G4 Geometry status & plans John Apostolakis for Geometry and Transportation Working Group

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


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


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


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


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


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


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)


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


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


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


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


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


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, ..)


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


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


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


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


Atlas Geometry Atlas Geometry


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


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


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)

Documents

G4 Geometry status & plans John Apostolakis for Geometry and Transportation Working Group