The mandate of the Geant4 Review Committee in 2007 is to investigate the physics precision, computational speed and general usability of the Geant4 software for the major existing and upcoming Geant4 use cases in its various application domains, and to issue recommendations for future software improvements and developments. In performing this task, the Commitee may also address auxiliary issues that it considers relevant.
Several speakers only had a few days to collect information and assemble the talks
This presentation
Covers only select topics
Provides excerpts of some user talks
I have picked a few topics, trying to
Emphasize HEP aspects different from the ones we see regularly at LCG Physics Validation meetings
Give a flavour of Geant4’s use and requirements from outside HEP
Also selected
Small sample of Geant4 results
Key reviewers’ observations and recommendations
User topics selected
HEP: ILC
Requirements
Challenges and opportunities
Space
Electronics in space
the system, strengths, needs
Medical
Outline:
ILC physics focus
hadronic showers data and simulation
requests from other HEP experiments
some considerations
New Physics:
- rare processes/limited statistics
Many final states involving heavy bosons (Z,W,H):
e+e- WW , e+e- ZZ
Hadronic decay of W and Z
- branching ratio ~70%
- result in two hadronic jets
Requires excellent
CALICE: from MC to reality
Event display
Hadron event
Deep Analysis of hadronic shower
Getting ready to compare data/MC
Models comparison
The ILC request to G4
The ILC community has to design, optimize and compare concepts of the next generation of HEP detectors
The most controversial part for simulations is the hadronic sector
The energy of interest for ILC hadronic physics is lower than that of LHC (mean E~5-10 GeV, @ 500 GeV s)
In this energy range hadronic models in G4 are sometimes inadequate or outdated
CALICE can offer to G4 the possibility of active collaboration in comparing and tuning all models with unique precision and new benchmark parameters
For our community it is convenient to work within one framework but it is vital to have available all intra-nuclear cascade models (from FLUKA and MCNP)
A clear set of expert-recommended parameters is needed to ease the user task
The rest of the non-LHC community
F. Gaede and C. Young collected answers to a poll among HEP experiments:
here reported only the comments concerning additional physics request to G4
MINOS / NOVA
Try to migrate from G3 to G4, problems with geometry, no phys request yet
NUMI (beamline simulation)
Default G3+FLUKA, started with G4, request to use FLUKA
MiniBooNE
G4 only for neutrino flux prediction p-Be interaction (100MeV – 10 GeV)
Request broader range of models, in particular FLUKA
BaBar
Finished validation of G4.7, improvements compared to G4.6, proceed to G4.8
no additional physics requests
Also other experiments have replied which do not use G4:
Belle, STAR and PHENIX (RHIC), OPERA, K2K/T2K (because of no FLUKA),
KEK/E391, J-PARK/E14 (not yet, planed if FLUKA)
Additional Remarks
Comments/suggestions collected:
Request of improvement of default parameter sets
possibility: multiple recommended sets for different users
not all uses are MC experts, choice from experts is normally the best
Request to improve geometry: more flexible definition and debug (GUI), possibility to interface to existing programs (CAD)
Both BaBar and Bell are interested to know how good are hadronic interactions in G4 for B and super-B factories
Offers of cooperation from the users:
Some users have offered to collaborate with GEANT4 on areas where they have particular expertize and interest, e.g. polarized EM processes (DESY Zeuthen), hadronic showers model validation (CALICE) Is GEANT4 interested in such collaboration? How should users proceed?
Geant4 & Radiation Effects in Electronics The RADSAFE Strategy
Robert A. Weller
Institute for Space & Defense Electronics
Vanderbilt University, Nashville, TN, USA
Vanderbilt: R. A. Reed M. H. Mendenhall
B. D. Sierawski K. M. Warren R. D. Schrimpf
L. W. Massengill A. F. Witulski D. R. Ball
J. A. Pellish C. L. Howe A. D. Tipton
M. L. Alles A. L. Sternberg B. E. Templeton
SLAC: M. Asai T. Koi D. H. Wright
NASA Goddard: M. A. Xapsos K. A. LaBel
NASA Marshall: J. H. Adams J. W. Watts
Sponsoring Agencies: NASA, DTRA, AFOSR, AEDC
Overview
Application: First-principles simulation ofradiation effects in semiconductors in terrestrial and space systems.
• Motivation: Maximize efficiency and minimize cost of design and testing for arbitrary radiation environments.
Approach: RADSAFE - A strategy for integrating commercial and custom software systems.
Geant4 application: MRED, the radiation event generator.
Why [RADSAFE] use[s] Geant4 (Instead of X, Y, or Z)
Comprehensive physics.
Range of available processes, classes.
Quality/size of the developer community.
Continuing developer/user interaction.
The toolkit philosophy. (It’s not a program!)
Total user control over input and output.
Available source code.
Platform independence.
C++ language. (Not Fortran, Java, etc.)
Our (unique?) requirements described above.
Priorities for Semiconductor Electronics Applications
Physics, tracking down to nm scale (at least nothing, i.e. cuts, breaks).
The best possible dE/dx for all particles, including ions especially, at all energies, few keV to 100+ GeV.
a) Correct fluctuation.
b) Discrete/continuous partitioning.
c) Microstructure of individual tracks, including e-h production (research area).
Coulomb scattering of nuclei for computing displacement damage. (VU is donating ScreenedScattering class.)
Must have accurate mass, energy, angle distributions of nuclear reaction fragments.
a) Heaviest fragments are most important.
b) Goal: threshold-100 GeV/u; Interim goal 5-10 MeV/u to 20 GeV/u.
…
Profiling of GATE-Geant4 performance
Current VRT Implementations
Variance Reduction Techniques (VRTs)
Importance sampling
Photon splitting
Russian roulette
Weight window sampling
Weight roulette
Scoring
A number of VRT implementations are already available in Geant4, but
Some of the Geant4 classes can be optimized more,
Further classes implementing VRTs could be developed
Suggested actions regarding VRTs
Collaboration between
GATE VRTs workgroup
Geant4 VRTs workgroup
Aim of collaboration
Determination of the existing G4 classes need to be optimized
Determination of further G4 classes possibly needed to be implemented
Implementation of GATE-specific classes within the Geant4 framework
Publication of a GATE-specific patch for Geant4
Suggested VRTs for Geant4 follow:
Implementation of flags (probably at GATE) for each one of the following VRTs
=> VRTs should be activated or deactivated by the user
Contact: Nicolas Karakatsanis : knicolas@mail.ntua.gr
Using G4 for medical applications – Further suggestions
The documentation on the facrange (facgeom and related) parameters seems important for medical application users
“Wiki” documentation
cooperative community-build documentation in a “wiki” format
interesting way to improve the documentation, particularly in the developer section
“Wiki” technology is now well known and mature
allows any user to modify and improve the on-line documentation
Our experience shows that
is very efficient and
it also encourages information exchange in the community
Beta Ray Point Source Distributions Using GEANT4 – Comparative Study
L. Maigne, C.O. Thiam
Laboratoire de Physique Corpusculaire, 24 avenue des Landais, 63177 AUBIERE cedex
Beta Ray Point Source Distributions Using GEANT4 – Comparative Study
Comparison of G4 Versions (1MeV, 2MeV)
Beta Ray Point Source Distributions Using GEANT4 – Comparative Study
Conclusion
High discrepancies between G4.5 and G4.6, G4.6 and G4.7 =>
Possible cause: Multiple scattering implementation?
Beta Ray Point Source Distributions Using GEANT4 – Comparative Study
Comparison of Geant4 with other MC calculations ( kinetic energy = 3MeV, 4MeV )
Beta Ray Point Source Distributions Using GEANT4 – Comparative Study
Conclusion
High discrepancies between Geant4.8 and other MC packages (around 10%)
Possible reason: still undefined
Dosimetric characteristics of an I125 Brachytherapy Source Using Geant4 – A comparative study
Comparison of G4 Standard / Low Energy
Themes
Computing Performance is vital
in many HEP, Space, Medical applications
More validation of physics models
Demonstrating physics performance
Larger choice of physics models
Ion-ion, hadronics (1
Simpler documentation
Physics lists choice
How to improve application performance
And the Geant4 presentations
Twice as many as the user presentations
… choose a few …
Simulation of the Fano cavity setup
Sabine Elles, Vladimir Ivanchenko,
Michel Maire, Laszlo Urban
March 2007
Fano Cavity: Geant4 v 6.2 results
Effects of all improvements (8.2ref3)
TARC Fluence Binary cascade
2.5 GeV/c p
Simulated with ‘QGSP_BIC_HP’ physics list
Binary Cascade
HP ‘High Precision’ Neutrons
Red: cylinder
Yellow: sphere
Black: Full 4/cos
Ratios of fluence
Ratio of simulated 4/cos versus Data
Two-sets of data
Dominated by systematic errors of experiment
n-C total cross-section
CPU Performance – with hadronics
From the Reviewers
(draft form – closeout session)
20 April 2007
JA Note: I have summarised and simplified – the original slides are available in the agenda
EM Physics
Observations
heavy ion stopping models not fully available.
Documentation hard to find
…
Recommendations
Provide guidance on selection between the [std vs low-energy] models for specific species, energies, etc.
Integrate models into a single package for EM physics, …
Encourage the rapid integration of ICRU 73 heavy ion stopping
Setup a validation webpage for EM physics
Provide detail references for validation papers for various models
Comparisons to data etc…
Provide guidance about trade off between accuracy and speed for various range cuts
Hadronic Physics
the committee notes that there is a strong request to use the FLUKA hadronic model with Geant4.
a serious effort has been undertaken by the Geant4 collaboration and the LCG Physics Validation group to test and validate the Geant4 hadronic transport models.
G4 Hadronic Physics
comparison to test beam data has pointed to important shortcomings of the G4 hadronic models
Note ongoing improvement. Concern on not seeing ‘a detailed planning (milestones, manpower) for an improvement of the hadronic package’.
‘put in place a set of simple hadronic benchmarks which allow to identify such very basic problems like disagreement with well-known shower shapes’.
Computing Performance
Observations
CPU optimization is critical for LHC and other heavy users (eg medical and space).
Multi-prong approach is needed.
Optimization of GEANT4 toolkit.
Trade-off between CPU time and simulation detail. This is a user choice. - yet help from GEANT4 is crucial
Variance reduction techniques (VRT) can cut CPU needs greatly. A number of VRT are available in GEANT4.
CPU Performance Recommendations
Systematically track code performance, for each part, model.
Perform systematic checks on
Memory use
Architecture, compiler/options
Multi core CPUs/advanced instructions
Encourage users to do same and provide feedback.
Extend the computing professionals to review/optimize other parts.
Provide a plan regarding the expected performance in the next few years.
Create a document on performance optimization guides.
Provide a simple mechanism for users to turn off “irrelevant” processes for a given region.
Documentation: Observations
GEANT4 has provided among others
Application Developers Guide.
Installation Guide, ..
No clear recommendation about the validity ranges for the many physics models (e.g. the two EM models) and the different Physics Lists.
Few references to validation and benchmarking papers on GEANT4 web.
Limited information about connection between the physics models and their implementation.
Documentation: Recommendations
Provide clear recommendations when the different packages and Physics Lists should be used and their validity ranges.
Document the limitations, and validity and applicability ranges of various hadronic/EM models.
When models overlap in validity range, document the tradeoffs.
Describe the connection between physics models and how they are implemented.
Provide greater details in release notes.
…
Validation: Recommendations
Create a common validation procedure, possibly automated, to be run at every release.
Define a procedure that quantifies the validation results, and make them easily available to users.
For example,
Timing checks, reporting key results in release notes.
Benchmarking against other MC transport codes.
“Recruit” additional beta testers from different user communities.
Provide references of validation and benchmarking on the web
