bremsstrahlung nss2006

Validation of theBremsstrahlung models: 

Validation of the Bremsstrahlung models Susanna Guatelli, Barbara Mascialino, Luciano Pandola, Maria Grazia Pia, Pedro Rodrigues, Andreia Trindade IEEE Nuclear Science Symposium San Diego, 30 October – 4 November 2006 INFN Genova – INFN Gran Sasso Laboratory - LIP

Geant4 electron Bremsstrahlung: 

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

Validation of Geant4 EM physics: 

Validation of Geant4 EM physics K. Amako et al., IEEE Trans. Nucl. Sci. 52 (2005) 910 Ongoing large-scale project Photon mass attenuation coefficient Range, Stopping power (e, p, a) NIST NSS 2006 Atomic relaxation (fluorescence, Auger effect) Proton Bragg peak Electron Bremsstrahlung 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

The experimental set-up: 

The experimental set-up e- beam(70 keV-10 MeV) incident on a slab of material Z axis electrons Photon (energy, θ) Yield, Energy and Polar Angle of the emitted photons Electrons and d-rays are absorbed Bremsstrahlung photons can be transmitted Secondary production threshold = 0.5 mm Quantitatitative comparison of experimental - simulated distributions Statistical Toolkit Goodness-of-Fit test

Data sets: 

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 Preliminary results Work in progress!

Double differential s at 2.7 MeV on thin (2.63 mg/cm2) Be target: 

Double differential s at 2.7 MeV on thin (2.63 mg/cm2) Be target Energy (MeV) Energy (MeV) N. Starfelt et al., Phys. Rev. 102 (1956) 1598

Double differential s at 4.5 MeV on thin (2.63 mg/cm2) Be target: 

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

Double differential s at 9.7 MeV on thin (2.63 mg/cm2) Be target: 

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

Double differential s at 2.7 MeV on thin (0.878 mg/cm2) Al target: 

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

Double differential s at 2.7 MeV on thin (0.878 mg/cm2) Al target: 

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

Double differential s at 4.5 MeV on thin (0.878 mg/cm2) Al target: 

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

Double differential s at 9.7 MeV on thin (0.878 mg/cm2) Al target: 

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

Double differential s at 2.7 MeV on thin (0.209 mg/cm2) Au target: 

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

Double differential s at 4.5 MeV on thin (0.209 mg/cm2) Au target: 

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

Double differential s at 9.7 MeV on thin (0.209 mg/cm2) Au target: 

Double differential s at 9.7 MeV on thin (0.209 mg/cm2) Au target Energy (MeV) Energy (MeV) N. Starfelt et al., Phys. Rev. 102 (1956) 1598

Angular distribution: 

Angular distribution Red = data Black = simulation o  Al   Fe Standard package Absolute comparison Ethr = 46 keV 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 500 keV

Angular distribution: 

Angular distribution precise agreement! W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 500 keV

Angular distribution: 

Angular distribution W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 500 keV

Angular distribution: 

Angular distribution Red = data Black = simulation o  Al   Fe Same test for 1 MeV primary electrons (threshold: 50 keV) Standard package Absolute comparison W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 Targets: Al (0.548 g/cm2) and Fe (0.613 g/cm2) 1 MeV

Angular distribution: 

Angular distribution Good agreement for Al - Reasonable also for Fe (2BN) precise agreement! W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 1 MeV

Angular distribution: 

Angular distribution 2BS: good for Al and Fe (except in the backward direction) W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881 500 keV

Integral g yield: 

Integral g yield Total g yield on Al integrated on  (0  p) and on energy (Eth  Emax) Standard process o  dat a   simul. W.E. Dance et al., Journal of Applied Physics 39 (1968) 2881

Angular distributions: 

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

Energy distribution at 70 keV: 

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

Relative comparison at 70 keV: 

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

Conclusions: 

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