Transcript Joanne

GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Generic Geometry in XML
Current methods of geometry description
Requirements
Proposal
Status
Generic Geometry
J. Bogart
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GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Simulation Geometry Now
 Glastsim (simulation using gismo) reads geometry
parameters (dimensions, materials, etc.) from
instrument.xml. Constants are separated from code;
assumptions about structure, relation between volumes
are not.
 Nothing in instrument.xml addresses assignment of ids to
readout volumes; this knowledge is embedded in
Glastsim.
 Geant4 balloon simulation currently has hard-coded
geometry.
Generic Geometry
J. Bogart
2
GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Event Data Clients Now
 The association between readout id and detector location
is made available to Recon by Glastsim dumping detector
objects to a 40k line XML file glast.prs
 Minor detector design changes can be handled by writing
a new version of glast.prs from Glastsim.
 Changes in the information Recon needs (e.g., to
interpret energy-accounting data) require mods to
Glastsim and the glast.prs format as well as to Recon.
Generic Geometry
J. Bogart
3
GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Requirements
 Support several configurations (e.g., flight instrument,
balloon instrument), and variants. Get geometry
assumptions, parameters out of the code.
 Recon and other data clients need part of geometry info
known to simulator. At least must reconstitute the
association between readout ids and location.
 Geometry description must be accessible to humans and
to multiple programs (Geant4 simulation, gismo?,
Recon,...).
Generic Geometry
J. Bogart
4
GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Geometry Information Flow
Now
parameters
Simulator
To come
volumes,
relations, id
specification
ids, nesting
sensitive
detectors
dump
Simulator
Recon
Recon
Generic Geometry
J. Bogart
5
GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Proposal
Use variant of the XML language being
developed by the ATLAS experiment.
Encodes structural information (relationships between
volumes) as well as constants.
Handles association of ids with volumes
Natural mapping to Geant4 geometry description
Generic parameter blocks if we need them
Generic Geometry
J. Bogart
6
GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
How It Works
 Describe logical (platonic) fundamental volumes, such as
a diode, in terms of shape, dimensions, material. May
make stacks or arbitrary composite logical volumes.
 Make a physical copy of a logical volume by positioning it
inside another volume.
 Can associate an identifier with any positioned volume.
Can associate an arbitrary parameter block with any
logical volume.
 Part of a tower description uses most of this.
Generic Geometry
J. Bogart
7
GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Status
 Define description language (GGDD) About done;
may need math expression addendum.
 Use it. Flight instrument description is mostly done.
Balloon would be straightforward.
 Geant4 interface utilities. Not yet begun. But GDDD
is G4-like. And ATLAS has a stand-alone tool
(G4Builder) which may be cannibalized.
 Gismo interface utilities. Not yet begun. Do we want
it?
Generic Geometry
J. Bogart
8
GLAST LAT Offline Software
Workshop - SLAC, Jan. 16-19, 2001
Status
(cont’d)
 Use by Recon, etc. Not done and not obvious what
the best approach is (use simulation input file or
something derived from it?)
 Schedule issues
– This work is not needed for the balloon, but the
flexibility it offers would be welcome as soon as
possible
– Total time is measured in months
– Work naturally splits into several separate projects
Generic Geometry
J. Bogart
9