Gabriele Cosmo
161 lines
4.8 KiB
Plaintext
161 lines
4.8 KiB
Plaintext
$Id: README,v 1.13 2005/11/30 19:58:30 santin Exp $
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-------------------------------------------------------------------
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=========================================================
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Geant4 - X-Ray Telescope Example
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=========================================================
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NEW: May 2004: Migration to AIDA 3.2.1 - see below
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Introduction
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------------
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XrayTel is an advanced Geant4 example based on a realistic simulation of
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an X-ray Telescope. It is based on work carried out by a team of Geant4
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experts to simulate the interaction between X-ray Telescopes XMM-Newton
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and Chandra with low energy protons present in the orbital radiation
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background. The X-ray mirrors are designed to collect x-ray photons at
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grazing-incidence angles and focus them onto detectors at the focal plane.
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However, this mechanism also seems to work for low energy protons which,
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if they reach the detectors in sufficient numbers, can cause damage.
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In this example, the geometry has been simplified by using a single mirror
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shell and no baffles, but all the dimensions and materials are realistic.
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The aim of this advanced example is to illustrate the use advanced
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GUI, visualisation, particle generation and analysis schemes available
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in Geant4:
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- the simulation can be run from GAG or the command prompt
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- macros are provided to display the geometry and particle tracks with
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OpenGL, DAWN Postscript or VRML visualisation
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- the generation of particles is done via the new General Particle Source
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- histograming facilities are available through the AIDA 3.0 interfaces.
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- on-line visualisation of histograms is provided through the AIDA 3.0 interface.
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In order to be able to use any of these packages, prior installation is
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necessary and a number of environment variables will have to be set.
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1. Setting up the environment variables for GAG, Visualisation and
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Analysis options (example based on Linux at CERN)
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#set up GAG
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setenv G4UI_BUILD_GAG_SESSION 1
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setenv G4UI_USE_GAG 1
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#set up VRMLview
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setenv G4VIS_USE_VRML 1
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setenv G4VRMLFILE_MAX_FILE_NUM 100
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setenv G4VRMLFILE_VIEWER vrmlview #if installed
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setenv G4VIS_USE_VRML 1
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setenv PATH ${PATH}:"/afs/cern.ch/sw/contrib/VRML/bin/Linux" # example at CERN
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#set up OpenGL
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setenv G4VIS_BUILD_OPENGLX_DRIVER 1
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setenv G4VIS_USE_OPENGLX 1
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#set up DAWN
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setenv G4VIS_BUILD_DAWN_DRIVER 1
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setenv G4VIS_USE_DAWN 1
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NOTE: The geometry is refreshed on the viewer at the beginning of each run,
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but the tracks are plotted only in case an interesting event occurs.
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This is the case only for about 1 every 10**4 events.
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Sources
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-------
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GAG can be found in:
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geant4/environments/MOMO
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DAWN can be obtained from:
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http://geant4.kek.jp/~tanaka/
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VRMLview for Linux can be obtained from:
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http://www.sim.no
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2. Run
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To execute a sample simulation with visualisation of proton tracks
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reaching the detector run:
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XrayTel
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execute command "/control/execute xxxxx.mac"
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visualisation macros provided are
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- opengl.mac for OpenGL display
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- vrml.mac for VRML display and output file
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- dawn.mac for dawn display and PS output file
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To execute a run without visualisation use
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- test.mac
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If the analysis options are set, histograming windows will
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automatically open and the corresponding files will be created.
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A 1D histogram will display the energy distribution of the protons
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that reach the detector at the end of the run.
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3. Detector description
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The telescope and detector geometry is defined in
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XrayTelDetectorConstruction.cc
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4. Physics processes
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The physics processes are in XrayTelPhysicsList.cc
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The main process in this example is MultipleScattering of the protons
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on the mirror surfaces.
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5. Event generation
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This is done using the new General Particle Source. Documentation for
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this can be found in:
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http://reat.space.qinetiq.com/gps/
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6. Analysis
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In case the variable G4ANALYSIS_USE is set:
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setenv G4ANALYSIS_USE 1
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relevant information from the simulation is processed in the XrayTelAnalysis
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class and saved, through the AIDA interface, to Histograms and Tuples.
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Compilation and link flags to hook any AIDA compliant system are passed
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to the Geant4 GNUmakefile system by using the "aida-config" tool
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that should come with any AIDA compliant system.
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Specifically in the GNUmakefile you find the 2 lines:
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CPPFLAGS += `aida-config --include`
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LDFLAGS += `aida-config --lib`
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For more information about AIDA and PI please look at:
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http://aida.freehep.org/
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http://www.cern.ch/PI
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Presently, the tools
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- PI (http://cern.ch/pi)
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- OpenScientist (http://openscientist.lal.in2p3.fr/)
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- JAS (http://jas.freehep.org/jas3/)
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provide an implementation of AIDA 3.2.1
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To build and execute the example on platforms where there is no
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implementation of the analysis system, the environment variables
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must not be set.
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