G4 Geometry status & plansG4 Geometry status & plans
John ApostolakisJohn Apostolakis
forfor
Geometry and Transportation Geometry and Transportation Working GroupWorking Group
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 22
What I will talk aboutWhat I will talk about
Briefest overview of GeometryBriefest overview of Geometry Developments over the last yearDevelopments over the last year
• since beta01 / Niigatasince beta01 / Niigata Changes since production releaseChanges since production release
• improvements, fixesimprovements, fixes Plans for futurePlans for future Some detectorsSome detectors
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 33
What the geometry does ...What the geometry does ...
Describes a DetectorDescribes a Detector Hierarchy of volumesHierarchy of volumes Many volumes repeatMany volumes repeat
• Volume & sub-treeVolume & sub-tree
Up to millions of Up to millions of volumes for LHC eravolumes for LHC era
Import detectors from Import detectors from CAD systemsCAD systems
Navigates in DetectorNavigates in Detector Locates a pointLocates a point Computes a stepComputes a step
• Linear intersectionLinear intersection
Field propagation:Field propagation: Integration of motion Integration of motion Chord intersectionChord intersection
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 44
Major developments in last yearMajor developments in last year Boolean solidsBoolean solids
• new solids from Union, Intersection, Subtr.new solids from Union, Intersection, Subtr.
New specific solids New specific solids (CSG-like implementations)(CSG-like implementations)
• new Hype solidnew Hype solid• Pcone and polyhedra:new implementationsPcone and polyhedra:new implementations
BREPs and STEP: BREPs and STEP: see later talk (G.Cosmo)see later talk (G.Cosmo)
FieldField• tracking of spintracking of spin• ability to track in Electric fieldability to track in Electric field
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 55
Creating a Detector VolumeCreating a Detector Volume
Start withStart with its Shape & its Shape & SizeSize• Box 3x5x7 cm, sphere R=8mBox 3x5x7 cm, sphere R=8m
Add properties:Add properties:• material, B/E field, material, B/E field, • make it sensitivemake it sensitive
Place it in another volumePlace it in another volume• in one placein one place• repeatedly using a functionrepeatedly using a function
• SolidSolid
• Logical-VolumeLogical-Volume
• Physical-VolumePhysical-Volume
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 66
Boolean Solids: what are theyBoolean Solids: what are they
STEP compliant Boolean operationsSTEP compliant Boolean operations A Boolean solid is built fromA Boolean solid is built from
• two solidstwo solids• an operationan operation• an optional tranformation for one solidan optional tranformation for one solid
Solids that can be used:Solids that can be used:• CSG solidsCSG solids• other Boolean solidsother Boolean solids
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 77
Boolean Solids (status)Boolean Solids (status)
Boolean solids can be used Boolean solids can be used • exactly like any other solidsexactly like any other solids
Implementation: V. GrichineImplementation: V. Grichine• Design: J. Apostolakis, S.Giani.Design: J. Apostolakis, S.Giani.
First implementation completeFirst implementation complete Further testingFurther testing
• improvements in progressimprovements in progress
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 88
New Specific SolidsNew Specific Solids
New Hype solidNew Hype solid• Created, eg, by rotation hyperbola / axis Created, eg, by rotation hyperbola / axis
– E. Lamana’s group (Rome / IGD)E. Lamana’s group (Rome / IGD)
Polycone and polyhedraPolycone and polyhedra• alternative implementation (to BREP)alternative implementation (to BREP)
– D. Williams (BaBar)D. Williams (BaBar)
• angle-limitted Pcone angle-limitted Pcone – S. Magni (Milano/IGD)S. Magni (Milano/IGD)
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 99
Magnetic FieldMagnetic Field
Integrates motion in a fieldIntegrates motion in a field Finds intersection with volume Finds intersection with volume
boundaryboundary Framework could support any type of Framework could support any type of
fieldfield• but in beta-01 but in beta-01
– only magnetic field workedonly magnetic field worked– only position/momentum direction trackedonly position/momentum direction tracked
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1010
Field developments Field developments (Niigata to now)(Niigata to now)
Modifications to stateModifications to state• adding Energy, Spin, Time of flightadding Energy, Spin, Time of flight
– J. ApostolakisJ. Apostolakis
New forcesNew forces• spin precessing in magnetic fieldspin precessing in magnetic field
– P. Gumplinger (in release 4.0.1)P. Gumplinger (in release 4.0.1)
• in electric field (including E & B)in electric field (including E & B)– V. GrichineV. Grichine
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1111
Accuracy in fieldAccuracy in field
5mm thick cone 5mm thick cone • Aluminium in AirAluminium in Air
Geant3 misses Geant3 misses • for 10 degrees max for 10 degrees max
deviation (default=20)deviation (default=20)• in 50% of trial tracksin 50% of trial tracks• need small angle <2need small angle <2 deg deg
Geant4 always hitsGeant4 always hits
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1212
Geometry ImprovementsGeometry Improvements
Optimisation of VoxelisationOptimisation of Voxelisation– Request: BaBar, CMS, BorexinoRequest: BaBar, CMS, Borexino
• small code change small code change • much faster initialisationmuch faster initialisation• no runtime penaltyno runtime penalty
– S. GianiS. Giani
Visualise voxelsVisualise voxels– L. Graignac … curved tracks unfinishedL. Graignac … curved tracks unfinished
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1313
Fixes have been made to correctFixes have been made to correct
Replica volume navigationReplica volume navigation• problem leading to loop eliminatedproblem leading to loop eliminated
Race condition in field at boundaryRace condition in field at boundary– Reported by BaBar, Ecole Polyt.Reported by BaBar, Ecole Polyt.
• in strong field and detailed geometryin strong field and detailed geometry
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1414
Plans/ExtensionsPlans/Extensions
A new concept: a “frame”A new concept: a “frame”• it is a collection of logical volumeit is a collection of logical volume• each one positioned in frame’s coordinateseach one positioned in frame’s coordinates• that can be placed that can be placed
– as a unit in a “mother” logical volumeas a unit in a “mother” logical volume– this can be done repeatedlythis can be done repeatedly
• it is a factory/only aids in creating geometryit is a factory/only aids in creating geometry– the Navigator does not see ‘frames’ the Navigator does not see ‘frames’
• request: Atlas (M.Asai, ..)request: Atlas (M.Asai, ..)
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1515
Plans (cont.)Plans (cont.)
Improve field perfomanceImprove field perfomance• work on benchmarkingwork on benchmarking• modify code to use safety informationmodify code to use safety information
Converting Geant3 ‘many’ geometriesConverting Geant3 ‘many’ geometries• find out whether/where there are use casesfind out whether/where there are use cases
– contact uscontact us
• document how Geant4 handles thesedocument how Geant4 handles these• possibly provide a tools for simple casespossibly provide a tools for simple cases
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1616
Physical VolumesPhysical Volumes
Placement: Placement: it is one positioned volumeit is one positioned volume
Repeated: Repeated: a volume placed many timesa volume placed many times
• can represent any number of volumescan represent any number of volumes• reduces use of memory.reduces use of memory.
• Replica: Replica: simple repetition, like G3 divisionssimple repetition, like G3 divisions
• Parameterised: Parameterised: function function (NEW)(NEW)
A A mothermother volume volume can contain either either • many placementmany placement volumes volumes OROR • one repeatedone repeated volume volume repeated
placement
19th May 199919th May 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1717
Plans (cont.)Plans (cont.)
Parameterising the daughters of a Parameterising the daughters of a Parameterised Physical volumeParameterised Physical volume• extends flexibilityextends flexibility• allows volumes of different size/solidallows volumes of different size/solid
– to have their own daughtersto have their own daughters• because up to now they could only be ‘leaf’ because up to now they could only be ‘leaf’
nodesnodes
• it is currently under study/discussionit is currently under study/discussion
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1818
NavigationNavigation
Responsible forResponsible for• Locating a point’s VolumeLocating a point’s Volume• Step ComputationStep Computation
– computes safety with stepcomputes safety with step– must relocatemust relocate before each computeStep before each computeStep
• can be ‘expensive’can be ‘expensive’
New capabilities:New capabilities:• Safety ComputationSafety Computation• Relocate Within VolumeRelocate Within Volume
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 1919
Changes in the past yearChanges in the past year Boolean solidsBoolean solids
• new solids from Union, Intersection, Subtr.new solids from Union, Intersection, Subtr.
New specific solids New specific solids (CSG-like implementations)(CSG-like implementations)
• new Hype solidnew Hype solid• Pcone and polyhedra:new implementationsPcone and polyhedra:new implementations
FieldField• tracking of spintracking of spin• ability to track in Electric fieldability to track in Electric field
Fixes in solids, navigator, field.Fixes in solids, navigator, field.
2020V. Lefebure CMS/CERN V. Lefebure CMS/CERN AIHENP 99, Crete, AAIHENP 99, Crete, April 99pril 99
CMS Geometry in GCMS Geometry in GEANTEANT44current statuscurrent status
Beam PipeBeam Pipe Tracker Tracker
• Si Pixel DetectorsSi Pixel Detectors– Barrel Si Pixel Barrel Si Pixel – Forward Si PixelForward Si Pixel
• Si Strip Detectors Si Strip Detectors – Barrel Si Strip Barrel Si Strip
• MSGC MSGC – Barrel MSGCBarrel MSGC
CalorimetersCalorimeters • Electromagnetic Calorimeter Electromagnetic Calorimeter
– Barrel ECALBarrel ECAL • Hadron Calorimeter Hadron Calorimeter
– Barrel HCAL Barrel HCAL Muon System Muon System
• Barrel Muon Barrel Muon
2121V. Lefebure CMS/CERN V. Lefebure CMS/CERN AIHENP 99, Crete, AAIHENP 99, Crete, April 99pril 99
Barrel Si PixelBarrel Si Pixel
GEANT4.0.0max. radius = 11 cmlength = 60 cm
Magnetic FieldMagnetic Field
2222J. Apostolakis, CERNJ. Apostolakis, CERN 20th September 199920th September 1999
Simulation in BorexinoSimulation in Borexino
Old code: ray tracerOld code: ray tracer • simplified trackingsimplified tracking• no reflections, phys.no reflections, phys.
Geant4 codeGeant4 code• reproduces resultsreproduces results• photons tracked photons tracked
everywhereeverywhere• flexible, extensibleflexible, extensible• immediate benefit: immediate benefit:
new under-standingnew under-standing
2323J. Apostolakis, CERNJ. Apostolakis, CERN 20th September 199920th September 1999
Benefits of Geant4 (Borexino)Benefits of Geant4 (Borexino)
Full geometryFull geometry All optical processesAll optical processes
• reflection, refractionreflection, refraction
New process New process • for specialised for specialised
physics of scintilatorphysics of scintilator– scatter, absorption, scatter, absorption,
re-emissionre-emission
• S. Magni, G. PieriS. Magni, G. Pieri
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 2424
Atlas Geometry Atlas Geometry
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 2525
BaBar’s Simulation: “Bogus”BaBar’s Simulation: “Bogus”
Fast Simulation Fast Simulation commisioned April 99commisioned April 99
Simple geometrySimple geometry Parameterisation Parameterisation
processesprocesses• hits on detector elements hits on detector elements
create reconstruction create reconstruction objectsobjects
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 2626
BaBar BaBar full simulationfull simulation
SVTSVT• N. Kuznetsova,UCSBN. Kuznetsova,UCSB
Under developmentUnder development First full version of First full version of
Geometry soon, e.g.Geometry soon, e.g.• EMC from g3tog4EMC from g3tog4
– J. AllisonJ. Allison
20th September 199920th September 1999 J. Apostolakis, CERNJ. Apostolakis, CERN 2727
Geometry: Recent developmentsGeometry: Recent developments
Boolean operations, Boolean operations, a-la STEP:a-la STEP:• a solid is created by usinga solid is created by using
– an operation (union, intersection, subtraction)an operation (union, intersection, subtraction)– between two solidsbetween two solids
• for CAD export, only use with CSG solidsfor CAD export, only use with CSG solids Tracking of spin in magnetic fieldTracking of spin in magnetic field New solids (hype, New solids (hype, alternativealternative pcon/pgon) pcon/pgon)