Advanced Examples

1
Advanced Examples

• Maria Grazia Pia, INFN Genova
• on behalf of the LowE-advanced examples WG

http//www.ge.infn.it/geant4/examples/index.html
Geant4 D Review, CERN, October 2002
2
Advanced examples

• Advanced examples are complete applications,
  corresponding to simplified typical real-life
  experimental situations
• e.g. a test-beam set-up, a module of a detector
  etc.
• They represent a valuable form of user support
• They are developed in close collaboration with
  user groups
• Users bring the knowledge of their experimental
  domain
• Geant4 collaborators bring the knowledge of
  Geant4
• The synergy of the two sides produces a valuable
  reference for other users
• They are also playgrounds to identify new user
  requirements, or to verify the suitability of
  Geant4 for application to specific experimental
  problems
• They illustrate not only the usage of simulation
  components in a typical experimental environment,
  but also of complementary interactive features,
  as needed in every-day life
• graphics, (G)UI, histogramming, plotting the
  physics results of the simulation while it is
  still running etc

3
The historical path

• A directory examples/advanced was created in
  geant4 since the very first production release in
  December 1998
• The actual development of Geant4 advanced
  examples was first proposed by the LowE e.m.
  Working Group soon after its creation in spring
  2000
• the topics of the advanced examples are not
  necessarily related to LowE e.m. physics
• e.g. the currently LowE e.m. WG supports an
  example on LHC calorimetry, and the main LowE
  support comes from collaborators in a dark matter
  experiment!
• this is an example of the collaborative spirit at
  the base of Geant4
• The first 3 advanced examples were released in
  December 2000
• Since then, 2 other advanced examples have been
  released
• 2 new advanced examples are at an advanced
  development stage
• 3 LHC-like advanced examples have been agreed
• and more are spontaneously proposed by users!

4
The process inception

• Advanced examples are proposed
• either spontaneously by experimental groups on
  topics they consider of interest
• or by members of the Geant4 Collaboration, as a
  response to identified needs of user support (in
  which case a volunteer collaborating user group
  must be found which is not always easy!)
• The proposed examples are presented to the TSB
  for inclusion in a future Geant4 release
• In several cases the advanced examples have been
  proposed initially as workshop projects in the
  annual Collaboration Workshop, then evolved into
  longer term projects
• The ex.-developers prepare a description of what
  they want the software to do
• which the LowE WG transforms into a simple URD to
  establish the requirements for the example (the
  URD is then maintained by the LowE-advanced ex.
  WG)

5
The process construction

• Ex.-developers should provide at least an
  architectural design of the example, in response
  to the URs
• in practice, users are often not familiar with
  OOAD
• so, pragmatically, we reverse engineer their
  code, and donate them the design models for
  further evolutions
• The design is reviewed with Geant4 collaborators
• we suggest improvements, better usage of toolkit
  components etc.
• The implementation is done in close collaboration
  with Geant4 and Anaphe members
• through the assistance of the LowE WG
  coordinator, example developers are put in
  contact with Geant4 experts to help them in the
  specific problems
• The code is tested by the ex. development group
• Of course, all this is carried on through an
  incremental and iterative process

6
The process deployment

• The code is reviewed together with Geant4
  collaborators
• we would like to do more code reviews, but the
  resources are limited
• The examples are tested against the candidate
  global release tag prepared by the Release
  Manager at the end of the system testing phase
• A documentation, consisting of a README web
  page(s), is prepared by the ex.-developers
• The ex.-developers update the requirements
  traceability matrix
• The LowE WG coordinator assemble the existing
  material into a cohesive documentation
• links to example documentation, URD, design
  diagrams, results, traceability etc.

7
The process maintenance

• Advanced examples must be maintained
• evolutions in Geant4, in AIDA, in the supported
  platforms, in the user requirements etc.
• Often the whole workload of maintenance falls on
  the LowE WG
• it is a significant workload
• as well as the support during the construction
  phase
• Advanced examples facilitate the user support
  process
• Often, the response to a user question is look
  into advanced example X, class Y, and youll find
  a solution to a problem quite similar to yours

8
Analysis

• In real life simulation is often accompanied by
  analysis
• Histograms, ntuples to plot relevant distribution
  resulting from the simulation
• UR possibility to plot histograms while the
  simulation is running, to monitor whether
  everything looks fine, or to decide when to stop
  the accumulation of statistics
• All advanced examples adopt AIDA (Abstract
  Interfaces for Data Analysis)
• To avoid introducing into Geant4 dependencies
  from any specific analysis tool
• Users can choose their preferred analysis system
  (without having to change one single line of
  code) by loading the appropriate shared library
• Documentation in http//www.ge.infn.it/geant4/exam
  ples/analysis.html
• Close collaboration with the AIDA team
• Very valuable support to ex.-developers and users
  by the Anaphe team

9
Underground physics

• A liquid Xenon cell, with a typical underground
  background environment
• Record scintillation light in PMs
• Physics neutrons, LowE processes for ions,
  scintillation, radioactive decay module etc.
• Full lab geometry (important for n scattering)
• Cavern door, cupboards, desks in the
  experimental environment
• Xenon vessel accurately reproducing a real
  prototype
• Complex primary generator (GPS)

10
X-ray fluorescence

• Test beam set-up of a typical X-ray analysis
• A photon beam impinging on a material sample the
  fluorescence spectrum of the material is measured
  by a semiconductor detector
• Physics Low Energy processes, atomic relaxation

11
g telescope

• A tracker a calorimeter a veto counter
• Standard electromagnetic processes
• Example of how to build a simple trigger out of
  digitised signals
• How to plot histograms with physics distribution
  while the simulation is running

12
X-ray telescope

• The first advanced example
• Originally a workshop project (Geant4 Workshop
  1999, hosted by ESA)
• A module of a Chandra/XMM-like telescope
• Physics for space radiation background studies

Well documented example of how to use a variety
of visualisation drivers, various (G)UI options,
GGE, GPE, histograms, ntuples etc.
13
brachytherapy

• A general purpose application for the calculation
  of dose distributions from a radiotherapy source
• Fancy geometry to configure different
  brachyterapy techniques in the same application
• How to create/destroy/replace a geometry at
  run-time
• Low energy electromagnetic processes for precise
  calculation of dose distribution
• Developed in collaboration with cancer research
  groups in hospitals

14
In preparation

• Gravitational waves experiment
• Space charging
• LHC-like test beam set-ups
• Atlas-like electromagnetic calorimeter
• CMS-like electromagnetic calorimeter
• LHCb-like RICH
• Radioprotection
• Contamination from radioactive isotopes in human
  body (and environment?)
• IORT
• Model of a compact accelerator
• and more to come

15
Conclusions

• The advanced examples have been created in
  response to typical user questions
• They offer (simplified) solution to real-life
  experimental situations
• They offer a valuable user support
• GLAST simulation started from the
  gammaray_telescope example
• underground_physics (developed by UKDM) has
  become the reference for many experiments at the
  Gran Sasso Lab
• brachytherapy has become a classic for
  radiotherapic dosimetry
• Users feedback is very positive
• More information in http//www.ge.infn.it/geant4/l
  owE/index.html