Gabriele Cosmo
174 lines
6.0 KiB
Plaintext
174 lines
6.0 KiB
Plaintext
$Id: README,v 1.6 2007/11/13 12:13:32 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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TestEm14
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--------
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How to compute cross sections from the direct evaluation of the mean
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free path ( see below, item Physics).
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How to plot final state of a process.
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1- GEOMETRY DEFINITION
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It is a single box representing a 'semi infinite' homogeneous medium.
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Two parameters define the geometry :
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- the material of the box,
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- the (full) size of the box.
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The default geometry (100 m of water) is constructed in
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DetectorConstruction, but the above parameters can be changed
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interactively via the commands defined in DetectorMessenger.
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2- PHYSICS LIST
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The physics list contains the standard electromagnetic processes.
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In order not to introduce 'artificial' constraints on the step size, the
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multiple scattering is not instanciated, and there is no limitation from
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the maximum energy lost per step.
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3- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle starting at the edge
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of the box. The type of the particle and its energy are set in
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PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4
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build-in commands of ParticleGun class (see the macros provided with
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this example).
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4- PHYSICS
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An event is killed at the first interaction of the incident paticle.
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The absorption length, also called mean free path, is computed as
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the mean value of the track length of the incident particle.
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This is why the medium must be 'infinite' : to be sure that interaction
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occurs at any events.
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The result is compared with the 'input' data, i.e. with the cross
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sections stored in the PhysicsTables and used by Geant4.
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The energy spectrum and the angular distribution of the scattered
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particle (if any) and of the created secondaries are plotted (see
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SteppingAction).
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A set of macros defining various run conditions are provided.
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The processes are actived/inactived in order to survey the processes
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individually.
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5- HISTOGRAMS
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The test contains 6 built-in 1D histograms, which are managed by the
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HistoManager class and its Messenger. The histos can be individually
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activated with the command :
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/testem/histo/setHisto id nbBins valMin valMax unit
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where unit is the desired unit for the histo (MeV or keV, etc..)
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(see the macros xxxx.mac).
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1 "scattered primary particle: energy spectrum"
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2 "scattered primary particle: costheta distribution"
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3 "charged secondaries: energy spectrum"
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4 "charged secondaries: costheta distribution"
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5 "neutral secondaries: energy spectrum"
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6 "neutral secondaries: costheta distribution"
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See below the note on histogram tools.
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One can control the name and the type of the histograms file with
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the commands:
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/testem/histo/setFileName name (default testem14)
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/testem/histo/setFileType name (default hbook)
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It is also possible to print selected histograms on an ascii file:
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/testem/histo/printHisto id
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All selected histos will be written on a file name.ascii
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(default testem14)
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Note that, by default, histograms are disabled. To activate them,
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uncomment the flag G4ANALYSIS_USE in GNUmakefile.
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6- 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. To get visualisation:
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> /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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box.
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The tracks are drawn at the end of event, and erased at the end of run.
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7- HOW TO START ?
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compile and link to generate an executable
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% cd geant4/examples/extended/electromagnetic/TestEm14
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% gmake
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execute TestEm14 in 'batch' mode from macro files :
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% TestEm14 compt.mac
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execute TestEm14 in 'interactive mode' with visualization :
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% TestEm14
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Idle> control/execute vis.mac
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....
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Idle> type your commands
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....
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Idle> exit
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8- USING HISTOGRAMS
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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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Before compilation of the example it is optimal to clean up old files:
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gmake histclean
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gmake
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To use histograms, at least one of the AIDA implementations should be
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available (see http://aida.freehep.org).
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8a - PI
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A package including AIDA and extended interfaces also using Python is PI,
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available from: http://cern.ch/pi
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Once installed PI or PI-Lite in a specified local area $MYPY, it is required
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to add the installation path to $PATH, i.e. for example, for release 1.2.1 of
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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 running the example the command should be issued:
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eval `aida-config --runtime csh`
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8b - OpenScientist
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OpenScientist is available at http://OpenScientist.lal.in2p3.fr.
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You have to "setup" the OpenScientist AIDA implementation before compiling
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(then with G4ANALYSIS_USE set) and running your Geant4 application.
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On UNIX you setup, with a csh flavoured shell :
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csh> source <<OpenScientist install path>/aida-setup.csh
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or with a sh flavoured shell :
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sh> . <<OpenScientist install path>/aida-setup.sh
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On Windows :
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DOS> call <<OpenScientist install path>/aida-setup.bat
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You can use various file formats for writing (AIDA-XML, hbook, root).
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These formats are readable by the Lab onx interactive program
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or the OpenPAW application. See the web pages.
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With OpenPAW, on a run.hbook file, one can view the histograms
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with something like :
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OS> opaw
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opaw> h/file 1 run.hbook ( or opaw> h/file 1 run.aida or run.root)
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opaw> zone 2 2
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opaw> h/plot 1
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opaw> h/plot 2
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