Virtual MC, Geant4

Virtual MC, Geant4

I. Hrivnacova, IPN, Orsay

ALICE Offline Meeting, CERN, 4 March 2003

I. Hrivnacova ALICE Offline Meeting, CERN, 4 March 2003

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Outline

Virtual MC – Example E03– TMCVerbose– Performance tests– New VMC users

RootToG4 Geant4

– Release 5.0


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Virtual MC

Examples E01, E02

Geant4 novice example N01, N02 rewritten with usage of the Virtual Monte Carlo

E01 – Builds simple geometry, tracks geantino and prints

info at each step

E02 – Builds parameterised geometry with magnetic field,

tracks proton, registers hits in a tracker and saves hits and kinematics in a Root file

– Default cuts in each MC (different) –> different results


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Virtual MCNew E03

E03:– Builds geometry with divided volumes, with magnetic

field– Primary particles: e- with (optionally) randomised

position and fixed direction– Calorimeter hits – total energy deposit and track

length in the absorber and gap layers– Storing hits, particles stack

• Using E02 Root manager class– Verbosity (usage of TMCVerbose)

Same cuts -> Comparable results– G4: cut in range 1mm + /run/particle/applyCuts– G3: cuts in kin. energy set to correspond to G4 cut


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Virtual MC

New E03


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Virtual MCNew E03

Some setting in the G4 example N03 could not be ported to VMC:– Material from elements and/or other materials

(mixture of mixtures)– Gas in non STP conditions– Update geometry

New example of particles stack class– Simpler, only reference from daughter to mother– Better performance


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Virtual MC

TMCVerbose

Inspired by verbose in Geant4– /tracking/verbose command enables a user to run

Geant4 with printing a detailed information from each step

Very useful for debugging, understanding what is going on

TMCVerbose – new class in root/mc For each TVirtualMCApplication function a

corresponding function is defined in TMCVerbose Defined levels of output: 0 – 3

– If level = 0 – no printing


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Virtual MC

TMCVerbose Usage

Including MC Verbose in MC application is not automatic

User can add calls to MC verbose in some/all MC application functions; Eg.

void Ex03MCApplication::Stepping() {

// User actions at each step

fVerbose.Stepping();

fCalorimeter->ProcessHits();

}

Suggestion: to be included in AliRun in AliRoot


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Virtual MC TMCVerbose Output

**************************************************************************************************** Particle = gamma Track ID = 13 Parent ID = 4****************************************************************************************************Step# X(cm) Y(cm) Z(cm) KinE(MeV) dE(MeV) Step(cm) TrackL(cm) Volume Process # 0 -6.634 -0.228 -0.067 0.6481 0.0000 0.000 0.000 ABSO No active process# 1 -6.500 -0.280 -0.134 0.6481 0.0000 0.159 0.159 ABSO Transportation# 2 -6.500 -0.280 -0.134 0.6481 0.0000 0.000 0.159 GAPX Transportation# 3 -6.000 -0.475 -0.385 0.6481 0.0000 0.592 0.751 GAPX Transportation# 4 -6.000 -0.475 -0.385 0.6481 0.0000 0.000 0.751 ABSO Transportation# 5 -5.758 -0.569 -0.506 0.0000 0.0880 0.287 1.038 ABSO Photoelectric effect

**************************************************************************************************** Particle = e- Track ID = 14 Parent ID = 13****************************************************************************************************Step# X(cm) Y(cm) Z(cm) KinE(MeV) dE(MeV) Step(cm) TrackL(cm) Volume Process # 0 -5.758 -0.569 -0.506 0.5601 0.0000 0.000 0.000 ABSO No active process# 1 -5.755 -0.570 -0.503 0.0551 0.1598 0.010 0.010 ABSO Bremstrahlung# 2 -5.755 -0.570 -0.503 -0.0000 0.0551 0.001 0.011 ABSO Energy loss


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Virtual MC

Performance test

E03 – enables to compare performance of G3, G4 VMC and

G4 (native) on a simple geometry & physics problem Test:

– 50 events– 1000 primary e-, 50 MeV– 10 layers: 1cm Lead + 0.5 cm Liquid Argon– Default material (world): vacuum– EM physics

• G3: LOSS=1, DRAY=1, HADR=0• G4: TG4 EM Physics Constructor


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Virtual MC

Performance test

Geant4 VMC configurations:– TG4SteppingAction, TG4TrackingAction on/off

• These classes insure performing special steps of zero length for new track and on boundary

– Magnetic field on/off– Saving secondaries to MC stack on/off

• If comparing with native G4 simulation be aware that G4 does not make secondaries persistent


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Performance test G4 VMC Configurations

C1

fastest

No TG4SteppingAction, TG4TrackingAction

Not saving secondaries in MC stack

No magnetic field/ Mag. Field 0.2 tesla

C2 With TG4SteppingAction, TG4TrackingAction


No magnetic field/ -

C3 With TG4SteppingAction, TG4TrackingAction


Magnetic field 0 tesla / Uniform mag. Field 0.2 tesla

C4

slowest

With TG4SteppingAction, TG4TrackingAction

With saving secondaries in MC stack

Magnetic field 0 tesla / Uniform mag. Field 0.2 tesla


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Virtual MC Performance test results

No mag. field Field 0.2 tesla

MC Time [s] Time [s]

G3 VMC 117 (0.60) 117 (0.60)

G4 native 193 (1.00) 1182 (6.13) vac

227 (1.18) air

G4 VMC c1 214 (1.11) 245 (1.27)

G4 VMC c2 240 (1.25) -

G4 VMC c3 292 (1.51) 272 (1.41)

G4 VMC c4 350 (1.81) 349 (1.81)


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G3/G4:– 0.60– Cuts in G4

• Production treshold • Not tracking cut – particles are tracked till

stopping

G4 VMC / G4 native:– 1.25 in standard VMC application– 1.11 if no need to perform specials steps at

boundary, new track


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No field/ Mag. Field:– G3: 1.0– G4 native: 6.13 !!

• If vacuum changed to air: 1.18 – G4 VMC: 1.27

• In low density materials G4 VMC defines automatically limited step

• In G4 user can customize accuracy parameters of magnetic field – not yet passed to Geant4 VMC

Saving secondaries in MC Stack (c4/c3):– 1.29

• Now optional – can be switched off if not needed


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Virtual MC New users

OPERA – Neutrino oscillations, international collaboration

CBM – Nucleus-nucleus collision program at the future

accelerator facility, GSI, Darmstadt– Considering of building simulation based on VMC

Proposal by CBM– Meetings of VMC users with VMC developers per ~ 3

months


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Virtual MC

New users (requirements)

Need/Would like to have– User defined particles, ions

• Gspart in TGeant3 has to be revised• Ions as primary particles

– Customisable G4 VMC physics list• Available already now, but requires to add

infrastructure and documentation– More documentation

• eg. on mapping G4 physics processes to TMCProcess

– G4 visualisation (Open Inventor driver)– Root geometry modeller -> VMC


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Virtual MC New users (contribution)

Have done– Geant4 VMC HTML source code documentation

• Available at: http://www-linux.gsi.de/~gsisim/geant4_vmc

• By D. Bertini, GSI, using Doxygen– To be linked/included at VMC Web


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RootToG4 Convertor

Convertor from Root TGeo geometry to Geant4 geometry

Independent from Geant4 VMC– Usable also for native Geant4 application

Will be used by Geant4 VMC – To support the new way of defining geometry with

direct usage of TGeo in a user VMC application In development, already operational

– Geometries from examples gexam1, gexam3, gexam4 have been successfully converted

Not yet available from VMC site


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RootToG4 Convertor

Present Status

Supported– Shapes, Volumes, Positions, Materials, Divisions

• TArb8 not supported by Geant4• Divisions temporarily implemented as multiple

G4PVPlacement (to be revised when G4Divison is available)

To be done– Medias (using G3toG4), Boolean shapes

Not to be supported– Overlapping volumes (not supported by Geant4)


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RootToG4 Convertor

g2root roottog4 g4toxmlGeant3 -> Root TGeo -> Geant4 -> GraXML


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Geant4 5.0

Release 5.0 – 13 Dec 2003– Patch01 – 25 Feb 2003– Geant4-05-00-beta-02

From Release notes:– First release of the cascade part of the HETC re-write– First release of the binary-cascade (kinetic) model– First implementation of HepMC interfaces– Implementation of abstract layer for persistency;

removed ODBMS specific implementations and setup• Example for use of Root: examples/extended/persistency/PersEx01


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Geant4 5.0

From Release notes (cont):– Compilation of g3tog4 optional (G4USE_G3TOG4)

• Has to be set by Geant4 VMC users– New G4Exception scheme based on severity level– G4RunManager: introduced ResetNavigator() method

(could be useful for Flugg ?) – …


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Geant4 5.0

J.P.Wellish, GSI, Feb 2003


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Virtual MC, Geant4

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