Gabriele Cosmo
151 lines
5.6 KiB
Plaintext
151 lines
5.6 KiB
Plaintext
$Id: README,v 1.8 2001/11/27 11:10:31 maire 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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ExampleN03
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----------
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This example simulates a simple Sampling Calorimeter setup.
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1- GEOMETRY DEFINITION
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The calorimeter is a box made of a given number of layers. A layer
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consists of an absorber plate and of a detection gap. The layer is
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replicated.
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Six parameters define the calorimeter :
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- the material of the absorber,
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- the thickness of an absorber plate,
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- the material of the detection gap,
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- the thickness of a gap,
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- the number of layers,
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- the transverse size of the calorimeter (the input face is a square).
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In addition a transverse uniform magnetic field can be applied.
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The default geometry is constructed in DetectorConstruction class,
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but all of the above parameters can be modified interactively via
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the commands defined in the DetectorMessenger class.
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NB. The thickness of the absorber or of the gap can be set to zero
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(but not together), and the number of layers to 1. In this case we
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have a unique homogeneous block of matter, which looks like
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a bubble chamber rather than a calorimeter ...
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(see the macro of commands: newgeom.mac)
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2- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle which hits the
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calorimeter 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 (see
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the macros provided with this example).
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In addition one can choose randomly the impact point of the incident
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particle. The corresponding interactive command is built in
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PrimaryGeneratorMessenger class.
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A RUN is a set of events.
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3- DETECTOR RESPONSE
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A HIT is a record, event per event and volume per volume, of all the
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informations needed to simulate and analyse the detector response.
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In this example a CalorHit is defined as a set of 4 informations per
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layer :
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- the total energy deposit in the absorber plate,
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- the total tracklength of all charged particles in the absorber plate,
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- the total energy deposit in the detection gap,
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- the total tracklength of all charged particles in the detection gap.
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Therefore both the absorber and the detection gap are declared
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'sensitive detector' (SD), which means they can contribute to the hit.
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At the end of a run, from the CalorHitsCollection, one can study the
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calorimeter performances such as :
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- shower profile,
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- calorimeter resolution,
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- pi/e ratio ...
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4- 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 in case of interactive running mode.
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The detector has a default view which is a longitudinal view of the
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calorimeter.
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The tracks are drawn at the end of event, and erased at the end of run.
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Optionaly one can choose to draw all particles, only the charged,
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or neutral or none. This command is build in EventActionMessenger class.
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NB 1: 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- exampleN03.cc has been compiled with G4VIS_USE_OPENGLX.
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NB 2: the visualization (with DAWNFILE 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_DAWNFILE_DRIVER.
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2- exampleN03.cc has been compiled with G4VIS_USE_DAWNFILE.
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NN 3: The macros "visTutor/exN03VisX.mac" are tutorial macros for
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visualization. They can be tried as:
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% $G4BINDIR/exampleN03
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idle > /control/execute visTutor/exN03VisX.mac
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For details, see comment lines described in the macro files.
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These macros are designed to help your understanding the
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User's Guide.
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5- PHYSICS DEMO
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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 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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Then one can well visualize the processes one by one, especially
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in the bubble chamber setup with a transverse magnetic field.
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As a homework try to visualize a gamma conversion alone,
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or the effect of the multiple scattering.
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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
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On can use a Motif driven command interface (called G4UIXm) if:
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1- interfaces category has been compiled with G4UI_BUILD_XM_SESSION
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2- exampleN03.cc has been compiled with G4UI_USE_XM.
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7- HOW TO START ?
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- compile and link to generate an executable
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% cd N03
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% gmake
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- execute N03 in 'batch' mode from macro files
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% exampleN03 run1.mac
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- execute N03 in 'interactive mode' with visualization
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% exampleN03
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....
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Idle> type your commands. For instance:
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Idle> /control/execute newgeom.mac
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....
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Idle> exit
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