$Id: README,v 1.7 2004/06/23 11:29:50 maire Exp $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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TestEm7
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This example is devoted to the energy deposited by particles which
are absorbed in a given material (Bragg peak).
Also it computes the dose deposited in small 'test volumes' called tallies.
In addition, it illustrates how to use the concept of 'process' in order
to implement a constraint on the step size of the particle trajectories.
1- GEOMETRY DEFINITION
The geometry consists of a single block of a homogenous material,
placed in a world.
Three parameters define the geometry :
- the material of the box,
- the thickness of the box (sizeX),
- the tranverse dimension of the box (sizeYZ).
The default is 20 cm of water.
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.
The size, matter, positions of several test-volumes (tallies) can be
defined via UI commands : /testem/det/tally...
2- PHYSICS LIST
Physics Lists are subdivided on 4 following modules:
1. "particles" - particle definitions
2. "general" - decays and transportation
3. "standard" (alternative) - standard EM physics
4. "model" (alternative) - standard EM physics using model approach
Notice that there is an example of definition of a static ion : IonC12
(see PhysListParticle.cc) and an example of use : ionC12.mac
3- AN EVENT : THE PRIMARY GENERATOR
The primary kinematic consists of a single particle which hits the
block perpendicular to the input face. The type of the particle
and its energy are set in the PrimaryGeneratorAction class, and can
changed via the G4 build-in commands of ParticleGun class (see
the macros provided with this example).
The default is proton 160 MeV
In addition one can define 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 command
> /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/TestEm7
% gmake
- execute Test in 'batch' mode from macro files
% TestEm7 run01.mac
- execute Test in 'interactive mode' with visualization
% TestEm7
....
Idle> type your commands
....
Idle> exit
6- HISTOGRAM OF THE BRAGG PEAK
Testem7 computes the total energy deposited along the trajectory of
the incident particle : the so-called Bragg peak.
In order to control the accuracy of the deposition, the user can limit
the maximum allowed for the step size of charged particles.
(command /testem/stepMax )
The result is a 1D histogram which is the total energy deposited along
the trajectory of the incident particle.
The histogram is saved in paw (testem7.paw)
The bin size is egal to stepMax. The number of bins is determined by
the thickness of the absorber (with a minimum of 100 bins).
The total energy deposited is plotted in MeV/mm.
Note that, by default, histograms are disabled. To activate them, uncomment
G4ANALYSIS_USE in GNUmakefile.
7- DOSE IN 'TEST-VOLUMES'
The energy deposited in the test-volumes (tallies) defined in
DetectorConstruction are printed at EndOfRun, both in MeV and gray.
Notice that the doses are not re initialized between runs, i.e. they are
cumulative over the runs. (idem for the histogram of the Bragg peak.)
8- Using histograms
-------------------
By default the histograms are not activated. To activate histograms
the environment variable G4ANALYSIS_USE should be defined. For instance
uncomment the flag G4ANALYSIS_USE in GNUmakefile.
To use histograms any of implementations of AIDA interfaces should
be available (see http://aida.freehep.org).
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 compilation of the example it is optimal to clean up old
files:
gmake histclean
gmake
Before running the example the command should be issued:
eval `aida-config --runtime csh`
It is possible to choose the format of the output file with
histograms using UI command:
/testem/histo/setFileType type
The following types are available: hbook, root, xml.
Gabriele Cosmo