Gabriele Cosmo
125 lines
4.9 KiB
Plaintext
125 lines
4.9 KiB
Plaintext
$Id: README,v 1.1 2002/03/05 15:21:55 gcosmo Exp $
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-------------------------------------------------------------------
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=========================================================
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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=========================================================
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ParN02
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------
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This example simulates a simplified fixe target experiment.
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Read 000README for a description of how to run it in parallel.
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1- GEOMETRY DEFINITION
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The setup consists of a target followed by six chambers of increasing
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transverse size. These chambers are located in a region called Tracker
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region. Their shape are boxes, constructed as parametrised volumes
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(ChamberParametrisation class).
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The default geometry is constructed in DetectorConstruction class.
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One can change the material of the target and of the chambers
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interactively via the commands defined in the DetectorMessenger class.
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In addition a transverse uniform magnetic field can be applied (see
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N02MagneticField and DetectorMessenger classes).
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2- PHYSICS LIST
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The particle's type and the physic processes which will be available
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in this example are set in PhysicsList class.
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In this example, all the so called 'electromagnetic processes' are
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introduced for gamma, charged leptons, and charged hadrons (see the
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method PhysicsList::ConstructEM()).
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An important data member of this class is the defaultCutValue which
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defines the production threshold of secondary particles
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(mainly Ionisation and Bremsstrahlung processes are concerned by this
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CutValue).
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Notice that the CutValue must be given in unit of length, corresponding
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to the stopping range of the particle. It is automatically converted
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in energy for each material, and a table is printed in the method
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PhysicsList::SetCuts()
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In addition the build-in interactive command:
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/process/(in)activate processName
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allows to activate/inactivate the processes one by one.
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3- RUNS and EVENTS
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The primary kinematic consists of a single particle which hits the
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target perpendicular to the input face. The type of the particle
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and its energy are set in the PrimaryGeneratorAction class, and can
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be changed via the G4 build-in commands of ParticleGun class.
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A RUN is a set of events.
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The user has control:
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-at Begin and End of each run (class RunAction)
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-at Begin and End of each event (class EventAction)
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-at Begin and End of each track (class TrackingAction, not used here)
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-at End of each step (class SteppingAction)
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The class SteppingVerbose prints some informations step per step,
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under the control of the command: /tracking/verbose 1
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It inherits from G4SteppingVerbose, and has been setup here in order
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to illustrate how to extract informations from the G4 kernel during
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the tracking of a particle.
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4- DETECTOR RESPONSE
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A HIT is a record, track per track (even step per step), of all the
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informations needed to simulate and analyse the detector response.
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In this example the Tracker chambers are considered as the detector.
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Therefore the chambers are declared 'sensitive detectors' (SD) in
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the DetectorConstruction class.
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Then, a Hit is defined as a set of 4 informations per step, inside
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the chambers, namely:
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- the track identifier (an integer),
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- the chamber number,
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- the total energy deposit in this step,
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- the position of the deposit.
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A given hit is an instance of the class TrackerHit which is created
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during the tracking of a particle, step by step, in the method
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TrackerSD::ProcessHits(). This hit is inserted in a HitsCollection.
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The HitsCollection is printed at the end of event (via the method
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TrackerSD::EndOfEvent()), under the control of the command: /hits/verbose 1
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5- VISUALIZATION
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The Visualization Manager is set in the main().
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The initialisation of the drawing is done via a set of /vis/ commands
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in the macro vis.mac. This macro is automatically read from
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the main when running in interactive mode.
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The tracks are automatically drawn at the end of event and erased at
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the beginning of the next run.
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The visualization (with OpenGL driver) assumes two things:
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1- the visualisation & interfaces categories have been compiled
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with the environment variable G4VIS_BUILD_OPENGLX_DRIVER.
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2- ParN02.cc has been compiled with G4VIS_USE_OPENGLX.
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(The same with DAWNFILE instead of OPENGLX)
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6- USER INTERFACES
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The default command interface, called G4UIterminal, is done via
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standart cin/G4cout.
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On Linux and Sun-cc on can use a smarter command interface G4UItcsh.
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It is enough to set the environment variable G4UI_USE_TCSH before
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compiling ParN02.cc
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