Gabriele Cosmo
127 lines
4.3 KiB
Plaintext
127 lines
4.3 KiB
Plaintext
$Id: README,v 1.2 2000/01/21 09:11:04 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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TestEm3
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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.
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A layer consists of a sequence of various absorbers (maximum 10).
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The layer is replicated.
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Parameters defining the calorimeter :
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- the number of layers,
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- the number of absorbers within a layer,
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- the material of the absorbers,
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- the thickness of the absorbers,
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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 number of absorbers and the number of layers can be set to 1.
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In this case we have a unique homogeneous block of matter,
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which looks like 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 2*N informations per
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layer :
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- the total energy deposit in the absorber[i],
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- the total tracklength of all charged particles in the absorber[i],
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Therefore all the absorbers are declared 'sensitive detector' (SD),
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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 commands
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/vis/... in the macro init.mac. This macro is
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automatically read from 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 one,
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or none. This command is defined in EventActionMessenger class.
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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 a build-in interactive command (/process/inactivate proname)
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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- HOW TO START ?
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- compile and link to generate an executable
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% cd TestEm3
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% gmake
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- execute TestEm3 in 'batch' mode from macro files
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% TestEm3 run01.mac
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- execute TestEm3 in 'interactive mode' with visualization
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% TestEm3
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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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7- NTUPLE
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Testem3 produce an Ntuple which is saved as testem3.histo
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Content of this Ntuple:
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EAbs0 = energy deposit in absorber[0] per event
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LAbs0 = charged track length in absorber[0] per event
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........
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EAbsN = energy deposit in absorber[N] per event
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LAbsN = charged track length in absorber[N] per event
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