$Id: README,v 1.4 2008/09/26 20:26:01 maire Exp $
-------------------------------------------------------------------

     =========================================================
     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
     =========================================================

                            TestEm18
                            --------
    This example allows to study the energy lost by a charged particle in a
    single layer, due to ionization and bremsstrahlung. Results are compared to
    'reference' values.
	
 1- GEOMETRY DEFINITION
 
    It is a single box of homogeneous medium.
    Two parameters define the geometry :
 	- the material of the box,
	- the (full) size of the box.
 	
    The default geometry (1 cm of water) is constructed in DetectorConstruction,
    but the above parameters can be changed interactively via the commands
    defined in DetectorMessenger.
 	
 2- PHYSICS
 
    The physics list contains the 'standard' electromagnetic processes.
    However the MultipleScattering is not registered, in order to focuse on
    fluctuations due to energy loss alone.
	 	 
 3- BEAM
 
    The primary kinematic is a single particle starting at the edge
    of the box. The type of the particle and its energy are set in 
    PrimaryGeneratorAction (e- 10 MeV), and can be changed via the G4 
    build-in commands of ParticleGun class.
 	
 4- RUN
 
    During the tracking of the incident particle, the secondary particles 
    are immediately killed, after that their energy has been registered
    (see StackingAction).
    Therefore, we study here the total energy lost by the incident particle,
    not the energy deposited in a layer of finite thickness.
    
    At EndOfRun, the above results are compared with 'reference' values,
    i.e. the values read from EnergyLoss tables.

 5- HISTOGRAMS
         
    The test contains 6 built-in 1D histograms, which are managed by the
    HistoManager class and its Messenger.
    
         1  continuous energy loss along primary track
         2  energy from secondaries
         3  total energy lost by primary track (1+2)
         4  energy spectrum of e-+
         5  energy spectrum of gamma
	 6  step size of primary track
	
    The histos can be activated individually with the command :
    /testem/histo/setHisto id nbBins valMin valMax unit
    where 'unit' is the desired unit for the histo (MeV or KeV, cm or mm, etc..)
								  
    One can control the name and the type of the histograms file with 
    the commands:
    /testem/histo/setFileName  name  (default testem18)
    /testem/histo/setFileType  name  (default root)
   
    It is also possible to print selected histograms on an ascii file:
    /testem/histo/printHisto id
    All selected histos will be written on a file name.ascii  (default testem18) 

    Note that, by default, histograms are disabled. To activate them, uncomment
    the flag G4ANALYSIS_USE in GNUmakefile. 	
 	 				
 6- 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.
	
 7- HOW TO START ?
 
    compile and link to generate an executable
 	% cd geant4/examples/extended/electromagnetic/TestEm18
 	% gmake
 		
    execute TestEm18 in 'batch' mode from macro files :
 	% TestEm18   electron.mac.mac
 		
    execute TestEm18 in 'interactive mode' with visualization :
 	% TestEm18
	Idle> control/execute vis.mac
 	....
 	Idle> type your commands
 	....
 	Idle> exit

 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.
  
    Before compilation of the example it is optimal to clean up old files:
  	gmake histclean
  	gmake
	 
    To use histograms, at least one of the AIDA implementations should be 
    available. See InstallAida.txt
  
