$Id: README,v 1.16 2004/06/23 11:30:51 maire Exp $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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TestEm2
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This example allows to do the shower development of an single primary
particle, and to survey the physics processes which occur,
with printing and visualization.
1- GEOMETRY DEFINITION
The geometry consists of a cylinder of homegenous material.
This cylinder is replicated longitudinaly (slice) and radialy (ring).
The default geometry is constructed in DetectorConstruction class,
but all of the above parameters can be modified interactively via
the commands defined in the DetectorMessenger class.
Material can be choosen: Air Water lAr Al Fe BGO PbWO4 Pb.
eg: /testem/det/setMat PbWO4
The size of the slices and rings are expressed in radiation length units
and can be changed.
eg: /testem/det/setLbin 20 1. ---> 20 slices of 1. radl
/testem/det/setRbin 5 0.25 ---> 5 rings of 0.25 radl
/testem/det/update ---> rebuild the geometry
An uniform magnetic field along the cylinder axis can be set.
eg: /testem/det/setField 5 tesla
2- PHYSICS LISTS
Modular PhysicsList are used. The following modules can be activated:
1. "standard" - (alternative) standard EM physics
2. "g4v52" - (alternative) standard EM physics version G4 5.2
3. "high_energy" - add high energy processes
To activate a specific module the UI command can be used:
"/testem/phys/addPhysics title"
By default "standard" module is loaded.
3- AN EVENT : THE PRIMARY GENERATOR
The primary kinematic consists of a single particle which hits the
cylinder 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).
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. In interactive session:
PreInit or Idle > /control/execute vis.mac
The detector has a default view which is a longitudinal view of the
cylinder.
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- PHYSICS DEMO
The particle's type and the physic processes which will be available
in this example are set in PhysicsList class.
In addition a build-in interactive command (/process/inactivate proname)
allows to activate/inactivate the processes one by one.
The threshold for producing secondaries can be changed.
eg: /testem/phys/setCuts 100 microm
/run/initialize
6- HOW TO START ?
- compile and link to generate an executable
% cd TestEm2
% gmake
- execute TestEm2 in 'batch' mode from macro files
% TestEm2 run01.mac
- execute TestEm2 in 'interactive mode' with visualization
% TestEm2
....
Idle> type your commands
....
Idle> exit
7- HISTOGRAMS
TestEm2 produces several histograms:
Content of these histo:
1 : energy deposit per event
2 : charged track length per event
3 : neutral track length per event
4 : longitudinal energy profile
5 : cumulated longitudinal energy profile
6 : rms of cumulated longitudinal energy profile
7 : gamma's flux
8 : positron's flux
9 : electron's flux
10 : radial energy profile
11 : cumulated radial energy profile
12 : rms of cumulated radial energy profile
Note that, by default, histograms are disabled. To activate them, uncomment
the flag G4ANALYSIS_USE in GNUmakefile. To define the output file name with
histograms and the type of these file the following UI commands can be used:
"/testem/histo/fileName name"
"/testem/histo/fileType type"
The following types are available: "hbook", "XML", "root"
By default the name is "testem2.paw" and the type "hbook".
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