source: trunk/examples/advanced/gammaray_telescope/README

$Id: README,v 1.21 2005/06/03 13:22:25 flongo Exp $
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     =========================================================
     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
     =========================================================

                            gammaray_telescope
                            ------------------
                     F.Longo, R.Giannitrapani & G.Santin
                     June 2003

--------------------------------------------------------------
Acknowledgments to GEANT4 people, in particular to R.Nartallo, 
A.Pfeiffer, M.G.Pia and G.Cosmo 
--------------------------------------------------------------

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, the three detectors are made
sensitive but only 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 the user has set up the 
AIDA (version 3.0 or compatible) environment or Anaphe/Lizard is available, 
then some histograms with relevant hits information are displayed 
and saved as PostScript files, and histograms and ntuples with
relevant information are stored on a HBOOK file.

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) Histograming facilities are presently provided for the Linux 
     environment either by using the AIDA interfaces, or through 
     the Anaphe/Lizard system. 

  e) User interfaces via Xmotif or normal terminal provided

  
1. Setting up the environment variables
---------------------------------------

 - Setup for storing ASCII data 

  If you want to store the output data in an ASCII file 'Tracks_x.dat'
  where x stays for the run number. You should specify the environment 
  variable:

  setenv G4STORE_DATA 1

 - 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 AIDA3.2.1 and PI1.3.3

  To compile the GammaRayTel example with the analysis tools activated, 
  set the following variables 

  setenv G4ANALYSIS_USE               1 # Use the analysis tools

  Users can download the analysis tools from:  
  > http://aida.freehep.org/
  > http://www.cern.ch/PI   

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 2 views made of
 4*4 Si single sided silicon detectors with Lead converter, and a CAL of 
 5 layers of CsI, each made of 2 views of 12 CsI bars orthogonally posed.
 4 lateral panels and a top layer of plastic scintillator (ACL and ACT) 
 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.

 The following baseline configuration is adopted:
 
 GEOMETRICAL PARAMETER                  VALUE

 Converter thickness                    300 microns  
 Silicon Thickness                      400 microns
 Silicon Tile Size XY                   9   cm
 Silicon Pitch                          200.micrometer 
 Views Distance                         1.  mm
 CAL Bar Thickness                      1.5 cm
 ACD Thickness                          1.  cm

 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 a modular physics list, with a sample of Hadronic processes 
 (see the web page http://cmsdoc.cern.ch/~hpw/GHAD/HomePage/ for more adeguate
 physics lists), the Standard or the LowEnergy 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. In the first case particles are generated on a spherical 
 surface which diameter is perpendicular to the arrival direction. In the second
 case the arrival directions are isotropic.

 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
 releases of this example, the 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 the hits from the TKR the CAL and the ACD are generated. 
 Only the hit from the TRK are saved. Each TKR 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. Analysis
----------------

 The analysis part of GammaRayTel is based on the AIDA interfaces and their
 implementation in Anaphe; please look at their documentation for more details.
 Keep in mind that the actual implementation of the analysis tools in GammaRayTel
 is of a pedagogical nature, so we kept it as simple as possible. 

 The actual analysis produces some histograms (see next section) and an ntuple. 
 Both the histograms and the ntuple are saved at the end of the run in the file 
 "gammaraytel.hbook". You can than analyze offline the contents of such a file; 
 the GammaRayTel contains also a very simple python script that can be used with 
 Lizard to plot the histograms  See the Lizard documentation on how to access 
 the ntuple.
 Please note that in a multiple run session, the last run always override the 
 hbook file.

9. Histogramming
----------------

 Some hits information can be visualized runtime using the Anaphe Plotter 
 (if it is available on the user platform); two 1D histograms can be 
 visualized during the simulation run. 

 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 again that these 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); 
 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.

10. Digi
--------

 For the TKR also the digits corresponding to the Hits are generated. 
 A digi is generated when the hit energy deposit is greater than a threshold 
 (in this example setted at 120 keV). 
 The TKR digi information are stored on the same file Tracks_N.dat and contain:

  a) ID of the event (this is important for multiple events run)
  b) Number of the strip 
  c) Number of the plane
  d) Type of the plane (1=X  0=Y)

11. 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 modular physics classes

  GammaRayTelGeneralPhysics
        Decay processes

  GammaRayTelEMPhysics
        Std and LowE physics processes (for gamma & e-/e+)

  GammaRayTelMuonPhysics
        Muon & its processes

  GammaRayTelIonPhysics
        Ions and their processes

  GammaRayTelHadronPhysics
        Sample of hadronic processes

  GammaRayTelTelVisManager
        Visualization manager class

  GammaRayTelDetectorConstruction
        Geometry and material definitions for the detector
        
  GammaRayTelDetectorMessenger
        Messenger for interactive geometry parameters 
        modification via the User Interface
        
  GammaRayTelAnalysis
        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

  GammaRayTelTrackerHit
        Description of the hits on the tracker

  GammaRayTelDigi
        Description of the digi on the tracker

  GammaRayTelDigitizer
        Description of the digitizer for the tracker

  GammaRayTelTrackerROGeometry
        Description of the readout geometry for strips subdivision

  GammaRayTelTrackerSD
        Description of the TKR sensitive detector

  GammaRayTelAnticoincidenceHit
        Description of the hits on the anticoincidence

  GammaRayTelAnticoincidenceSD
        Description of the ACD sensitive detector

  GammaRayTelCalorimeterHit
        Description of the hits on the calorimeter

  GammaRayTelCalorimeterSD
        Description of the CAL sensitive detector