Gabriele Cosmo
154 lines
5.8 KiB
Plaintext
154 lines
5.8 KiB
Plaintext
$Id: README,v 1.6 2009-08-29 08:48:30 maire Exp $
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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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amsEcal
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-------
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1- GEOMETRY DEFINITION
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AMS Ecal calorimeter is described in the joined documument : ams_ecal.pdf
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- A single layer is a plane of scintillating fibers within a box of
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absorber material.
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- Single layers are positionned (eg. placement) within Module
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(called SuperLayer in the descriptive document),
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alternatively with a relative offset of +- 0.25*distanceInterFibers.
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- Modules are positionned within calorimeter, alternatively rotated of
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90 deg around beam axis (X_axis).
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Therefore all fibers are along Y_axis or Z_axis calorimeter.
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The default geometry is constructed in DetectorConstruction class.
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In addition a transverse uniform magnetic field can be applied.
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2- PHYSICS LISTS
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Physics lists can be local (eg. in this example) or from G4 kernel
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physics_lists subdirectory.
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- "emstandard_local standard EM physics with current 'default' options.
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These options are explicited in PhysListEmStandard
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From geant4/source/physics_lists/builders:
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- "emstandard_opt0" standard EM physics with all default options
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- "emstandard_opt1" best CPU performance standard physics for LHC
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- "emstandard_opt2"
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- "emstandard_opt3"
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Physics lists and options can be (re)set with UI commands
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Please, notice that options set through G4EmProcessOPtions are global, eg
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for all particle types. In G4 builders, it is shown how to set options per
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particle type.
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3- PRIMARY GENERATOR : mono-energetic pencil beam
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The primary kinematic is a single particle which hits the calorimeter
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perpendicular to the input face (eg. along X_axis).
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The type of particle and its energy are set in the PrimaryGeneratorAction,
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and can be changed via the G4 build-in commands of ParticleGun class
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(see the macros provided with this example).
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One can choose randomly the tranverse position of the incident particle,
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eg. the width of the beam. The associated interactive command is built
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in PrimaryGeneratorMessenger.
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4- DETECTOR RESPONSE
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The program computes the 'visible' energy, eg. the energy deposited
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in scintillating fibers. The fibers are packed in pixels.
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It also computes the total energy deposited per pixel, either in absorber
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material or in scintillator material.
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The list of pixels fired are written event per event, on an ascii file.
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The file is created at RunAction::BeginOfRun() and filled at EndOfEvent();
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See EventAction::WritePixels() and the format description : eventFormat.txt
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There is also the command /ams/event/writePixels (true/false)
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NB: visible energy can be corrected for Birk's attenuation:
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see the function SteppingAction::BirksAttenuation() (not activated)
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5- HISTOGRAMS and NTUPLE
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The Program contains 5 built-in 1D histograms, managed by HistoManager class
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and its Messenger. These histograms can be activated individually
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with the command :
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/ams/histo/setHisto id nbBins valMin valMax unit
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where unit is the desired unit for the histo (MeV, keV, etc..)
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(see the macros xxxx.mac).
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1 total visible energy in calorimeter (eg. summed all pixels)
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2 total deposit energy in calorimeter (eg. summed all pixels)
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3 visible energy per subModule (eg. longitudinal profile)
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4 deposit energy per subModule (eg. longitudinal profile)
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5 nb of radiation length seen by geantino
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Histograms can be viewed using ROOT or PAW. See below the note on AIDA.
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One can control the name and format of the histograms file with the command:
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/ams/histo/setFileName name (default ecal)
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/ams/histo/setFileType type (choice: hbook, root(default), XML)
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It is also possible to print selected histograms on an ascii file:
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/ams/histo/printHisto id
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All selected histos will be written on a file name.ascii (default ecal)
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An Ntuple is also predefined. It contains energies, visible and total,
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per subModule and per event.
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The Ntuple is activated with the command: /ams/histo/setNtuple 1
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Note that, by default, histograms are disabled. To activate them, uncomment
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the flag G4ANALYSIS_USE in GNUmakefile.
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Before compilation of the example it is optimal to clean up old files:
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gmake histclean
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gmake
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6- VISUALIZATION
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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. In interactive session:
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PreInit or Idle > /control/execute vis.mac
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Default view is a longitudinal view of the calorimeter.
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Tracks are drawn at end of event, and erased at end of run.
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Optionaly one can choose to draw all particles, only charged one, or none.
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This command is defined in EventActionMessenger.
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7- HOW TO START ?
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- compile and link to generate an executable
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% cd amsEcal
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% gmake
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- execute amsEcal in 'batch' mode from macro files
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% amsEcal run1.mac
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- execute amsEcal in 'interactive mode' with visualization
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% amsEcal
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....
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Idle> type your commands. For instance:
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Idle> /control/execute run1.mac
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....
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Idle> exit
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8- HANDLE RANDOM NUMBER SEEDS
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The macro rndmSeed.mac shows how to create a set a random number seeds.
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Here we save the seed at begin of each run (the number of events per run
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is arbitrary). The seeds are stored in subdirectory random.
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Macro run2.mac shows how to start a run from one of these seeds.
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9- USING HISTOGRAMS
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To use histograms, at least one of the AIDA implementations should be
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available. See InstallAida.txt
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