$Id: README,v 1.2 2000/12/06 16:53:12 flongo Exp $
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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gammaray_telescope
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F.Longo, R.Giannitrapani & G.Santin
December 2000
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Acknowledgments to GEANT4 people, in particular to R.Nartallo,
A.Pfeiffer, M.G.Pia and G.Cosmo
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GammaRayTel is an example of application of Geant4 in a space
envinronment. It simulates a typical telescope for gamma ray analysis;
the detector setup is composed by a tracker made with silicon planes,
subdivided in ladders and strips, a CsI calorimeter and an
anticoincidence system. In this version, only the tracker is made
sensitive; the hits on the tracker strips are registered and relevant
information (energy deposition, position etc) are dumped to an external
ASCII file for subsequent analysis. If Lizard is available on the user
platform, than some histograms with relevant hits information are
displayed and saved as PostScript files.
The main features of this example are
a) Macros for the visualization of geometry and tracks with
OpenGL, VRML and DAWN drivers
b) Implementation of messengers to change some parameters of
the detector geometry, the particle generator and the analysis
manager (if present) runtime
c) Readout geometry mechanism to describe an high number of
subdivisions of the planes of the tracker (strips) without
affecting in a relevant way the simulation performances
d) Histogramming for Linux and Solaris platform via the
Lizard system (tested on Linux platform); this is a preliminary
feature of GEANT4, so expect some changes and/or improvements in
future releases
e) User interfaces via Xmotif or normal terminal provided
1. Setting up the environment variables
---------------------------------------
- Setup for Visualization
IMPORTANT: be sure that your Geant4 installation has been done
with the proper visualization drivers; for details please see the
file geant4/source/visualization/README.
To use the visualization drivers set the following variables in
your local environment:
setenv G4VIS_USE_OPENGLX 1 # OpenGL visualization
setenv G4VIS_USE_DAWNFILE 1 # DAWN file
setenv G4VIS_USE_VRMLFILE 1 # VRML file
setenv G4VRMLFILE_VIEWER vrmlview # If installed
- Setup for Xmotif user interface
setenv G4UI_USE_XM 1
- Set up for analysis using Lizard
IMPORTANT: be sure that your G4 installation has been done properly;
in particular be sure that the following environment variables are
set prior to build the library (this is working only on Linux and
Solaris platform)
setenv G4ANALYSIS_BUILD 1 # Build the analysis tools
setenv G4ANALYSIS_BUILD_LIZARD 1 # Build the Lizard interface
setenv LIZARDROOT /usr/local/freeLizard/3.2.0 #get correct path
For example at CERN the path is
setenv LIZARDROOT /afs/cern.ch/project/asddat/lhcxx/3.2.0/freeLizard/3.2.0
To compile the GammaRayTel example with the analysis tools activated,
set the following variables
setenv G4ANALYSIS_USE 1 # Use the analysis tools
setenv G4ANALYSIS_USE_LIZARD 1 # Use the Lizard one
and be sure to have the right path to the Lizard library
#add to the LD_LIBRARY_PATH (get correct path)
setenv LD_LIBRARY_PATH /usr/local/freeLizard/3.2.0/Linux/lib
For example at CERN the path is
setenv LD_LIBRARY_PATH /afs/cern.ch/project/asddat/lhcxx/3.2.0/freeLizard/3.2.0/Linux/lib
2. Sample run
-------------
To run a sample simulation with gamma tracks interacting with
the detector in its standard configuration and without any
visualization, execute the following command in the example main
directory:
$G4WORKDIR/bin/$G4SYSTEM/GammaRayTel
It is possible also to run three different configuration defined in
macro1.mac, macro2.mac and macro3.mac for visualization (OpenGL, VRML
and DAWN respectively) with the following command
$G4WORKDIR/bin/$G4SYSTEM/GammaRayTel macroX.mac
where X can be 1, 2 or 3. Be sure to have the right environment (see
the preceding section) and the proper visualization driver enabled in
your local G4 installation (see geant4/source/visualization/README for
more information).
3. Detector description
-----------------------
The detector is defined in GammaRayTelDetectorConstruction.cc
It is composed of a Payload with three main detectors, a Tracker (TKR), a
Calorimeter (CAL) and an Anticoincidence system (ACD).
The standard configuration is made of a TKR of 15 Layers of Si detectors,
with Lead converter, and a CAL of 8 layers of CsI. 4 lateral panels and a
top layer of plastic scintillator (ACT and ACL) complete the configuration.
The Si detectors are composed of two silicon planes subdivided in strips
aligned along the X axis in one plane and along the Y axis for the other.
It is possible to modify in some way this configuration using the
commands defined in GammaRayTelDetectorMessenger.
This feature is available in the UI throught the commands subtree
"/payload/" (see the help command in the UI for more information).
4. Physics processes
--------------------
This example uses the standard Electromagnetic processes.
5. Particle Generator
---------------------
The GammaRayTelParticleGenerationAction and its Messenger let the user define
the incident flux of particles, from a specific direction or from an
isotropic background. The user can define also between two spectral options:
monochromatic or with a power-law dependence. The particle
generator parameters are accessible throught the UI tree "/gun/" (use the
UI help for more information). We are planning to include, in the next
release of this example, the new General Particle Source module of G4.
6. ReadOutGeometry
------------------
The tracker is made of Silicon Microstrips detectors. The ReadOut geometry
provides the description of the strips.
7. Hit
------
In this version only the hits from the TKR are recorded. Each hit
contains the following information
a) ID of the event (this is important for multiple events run)
b) Energy deposition of the particle in the strip (keV)
c) Number of the strip
d) Number of the plane
e) Type of the plane (1=X 0=Y)
f) Position of the hit (x,y,z) in the reference frame of the payload
The hit information are saved on an ASCII file named Tracks_N.dat, where
N is the progressive ID number associated to the run.
8. Histogramming
----------------
Some hits information can be visualized runtime using Lizard (if it is
available on the user platform); two 2D histograms and two 1D histograms
can be visualized and saved (as PostScript files) during the simulation
run. The 2D histograms contain the hits positions on the TKR projected on
the XZ plane and the YZ plane; the 1D histograms contain the energy
deposition in the last X plane of the TKR and the hits distribution along
the X planes of the TKR (note that this histograms have been chosen more
for pedagogical motivation than for physical one).
These histograms are filled and updated at every event and are initialized
with each new run; the scale of the histograms is automatically derived from
the detector geometry.
Throught a messenger it is possible to set some options with
the UI subtree "/analysis/" (use the UI help for more info); in particular
it is possible to enable or disable the drawing of the 1D and 2D histograms
at every event and to enable or disable the saving of PostScript files at the
end of each run. If you feel that the simulation is too slow with the
histograms updated every event, you can disable the drawing and retain
the saving. Please note that the updating of the histograms is triggered
only when there is some hit in an event.
In this example we only show the use of very basic feature of this new
simulation/analysis framework; histogramming and analysis in Geant4
are in an evolving phase, so expect some changes and/or improvements
for next releases.
9. Classes Overview
-------------------
This is the overview of the classes defined in this example
GammaRayTelPrimaryGeneratorAction
User action for primaries generator
GammaRayTelPrimaryGeneratorMessenger
Messenger for interactive particle generator
parameters modification via the User Interface
GammaRayTelPhysicsList
Determination of particles and processes active in this
example
GammaRayTelTelVisManager
Visualization manager class
GammaRayTelDetectorConstruction
Geometry and material definitions for the detector
GammaRayTelDetectorMessenger
Messenger for interactive geometry parameters
modification via the User Interface
GammaRayTelAnalysisManager
Analysis manager class with Lizard tool (experimental)
GammaRayTelAnalysisMessenger
Messenger for interactive analysis options modification
via the User Interface
GammaRayTelRunAction
User run action class
GammaRayTelEventAction
User event action class
GammaRayTelPayloadHit
Description of the hits on the tracker
GammaRayTelPayloadROGeometry
Description of the readout geometry for strips subdivision
GammaRayTelPayloadSD
Description of the sensitive detector
Gabriele Cosmo