Gabriele Cosmo
81 lines
2.7 KiB
Plaintext
81 lines
2.7 KiB
Plaintext
$Id: README 66241 2012-12-13 18:34:42Z gunter $
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-------------------------------------------------------------------
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=========================================================
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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=========================================================
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TestEm13
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--------
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How to compute cross sections from the transmition coefficient
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( see below, item Physics).
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1- GEOMETRY DEFINITION
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It is a single box representing a layer of finite thickness of
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homogeneous material.
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Two parameters define the geometry :
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- the material of the box,
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- the (full) size of the box.
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The default geometry (1 cm of water) is constructed in
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DetectorConstruction, but the above parameters can be changed
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interactively via the commands defined in DetectorMessenger.
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2- PHYSICS LIST
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The physics list contains the standard electromagnetic processes.
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In order not to introduce 'artificial' constraints on the step size, the
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multiple scattering is not instanciated, and all processes are
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registered as discrete : there is no continuous energy loss.
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3- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle starting at the edge
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of the box. The type of the particle and its energy are set in
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PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4
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build-in commands of ParticleGun class (see the macros provided with
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this example).
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4- PHYSICS
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An event is killed at the first step of the incident paticle.
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Either the particle has interacted or is transmitted through the layer.
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The cross section, also called absorption coefficient, is computed from
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the rate of unaltered transmitted incident particles.
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The result is compared with the 'input' data, i.e. with the cross
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sections stored in the PhysicsTables and used by Geant4.
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A set of macros defining various run conditions are provided.
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The processes are actived/inactived in order to survey the processes
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individually.
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6- VISUALIZATION
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The Visualization Manager is set in the main().
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The initialisation of the drawing is done via the commands
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/vis/... in the macro vis.mac. To get visualisation:
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> /control/execute vis.mac
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The detector has a default view which is a longitudinal view of the
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box.
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The tracks are drawn at the end of event, and erased at the end of run.
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7- HOW TO START ?
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execute TestEm13 in 'batch' mode from macro files :
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% TestEm13 compt.mac
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execute TestEm13 in 'interactive mode' with visualization :
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% TestEm13
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Idle> control/execute vis.mac
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....
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Idle> type your commands
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....
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Idle> exit
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