$Id: README,v 1.4 2004/10/27 11:19:13 japost Exp $
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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.

	
 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.

 	In addition a transverse uniform magnetic field can be applied.
 	
 	The default geometry is constructed in DetectorConstruction class,
 	but all the parameters can be changed via
 	the commands defined in the DetectorMessenger 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 PrimaryGeneratorAction class, and can
 	be changed via the G4 build-in commands of ParticleGun class (see
 	the macros provided with this example).
 	
 	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 CalorHit 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), which means they can contribute to the hit.

 				
 4- PHYSICS DEMO
 
 	The particle's type and the physic processes which will be available
 	in this example are set in PhysicsList class.
 	
 	The  messenger classes introduce interactive commands . Using these
        commands the geometry of the detector, the data of the primary
        particle, etc. can be changed.
 	

 5- HOW TO START ?
 
 	- compile and link to generate an executable
 		% cd $G4INSTALL/example/extended/field/field03
 		% gmake
 		
 	- execute field03 in 'batch' mode from macro files e.g.
 		% $(G4INSTALL)/bin/$(G4SYSTEM)/field03 field03.in
		
 	- execute field03 in 'interactive' mode with visualization e.g.
 		% $(G4INSTALL)/bin/$(G4SYSTEM)/field03
		....
		Idle> type your commands
		....