Wednesday, July 11, 2012

Morning Talks

Scoring I

• score energy deposition, for example, on the surface of a volume
• don't have to worry about overlapping with scoring mesh?

Geometry III - GDML and CAD

• use if you want to make changes without having to rebuild
• can do ALMOST everything that you can with the GDML geometry
• defining "dummy" materials and then using hard-coded def'ns is the way to do it (pending reply of

an expert)

• slide 22 - links to forum and tech note for GDML
• cadmesh - can get tesselated solid from CAD but can't go from G4 to CAD

• layer to read step files in directly is abandoned
• child gdml files are not assembly volumes - the development for adding assembly volumes is "frozen"

User Interface II

Could use notes for this

EM Physics II

• Livermore Physics
  • have some process classes, but model classes are different
• Polarized Livermore models
• Penelope models

Hadronic Physics I

• models need to cover the whole energy range that you want
• only defaults in hadronic physics are for cross-section sets
• quark-gluon string - QGSP
• slide 10 - LEP, HEP, old GEISHA code, translated from FORTRAN to C++
• slide 11 - partial inventory of available physics lists
• can't have a model with an energy range fully covered by another model

• slide 14 explanation
  • top-left
    • high energy hadron coming into a nucleus
    • excite nucleons in a relatively small cylinder around the track - quark cascade
    • hadron can interact in nucleus, and particles are QM entangled
    • secondaries don't form until outside nucleus
    • covered by QGS, FPF

• • top-right
    • within nucleus, nucleon interactions - intranuclear cascade

• • lower-left
    • highly excited nucleus
    • exciton models are used

• • lower-right
    • de-excitation stage
    • nucleus at equilibrium - evaporating photons and neutrons
    • HP models are starting to be used

• Specific Models
  • Elastic scattering
    • valid for all energies
  • coherent elastic
    • sees nucleus as a whole
  • neutron elastic from HP models

• Validation
  • G4HadronElastic - not valid above about 20 degrees (need coherent model)
  • Low energy neutron physics data-driven - large database
    • if thermal is important, need to download add'l DB
    • G4NDL - update to 4.9.5 - big step in quality of HP data
    • multiple DB with different formats
    • now we know it all comes from ENDF/B-VII DB w/ format
    • small energy non-conservation because data is binned
  • Inelastic neutron
    • pretty good for something that fed the DB (interpolation of data)
  • Neutron capture

• If you don't have an isotope, what does G4 do?
  • uses LEP - old GEISHA model automatically
  • does tell you what it is doing

• even if you don't need thermal - 4.0 or later - should get them

• QMD is better than binary cascade when compared to data (nuclear fragments)
  • takes a long time
  • slide 37 - instructions to include it in your physics list

Afternoon Talks

Hands On III

Return to JLAB GEANT4 Workshop, July 9-13, 2012
Return to MOLLER GEANT4 Simulations
Return to MOLLER at 11 GeV E09-005