Monday, July 9, 2012

Morning Talks

Kernel 1

• Physics lists models overlap in energy range.
• NIM articles about GEANT4.
• Use trajectory class instead of track to record trajectories
• Use pre-step and post-step for reflection/refraction simulations (knows both materials)
• Can use G4VTrajectory class to store all the members you need (see talk on Thursday)
• Geometry in G4Track; physics in G4DynamicParticle; "static" properties in G4ParticleDefinition
• Tracking and SteppingAction or G4 scoring functionality
• Each hard-coded number must be multiplied by its proper unit; to get the number, you must divided by its proper unit.

User Documents and Examples I

• Have to use cmake if you are installing GEANT4 from the source
• Novice examples
  • N01 - can only compile it an run it; can't change it.
  • N02 - parameterized volumes (size is fn. of position); can extract hit info, visualize
  • N03 - sampling calorimeter - lAr does detection, replica volumes, different ways to define materials, randomization,

random seed handling, EM physics, visualization tutorial

• • N04 - collider detector, Pythia - 3 events, full set of EM and hadronic physics
  • N05 - EM or pion showers - G4VFastSimulationModel - parameterize shape of EM shower (pion shower won't work)
  • N06 - Optical photons with water cerenkov detector
  • N07 - run based rather than event based, 3 sandwich calorimeters, ghost volumes for scoring, change geometry without

re-building world; set cuts

• Secondary production cuts!!!

• Code Browsers
  • LXR - www-geant4.kek.jp/LXR - searchable by filename, identifier, text
  • DOxygen version - www-geant4.kek.jp/Reference

• HyperNews forum - hypernews.slac.stanford.edu/HyperNews/geant4/cindex - join!!!

User Interface I

• UI commands - command syntax, macro file, G4UI

• <directory>/<command> <parameters>

• some commands don't take parameters, if they do, space is delimiter, ! means default
• hard-coded implementation is slow and should NOT be used in an event loop
  • ---> requires string manipulations - could become order of magnitude slower
  • use to read default macro file in main

• /control/manual [directory]
• /control/createHTML [directory] - will create a manua for you

• /myCmd/getFile {file1{run}} after creating aliases for file1 and run

• /control/loop - slide 9

• pwd, ls, other commands on slide 11 - can't be used in macro file

These notes have significant gaps, if someone can help fill it in...

• What can be visualized - can get smooth curve with steps, can use scales with color
• can write code to add "whatever you want" - axes, text - some drivers don't handle text properly

• Different interfaces used for different reasons

• OpenGL <-- will use the fanciest version you have the ability to use, or you can specify a version
  • Stored, QT, etc.
  • Postscript printing
  • Can do movies
    • stores frames - has time delay so tracks don't just overlap
    • can change viewpoint

• Open Inventor - comes with GEANT4 installation?
  • Pictures in slides are somewhat old - doesn't look that primitive
  • type commands in GUI, not only in terminal window (as with QT)
  • command tree set up as pull-down menus

• HepRep - need to install separately

• • GEANT4 can write it out
  • have to install it if you want to use the files that are written out

• • can zoom rotate, etc. after the fact (not in a GEANT4 session)
  • click on elements and see info about hits or volumes

• • HepRApp
    • Apply cuts offline - show tracks with cuts

• • WIRED4 - part of JAS
    • sort of like root, only JAVA based

• • FRED
  • HepRep can't handle complex geometries

• DAWN
  • useful for debugging - can isolate particular volumes
  • renders drawings nicely - retain resolution so you can zoom later - true vector .ps output
  • can use DAWN renderer after the fact, otherwise have to link properly when you set up GEANT4
  • DAVID will show you overlaps in detail
  • can send .prim files in emails (kB vs. MB)

• Raytracer
  • uses geantinos to create envelope of what tracking sees
  • check for overlaps, other geo mistakes
  • can handle complicated boolean solids

• gMocren
  • biological applications

• Ascii tree - also useful to check geometry
  • what the volume names really are
  • calculated mass of components

Afternoon Talks

Material Definition

This needs some notes, however, not much was said that was not on the slides. There were some questions which I didn't catch.

• FindorBuildMaterial <-- must be in database.

Geometry I

• Diagram definition
  • Boxes are classes
  • arrow from one box to another indicates a class derived from a base class
  • lines with diamonds indicate members?
• Can reuse solids, but may need to have different logical volumes
• G4VSolid defines all methods
• BREP
  • define 6 planes instead of defining a box
• In the geometry section of the users manual, a java applet will let you rotate the volumes if you click on the picture
• BREP - volume must be closed!
• Solids may never ever ever overlap - you must combine using Boolean solids
• cannot combine BREP solids, only CSG solids
• the coordinate system is always that of the first solid used in the boolean operation, even if the origin ends up being outside of the final boolean solid

Hands-on I

• getting installation to work

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