1. Update G4builder issues Talk written almost entirely by Stan Bentvelsen with a few updates from Christopher Lester ATLAS G4 Workshop December 2000 CAMBRIDGE

2. December 2000Stan Bentvelsen / Christopher Lester2 G4builder: Goal  Client of the AGDD generic model  Automatically create Geant4 geometry from AGDD xml files  Material definitions also from AGDD xml  Generic (i.e. Detector NON-specific)  Provide set of tools to examine geometry: –Visualization using ‘DAWN’ –HBOOK histograms with observables as function of ( ,  ) radiation length track length step-counter....

3. December 2000Stan Bentvelsen / Christopher Lester3 G4builder: Remarks  No ‘Mother envelope’ volumes are required in AGDD: –so an iterative method is implemented to calculate the mother- envelopes –effective slow-down of tracking of particles (estimate factor ~6) –but still generic!  Better use could be made of AGDD features: –no use is made of envelopes where users HAVE defined them. –no identifier scheme  But most of ‘Stack’ is implemented –Stacks of boxes & tubes –Stacks of stack –Stacks of compositions

4. December 2000Stan Bentvelsen / Christopher Lester4 G4builder: Remarks  libG4Builder: –G4Builder methods are encapsulated in one library. In principle you just link to this.  Readout geometries and sensitive detectors –must be written by user in standard way. G4Builder joins them to physical geometry!  “Tweaking” –users wishing to generate a “specialised” geometry (eg non-standard step length in a particular volume) may do so in a standard way  Bug fixes: –Rotation directions fixed (hopefully!) –AGDD-boolean operations are now permitted

5. December 2000Stan Bentvelsen / Christopher Lester5 G4builder: Usage  Two valid AGDD xml files are read-in: –Material_AGDD.xml –ATLAS_AGDD.xml  The complete geometry inside volume ‘ATLAS’ is constructed.  May choose to view geometry using ‘DAWN’ program.  Use DAWN to format the picture: –rotation, zoom, re- coloring, style, postscript output

6. December 2000Stan Bentvelsen / Christopher Lester6 G4builder: SCT Modules  Szymon Gadomski fires muons through SCT barrel modules created by the G4Builder.  Particle step length in the silicon is varied and results compared to testbeam.

7. December 2000Stan Bentvelsen / Christopher Lester7 CHAOS + Accumulator  CHAOS: a 2D grid generator –set ( ,  ) start, step and stop values ‘spread’ option: randomly generate in bin ( ,  ) n tracks –set particle ID, energy, vertex. –Available as UI commands  StepAccumulator –Define & register observable in header file –Automatic accumulation during each G4Step –Separated for ‘detector’ and ‘material’ names –Interfaced to Hbook histogram Manager  Useful tool to inspect AGDD geometry Dell’Acqua

8. December 2000Stan Bentvelsen / Christopher Lester8 Geantinos in SCT  An AGDD geometry file for the SCT barrel exists –equivalent DICE geometry  Scan geantinos in ( ,  ) to determine characteristics of the SCT geometry –‘StepAccumulator’

9. December 2000Stan Bentvelsen / Christopher Lester9 SCT materials  Scan  (0-90 o ) at fixed value of  (0)  Accumulate the radiation- and track length  Display for various material –cabling and mounting boards clearly visible

10. December 2000Stan Bentvelsen / Christopher Lester10 Material in SCT  Determine –radiation length –track length –step-counter  Function of  Scintillator Copper+alumium support

11. December 2000Stan Bentvelsen / Christopher Lester11 G4builder remarks  Find the source code for version v4 (compliant to AGDD v4) –/afs/cern.ch/atlas/software/cvs/offline/Simulation/G4Utilities/G4Builder  Checkout the software and try: –make install –make test (should run a little example)