Gabriele Cosmo
186 lines
7.7 KiB
Plaintext
186 lines
7.7 KiB
Plaintext
$Id: README 107962 2017-12-14 13:08:45Z 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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TestEm3
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-------
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How to collect energy deposition in a sampling calorimeter.
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How to survey energy flow.
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how to print stopping power.
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1- GEOMETRY DEFINITION
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The calorimeter is a box made of a given number of layers.
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A layer consists of a sequence of various absorbers (maximum MaxAbsor=9).
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The layer is replicated.
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Parameters defining the calorimeter :
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- the number of layers,
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- the number of absorbers within a layer,
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- the material of the absorbers,
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- the thickness of the absorbers,
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- the transverse size of the calorimeter (the input face is a square).
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In addition a transverse uniform magnetic field can be applied.
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The default geometry is constructed in DetectorConstruction class, but all
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of the above parameters can be modified interactively via the commands
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defined in the DetectorMessenger class.
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|<----layer 0---------->|<----layer 1---------->|<----layer 2---------->|
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==========================================================================
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|| abs 1 | abs 2 || abs 1 | abs 2 || abs 1 | abs 2 ||
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beam || | || | || | ||
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======> || | || | || | ||
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|| cell 1 | cell 2 || cell 3 | cell 4 || cell 5 | cell 6 ||
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==========================================================================
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^ ^ ^ ^ ^ ^ ^
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pln1 pln2 pln3 pln4 pln5 pln6 pln7
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NB. The number of absorbers and the number of layers can be set to 1.
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In this case we have a unique homogeneous block of matter, which looks like
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a bubble chamber rather than a calorimeter ...
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(see the macro emtutor.mac)
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2- PHYSICS LISTS
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Physics lists are based on modular design. Several modules are instantiated:
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1. Transportation
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2. EM physics
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3. Decays
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4. StepMax - for step limitation
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EM physics builders can be local (eg. in this example) or from G4 kernel
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physics_lists subdirectory.
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Local physics builders:
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- "local" standard EM physics with current 'best' options setting.
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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" recommended standard EM physics for LHC
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- "emstandard_opt1" best CPU performance standard physics for LHC
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- "emstandard_opt2" similar fast simulation
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- "emstandard_opt3" best standard EM options - analog to "local" above
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- "emstandard_opt4" best current advanced EM options standard + lowenergy
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- "emstandardWVI" standard EM physics and WentzelVI multiple scattering
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- "emstandardSS" standard EM physics and single scattering model
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- "emlivermore" low-energy EM physics using Livermore data
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- "empenelope" low-energy EM physics implementing Penelope models
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- "emlowenergy" low-energy EM physics implementing experimental
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low-energy models
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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- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle which hits the calorimeter
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perpendicular to the input face. The type of the particle and its energy are
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set in the PrimaryGeneratorAction class, and can be changed via the
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G4 build-in commands of G4ParticleGun class (see the macros provided with this
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example).
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In addition one can choose randomly the impact point of the incident particle.
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The corresponding interactive command is built in PrimaryGeneratorMessenger.
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A RUN is a set of events.
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TestEm3 computes the energy deposited per absorber and the energy flow through
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the calorimeter.
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4- VISUALIZATION
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The Visualization Manager is set in the main() (see TestEm3.cc).
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The 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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The default view is a longitudinal view of the calorimeter.
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The tracks are drawn at the end of event, and erased at the end of run.
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Optionally one can choose to draw all particles, only the charged ones, or
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none. This command is defined in EventActionMessenger class.
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5- PHYSICS DEMO
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The particle's type and the physics processes which will be available
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in this example are set in PhysicsList class.
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In addition a built-in interactive command (/process/inactivate processName)
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allows to activate/inactivate the processes one by one.
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Then one can well visualize the processes one by one, especially
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in the bubble chamber setup with a transverse magnetic field.
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As a homework try to visualize a gamma conversion alone,
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or the effect of the multiple scattering.
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Notice that one can control the maximum step size in each absorber, via the
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StepMax process and the command /testem/stepMax/absorber
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(see StepMax and PhysicsList classes)
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6- HOW TO START ?
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- Execute TestEm3 in 'batch' mode from macro files
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% TestEm3 run01.mac
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- Execute TestEm3 in 'interactive mode' with visualization
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% TestEm3
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....
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Idle> type your commands. For instance:
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Idle> /control/execute run01.mac
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....
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Idle> exit
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7- HISTOGRAMS
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Testem3 can produce histograms :
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histo 1 : energy deposit in absorber 1
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histo 2 : energy deposit in absorber 2
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...etc...........
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histo 11 : longitudinal profile of energy deposit in absorber 1 (MeV/event)
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histo 12 : longitudinal profile of energy deposit in absorber 2 (MeV/event)
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...etc...........
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histo 21 : energy flow (MeV/event)
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histo 22 : lateral energy leak (MeV/event)
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...etc...........
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NB. Numbering scheme for histograms:
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layer : from 1 to NbOfLayers (included)
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absorbers : from 1 to NbOfAbsor (included)
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planes : from 1 to NbOfLayers*NbOfAbsor + 1 (included)
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One can control the binning of the histo with the command:
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/analysis/h1/set idAbsor nbin Emin Emax unit
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where unit is the desired energy unit for that histo (see TestEm3.in).
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One can control the name of the histograms file with the command:
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/analysis/setFileName name (default testem3)
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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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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 testem3)
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