$Id: README,v 1.11 2009-09-22 14:20:31 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 stack of one or several blocks of homogenous
material, called absorbers.
Optionally, each absorber can be divided in thinner layers (replica)
A minimum of 5 parameters define the geometry :
- the number of absorbers (NbOfAbsor)
- the material of each absorber,
- the thickness of each absorber,
- the tranverse dimension of the stack (sizeYZ),
- the number of divisions of each absorber (NbOfDivisions)
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:
- "local" standard EM physics with current 'best' options setting.
these options are explicited in PhysListEmStandard
From geant4/source/physics_lists/builders:
- "emstandard_opt0" recommended standard EM physics for LHC
- "emstandard_opt1" best CPU performance standard physics for LHC
- "emstandard_opt2"
- "emstandard_opt3" best current advanced EM options.
analog to "local" above
- "emlivermore" low-energy EM physics using Livermore data
- "empenelope" 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 ?
- 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 distribution of 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
histograms 1 and 8 (see RunAction).
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.
StepMax is evaluated at RunAction::BeginOfRun(),
and passed to the StepMax process.
A boolean UI command allows to desactivate this mechanism.
Another UI command allows to define directly a stepMax value.
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 G4Analysis classes.
The histos can be individually activated with the command :
/analysis/h1/set 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:
/analysis/setFileName name (default testem11)
It is possible to choose the format of the histogram file : root (default),
hbook, xml, csv, by using namespace in HistoManager.hh
It is also possible to print selected histograms on an ascii file:
/analysis/h1/setAscii id
All selected histos will be written on a file name.ascii (default testem11)
Using hbook format
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Need a special treatement : the Cern Library must be installed and the
environment variable CERNLIB correctly set. Then, *before* compiling,
activate G4_USE_HBOOK in GNUmakefile and g4hbook.hh in HistoManager.hh
Gabriele Cosmo