$Id: README,v 1.8 2007/11/12 18:19:30 maire Exp $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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fanoCavity2
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This program computes the dose deposited in an ionization chamber by an
extended (one dimensional) monoenergetic electron source.
The geometry of the chamber satisfies the conditions of charged particle
equilibrium. Hence, under idealized conditions, the ratio of the dose
deposited over the beam energy fluence must be equal to 1.
This variante of the Fano cavity test make use of an reciprocity theorem.
J.Sempau and P.Andreo, Phys. Med. Biol. 51 (2006) 3533
1- GEOMETRY
The chamber is modelized as a cylinder with a cavity in it.
5 parameters define the geometry :
- the radius of the chamber (must be big)
- the material of the wall
- the thickness of the wall
- the material of the cavity
- the thickness of the cavity
Wall and cavity must be made of the same material, but with different
density.
Radius must be bigger than range of electrons in cavity.
All above parameters can be redifined via the UI commands built in
DetectorMessenger class.
_________________
radius (infinite) | | | |
| | | |
| | | |
| | | |
| | <-+-----+--- cavity
| | | |
| | | |
---------------------------- cylinder axis = e- source
| | | |
| | | |
| | | |
|wall | |wall |
| | | |
| | | |
| | | |
-----------------
2- BEAM
Monoenergetic (E0) incident electron source is uniformly distribued along
cylinder axis, within wall and cavity, with constant lineic density
per mass: I.
An effective wall thickness is defined from the range of e- at energy E0.
Beam_energy_fluence is E0*I
3- PURPOSE OF THE PROGRAM
The program computes the dose deposited in the cavity and the ratio
Dose/Beam_energy_fluence. This ratio must be 1.
The program needs high statistic to reach precision on the computed dose.
The UI command /testem/event/printModulo allows to survey the convergence of
the dose calculation.
The simplest way to study the effect of e- tracking parameters on dose
deposition is to use the command /testem/stepMax.
4- PHYSICS
The physics list contains the standard electromagnetic processes, with few
modifications listed here.
- Bremsstrahlung : Fano conditions imply no energy transfer via
bremsstrahlung radiation. Therefore this process is not registered in the
physics list. However, it is always possible to include it via an UI
command. See PhysicsListMessenger class.
- Ionization : In order to have same stopping power in wall and cavity, one
must cancel the density correction term in the dedx formula. This is done in
a specific MollerBhabha model (MyMollerBhabhaModel) which inherites from
G4MollerBhabhaModel.
To prevent explicit generation of delta-rays, the default production
threshold (i.e. cut) is set to 10 km (CSDA condition).
The finalRange of the step function is set to 10 um, which more on less
correspond to a tracking cut in water of about 20 keV. See emOptions.
Once again, the above parameters can be controled via UI commands.
- Multiple scattering : is switched in single Coulomb scattering mode near
boundaries. This is selected via EM options in PhysicsList, and can be
controled with UI commands.
- All PhysicsTables are built with 100 bins per decade.
5- HISTOGRAMS
fanoCavity2 has several predefined 1D histograms :
1 : emission point of e+-
2 : energy spectrum of e+-
3 : theta distribution of e+-
4 : emission point of e+- hitting cavity
5 : energy spectrum of e+- when entering in cavity
6 : theta distribution of e+- before enter in cavity
7 : theta distribution of e+- at first step in cavity
8 : track segment of e+- in cavity
9 : step size of e+- in wall
10 : step size of e+- in cavity
11 : energy deposit in cavity per track
The histograms are managed by the HistoManager class and its Messenger.
The histos can be individually activated with the command :
/testem/histo/setHisto id nbBins valMin valMax unit
where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
One can control the name of the histograms file with the command:
/testem/histo/setFileName name (default fanoCavity)
It is possible to choose the format of the histogram file (hbook, root, XML)
with the command /testem/histo/setFileType (hbook by default)
It is also possible to print selected histograms on an ascii file:
/testem/histo/printHisto id
All selected histos will be written on a file name.ascii (default fanocavity2)
Note that, by default, histograms are disabled. To activate them, uncomment
the flag G4ANALYSIS_USE in GNUmakefile.
6- HOW TO START ?
- compile and link to generate an executable
% cd geant4/examples/extended/medical/fanoCavity2
% gmake
- execute fanoCavity2 in 'batch' mode from macro files
% fanoCavity2 run01.mac
- execute fanoCavity2 in 'interactive mode' with visualization
% fanoCavity2
....
Idle> type your commands
....
Idle> exit
7- USING HISTOGRAMS
To use histograms, at least one of the AIDA implementations should be
available (see http://aida.freehep.org).
8a - PI
A package including AIDA and extended interfaces also using Python is PI,
available from: http://cern.ch/pi
Once installed PI or PI-Lite in a specified local area $MYPY, it is required
to add the installation path to $PATH, i.e. for example, for release 1.2.1 of
PI:
setenv PATH ${PATH}:$MYPI/1.2.1/app/releases/PI/PI_1_2_1/rh73_gcc32/bin
CERN users can use the PATH to the LCG area on AFS.
Before running the example the command should be issued:
eval `aida-config --runtime csh`
8b - OpenScientist
OpenScientist is available at http://OpenScientist.lal.in2p3.fr.
You have to "setup" the OpenScientist AIDA implementation before compiling
(then with G4ANALYSIS_USE set) and running your Geant4 application.
On UNIX you setup, with a csh flavoured shell :
csh> source <<OpenScientist install path>/aida-setup.csh
or with a sh flavoured shell :
sh> . <<OpenScientist install path>/aida-setup.sh
On Windows :
DOS> call <<OpenScientist install path>/aida-setup.bat
You can use various file formats for writing (AIDA-XML, hbook, root).
These formats are readable by the Lab onx interactive program
or the OpenPAW application. See the web pages.
With OpenPAW, on a run.hbook file, one can view the histograms
with something like :
OS> opaw
opaw> h/file 1 run.hbook ( or opaw> h/file 1 run.aida or run.root)
opaw> zone 2 2
opaw> h/plot 1
opaw> h/plot 2
Gabriele Cosmo