Detector Description in LHCb Detector Description Workshop 13
Detector Description in LHCb Detector Description Workshop 13 June 2002 S. Ponce, P. Mato / CERN 13 June 2002 LHCb Detector Description
Contents u Architecture u Transient layer u Persistency layer : XML u Condition Database u Visualization u Interfacing Geant 4 u Status & examples 13 June 2002 LHCb Detector Description 2
Architecture Overview Visualization (Panoramix) XML Transient Store Calibration Condition Database … Simulation (Gauss/Geant 4) Materials Structure Reconstruction (Brunel) Geometry Analysis (Da Vinci) GDML ? DAQ ? 13 June 2002 LHCb Detector Description 3
Architecture u u u Sub-Architecture of Gaudi – Same principles – Transient/Persistent representations Focus on the “Physics Algorithm” Coherent access to “all” detector data – Geometry, Calibration, Slow Control, etc. Gaudi Architecture Application Manager Message Service Job. Options Service Event Data Service Other Services LHCb Detector Description Persistency Service Data Files Transient Event Store Algorithm Particle Prop. Service 13 June 2002 Converter Event Selector Detec. Data Service Transient Detector Store Persistency Service Data Files Histogram Service Transient Histogram Store Persistency Service Data Files 4
Logical Structure u u The basic object is a Detector Element – Identification – Navigation (tree-like) Det. Element as information center – Be able to answer any detector related question » E. g. global position of strip#, temperature of detector, absolute channel gain, etc. Det. Element * My. Detector – Placeholder for specific code » The specific answers will be coded by “Physicists” 13 June 2002 LHCb Detector Description 5
Algorithm Accessing Detector Data • Manages store • Synchronization updates begin. Event request Detector. Data Service request: get, update Persistency Service IDet. Element IGeometry. Info Geometry Info Algorithm Det. Element ICalibration IRead. Out reference Geometry Conversion Service Conditions DB Conversion Service Other DBs Read. Out Muon. Station Transient Detector Store 13 June 2002 Conversion Service LHCb Detector Description 6
Simplified Diagram Data. Object Hierarchy IDetector. Element IGeometry. Info Geometry Info Detector. Element IRead. Out ICalibration Muon. Station Calibration Specific detector description questions from algorithms Detector Description 13 June 2002 Read. Out Association resolved on demand * ILVolume * LVolume Material ISolid IPVolume Solid. Box Geometry LHCb Detector Description Mixture Element * Isotope * Material 7
Persistency based on XML files u XML is used as persistent representation of the Structure, Geometry and Materials (eventually also Conditions) u Mapping each C++ class into an XML element – Inheritance emulation (Generic and Specific Detector Element) – Relationships using “Links” and symbolic names u Allow math expressions with parameters and physical units – Using expression evaluator (available in CLHEP) 13 June 2002 LHCb Detector Description 8
XML Files u Separated XML files – By sub-detector and data type (structure, geometry, material) – Low coupling of developments u Links between files through references – allows to see the whole description as a single XML tree u Versioning done using CVS u Possible migration to the “Conditions DB” 13 June 2002 LHCb Detector Description 9
XML Converters u u Capable of converting (one way for the time being) XML into C++ objects – Using DOM interface (Xerces-C) – Specific converters for specific “Det. Element” (to be provided by users) Available Converters – Structure: Catalog, Det. Element – Geometry: LVolume, Surface, Solids (various shapes, boolean), PVolumes (parametric) – Materials: Isotope, Element, Mixture, Tabulated. Property 13 June 2002 LHCb Detector Description 10
XML Detector Description Editor u Developed a graphical editor to “hide” XML to the end-users (physicists) – It understands our model (DTD) – But it’s generic (possible to use another DTD) – It understands “links” and allow us to edit a web of XML files as a single tree – It’s implemented in Java (portable) 13 June 2002 LHCb Detector Description 11
XMLEditor 13 June 2002 LHCb Detector Description 12
Conditions DB u u Accessing detector conditions data (calibration, slow control, alignment, etc. ) should be the same as geometry data – Time validity period and Versioning in addition – Conditions are integrated into the transient data model – Converters are responsible for converting from database rather than from XML Conditions are attached to Detector Elements as for geometry – each element has many conditions (calibration, alignment, slowcontrol, fastcontrol …) 13 June 2002 LHCb Detector Description 13
Conditions DB Implementation u Condition objects are stored in XML u The XML fragments are stored using the Oracle condition DB developed by IT u XML references are used to select between XML and condition DB : – <conditionref href=“. . /Ecal/condition. xml#ca. Ecal"/> XML – <conditionref href=“cond: //dd/Calibration/Ecal/ca. Ecal"/> Data. Base 13 June 2002 LHCb Detector Description 14
Geometry Visualization u Visualization is essential for developing the geometry – Applicable at the different data representations u Generic geometry information conversion to 3 D graphics data u Panoramix (On. X) 13 June 2002 Structure + Geometry Vis Display Cnv. Svc Transient Store Visual Cnv. Svc Display Giga Cnv. Svc G 4 Geometry LHCb Detector Description Visual Cnv. Svc Display 15
Interfacing With Geant 4 u We integrate Gaudi with Geant 4 by providing a number of “Gaudi Services” (Gi. Ga) u The Gi. Ga. Geom. Cnv. Svc is able to convert transient objects (Det. Elem, LVolume, Surfaces, etc. ) into G 4 geometry objects – The conversion does not require “user” code – Flexibility in mapping Gaudi model to Geant 4 model u Single source of Geometry information 13 June 2002 LHCb Detector Description 16
Status of LHCb Detector Description u The Det. Desc framework is fully functional (transient classes, XML DTD, XML converters, editor, etc) u All sub-detectors are already described (structure, geometry and materials) using the provided framework u Visualization based on On. X : Panoramix. Allows to see geometry, events, histograms, … u Conversion to Geant 4 through Gi. Ga is complete 13 June 2002 LHCb Detector Description 17
Example 1 : Velo and Rich 1 13 June 2002 LHCb Detector Description 18
Example (2) : Zoom on Ecal 13 June 2002 LHCb Detector Description 19
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