Low Energy Electromagnetic Physics - Geant4 - CERN

Low Energy Electromagnetic Physics 

Maria Grazia Pia, INFN Genova 

on behalf of the LowE WG 

http://www.ge.infn.it/geant4/lowE/index.html 

Geant4 Workshop and Geant4 ∆ Review, CERN, October 2002 

Maria Grazia Pia, INFN Genova

The process in a nutshell 

We have and maintain a URD 

– Regular contacts with users 

We have a process for requirements 

management 

– But we would like to have a tool for it! 

We do analysis and design 

– We validate our designs against use cases 

We do design and code reviews 

– not enough, however… 

– main problem: geographical spread 

Unit, package integration, system tests 

+ validation (acceptance) 

– we do a lot… but we would like to do more 

– Limited by availability of resources for core 

testing 

– Need a more systematic approach and better 

toolsè Test & Analysis Project 

– Close collaboration with users 

Ample requirements traceability 

– Still improving it: added documentation 

and validation results as traceability items 

– in progress: traceability documentation 

from simple matrix to Rose model 

We regularly hold WG meetings to 

discuss and agree together our project 

planning (GDPM approach) 

We have a SPI process 

– With some spells of SPD sometimes… 

– Collaboration with Anaphe for a common 

(tailored) process 

We keep everything in CVS 

(not in our head…) 

– Code, designs, tests, documents etc. 

We maintain a web site 

– LowE, advanced examples, WG projects 

More details: see talk on Software Process in Physics, Geant4 Review 2001 


Recent physics activities 

Electron processes 

– New parameterisations of LLNL data 

– Various bug fixes 

– Tests against NIST database (range) 

– Tests against Sandia database 

Photon processes 

– Rather stable 

– Tests of angular distributions in 

progress 

Polarisation 

– Improvement of Compton 

– γ conversion in progress 

– Contacts with experiments for 

common validation tests 

Auger effect 

– New 

Fluorescence 

– Small fixes and improvements while reimplementing 

in a design iteration 

– Test beam validation in collaboration with 

ESA Science Payload Division 

PIXE 

– Toy model 

– Established contacts for databases, plans for 

new model 

Protons, ions 

– Stable, minor improvements 

– Bragg peak tests in progress 

Antiprotons 

– Paper in progress, very close to submission 


Photons: mass attenuation coefficient 

Comparison against NIST data 

Tests by IST - Natl. Inst. for Cancer 

Research, Genova (F. Foppiano et al.) 

LowE accuracy ~ 1% 

E (%) 

UR 1.1 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

-2 

-4 

-6 

-8 

-10 

-12 

-14 

-16 

-18 

E = (NIST-G4EMStandard)/NIST 

E = (NIST-G4LowEn)/NIST 

0.01 0.1 1 10 

Photon Energy (MeV) 

Fe 

This test will be introduced into the Test & Analysis project 

for a systematic verification 

Also water, Pb 


µ /ρ (cm 2 /g) in water 

10 

1 

0.1 

Photon attenuation: Geant4 vs. NIST data 

Test and validation by IST - Natl. Inst. for Cancer Research, Genova 

Geant4 LowEn 

NIST 

1000 

100 

100 

water Fe Pb 

10 

µ /ρ (cm 2 /g) in iron 

10 

1 

0.1 

UR 1.1 


NIST 

µ/ρ (cm 2 / g in lead 

1 

0.1 

0.01 


NIST 

0.01 0.1 1 10 


0.01 

0.01 0.1 1 10 


0.01 0.1 1 

Photon energy (MeV) 

Delta (%) 

16 

14 

12 

10 

8 

6 

4 

2 

0 

-2 

-4 

-6 

-8 

-10 

-12 

-14 

-16 

Delta = (NIST-G4EMStand) / NIST 

Delta = (NIST-G4LowEn) / NIST 

0.01 0.1 1 10 


E (%) 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

-2 

-4 

-6 

-8 

-10 

-12 

-14 

-16 

-18 

• Low Energy EM 

• Standard EM 

w.r.t. NIST data 

E = (NIST-G4EMStandard)/NIST 

E = (NIST-G4LowEn)/NIST 

accuracy within 1% 

0.01 0.1 1 10 


E (%) 

10 

8 

6 

4 

2 

0 

-2 

-4 

-6 

-8 

-10 

E = (NIST - G4EM Standard)/NIST 

E = (NIST- G4LowEn)/NIST 

0.01 0.1 1 



Photons: angular distributions 

UR 1.1 


Rayleigh scattering: Geant4-LowE and expected distribution 

(more work in progress)

Photons, evidence of shell effects 

UR 1.1 

Photon transmission, 1 µm Pb 

Photon transmission, 1 µm Al 


Electron Bremsstrahlung 

UR 1.1 

New parameterisations of 

EEDL data library 

– in response to problem reports 

from various users 

– precision is now ~ 1.5 % 

Plans 

– Systematic verification over Z 

and energy 

– Need Test & Analysis Project 

for automated verification 


Electron ionisation 

UR 1.1 

New parameterisations 

of EEDL data library 

– in response to problem 

reports from various users 

– precision is now better than 

5 % for ~ 50% of the shells, 

poorer for the 50% left 

Plans 

– Systematic verification over 

shell, Z and energy 

– Need Test & Analysis Project 

for automated verification 

(all shells, 99 elements!) 


Electrons: range 

UR 1.1 

Range in various simple and 

composite materials 

Compared to NIST database 

Al 

Also Be, Fe, Au, Pb, Ur, air, 

water, bone, muscle, soft tissue 

Testbed for 

Test&Analysis prototype 


Electrons: dE/dx 

UR 1.1 

Ionisation energy loss in 

various materials 

Compared to Sandia database 

More systematic verification 

planned (for publication) 


Also Fe, Ur

Electrons, transmitted 

20 keV electrons, 0.32 and 1.04 µm Al 

UR 1.1 


UR 2.1 

Protons 

Stopping power 

Z dependence for various energies 

Ziegler and ICRU models Ziegler and ICRU, Fe Ziegler and ICRU, Si 

Straggling 

UR 2.5 

Nuclear stopping power 


Bragg peak (with hadronic interactions)

Antiprotons 

UR 2.3 

New: comparison with another 

theoretical model 

– Non-linear calculation by Arista 

and Lifschitz 

Dashed 

– Geant4 LowE proton 

Solid 

– Geant4 LowE Quantal Harmonic 

Oscillator model 

Dotted-dashed 

– Calculation by Arista and Lifschitz 

Points 

– Data from ASACUSA 


Ions 

Deuterons 

UR 2.2 

Ar and C ions 


Polarisation 

x 

250 eV -100 GeV 

ξ φ 

hν 

hν 

ε A 

0 θ 

O α 

C 

Cross section: 

UR 4.1, D.1 

z 

d 

dΩ 

σ 1 

2 

= 

' ⎛ 

ε|| 

= ⎜Nî− 

⎝ 

θ Polar angle 

φ Azimuthal angle 

ε Polarization vector 

2 

2 hν 

⎡hν0 

hν 

2 

r0 ⎢ + − 2sin θ cos 

2 

2 hν0 

⎣ hν 

hν0 

1 

N 

cosξ = sinθcosφ 

Scattered Photon Polarization 

' 

ε ⊥ 

= 

⇒ 

1 

N 

2 

sin θ sinφ 

cosφĵ− 

1 

N 

sinξ = 

⎤ 

φ⎥ 

⎦ 

2 2 

1−sin 

θcos 

φ = N 

( cosθ 

ĵ − sin θsin 

φ kˆ ) sinβ 

⎞ 

sinθ 

cosθ 

cosφkˆ 

⎟cosβ 

⎠ 

Low Energy 

Polarised Compton 

y 

100 keV 

1 MeV 

10 MeV 

small ϑ 

small ϑ 

More details: talk on 

small ϑ 

Geant4 Low Energy 

Electromagnetic Physics 

large ϑ 

large ϑ 

large ϑ 


Other polarised processes under development

Fluorescence 

Microscopic validation: 

against reference data 

UR 3.1 

Experimental validation: 

test beam data, in collaboration with 

ESA Science Payload Division 

Fe lines 

Spectrum from 

a Mars-simulant 

rock sample 

GaAs lines 

Scattered 

photons 


Auger effect 

UR 3.1 

New process, 

validation in progress 

Auger electron emission 

from various materials 

Sn, 3 keV photon beam, 

electron lines w.r.t. published 

experimental results 


Contribution from users 

Many valuable contributions to the validation of LowE 

physics from users all over the world 

– excellent relationship with our user community 

User comparisons with data usually involve the effect 

of several physics processes of the LowE package 

A small sample in the next slides 

– no time to show all! 


GEANT4 Workshop, 2002 

30 September – 4 October 

GEANT4 Medical Applications at LIP 

P. Rodrigues, A. Trindade, L.Peralta, J. Varela 

LIP – Lisbon 


Homogeneous Phantom 

P. Rodrigues, A. Trindade, L.Peralta, J. Varela, LIP 

• Simulation of photon beams produced by a Siemens 

Mevatron KD2 clinical linear accelerator 

• Phase-space distributions interface with GEANT4 

• Validation against experimental data: depth dose and 

profile curves 

Differences 

LIP – Lisbon 

10x10 cm 2 

15x15 cm 2 

10x10 cm 2 15x15 cm 2 


Electron Transport at Low Energies 


• Evaluation of electron range for different GEANT4 GEANT4 releases (Low+Std) 

Styrophoam 

Lead 


Dose Calculations with 12 12 C 


• Bragg peak localization calculated with GEANT4 (stopping powers 

from ICRU49 and Ziegler85) and GEANT3 in a water phantom 

• Comparison with GSI data 


Geant4 low energy validation 

Jean-Francois Carrier, Louis Archambault, Rene Roy and Luc Beaulieu 

Service de radio-oncologie, Hotel-Dieu de Quebec, Quebec, Canada 

Departement de physique, Universite Laval, Quebec, Canada 

The following results will be published soon. They are part 

of a general Geant4 low energy validation project. 


• Using Geant4, we calculated depth-dose curves for many 

different electron or photon sources: 

•Beams 

•monoenergetic beam 

•realistic clinical accelerator beam 

•Point sources 

•monoenergetic source 

•source with real nuclide energy spectra 

•and different irradiated media: 

•Homogeneous 

•water, Be, Mo or U 

•Heterogeneous 

•water/Al/lung/water 

•water/air/steel/air/water 


Jean-Francois Carrier, Louis Archambault, Rene Roy and Luc Beaulieu

Uranium irradiated by electron beam 


Fig 1. Depth-dose curve for a semi-infinite uranium slab irradiated by a 0.5 

MeV broad parallel electron beam 


1 Chibani O and Li X A, Med. Phys. 29 (5), May 2002

Multi-slab medium irradiated by photons 


Fig 2. Depth-dose curve for a multi-slab medium irradiated by a 18 MV 

realistic clinical accelerator photon beam 

2 Rogers D W O and Mohan 

R,http://www.irs.inms.nrc.ca/inms/irs/papers/iccr00/iccr00.html 


Water phantom irradiated by clinac beam 


Fig 3. Relative dose distribution for a water phantom irradiated by a 6 

MeV Clinac 2100C electron beam 


3 Ding G X and Rogers D W O 

http://gold.sao.nrc.ca/inms/papers/PIRS439/pirs439.html

Ions 

Independent validation at 

Univ. of Linz (H. Paul et al.) 

Geant4-LowE reproduces the right 

side of the distribution precisely, 

but about 10-20% discrepancy is 

observed at lower energies 


Dose distribution: TG 43 protocol, 

experimental data (S. Paolo Hospital, Savona), G4-LowE 

o Protocol 

ê Data (SV) 

m G4-LowE 


S. Guatelli’s thesis

Application 

Cosmic rays, 

jovian electrons 

Solar X-rays, e, p 

and more! 

Courtesy SOHO EIT 


Courtesy of S. Magni, Borexino 

Not only 

“space and medical”!

Team work! 

Geant4 Low Energy Electromagnetic Working Group 

+ 

users all over the world 

The validation plots in this presentation 

have been contributed by 

19 people from 9 countries 

Thanks to all! 

Students 

Jean-Francois Carrier 

Stephane Chauvie 

Elena Guardincerri 

Susanna Guatelli 

Alfonso Mantero 

Pedro Rodrigues 

Andreia Trindade 

Matteo Tropeano 


Further physics improvements and extensions 

Various projects in progress 

– all motivated by requirements in the URD 

Some examples in the following slides 

– no time to show all! 


Bremsstrahlung Models 

UR A.5 

• Current bremstrahlung polar angle generation scheme is independent 

of both atomic number, Z, and emitted photon momentum, k 

• Does not account variations due to the screening of the nucleus by 

the atomic electrons 

• At generator level, for 50 keV incident electrons with k/T=0.7 in Ag 

New model (2BN) to be 

implemented by LIP group 


Polarisation 

UR 1.4, 4.1 

theory 

500 million events 

simulation 

Polarisation of a non-polarised photon 

beam, simulation and theory 


Ratio between intensity with perpendicular and parallel polarisation 

vector w.r.t. scattering plane, linearly polarised photons

Ongoing significant effort in OOAD 


Other activities in the WG 

Advanced examples 

Simulation + analysis in a distributed computing environment 

Test & Analysis 

Technology transfer 

Training 


Technology transfer 

Particle physics 

software aids space 

and medicine 

M.G. Pia and J. Knobloch 

Geant4 is a showcase example of 

technology transfer from particle 

physics to other fields such as 

space and medical science […]. 

CERN Courier, June 2002 


Talks 

since last 

workshop 

in WG web 

1. The Geant4 Toolkit: simulation capabilities and application results 

M.G. Pia et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002 

2. Geant4: a powerful tool for medical physics 

E.Lamanna et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002 

3. Dose calculation for radiotherapic treatment on a distributed computing environment 

S.Chauvie et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002 

4. Parallel Geant4 simulation in medical and space science applications 

J. Moscicki et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002 

5. Simulation and analysis for astroparticle experiments 

A. Howard et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002 

6. Leipzig applicators Montecarlo simulations: results and comparison with experimental and manufacturer's data 

M. Tropeano et al., 21st ESTRO Meeting, Prague, 2002 

7. Tools for simulation and analysis 

A. Pfeiffer and M.G. Pia (for the Geant4 and Anaphe Collaborations), ICHEP02, Amsterdam, 2002 

8. The Geant4 Simulation Toolkit and Its Low Energy Electromagnetic Physics Package 

S.Chauvie et al., 44th Annual Meeting of the American Ass. of Physicists in Medicine, Montreal, 2002 

9. The Geant4 Toolkit: Overview 

M. G. Pia, Invited lecture at the MCNEG Workshop, Stoke-on-Trent, UK, 2002 

10. Medical applications of the Geant4 Simulation Toolkit 

M. G. Pia, Invited lecture at the MCNEG Workshop, Stoke-on-Trent, UK, 2002 

11. Simulation software: applications and results in the bio-medical domain 

M. G. Pia et al., VII International Conference on Advanced Technologies and Particle Physics, Como, 2001 

12. From HEP computing to bio-medical research and vice-versa: technology transfer and application results 

M. G. Pia et al., Plenary talk at CHEP 2001, Beijing, China, 2001 

13. Architecture of Collaborating Frameworks 

A.Pfeiffer et al., CHEP2001, Beijing, China, 2001 

14. Simulation For Astroparticle Experiments And Planetary Explorations 

A.Brunengo (for the Geant4 Low Energy Electromagnetic Group), CHEP2001, Beijing, China, 2001 

15. Geant4 Low Energy Electromagnetic Physics 

M. G. Pia (for the Geant4 Low Energy Electromagnetic Group), CHEP2001, Beijing, China, 2001 

16. The GEANT4 simulation toolkit 

G. Santin, Monte Carlo Workshop for Nuclear Medicine applications, July 2001 

17. Geant4: simulation capabilities and application results 

M.G. Pia (for the Geant4 Collaboration), EPS-HEP Conference, Budapest, July 2001 


Training 

National School on Detector Technologies, Torino, Feb. 2002 

– Lectures + “Geant4 through an example” 

Geant4 & Anaphe mini-workshop, Gran Sasso Lab, July 2002 

– Tutorials + “Geant4 through an example” +demo 

Geant4 User Workshop, Salamanca, July 2002 

– Lectures + exercises 

Geant4 & Anaphe mini-workshop, INFN-LNS Lab, November 2002 

– Tutorials + + “Geant4 through an example” +demo “Geant4 through an 

example” +demo 

User-centric approach: 

– Introduction to “advanced” software engineering concepts 

– Complete (from the user’s view) training: simulation + analysis 


Resources 

New collaborators: 

– Pablo Cirrone (INFN-LNS) 

– Luis Peralta, Pedro Rodrigues, Andreia Trindade (LIP, Lisbon) 

– Interest expressed by small group at INFN-Gran Sasso Lab 

Status on 1 September 2002 


We do a lot of work 

– and we do our best to do it well… 

– a rigorous software process, continuous SPI 

Conclusions 

– very effective team-work 

work, several brilliant and motivated young collaborators 

We have plenty of interesting physics results in a new (and difficult) 

simulation domain 

– significant progress in the last year in a few problematic areas 

– don’t forget in what status we inherited the package, when the WG was created! 

A huge user community worldwide 

– excellent, constructive relationship between users and developers 

– more support for our activities outside the Collaboration than inside 

Many projects in the WG, not only physics 

– Testing system, analysis, advanced examples, general electromagnetic OOAD, 

distributed computing, technology transfer 

More information in http://www.ge 

ge.infn.it/geant4/ 

.it/geant4/lowE

Low Energy Electromagnetic Physics - Geant4 - CERN

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