Gabriele Cosmo
141 lines
5.6 KiB
Plaintext
141 lines
5.6 KiB
Plaintext
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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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Extended Example for G4GeneralParticleSource (GPS)
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---------------------------------------
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exgps is created to demonstrate the usage of G4GeneralParticleSource for generating
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primary incident particle according to user defined distributions. These range from simple
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monocromatic point source to complicated mutiple sources with various biasing schemes.
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More detailed information on the usage of GPS are available on its home site:
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http://reat.space.qinetiq.com/gps
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1. GEOMETRY
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Simple geometry consists of a "Vacuum" world and, in it with two other components:
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- An alunimium box : 20 x 20 x 20 cm in size, cerntered at the origin.
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- A SiO2 sphere: 5 cm in radius and is placed in the centre of the aluminium box.
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2. PHYSICS
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Tranportation process only for all particles.
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3. EVENT:
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The event generator is the G4GeneralParticleSource (GPS). The instantiation of G4GeneralParticleSource
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is same as that for G4ParticleGun. See the exGPSPrimaryGeneratorAction.cc file for details .
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5. VISUALIZATION:
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Visualisation of the geometry and the tracks is possible with many of the G4 visualisation packages. An
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example of displaying the geometry and tracks using VRML is given in the macro file vis.mac.
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6. ANALYSIS:
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This example implements an AIDA-compliant analysis manager which creates histograms and ntuples.
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If user has an AIDA-compliant tool such as AIDAJNI, ANAPHE, OpenScientist or PI installed on his/her system. Some URLs :
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http://aida.freehep.org/
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http://java.freehep.org/aidajni
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http://www.cern.ch/PI
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http://OpenScientist.lal.in2p3.fr
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The analysis part of this example can be activated by doing a "source
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aida-setup" of the AIDA compliant tool (to activate the aida-config
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program) and by raising some environment variabless so that the
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G4 GNUmakefile system can take into account the AIDA tool.
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This can be done, for example on a UNIX under a csh like shell, with :
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csh> source <path_where_the_AIDA_tool_is_installed>/aida-setup.csh
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csh> aida-config # to check that this program is up and running
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G4 related part :
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csh> setenv G4ANALYSIS_USE 1
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csh> setenv G4ANALYSIS_AIDA_CONFIG_CFLAGS `aida-config --include`
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csh> setenv G4ANALYSIS_AIDA_CONFIG_LIBS `aida-config --lib`
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(It may be usefull to note that in the G4 GNUmakefile system,
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the upper variables are used in the file config/analysis.gmk).
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This needs to be done before building the executable.
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At the end of an excution, an xml file "exgps.aida" is created by default which contains
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histograms and ntuples. User can change the name and format of this output file with the commands
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/analysis/filetype new-type
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/analysis/fileName new-filename
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e.g.
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/analysis/filetype root
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/analysis/filename myfile.root
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these change the output file format to ROOT and output file name to "myfile.root". There are three file
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formats to choose from: xml, root or hbook.
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The output file conatins 6 histograms and one ntuple:
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histogram 1: The energy spectrum of the primary particles.
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histogram 2: 2d histogram of primary particle incident position distribution in the X-Y plane.
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histogram 3: 2d histogram of primary particle incident position distribution in the X-Z plane.
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histogram 4: 2d histogram of primary particle incident position distribution in the Y-Z plane.
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histogram 5: 2d histogram of primary particle incident angle distribution in terms of Phi/Cos(Theta).
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histogram 6: 2d histogram of primary particle incident angle distribution in terms of Phi/Theta.
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The binnings of the histograms can be changed with the UI commands avialable under the
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/analysis directory.
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In the ntuple the following data are recorded for each incident particle:
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Particle ID
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Incident Position (x,y,z);
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Incident Angle (theta,phi);
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Particle weight;
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7. GETTING STARTED:
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i) If you have an AIDA-compliant analysis package installed, then you should switch on the analysis
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part of the example by:
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setenv G4ANALYSIS_USE 1
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otherwise do
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unsetenv G4ANALYSIS_USE
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to remove the generation of an output file.
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ii) Build the exgps executable:
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cd to exgps
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gmake clean
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gmake
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gmake will create tmp and bin directories in your $G4TMP and $G4BIN directories.
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The executable, named exgps, will be created in the $G4BIN/$G4SYSTEM/ directory.
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iii) Run the executable:
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while in the exgps directory do
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$G4BIN/$G4SYSTEM/exgps exrgps.in
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If G4ANALYSIS_USE is defined, and dpends on the particular AIDA system used, e.g. JAIDA, one could see
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a display window of the six histograms. It may be neccessary to close the plotter window in order to
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terminate the execution. After the termination one will find the "exgps.aida", as well as a vrml file
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"g4_00.wrl" in the directory.
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8. FURTHER EXAMPLES of MACRO FILES:
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There are a number of g4mac files in the ./macros subdirectory, to show the various features of GPS.
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Most of them will lead to the creation of an aida file in the same name as the macro file.
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These aida files can be examed and analysed with an analysis tool such as JAS3.
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Please see the README file there for further information.
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