Gabriele Cosmo
124 lines
4.9 KiB
Plaintext
124 lines
4.9 KiB
Plaintext
-------------------------------------------------------------------
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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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TestEm18
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--------
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This example allows to study the various contributions of the energy lost
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by a charged particle in a single layer of an homogeneous material.
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See any textbook of interactions of charged particles with matter, in particular :
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1- geant4.web.cern.ch --> UserSupport --> Physics Reference Manual
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2- lappweb.in2p3.fr/~maire/tutorials/index.html
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1- GEOMETRY DEFINITION
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It is a simple cubic box of 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 thickness of the box.
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The default geometry (1 cm of water) is constructed in DetectorConstruction,
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but the above parameters can be changed interactively via the commands
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defined in DetectorMessenger.
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2- PHYSICS
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The physics list contains the 'standard' electromagnetic processes.
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However the MultipleScattering is not registered, in order to focuse on
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fluctuations of to energy loss alone.
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3- BEAM
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The primary kinematic is 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 (e- 10 MeV), and can be changed via the G4
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build-in commands of ParticleGun class.
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4- RUN
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During the tracking of the incident particle, by default, the secondary
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particles are immediately killed, after that their energy has been registered
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(see SteppingAction and StackingAction).
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Therefore, we study here the various components of the total energy lost
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by the incident particle, not the energy deposited in a layer of finite
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thickness.
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With the option /testEm/trackSecondaries one can compute and plot the energy
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deposited in the layer. See edep.mac
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At EndOfRun, the above results are compared with 'reference' values,
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i.e. the input data read from EnergyLoss and Range tables.
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See reference 2 : Energy-Range relation, slide 4.
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5- HISTOGRAMS
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The test contains 13 built-in 1D histograms, which are managed by
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G4AnalysisManager and its Messenger.
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1 step size of primary track
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2 energy continuously deposited along primary track
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3 energy transfered to secondaries by ionisation
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4 energy transfered to secondaries by Bremsstrahlung
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5 energy transfered to secondaries by (e+,e-) production
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6 total energy transfered to secondaries
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7 total energy lost by primary track
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8 total energy lost by primary track from energy balance
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9 energy continuously deposited along secondary tracks
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10 total energy deposited
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11 energy spectrum of gamma
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12 energy spectrum of e-
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13 energy spectrum of e+
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The histograms are defined in HistoManager.
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The histos can be activated individually 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, cm or mm, 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 testem18)
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It is possible to choose the format of the histogram file : root (default),
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xml, csv, by using namespace in HistoManager.hh
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For convenience, few simple Root macros are provided : plotHisto.C pixe.C
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It is also possible to print selected histograms on an ascii file:
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/analysis/h1/setAscii id
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All selected histos will be written on a file name.ascii (default testem18)
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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 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 TestEm18 in 'batch' mode from macro files :
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% TestEm18 electron.mac
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execute TestEm18 in 'interactive mode' with visualization :
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% TestEm18
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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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Macros provided in this example:
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- csda.mac: test independance of user step max
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- edep.mac: track secondary particles and plot energy deposited
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- electron.mac: e- (10 MeV) on 1 cm of water
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- ion.mac: ion C12 (4 GeV) on 1 cm of water
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- muon.mac: mu+ (1 TeV) on 1 m of water
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- pixe.mac: proton (20 MeV) on 50 um of gold. Plot gamma pixe
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- proton.mac: proton (1 GeV) on 10 cm of water
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- plotHisto.C, pixe.C: Root macros
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Macros to be run interactively:
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- vis.mac: To activate visualization
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