Gabriele Cosmo
91 lines
3.3 KiB
Plaintext
91 lines
3.3 KiB
Plaintext
$Id: README 68024 2013-03-13 13:42:01Z gcosmo $
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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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GunGPS
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------
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This example compares G4particleGun and G4GeneralParticleSource (GPS) in 2 simple situations.
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1) point source, isotropic radiation, monoenergetic
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2) spherical surface source, isotropic radiation within the cavity, monoenergetic
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1- Geometry construction
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---------------------
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It is a simple box which represents an 'infinite' homogeneous medium.
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2- Physics list
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------------
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PhysicsList.cc defines only geantino and transportation process.
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3- Primary generators
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------------------
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There are 3 concrete primary generator action classes :
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PrimaryGeneratorGPS, PrimaryGeneratorGun1, PrimaryGeneratorGun2
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In main GunGPS.cc, select one of them before to compile.
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Each concrete generator action shoots geantinoes in a distribution decribed below.
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3.1- Point source, isotropic radiation
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---------------------------------
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Use PrimaryGeneratorGun1 with gun1.mac, or PrimaryGeneratorGPS with gps1.mac
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3.2- Spherical surface source, isotropic radiation within the cavity
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---------------------------------------------------------------
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Use PrimaryGeneratorGun2 with gun2.mac, or PrimaryGeneratorGPS with gps2.mac
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One wants to limit particle direction uniformly within (alphaMin, alphaMax).
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First, one generates momentum direction in the master frame (eg. World).
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Then, one rotates momentum in vertex_position frame, using rotateUz() function.
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RotateUz() transforms uz to ur. It is composition of two elementary rotations:
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theta around oy, then phi around oz (non commutative).
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Histograms 4,5 show particle direction in vertex_position frame.
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4- Visualisation
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-------------
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Visualization Manager is set in the main().
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Initialisation of the drawing is done via the commands
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/vis/.. in the macro vis.mac. This macro is automatically read from the main
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in case of interactive running mode.
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5- How to start ?
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--------------
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- execute GunGPS in 'batch' mode from macro files
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% GunGPS gun1.mac
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- execute GunGPS in 'interactive mode' with visualization
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% GunGPS
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....
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Idle> ---> type your commands. For instance:
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Idle> /control/execute gps0.mac
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Idle> /run/beamOn 10
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....
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Idle> exit
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6- Histograms
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----------
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GunGPS produces several 1D histograms which are saved as GunGPS.root by default.
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1: vertex posi: dN = f(radius)
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2: vertex posi: dN = f(costheta)
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3: vertex posi: dN = f(phi)
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4: particle dir in vertex frame: dN = f(cosalpha)
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5: particle dir in vertex frame: dN = f(psi)
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6: particle dir in master frame: dN = f(cosalphaM)
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7: particle dir in master frame: dN = f(psiM)
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The histograms are managed by the HistoManager class and its Messenger.
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The histos can be individually activated with the command :
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/analysis/h1/set id nbBins valMin valMax unit
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where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
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One can control the name of the histograms file with the command:
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/analysis/setFileName name (default GunGPS) |