Detector Geometry Description

1
Detector Geometry Description

• LHCb Software Week
• 24-26 November 1999
• P. Mato, on behalf of I. Belyaev

2
Outline

• Detector Description
• Geometry Description
• Design
• Using the geometry

3
Detector Description

• Logical Structure
• Breakdown of detectors
• Identification
• Geometry Structure
• Hierarchy of geometrical volumes
• LogicalVolumes (unplaced)
• PhysicalVolumes (placed)
• Other detector data
• Calibration, Alignment, Readout maps, Slow
  control, etc.

4
Two Hierarchies
Logical structure
Geometry structure
Detector Description
Geometry
5
Class Diagram (simplified)
Association resolved on demand
Hierarchy

IGeometryInfo
IDetElement
GeometryInfo
ILVolume
IReadOut
IMaterial

ISolid
IPVolume
ICalibration


Specific detector description questions from
algorithms
Detector Description
Geometry
Material
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Detector Element

• Provides an identifier
• e.g. /LHCb/VELO/Station1
• Time validity range and versioning
• Access point to all detector data
• Geometry, readout, slow control, etc.
• Specific code to answer specific questions can
  be implemented by inheriting from it
• e.g. MuonStation, EcalModule

7
Geometry Structure

• Constructed using Logical Volumes and Physical
  Volumes (Geant 4)
• Logical Volume Unplaced detector type described
  as a solid of a given material and a set of
  daughters (physical volumes).
• Physical Volume Association of a logical volume
  and a transformation (rotation translation).
• Solids
• A number of basic solids (boxes, tubes, cones,
  trds, spheres,)
• Boolean solids (unions, intersections and
  subtractions)

8
Geometry Info
class IGeometryInfo // transformation matrix
from the Global Reference system to the Local one
virtual const HepTransform3D matrix() 0
// from Global to Local // transformation
matrix from the Local Reference system to the
Global one virtual const HepTransform3D
matrixInv() 0 // from Local to Global //
transformation from the Global Reference System
to Local Reference system virtual
HepPoint3D toLocal( const HepPoint3D
globalPoint ) 0 // transformation from the
Local Reference System to Global Reference
system virtual HepPoint3D toGlobal(
const HepPoint3D localPoint ) 0 // Check
if a 3D point is inside volume virtual
bool isInside( const HepPoint3D
globalPoint ) 0 // C pointer to daughter
to which the given (global) point belongs to
virtual IGeometryInfo belongsTo( const
HepPoint3D globalPoint , // return the
information about the support virtual
StatusCode location( IGeometryInfo start
, ILVolumeReplicaPath replicaPath )
0
9
Usage Example
SmartDataPtrltDetectorElementgt setup(detDataService
(),"/dd/Structure/LHCb") if( !setup ) log ltlt
MSGERROR ltlt "Can't retrieve /dd/Structure/LHCb"
ltlt endreq return StatusCodeFAILURE // Get
the envelop solid ISolid sol
setup-gtgeometry()-gtlvolume()-gtsolid()-gtcoverTop()
SolidBox box dynamic_castltSolidBoxgt(sol) lo
g ltlt MSGINFO ltlt LHCb Z size is " ltlt
box-gtzHalfLength()2 ltlt endreq // Now
retrieve the custom, user defined detector
element "Vertex" with SmartDataPtrltDeVertexDetecto
rgt vertex( setup, "Vertex" ) if( !vertex )
log ltltMSGERRORltlt"Can't retrieve
/dd/Structure/LHCb/Vertex" ltlt endreq return
StatusCodeFAILURE log ltltMSGINFOltltVertex
has " ltlt vertex-gtstations() ltlt " stat" ltlt
endreq ILVolume lv vertex-gtgeometry()-gtlvolume
() log ltltMSGINFO ltltVertex is made of " ltlt
lv-gtmaterialName() ltlt endreq
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Detector Specific

• Sub-detector can start developing their specific
  Detector Element
• They need to answer the questions coming from
  Simulation, Reconstruction algorithms.
• Sub-detector specific data can be stored together
  with common data.