$Id: README,v 1.11 2004/05/29 10:02:08 mantero Exp $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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xray_fluorescence
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XrayFluo is an advanced Geant4 example based on a realistic simulation of
a test beam.
The aim of the test beam was to characterize the response function of various
X-Rays detectors used to measure fluorescence emissions from samples composed
of different materials irradiated with a monochromatic beam of photons.
In this example the geometry of the detector is simplified:
one single pixel is used, since the test beams has used monolithic detectors.
The response function is tabulated for different values of incident
energy and stored in the file response.dat and SILIresponse.dat.
At the moment, two kinds of detectors are available: HPGe and Si(Li).
The sample, a simple box whose material can be selected, can be irradiated
with different particles, with different spectra for the incident energy and
with different shapes of the primary generator.
Apart from the sample and the detector there are two diaphragm reproducing
those used to collimate the incident beam during the test beam.
Other two geometries are present for the user: an infinte-plane geometry and
a planetary one, with the status of "beta release". The user must select,
at the moment of the execution, which geometry wants to use.
If the program is executed in batch mode, it is possible to specify
geometry from command line. Example:
/path/XrayFluo macro.mac 1 (for test beam Geometry)
/path/XrayFluo macro.mac 2 (for infinite plane Geometry)
The aim of this advanced example is to illustrate the use of particle
generation and analysis schemes available in Geant4:
- the generation of particles is done via the G4ParticleGun: the example
shows how to use it in order to obtain a beam of circular section or
a particle source isotropic in space
- the example includes the possibility to shoot particles according to a
given energy spectrum: the files B_flare.dat, C_Flare.dat and M_flare.dat
store the spectra of photons during solar flares, the files
mercury2_flx_solmax.dat and mercury_flx_solmin.dat contain the spectra of
protons respectively during solar maximum and solar minimum conditions, and
merc2_flx_alp_max.dat merc_flx_alp_min.dat contain the spectra of alpha
particles again respectively during solar maximum and solar minimum
conditions.
- histograming facilities are presently provided for the Linux environment
by using the AIDA3 interfaces.
The AIDA compliant version has not been tested by the developers and is
here as a example of "forward compatibility" on how to use analysis.
In order to be able to use any of these packages, prior installation is
necessary and a number of environment variables will have to be set.
#set up VRMLview
setenv G4VRMLFILE_MAX_FILE_NUM 100
setenv G4VRMLFILE_VIEWER vrmlview #if installed
setenv PATH ${PATH}:"/afs/cern.ch/sw/contrib/VRML/bin/Linux"
#set up OpenGL or Mesa
setenv G4VIS_BUILD_OPENGLX_DRIVER 1
setenv G4VIS_USE_OPENGLX 1
setenv OGLHOME /afs/cern.ch/sw/geant4/dev/Mesa/Linux-g++
#set up DAWN
setenv G4VIS_BUILD_DAWN_DRIVER 1
setenv G4VIS_USE_DAWN 1
setenv PATH ${PATH}:"/afs/cern.ch/sw/geant4/dev/DAWN/Linux-g++"
# flag that we want to use analysis:
setenv G4ANALYSIS_USE 1
#select AIDA implementation: PI 1.2.1 (for cern AFS)
setenv G4ANALYSIS_BUILD 1
setenv PI_VERSION 1_2_1
setenv PATH ${PATH}:"/afs/cern.ch/sw/geant4/dev/PI/Linux-g++/bin"
eval `aida-config -r csh`
#path to the lowEnergy data base
setenv G4LEDATA /afs/cern.ch/sw/geant4/dev/data/G4EMLOW2.3
#path to Xray_Fluorescence data files, if not set, PWD is assumed:
setenv XRAYDATA /afs/cern.ch/user/u/username
1. Run
To execute a sample simulation with visualisation of tracks
reaching the detector run:
XrayFluo
execute command "/control/execute xxxxx.mac"
If the analysis options are set, histograms will
automatically stored in the corresponding files (hbook or XML)
2. Detector description
The telescope and detector geometry is defined in
XrayFluoDetectorConstruction.cc
3. Detector peculiar properties are described in XrayFluoSiLiDetectorType and
XrayFluoHPGeDetectorType, both derived from XrayFluoVDetectorType. Other
detector types can be added, creating other implementations of
XrayFluoVDetectorType objects.
Detector type selection is made in XrayFluoDetectorConstruction, and can be
modified trough /apparate/detector command of the UI.
Other commands (apparate/sample /apparate/sampleGranularity
/apparate/GrainDiameter) are present to simulate sample granulosity:
grains are spheres, disposed in a compact cubic structure, i.e superipmposition
of planes of maximum density with ABC ABC path. The fundamental cell is of type
cubic with centered-faces.
4. Physics processes
The physics processes are in XrayFluoPhysicsList.cc
The main process in this example is fluorescence emission from the sample.
5. Event generation
This is done using the G4ParticleGun with some modifications. See
XrayFluoParticleGeneratorAction.cc
6. Analysis
At present the analisys is provided by any AIDA-3.2.1 compliant analysis system.
In the example the Anaphe toolkit is used.
AIDA / Anaphe configuration for compilation and link are in GNUmakefile, once
is set the environmente as above:
ifdef G4ANALYSIS_USE
CPPFLAGS += `aida-config --include`
LDFLAGS += `aida-config --lib`
endif
To build and execute the example on platforms where there is no
implementation of the analysis system, the environment variables
must not be set.
It is possible to visualize the outpu of the simulation. In order to do this
is necessary to uncomment all lines in XrayFluoAnalysisManager.cc / .hh regarding plotting;
and the same must be done for plotting refernces in XrayFluoRunManager.cc and XrayFluoEventAction.cc.
And link against other AIDA compliant analysis sistems, such as Anaphe or JAS.
Finally, by setting visPlotter variable in XrayFluoAnalysisManager to true,
it is possible to display the simulated output of the detector while
simulation is in progress. Graph window is updated every 100000 events.
The example provides also a simple Python file used to display
histograms with Lizard 3.0.0.x (from Anaphe)
Various commads, with help, are available for Geant4 UI.
/analysis/outputFile and /analysis/fileType respectively for
changing the name and the type (xml or Hbook) of the file in wich results
are saved.
If these commends are used, to make the changes effective, another
command, /anaysis/update, must be executed.
NOTE: if a file named xrayfluo.hbk (default name) is present, it
will be deleted, even if /analysis/outputFile command is issued
before any run.
Gabriele Cosmo