source: trunk/examples/advanced/xray_fluorescence/README@ 850

$Id: README,v 1.14 2005/12/09 22:15:52 mantero Exp $
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     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                            xray_fluorescence
                            -----------------
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.

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 to configure you environment to get visulaization, as described in geant4 manual.
If we want to use analisys, we provide an example for the use of PI:

# flag that we want to use analysis:
setenv G4ANALYSIS_USE               1

#select AIDA implementation: PI 1.3.3

setenv G4ANALYSIS_BUILD  1

setenv PI_VERSION 1_3_3
setenv PATH /your/path/to/PI/app/releases/PI/PI_1_3_0/slc3_ia32_gcc323/bin/:${PATH}
eval `aida-config -r csh`

#path to the lowEnergy data base

setenv G4LEDATA /your/path/to/geant4/data/G4EMLOW3.0

#path to Xray_Fluorescence data files, if not set, PWD is assumed:

setenv XRAYDATA /path/to/detector/and/input/spctra/files

1. Run
After the compilation of the program, to execute a sample simulation type (for example):

$G4WORKDIR/bin/Linux-g++/XrayFluo 

The program gives, at tis point,the user 4 options:

Please Select Simulation Geometrical Set-Up:
1 - Test Beam
2 - Infinite Plane
3 - Planet and Sun
4 - Phase-Space Production

The first three choices are to choose different experimental set-ups 
(a test beam one, an infite plane and a planetary geometry), while 
the fourth is a simplified version of the first, without a detector, 
only to generate a tuple with particles genereted or exiting the sample.

In order to run a macro, type the following command:

idle> execute command "/control/execute xxxxx.mac"

If the analysis options are set, histograms will
automatically stored in the corresponding files (hbook or XML)

In order to launch the application in batch mode, it is necessary to specify, 
after the executable file name, the name of the macro file and the number of the choice:

$G4WORKDIR/bin/Linux-g++/XrayFluo xxxxx.mac 1

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

Event generation is controlled by commands in the /gun/category (see help for further details).
In this readme only two commands are undrlined: 

- /gun/loadGunData <filename>: to be used with the setup #1, loads the ntuple created 
        in the setup #4. The loaded particles will be generated and will be directed 
        ALL OF THEM to the detector. This can be useful to perform detector studies 
        with encreased efiiciency.

- /gun/loadRayleighFlag <true/false> This is used to let the user decide if backscattered 
        primary particles should be loaded and directed toward the detector. This command, 
        in order to be useful, must be used BEFORE the previous one.

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 implementation 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`
 LOADLIBS += `aida-config --lib`
endif

To build and execute the example on platforms where there is no
implementation of the analysis system, the environment variable
G4ANALYSIS_USE must not be set.

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 1000 events. 

The example provides also a simple Python file (readPY) used to display
histograms with the python interface of PI. This must be run after the 
configuration script config.csh and the python interpreter.

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.