$Id: README,v 1.16 2009/10/25 19:06:26 maire Exp $
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     =========================================================
     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                            fanoCavity
                            ----------

    This program computes the dose deposited in an ionization chamber by a
    monoenergetic photon beam.
    The geometry of the chamber satisfies the conditions of charged particle
    equilibrium. Hence, under idealized conditions, the ratio of the dose 
    deposited over the beam energy fluence must be equal to the 
    mass_energy_transfer coefficient of the wall material.
    
    E.Poon and al, Phys. Med. Biol. 50 (2005) 681
    I.Kawrakow, Med. Phys. 27-3 (2000) 499
	
 1- GEOMETRY
 
    The chamber is modelized as a cylinder with a cavity in it.
     	
    6 parameters define the geometry :
      - the material of the wall of the chamber
      - the radius of the chamber and the thickness of the wall
      - the material of the cavity
      - the radius and the thickness of the cavity

    Wall and cavity must be made of the same material, but with different
    density	 	
 	
    All above parameters can be redifined via the UI commands built in 
    DetectorMessenger class
    
			-----------------
			|		|
			| wall 		|    
			|     -----	|
			|     |   | 	|      
	   		|     | <-+-----+--- cavity     
	     ------>	|     |   | 	|
	     ------>	|     |   | 	|
	beam	-------------------------------- cylinder axis
	     ------>	|     |   | 	|
	     ------>	|     |   | 	|
			|     |   | 	|
			|     |   | 	|
			|     -----	|			
			|		|
			|		|
			-----------------
			
 2- BEAM
  
    Monoenergetic incident photon beam is uniformly distribued, perpendicular 
    to the flat end of the chamber. The beam radius can be controled with an
    UI command built in PrimaryGeneratorMessenger; the default is full wall 
    chamber radius.
    
    Beam regeneration : after each Compton interaction, the scattered photon is
    reset to its initial state, energy and direction. Consequently, interaction
    sites are uniformly distribued within the wall material.
    
    This modification must be done in the ParticleChange of the final state 
    of the Compton scattering interaction. Therefore, a specific model
    (MyKleinNishinaCompton) is assigned to the ComptonScattering process in
    PhysicsList. MyKleinNishinaCompton inherites from G4KleinNishinaCompton;
    only the function SampleSecondaries() is overwritten.
    
 3- PURPOSE OF THE PROGRAM
    
    The program computes the dose deposited in the cavity and the ratio
    Dose/Beam_energy_fluence. This ratio is compared to the mass_energy_transfer
    coefficient of the wall material.
    
    The mass_energy_transfer coefficient needs :
    	- the photon total cross section, which is read from the PhysicsTables
	by G4EmCalculator (see EndOfRunAction).
	- the average kinetic energy of charged secondaries generated in the
	wall during the run. 
 
    The program needs high statistic to reach precision on the computed dose.
    The UI command /testem/event/printModulo allows to survey the convergence of
    the kineticEnergy and dose calculations.
    
    In addition, to increase the program efficiency, the secondary particles
    which have no chance to reach the cavity are immediately killed (see
    StackinAction). This feature can be switched off by an UI command (see
    StackingMessenger).
    
    The simplest way to study the effect of e- tracking parameters on dose 
    deposition is to use the command /testem/stepMax.
    	 			 	
 4- PHYSICS
 
    The physics lists contains the standard electromagnetic processes, with few 
    modifications listed here.
    
    - Compton scattering : as explained above, the final state is modified in
    MyKleinNishinaCompton class.
    
    In order to make the program more efficient, one can increase the Compton
    cross section via the function SetCSFactor(factor) and its 
    associated UI command. Default is factor=1000.
    
    - Bremsstrahlung : Fano conditions imply no energy transfer via
    bremsstrahlung radiation. Therefore this process is not registered in the
    physics list. However, it is always possible to include it.
    See PhysListEmStandard class.
    
    - Ionisation : In order to have same stopping power in wall and cavity, one
    must cancel the density correction term in the dedx formula. This is done in
    a specific MollerBhabha model (MyMollerBhabhaModel) which inherites from 
    G4MollerBhabhaModel.
    
    To prevent explicit generation of delta-rays, the default production
    threshold (i.e. cut) is set to 10 km (CSDA condition).
    
    The finalRange of the step function is set to 10 um, which more on less
    correspond to a tracking cut in water of about 20 keV. See emOptions.
    Once again, the above parameters can be controled via UI commands.
    
    - Multiple scattering : is switched in single Coulomb scattering mode near
    boundaries. This is selected via EM options in PhysicsList, and can be
    controled with UI commands.
    
    - All PhysicsTables are built with 100 bins per decade.  
     	
 5- HISTOGRAMS
 
   fanoCavity has several predefined 1D histograms : 
  
      1 : emission point of e+-
      2 : energy spectrum of e+-
      3 : theta distribution of e+-
      4 : emission point of e+- hitting cavity
      5 : energy spectrum of e+- when entering in cavity
      6 : theta distribution of e+- before enter in cavity
      7 : theta distribution of e+- at first step in cavity      
      8 : track segment of e+- in cavity
      9 : step size of e+- in wall
     10 : step size of e+- in cavity
     11 : energy deposit in cavity per track     
      
   The histograms are managed by the HistoManager class and its Messenger. 
   The histos can be individually activated with the command :
   /testem/histo/setHisto id nbBins  valMin valMax unit 
   where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
   
   One can control the name of the histograms file with the command:
   /testem/histo/setFileName  name  (default fanoCavity)
   
   It is possible to choose the format of the histogram file (hbook, root, XML)
   with the command /testem/histo/setFileType (root by default)
   
   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 fanocavity)
           
   Note that, by default, histograms are disabled. To activate them, uncomment
   the flag G4ANALYSIS_USE in GNUmakefile.
 	
 6- HOW TO START ?
 
 	- compile and link to generate an executable
 		% cd geant4/examples/extended/medical/fanoCavity
 		% gmake
 		
 	- execute fanoCavity in 'batch' mode from macro files
 		% fanoCavity   run01.mac
 		
 	- execute fanoCavity in 'interactive mode' with visualization
 		% fanoCavity
 		....
 		Idle> type your commands
 		....
 		Idle> exit
		 
 7- USING HISTOGRAMS

  To use histograms, at least one of the AIDA implementations should be 
  available. See InstallAida.txt
  
