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     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                            field03
                            -------

    Example of tracking in magnetic field where field associated
    to selected logical volumes varies.

    A global and a local magnetic field are defined in the F03FieldSetup class,  which object
    is created in the ConstructSDandField() function in the F03DetectorConstruction
    class. The local magnetic field is set to the "Radiator" volume.
    The interactive commands are implemented in F03FieldMessenger.

	
 1- GEOMETRY DEFINITION
 
 	The "Absorber" is a solid made of a given material.                
 	
 	Three parameters define the absorber :
 	- the material of the absorber,
	- the thickness of an absorber,
 	- the transverse size of the absorber (the input face is a square). 
    
        The volume "World" contains the "Absorber". 
        In this test the parameters of the "World" can be changed , too.

    A transverse global uniform magnetic field can be applied.
 	In addition, the "Radiator" volume, which is placed in geometry next 
    to the absorber, has a local magnetic field.
 	
 	The default geometry is constructed in F03DetectorConstruction class,
 	but all the parameters can be changed via
 	the commands defined in the F03DetectorMessenger class.
 	
 2- AN EVENT : THE PRIMARY GENERATOR
 
 	The primary kinematic consists of a single particle which hits the
 	absorber perpendicular to the input face. The type of the particle
 	and its energy are set in the F03PrimaryGeneratorAction class, and can
 	be changed via the G4 build-in commands of G4ParticleGun class (see
 	the macros provided with this example).

    It is also possible to change the position of the primary particle vertex
    or activate its randomization via the commands defined in  the
    F01PrimaryGeneratorMessenger class.
 	
 	A RUN is a set of events.
 	
 3- DETECTOR RESPONSE
 
 	A HIT is a record, event per event , of all the 
 	informations needed to simulate and analyse the detector response.
 	
 	In this example a F03CalorHit is defined as a set of 2 informations:
 	- the total energy deposit in the absorber,
 	- the total tracklength of all charged particles in the absorber,  
 	
 	Therefore  the absorber is declared
 	'sensitive detector' (SD), see F03CalorimeterSD, which means they can contribute to the hit.
			
 4- PHYSICS LIST
 
     The particle's type and the physic processes which will be available
     in this example are set in the FTFP_BERT physics list. This physics list 
     requires data files for electromagnetic and hadronic processes.
     See more on installation of the datasets in Geant4 Installation Guide,     

 5- HOW TO START ?
 
 	- Execute field03 in 'batch' mode from macro files e.g.
 		% ./field03 field03.in
		
 	- Execute field03 in 'interactive' mode with visualization e.g.
 		% ./field03
		....
		Idle> /run/beamOn 1
		....
