1. Low-energy EM group : status and plans Geant Low Energy EM Physics working group 19-20 January 2009 CERN

2. 2 Content Working-group reorganisation Highlights since 2007 Review Workplan 2009 2010-2012

3. I – Working group reorganisation since July 2008

4. 4 coordinator : S. Incerti (IN2P3/CENBG) two steering-board representatives : G. Cuttone (INFN/LNS) G. Montarou (IN2P3/LPCC) contains 18 members who are members of the Geant4 collaboration ANSTO (Australia), CERN, CNSTN (Tunisia), FAMAF (Argentina), IN2P3 (France), INFN (Italy), Karolinska (Sweden), ESA (The Netherlands) in collaboration with 18 « external » members having their own expertise on specific items/activity they are not yet members of the Geant4 collaboration they will have the possibility to join the Geant4 collaboration after contribution to the low energy EM working group Re-organisation

5. 5 6 « mini » working groups Low-energy EM processes coordinator : S. Incerti (IN2P3/CENBG) Debugging of existing models coordinator : G. Santin (ESA/ESTEC) Computing performance coordinator : N. Karakatsanis (National Tech. Univ. of Athens) Testing coordinator : P. Guèye (Jefferson Lab/Hampton U.) Validation coordinator : P. Cirrone (INFN/LNS) Documentation coordinator : C. Zacharatou (Copenhagen University Hospital )

6. 6 A new web site accessible to users directly from Geant4 web site based on Twiki at CERN https://twiki.cern.ch/twiki/bin/view/Geant4/LowEnergyElectromagneticPhysicsWorkingGroup

7. II - Highlights since 2007 Review New Physics processes and models Ion ionisation model (ICRU’73) Doppler broadening PIXE ionisation cross sections Geant4-DNA processes for microdosimetry Software design migration for convergence Low-energy / Standard EM Livermore photon processes Penelope processes Software performance

8. Physics processes and models Note The plots shown do not contain reference data. Validation will be addressed during the second low energy talk.

9. 1) New ion ionisation model

10. G4IonParametrisedLossModel: a new low- energy electromagnetic model for ions G4IonParametrisedLossModel is a new stopping power model for ions, currently under developement Close collaboration between Low-Energy and Standard Electromagnetic group Model is part of the Low-Energy package, but follows the Standard interfaces Designated for use with the G4ionIonisation process A prototype version of the model was included in the December 2008 release of Geant4 Currently in validation phase Allows to plug in electronic stopping power tables: in its default configuration the model utilizes ICRU 73 data The ICRU 73 report provides stopping power tabulations for ions with atomic numbers ranging from 3 to 18, as well as for iron ions, covering many elemental materials and compounds relevant for various areas of application Stopping data for ion-material combinations not included in the ICRU 73 report are computed by applying a scaling procedure On behalf of A. Lechner

11. G4IonParametrisedLossModel: a new low- energy electromagnetic model for ions The new approach is expected to improve accuracy of ion loss description in Geant4 Previous models in Geant4 derive ion stopping powers by scaling proton or helium data (ICRU 49, NIST) using an effective charge approximation First tests: For some ion-target couples, differences are observed between new and old model in the prediction of the ion range (see Bragg peak in figure below) New model is expected to improve accuracy, where the effective charge approach is known to have deficiencies Fig.: Energy deposition as a function of depth for Ar-40 ions (135 MeV per nucleon)‏ impinging on aluminum oxide: Comparison of results derived with G4IonParametrisedLossModel (ICRU 73) and G4BraggIonModel (ICRU 49 + effective charge approach). Preliminary results.

12. 2) Doppler broadening in Compton scattering

13. 13 Doppler broadening in Compton scattering Au 50 keV G4PenelopeCompton includes it (analytical approach) G4LowEnergyCompton recently updated (by MGPia) to deal with Doppler broadening (EGS database approach) Good agreement Penelope-LowE Standard Compton includes cross section suppression, but samples final state according to Klein-Nishina Looking for suitable validation data Compton scattering: electrons bound and not at rest (as assumed for Klein-Nishina)  change of angular distribution, reduction of XS interesting < 0.5 MeV On behalf of L. Pandola

14. 3) New PIXE models

15. 15 New PIXE ionisation cross section models  PIXE is the standard method for quantitative elemental analysis in Ion Beam Analysis  New developments for the computation of ionisation cross sections in PIXE generation  Theoretical model for K-shell ionisation by protons  Theoretical model for K-shell ionisation by alpha particles  Semi-empirical model for Li-sub-shells ionisation On behalf of H. Abdelaouhed

16. 16 Theoretical ECPSSR Model for K-shell ionisation Semi-Empirical Orlic Model for Li-subshell ionisation Relaxation process X-Ray Fluorescence and/or Auger effect Final state EADL library PIXE generation process Incident protons Incident alpha Total ionisation cross section PIXE overview Data-Driven Model from Paul&Sacher data library for K-shell ionisation by protons New !

17. 4) « Geant4 DNA » project

18. 18 The Geant4-DNA project Purpose : extend Geant4 modelling capabilities for the simulation of ionising radiation effects at the molecular level Initiated in 2001 by P. Nieminen, Europen Space Agency/ESTEC Applications : Radiobiology, radiotherapy and hadrontherapy (ex. prediction of DNA strand breaks from ionising radiation) Radioprotection for human exploration of Solar system Not limited to biological materials (ex. Silicon)

19. 19 Physics models in Geant4 DNA epH , He+, He Elastic scattering > 7.4 eV Screened Rutherford > 7 eV Champion --- Excitation A 1 B 1, B 1 A 1, Ryd A+B, Ryd C+D, diffuse bands 7.4 eV – 10 MeV Emfietzoglou 10 eV – 500 keV Miller Green 500 keV – 10 MeV Born - Effective charge scaling from same models as for proton Charge Change - 1 keV – 10 MeV Dingfelder 1 keV – 10 MeV Dingfelder Ionisation 1b 1, 3a 1, 1b 2, 2a 1 + 1a 1 12.6 eV – 30 keV Born 100 eV – 500 keV Rudd 500 keV – 10 MeV Born 100 eV – 100 MeV Rudd Models available for liquid water only Models in black are analytical Models in purple use interpolated data

20. 20 Each physics process is characterized by one or several complementary or alternative models Each model provides : a computation of the total cross section a computation of the final state : kinematics, production of secondaries A specific advanced example is available (microdosimetry) for users Total cross sections

21. Software design migration for convergence Low-energy / Standard EM

22. 22 Objectives Our objective is to build a coherent aproach of EM interactions in Geant4, in full collaboration between the Standard Electromagnetic and Low Energy Electromagnetic working groups (see EM Physics talk by Vladimir) In particular, we foresee : common physics lists, where the best models for low and high energies are used a common software design common validation plans a coherent support of Geant4 hypernews cross references between Standard EM and Low Energy EM web pages

23. 23 Status all Penelope processes have been migrated and tested Livermore photon processes have been migrated and are being tested all Geant4-DNA processes have been migrated and are being tested

24. 24 Example : Photoelectric effect Standard and migrated LowE are similar

25. 25 Eexample: Penelope Compton Gold – 50 keVWater (compound) – 6 MeV absolute cross sections are consistent and energy spectra are unchanged preliminary CPU performances are improved - initialization time (at the beginning of run) is reduced by 30% (handling of Physics tables) - running time is reduced of ~10% for water and of ~5% for gold (G4EmElementSelector) Energy (MeV)

26. Software performance improvement

27. 27 Speeding-up of evaluated data based processes Poor performance of Low Energy Photoelectric, Compton and Rayleigh models measured using GATE, as reported during the 2007 Hebden Bridge meeting Step-by-step revision of G4EmDataSet and G4LogLogInterpolation classes, including checks in order to make sure that the revisions will induce negligible differences An initial revision of the G4LogLogInterpolation class has been validated and included in the G4 version 9.2. A gain of 6-10% (1.06 – 1.1 times) has been observed. A gain of 45% is expected (1.45 times faster) if the logarithmic operations of the G4LogLogInterpolation class are replaced by a load operation of pre-calculated logarithm values (validated for GATE simulations were photoelectric, compton and rayleigh processes are mainly used). Work under progress to expand this implementation for all low energy EM processes of Geant4. The performance, and therefore the gain, depends on the type of processes used and the frequency in which interpolation calculations are required by a simulation application. N. Karakatsanis, G. Loudos, J. Apostolakis in collaboration with Standard EM On behalf of N. Karakatsanis

28. III – Workplan 2009 2010-2012

29. 29 Plans for 2009 1) Software design (June 2009) (+Std EM) - (Recommendation #3, R4, R5) achieve testing of migrated Livermore photon processes (1 collaborator – FTE=0.25) migration of Livermore electron processes (ionisation, bremmstrahlung) (1 collaborator – FTE=0.25) 2) Software performance (June 2009) improvement of G4LogLogInterpolation class (1 collaborator – FTE=0.25) 3) Systematic testing (June 2009) (+Std EM) - (R1) (~10 collaborators – FTE ~ 2.0) extend coverage (particles, energies, materials) of automated tests 4) Build a reference data base for verification & validation (December 2009) (+Std EM) - (R1,R2,R3, R4, R18, R19, R21, R22, R24) (same number of collaborators as above) theoretical predictions experimental data other Monte Carlo codes 5) Debugging of processes (December 2009) – MANPOWER NEEDED (1 collaborator – FTE=0.10) G4LowEnergyIonisation G4hLowEnergyIonisation 6) New Physics models with common design (December 2009) (+Std EM) improvement of Penelope models (1 collaborator – FTE=0.25) polarized photoelectric and gamma conversion, triple conversion models (space applications) (2 collaborators – FTE=0.20) 7) Documentation (+Std EM) (December 2009) - (R1, R22, R24) (4 collaborators – FTE=0.40) common EM web pages

30. 30 Physics (+Std EM) – MANPOWER NEEDED (1 collaborator – FTE=0.25) Migration of fluorescence/Auger emission Software design (2010-2011) (+Std EM) – MANPOWER NEEDED (1 collaborator – FTE=0.25) Redesign full data handling Geant4-DNA (2009-2011) (+Std EM) (~4 collaborators – FTE~2.0) new Physics models in liquid water / other biological materials physico-chemistry processes implementation molecular geometries (DNA) biological damage quantification other applications : material sciences, injectors Plans for 2010-2012

31. 31 Manpower needs for low-energy EM Manpower will be needer for : Debugging of Physics bugs accumulated over the years in the LowE Physics processes (most urgent) Implementation/migration of fluorescence and Auger emission following standard EM design Redesign of data table handling

32. Backup slides

33. 33 Re-organisation Coordinator : S. Incerti (IN2P3/CENBG) SB representatives : G. Cuttone (INFN/LNS), G. Montarou (IN2P3/LPCC), 18 Members today (they are members of the Geant4 collaboration) Haifa Ben Albelwahed (CNSTN, Tunisia) Haifa Ben Albelwahed Stephane Chauvie (INFN, Torino U., Italy) Stephane Chauvie Pablo Cirrone (INFN/LNS, Italy) Pablo Cirrone Giacomo Cuttone (INFN/LNS, Italy) Giacomo Cuttone Gerardo De Paola (FAMAF, Argentina) Gerardo De Paola Francesco Di Rosa (INFN/LNS, Italy) Francesco Di Rosa Ziad Francis (CNRS/IN2P3/IPHC, France) Ziad Francis Susanna Guatelli (ANSTO, Australia) Susanna Guatelli Sebastien Incerti (CNRS/IN2P3/CENBG, France) Sebastien Incerti Anton Lechner (CERN, Switzerland) Francesco Longo (INFN/Trieste, Italy) Francesco Longo Alfonso Mantero (INFN/Genova, Italy) Alfonso Mantero Barbara Mascialino (Karolinska Institute, Sweden) Barbara Mascialino Gerard Montarou (CNRS/IN2P3/LPC Clermont, France) Gerard Montarou Jakub Moscicki (CERN, Switzerland) Jakub Moscicki Luciano Pandola (INFN/LNGS, GNO, Italy) Luciano Pandola Giorgio Russo (INFN/LNS, Italy) Giorgio Russo Giovanni Santin (ESA/ESTEC, The Netherlands) Giovanni Santin

34. 34 External « experts » collaborators with their own expertise they are not yet members of the Geant4 collaboration they will have the possibility to join the Geant4 collaboration after one year of contribution to the low energy EM working group