Gabriele Cosmo
166 lines
5.6 KiB
Plaintext
166 lines
5.6 KiB
Plaintext
$Id: README,v 1.18 2004/06/23 11:30:39 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- PHYSICS LISTS
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Physics Lists are subdivided on 4 following modules:
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1. "particles" - particle definitions
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2. "general" - decays and transportation
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3. "standard" (alternative) - standard EM physics
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4. "model" (alternative) - standard EM physics using model approach
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Notice that there is an example of definition of a static ion : IonC12
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(see PhysListParticle.cc) and an example of use : ionC12.mac
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3- 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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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 the commands
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/vis/... in the macro vis.mac. In interactive session:
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PreInit or Idle > /control/execute vis.mac
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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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Notice that one can control the maximum step size at tracking time,
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via G4UserLimit class and the command /tracking/stepMax
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(see DetectorConstruction and DetectorMessenger classes)
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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 run01.mac
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....
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Idle> exit
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7- HISTOGRAMS
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Testem3 produces histograms :
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histo 1 : energy deposit in absorber 0
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histo 2 : energy deposit in absorber 1
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...etc...........
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One can control the binning of the histo with the command:
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/testem/histo/setHisto idAbsor nbin Emin Emax unit
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...etc...........
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where unit is the desired energy unit for that histo (see TestEm3.in).
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One can control the name of the histograms file with the command:
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/testem/histo/setFileName name (default testem3.paw)
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Note that, by default, histograms are disabled. To activate them, uncomment
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the flag G4ANALYSIS_USE in GNUmakefile.
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8- Using histograms
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-------------------
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By default the histograms are not activated. To activate histograms
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the environment variable G4ANALYSIS_USE should be defined. For instance
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uncomment the flag G4ANALYSIS_USE in GNUmakefile.
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To use histograms any of implementations of AIDA interfaces should
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be available (see http://aida.freehep.org).
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A package including AIDA and extended interfaces also using Python
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is PI, available from: http://cern.ch/pi .
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Once installed PI or PI-Lite in a specified local area $MYPY, it is
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required to add the installation path to $PATH, i.e. for example,
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for release 1.2.1 of PI:
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setenv PATH ${PATH}:$MYPI/1.2.1/app/releases/PI/PI_1_2_1/rh73_gcc32/bin
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CERN users can use the PATH to the LCG area on AFS.
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Before compilation of the example it is optimal to clean up old
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files:
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gmake histclean
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gmake
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Before running the example the command should be issued:
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eval `aida-config --runtime csh`
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It is possible to choose the format of the output file with
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histograms using UI command:
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/testem/histo/setFileType type
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The following types are available: hbook, root, xml.
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