500 keV electrons on Al (0.548 g/cm2) and Fe
(0.257 g/cm2) Thick target experiment
Standard package
Red data Black simulation o ? Al ? ? Fe
Absolute comparison
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Angular distribution
500 keV
W.E. Dance et al., Journal of Applied Physics 39
(1968) 2881
precise agreement!
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Angular distribution
500 keV
W.E. Dance et al., Journal of Applied Physics 39
(1968) 2881
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Angular distribution
1 MeV
Same test for 1 MeV primary electrons (threshold
50 keV)
Standard package
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
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Angular distribution
1 MeV
W.E. Dance et al., Journal of Applied Physics 39
(1968) 2881
precise agreement!
Good agreement for Al - Reasonable also for Fe
(2BN)
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Angular distribution
500 keV
W.E. Dance et al., Journal of Applied Physics 39
(1968) 2881
2BS good for Al and Fe (except in the backward
direction)
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Integral g yield
Total g yield on Al integrated on ? (0 ? p) and
on energy (Eth ? Emax)
Standard process
W.E. Dance et al., Journal of Applied Physics 39
(1968) 2881
o ? dat a ? ? simul.
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Angular distributions
70 keV
Low Energy Package
Penelope Standard Low Energy (TSAI)
Penelope TSAI 2BS 2BN
Angle (deg)
Angle (deg)
Angular distribution of photons is strongly
model-dependent
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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)
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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
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Conclusions

• A project is in progress to test all Geant4
  Bremsstrahlung models
• Rigorous, quantitative comparison against
  experimental data
• Preliminary results at low energies
• Power of the toolkit strategy
• Geant4 models differ significantly at low energy