$Id: README,v 1.10 2008/10/24 16:12:26 maire Exp $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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TestEm11
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How to plot a depth dose profile in a rectangular box.
1- GEOMETRY DEFINITION
The geometry consists of a single block of an homogenous material.
Optionally, the block can be divided in thinner layers (replica)
4 parameters define the geometry :
- the material of the box,
- the thickness of the box (sizeX),
- the tranverse dimension of the box (sizeYZ).
- the number of layers (nbOfLayers)
In addition a transverse uniform magnetic field can be applied.
The default geometry is constructed in DetectorConstruction class,
but all of the above parameters can be changed interactively via
the commands defined in the DetectorMessenger class.
2- PHYSICS LIST
Physics lists can be local (eg. in this example) or from G4 kernel
physics_lists subdirectory.
Local physics lists:
- "standard" standard EM physics with current 'best' options setting.
these options are explicited in PhysListEmStandard
- "livermore" low-energy EM physics using Livermore data
- "penelope" low-energy EM physics implementing Penelope models
Physics lists and options can be (re)set with UI commands
Please, notice that options set through G4EmProcessOPtions are global, eg
for all particle types. In G4 builders, it is shown how to set options per
particle type.
3- AN EVENT : THE PRIMARY GENERATOR
The primary kinematic consists of a single particle starting at the
left face of the box. The type of the particle and its energy are set
in the PrimaryGeneratorAction class, and can be changed via the G4
build-in commands of ParticleGun class (see the macros provided with
this example).
In addition one can choose randomly the impact point of the incident
particle. The corresponding interactive command is built in
PrimaryGeneratorMessenger class.
A RUN is a set of events.
4- VISUALIZATION
The Visualization Manager is set in the main().
The initialisation of the drawing is done via the commands
/vis/... in the macro vis.mac. To get visualisation:
> /control/execute vis.mac
The detector has a default view which is a longitudinal view of the
box.
The tracks are drawn at the end of event, and erased at the end of run.
Optionaly one can choose to draw all particles, only the charged one,
or none. This command is defined in EventActionMessenger class.
5- HOW TO START ?
- compile and link to generate an executable
% cd geant4/examples/extended/electromagnetic/TestEm1
% gmake
- execute TestEm11 in 'batch' mode from macro files
% TestEm11 run01.mac
- execute TestEm11 in 'interactive mode' with visualization
% TestEm11
....
Idle> type your commands
....
Idle> exit
6- TRACKING and STEP MAX
Testem11 computes the total energy deposited along the trajectory of
the incident particle : the so-called longitudinal energy profile,
or depth dose distribution.
The energy deposited (edep) is randomly distribued along the step (see
SteppingAction).
In order to control the accuracy of the deposition, the maximum step size
of charged particles is computed automatically from the binning of
histogram 1 and 8 (see HistoManager).
As an example, this limitation is implemented as a 'full' process :
see StepMax class and its Messenger. The 'StepMax process' is registered
in the Physics List.
In RunAction::BeginOfRun() the stepMax value is passed from the
HistoManager to the StepMax process.
A boolean UI command allows to desactivate this mechanism.
7- HISTOGRAMS
Testem11 has several predefined 1D histograms :
1 : longitudinal energy profile (in MeV/mm and per event)
2 : total energy deposited in the absorber
3 : total track length of the primary track
4 : step size of the primary track
5 : projected range of the primary track
6 : total track length of charged secondary tracks
7 : step size of charged secondary tracks
8 : longitudinal energy profile (in MeV.cm2/g), as a function of x/r0
where r0 is the range of the primary particle
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 testem11)
It is possible to choose the format of the histogram file (hbook, root, XML)
with the command /testem/histo/setFileType (root 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 testem11)
Note that, by default, histograms are disabled. To activate them, uncomment
the flag G4ANALYSIS_USE in GNUmakefile.
8- USING HISTOGRAMS
To use histograms, at least one of the AIDA implementations should be
available. See InstallAida.txt
Gabriele Cosmo