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 D 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
– 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
tools Test & Analysis Project
– Close collaboration with users
Full 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
We keep everything in CVS
– Code, designs, tests, documents, papers etc.
We have a SPI process
– With some spells of SPD sometimes…
– Collaboration with Anaphe for a common
(tailored) process
We maintain a web site
– LowE, advanced examples, WG projects
More details: see talk on Software Process in Physics, Geant4 Review 2001
Maria Grazia Pia, INFN Genova
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
– g conversion in progress
– Contacts with experiments for
common validation tests
Maria Grazia Pia, INFN Genova
Auger effect
– New
Fluorescence
– Small fixes and improvements while reimplementing in 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
Comparison against NIST data
Tests by IST - Natl. Inst. for Cancer
Research, Genova (F. Foppiano et al.)
LowE accuracy ~ 1%
E (%)
Photons: mass attenuation coefficient
E = (NIST-G4EMStandard)/NIST
E = (NIST-G4LowEn)/NIST
18
16
14
12
10
8
6
4
2
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
Fe
0.01
0.1
1
10
Photon Energy (MeV)
Also water, Pb
This test will be introduced into the Test & Analysis project
for a systematic verification
Maria Grazia Pia, INFN Genova
Photon attenuation: Geant4 vs. NIST data
Test and validation by IST - Natl. Inst. for Cancer Research, Genova
Geant4 LowEn
NIST
10
Geant4 LowEn
NIST
Geant4 LowEn
NIST
1000
water
1
Pb
Fe
m/r (cm 2 / g in lead
m /r (cm 2 /g) in iron
m /r (cm 2 /g) in water
100
100
10
1
10
1
0.1
0.1
0.1
0.01
0.1
1
0.01
10
0.01
0.01
Photon Energy (MeV)
12
10
8
6
2
0
E (%)
Delta (%)
4
-2
-4
-6
-8
-10
-12
-14
-16
0.1
10
1
10
Photon Energy (MeV)
Maria Grazia Pia, INFN Genova
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

0.1
1
Photon energy (MeV)
Low Energy EM
Standard EM
w.r.t. NIST data

14
0.01
1
Photon Energy (MeV)
Delta = (NIST-G4EMStand) / NIST
Delta = (NIST-G4LowEn) / NIST
16
0.1
E = (NIST - G4EM Standard)/NIST
E = (NIST- G4LowEn)/NIST
10
8
6
4
accuracy within 1%
2
E (%)
0.01
0
-2
-4
-6
-8
-10
0.01
0.01
0.1
Photon Energy (MeV)
1
10
0.1
Photon Energy (MeV)
1
Photons: angular distributions
Rayleigh scattering: Geant4-LowE and expected distribution
(more work in progress)
Maria Grazia Pia, INFN Genova
Photons, evidence of shell effects
Photon transmission, 1 mm Pb
Photon transmission, 1 mm Al
Maria Grazia Pia, INFN Genova
Electron Bremsstrahlung
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
Maria Grazia Pia, INFN Genova
Electron ionisation
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!)
Maria Grazia Pia, INFN Genova
Electrons: range
Range in various simple and
composite materials
Compared to NIST database
Also Be, Fe, Au, Pb, Ur, air,
water, bone, muscle, soft tissue
Testbed for
Test&Analysis prototype
Maria Grazia Pia, INFN Genova
Al
Electrons: dE/dx
Ionisation energy loss in
various materials
Compared to Sandia database
More systematic verification
planned (for publication)
Also Fe, Ur
Maria Grazia Pia, INFN Genova
Electrons, transmitted
20 keV electrons, 0.32 and 1.04 mm Al
Maria Grazia Pia, INFN Genova
Protons
Stopping power
Z dependence for various energies
Ziegler and ICRU models
Ziegler and ICRU, Fe
Ziegler and ICRU, Si
Straggling
Nuclear stopping power
Maria Grazia Pia, INFN Genova
Bragg peak (with hadronic interactions)
Antiprotons
Dashed
– Geant4 LowE proton
Solid
– Geant4 LowE Quantal
Harmonic Oscillator model
Dotted-dashed
– Non-linear calculation by
Arista and Lifschitz
Points
– Experimental data from
ASACUSA
Maria Grazia Pia, INFN Genova
Ions
Ar and C ions
Deuterons
Maria Grazia Pia, INFN Genova
Polarisation

d 1 2 hn2  hn0 hn
 r0 2 

 2 sin 2 q cos2 f
Cross section:
d 2 hn0  hn hn0

Sample Methods:
Low Energy
Polarised Compton
x
250 eV -100 GeV
Integrating over f
• Sample q
• q - Energy Relation  Energy
• Sample of f from P(f) = a (b – c cos2 f) distribution
cos x  sin q cos f  sin x  1  sin 2 q cos2 f  N
x
hn0

O
hn
q
a
f
Scattered Photon Polarization
y
q Polar angle
f Azimuthal angle
 Polarization vector
Maria Grazia Pia, INFN Genova


1
cos q ˆj  sin q sin f k̂ sin 
N
1
1


||'   N î  sin 2 q sin f cos f ĵ  sin q cos q cos f k̂  cos 
N
N


A
C
' 
z
100 keV
1 MeV
10 MeV
small 
small 
small 
More details: talk on
large 
large 
Geant4 Low Energy
Electromagnetic Physics
large 
Other polarised processes under development
Fluorescence
Microscopic validation:
against reference data
Experimental validation:
test beam data, in collaboration with
ESA Science Payload Division
Spectrum from
a Mars-simulant
rock sample
Fe lines
GaAs lines
Scattered
photons
Maria Grazia Pia, INFN Genova
Auger effect
New process,
validation in progress
Auger electron emission
from various materials
Sn, 3 keV photon beam,
electron lines w.r.t. published
experimental results
Maria Grazia Pia, INFN Genova
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!
Maria Grazia Pia, INFN Genova
GEANT4 Workshop, 2002
30 September – 4 October
GEANT4 Medical Applications at LIP
P. Rodrigues, A. Trindade, L.Peralta, J. Varela
LIP – Lisbon
Maria Grazia Pia, INFN Genova
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
Differences
LIP – Lisbon
10x10 cm2
15x15 cm2
Maria Grazia Pia, INFN Genova
10x10
15x15 cm2
Electron Transport at Low Energies

Evaluation of electron range for different GEANT4 releases
GEANT4 (Low+Std)
Styrophoam
Maria Grazia Pia, INFN Genova
Lead
Dose Calculations with 12C


Bragg peak localization calculated with GEANT4 (stopping powers
from ICRU49 and Ziegler85) and GEANT3 in a water phantom
Comparison with GSI data
Maria Grazia Pia, INFN Genova
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.
Maria Grazia Pia, INFN Genova
• 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
Maria Grazia Pia, INFN Genova
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
1Chibani
Maria Grazia Pia, INFN Genova
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
2Rogers
D W O and Mohan
Maria Grazia Pia,R,http://www.irs.inms.nrc.ca/inms/irs/papers/iccr00/iccr00.html
INFN Genova
Water phantom irradiated by clinac beam
Fig 3. Relative dose distribution for a water phantom irradiated by a 6
MeV Clinac 2100C electron beam
3Ding
G X and Rogers D W O
http://gold.sao.nrc.ca/inms/papers/PIRS439/pirs439.html
Maria Grazia Pia, INFN
Genova
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
Maria Grazia Pia, INFN Genova
Dose distribution: TG 43 protocol,
experimental data (S. Paolo Hospital, Savona), G4-LowE
S. Guatelli’s thesis
Maria Grazia Pia, INFN Genova
Application
Cosmic rays,
jovian electrons
Solar X-rays, e, p
and more!
Courtesy SOHO EIT
Maria Grazia Pia, INFN Genova
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
from 9
19 people
countries
Argentina, Austria, Canada, Italy,
Portugal, Russia, Spain, Switzerland, UK
Thanks to all!
Maria Grazia Pia, INFN Genova
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!
Maria Grazia Pia, INFN Genova
Bremsstrahlung Models
 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
Maria Grazia Pia, INFN Genova
Polarisation
theory
simulation
Polarisation of a non-polarised photon
beam, simulation and theory
Maria Grazia Pia, INFN Genova
Ratio between intensity with perpendicular and parallel polarisation
vector w.r.t. scattering plane, linearly polarised photons
Ongoing significant effort in OOAD
Maria Grazia Pia, INFN Genova
Other activities in the WG
Advanced examples
Simulation + analysis in a distributed computing environment
Test & Analysis
Technology transfer
Training
Maria Grazia Pia, INFN Genova
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
Maria Grazia Pia, INFN Genova
1.
2.
3.
4.
5.
6.
7.
Talks
8.
9.
in WG web
10.
11.
12.
13.
14.
15.
16.
17.
The Geant4 Toolkit: simulation capabilities and application results
M.G. Pia et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002
Geant4: a powerful tool for medical physics
E. Lamanna et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002
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
Parallel Geant4 simulation in medical and space science applications
J. Moscicki et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002
Simulation and analysis for astroparticle experiments
A. Howard et al., 8th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, 2002
Leipzig applicators Montecarlo simulations: results and comparison with experimental and manufacturer's data
M. Tropeano et al., 21st ESTRO Meeting, Prague, 2002
Tools for simulation and analysis
A. Pfeiffer and M.G. Pia (for the Geant4 and Anaphe Collaborations), ICHEP02, Amsterdam, 2002
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
The Geant4 Toolkit: Overview
M. G. Pia, Invited lecture at the MCNEG Workshop, Stoke-on-Trent, UK, 2002
Medical applications of the Geant4 Simulation Toolkit
M. G. Pia, Invited lecture at the MCNEG Workshop, Stoke-on-Trent, UK, 2002
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
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
Architecture of Collaborating Frameworks
A.Pfeiffer et al., CHEP2001, Beijing, China, 2001
Simulation For Astroparticle Experiments And Planetary Explorations
A.Brunengo (for the Geant4 Low Energy Electromagnetic Group), CHEP2001, Beijing, China, 2001
Geant4 Low Energy Electromagnetic Physics
M. G. Pia (for the Geant4 Low Energy Electromagnetic Group), CHEP2001, Beijing, China, 2001
The GEANT4 simulation toolkit
G. Santin, Monte Carlo Workshop for Nuclear Medicine applications, July 2001
Geant4: simulation capabilities and application results
M.G. Pia (for the Geant4 Collaboration), EPS-HEP Conference, Budapest, July 2001
Maria Grazia Pia, INFN Genova
Resources
Status on 1 September 2002
New collaborators:
– Pablo Cirrone (INFN-LNS)
– Luis Peralta, Pedro Rodrigues, Andreia Trindade (LIP, Lisbon)
– Group from INFN-Gran Sasso also interested to join
Maria Grazia Pia, INFN Genova
We do a lot of work
– and we do our best to do it well…
Conclusions
– a rigorous software process, continuous SPI
– very effective team-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 new projects in the WG, not only physics
– Testing system, analysis, advanced examples, distributed computing, technology transfer
More information in http://www.ge.infn.it/geant4/lowE/index.html
Maria Grazia Pia, INFN Genova