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

                            ExUCN
                            -----
                       Peter Gumplinger
                  TRIUMF, Vancouver, Canada

This example exhibits the functionality of UCN physics


 1- GEOMETRY DEFINITION

     The geometry consists of a single hollow pipe (cylinder)
     placed in a world.

     Default World Size: G4Box - 1m x 1m x 100m

     The pipe wall is made of G4_Ni while the world and, hence,
     the inside of the pipe is made from G4_Galactic

     The G4UCNMaterialPropertiesTable properties are:

     "REFLECTIVITY" = 1
     "DIFFUSION" = 0.1
     "FERMIPOT" = 252.0 neV
     "SPINFLIP"= 0.
     "LOSS" = 12.5e-5
     "LOSSCS" = 0.
     "ABSCS"= 4.49    // 1/v loss cross-section  at room temp.
     "SCATCS" = 18.5  // (incoherent) "elastic" scattering cross-section

     The MicroRoughnessParameters are:

     Roughness correlation length w = 30nm
     Surface roughness b = 1nm
     # of angles theta_i in the look-up tables: 180
     # of energie bins in the look-up tables: 1000
     min. and max. values of theta_i: 0*degree and 90*degree
     min. and max values of Energy: 1neV and 1000neV
     # of angles theta_o in the look-up table calculation: 15
     # of angels phi_o   in the look-up table calculation: 15
     angular cut: 0.01*degree

     The default step limits in the vacuum is 1mm and maxTime is 100s

     The simulation is in a G4UniformGravityField

 2- PHYSICS LIST

    The ExUCNPhysicsList defines only G4Neutron, G4Proton, G4Electron,
    G4AntiNeutrinoE, G4MuonPlus, G4MuonMinus and G4GenericIon

    Through ExUCNExtraPhysics the following processes are instantiated:

    G4StepLimiter
    G4UserSpecialCuts

    and in ConstructUCN()

    G4UCNLoss
    G4UCNAbsorption
    G4UCNMultiScattering

 3- AN EVENT : THE PRIMARY GENERATOR

     The primary kinematic consists of a single ultra-colde neutron 
     (uniform between 1neV and 100neV from the origin uniform into 4pi

     A RUN is a set of events.


 4- VISUALIZATION

     The Visualization Manager is set in the main() for interactive session.
     The initialisation of the drawing is done via the command
       /control/execute vis.mac

 5- HOW TO START ?

   This example handles the program arguments in a new way.
   It can be run with the following optional arguments:
   % ExUCN [-m macro ] [-u UIsession] [-t nThreads]

   The -t option is available only in multi-threading mode
   and it allows the user to override the Geant4 default number of
   threads. The number of threads can be also set via G4FORCENUMBEROFTHREADS
   environment variable which has the top priority.

        - execute ExUCN in 'batch' mode from macro files e.g.
                % ExUCN -m ExUCN.in > ExUCN.out &

        - execute ExUCN in 'interactive' mode with visualization e.g.
                % ExUCN
                ....
                Idle> type your commands, for example:
                Idle> run/beamOn 1
                ....

 6- HISTOGRAMS

    - no histograms for now