SpaceSpecific Modules for the Geant4 Particle Transport Code

1
Space-Specific Modules for the Geant4 Particle
Transport Code

• P Truscott F Lei (DERA UK)
• R Gurriaran C Ferguson (University of
  Southampton, UK)
• P Nieminen E Daly (ESA/ESTEC, The Netherlands)
• J. Apostolakis, S. Giani, M-G Pia, L Urban (CERN
  Switzerland)
• M Maire (LAPP, France)
• and the
• Geant4 Collaboration

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Applications and Requirements for Radiation
Transport Modelling

• Applications of spacecraft radiation shielding
  tools
• Predict radiation effects in microelectronics
• Assess background levels in detectors
• Develop hardening strategies / optimise shielding
• Optimise detector/sensor designs
• Data interpretation (calculate detector
  efficiency, PIXE yield in mineralogy)
• Physics model requirements
• Wide range of particle species to be modelled
  secondaries as well as primaries (p, n, d, t,
  3He, 4He, e-, ?, ?, etc.)
• Energy range from 100s GeV to eV
• ?Great variety of physical processes
• Model geometries can range from atmospheric to
  microelectronics feature-size dimensions
• 1D shielding studies to 3D full spacecraft or
  subsystem simulation

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Model Requirements as a Function of Effect
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Traditional Overview of Physical Processes
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Geant4 Summary

• 100 collaborators from 40 institutes
• Geant4.0 released Dec 98, Geant4.1.0 due for Dec
  99
• Monte Carlo simulation for nuclei, hadrons and
  leptons
• Intended for hadronic showers detector design
  data interp.
• Object Oriented design (implemented in C)
• All new code
• Does contain C rewrite of old favourites (e.g.
  HETC98)
• Particle tracking in 3D
• Comprehensive range of physical processes already
  implemented as well as planned
• Fast simulation mode - response of a volume may
  be parameterised based on empirical or simulation
  data
• Facilities for event biasing

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Geant4 Summary (cont.)

• Geometry can be constructed from solid simple
  volumes or breps
• Defined by user-written C
• STEP interpreter for geometry input from CAD
  tools
• Excellent facilities for visualisation (geometry
  debugging)
• Data output to ODBMS, but can be interfaced to
  e.g. cernlib
• GUI interfaces available

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Geant Geometry Editor (GGE)
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Geometry Visualisation
Atlas
XMM mirror, baffle and grating
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Particles Simulated
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Physics Modelled

• Data driven model for high-energy hadrons
  (GHEISHA)
• Theory driven models
• Parton cascade and string models covering the
  highest energies
• Intra-nuclear cascade (HETC98) 10 MeV-few GeV,
  QMD, pre-equilibrium lt100 MeV
• Nuclear de-excitation evaporation / fission /
  Fermi break-up
• Neutron transport lt 20MeV based on assimilation
  of ENDF, JENDL, CENDL, EFF, FENDL, Brond, JEF and
  others
• Isotope production libraries (up to 100 MeV for
  neutrons)
• Photonuclear de-excitation using ENSDF (theory
  model at higher energies)

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Physics Modelled

• Electromagnetic interactions for leptons, hadrons
  and photons
• Compton, Rayleigh, photo-electric,
  pair-production, charged particle ionisation
  (inc. ?-ray production), Bremsstrahlung,
  annihilation
• Multiple scattering according to Goldsmit-
  Saunderson Lewis
• Recently extended down to 250 eV using LLNL
  cross-section libraries
• OO ? Relatively straightforward to inherit and
  extend the design, especially to include new
  processes

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Space Specific GEANT4 Modules
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Low-Energy EM Physics

• Objective application
• To extend EM physics to 250 eV to lepton-photon
  transport and 10 eV to hadrons/ions
• Induced X-ray fluorescence studies
• Functionality
• Use Lawrence Livermore EEDL, EPDL and EADL
  cross-section libraries for electrons and photons
• Positron cross-section libraries from PSI (TBC)
• Status
• Implementation for electrons/photons at GEANT4.0.1

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Radioactive Decay Module

• Objective application
• To allow production of ?, ?, ? and ? from
  radioactive decay, for subsequent tracking
• Induced radioactive background studies or
  determination of solar system body composition
  from radioactive gamma ray emission
• Functionality
• Treatment of decay of radionuclides through
  multiple generations
• Branching ratios and energies from ENSDF
• Isomeric transitions use existing photo-nuclear
  de-excitation model
• Applicable to nuclei in motion or at rest
• Status
• Delivery due February 1999

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CAD Front-End Tool

• Objective application
• To permit specification of materials data file to
  augment geometry STEP description
• Use with commercial CAD tools for simple geometry
  description
• Functionality
• Extension of GGE
• Access to database of standard spacecraft
  materials
• Manual cross-referencing of volumes, materials
  and visualisation attributes
• Automatic cross-referencing of volumes and
  materials using meta-data flag in the STEP
  PRODUCT field
• Status
• Beta version available

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Sector Shielding Analysis Tool

• Objective application
• To determine the physical distribution of
  shielding around a user-defined point in the
  geometry
• First-order assessment of shielding as a function
  of position
• Functionality
• Uses geantino
• Histogram of fraction of solid angle with
  shielding within a given interval as a function
  of shielding interval ( Poisson errors)
• 2D Histogram of mean shielding level (in g/cm2)
  as a function of (?,?) (standard deviation of
  shielding)
• Output as a function of material and/or element
• Status
• Code released at beta03
• Upgraded to meet additional user requirements
  beta04 beta05
• Web-version demonstrated on DERA intranet

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Sector Shielding Analysis Tool
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General Source Particle Module

• Objective
• To permit definition of an arbitrary source
  distribution without coding
• Functionality
• Spatial point, area source (disc, ellipse,
  rectangle), or simple volume (sphere, cylinder,
  RPP)
• Angular unidirectional, isotropic, cosine-law,
  arbitrary
• Energy mono-energetic, linear, exp, power-law,
  arbitrary spectrum
• Source particle biasing according to point of
  origin, first interaction, energy
• Status
• Delivery due February 1999

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Future Activities

• Event Scoring and Data Output
• To permit selection of standard scoring
  parameters without coding
• Generally applicable to spacecraft studies
• Spacecraft Radiation Shielding and Effects
  Toolkit (SPARSET) User interface
• To provide a default user environment for control
  standard GEANT4 execution without programming,
  potentially using a GUI
• Applicable to all categories of user, especially
  category A
• Physics enhancements
• Ion microdosimetry
• General variance reduction tools

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Conclusions

• Geant4 is a new-generation toolkit for Monte
  Carlo particle simulation
• Unlike other codes Geant4 has been developed to
  provide particle simulation in a single tool, but
  also allows easy extension of physics modelled .
  if required
• Intended primarily for the high-energy physics
  community, but has wider applications
• Geant4 has many of the functions required for
  space radiation effects studies and will be the
  basis of the next generation of spacecraft
  radiation shielding tools

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Documentation on DERA/GEANT4 Web-Site

• http//www.space.dera.gov.uk/space_env/geant_mn.ht
  ml