Gabriele Cosmo
190 lines
7.4 KiB
Plaintext
190 lines
7.4 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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TestEm11
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--------
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How to plot a depth dose profile in a rectangular box.
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1- GEOMETRY DEFINITION
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The geometry consists of a stack of one or several blocks of homogenous
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material, called absorbers.
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Optionally, each absorber can be divided in thinner layers (replica)
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A minimum of 5 parameters define the geometry :
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- the number of absorbers (NbOfAbsor)
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- the material of each absorber,
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- the thickness of each absorber,
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- the tranverse dimension of the stack (sizeYZ),
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- the number of divisions of each absorber (NbOfDivisions)
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In addition a transverse uniform magnetic field can be applied.
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eg: /globalField/setValue 0 0 5 tesla
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The default geometry is constructed in DetectorConstruction class,
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but all of the above parameters can be changed interactively via
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the commands defined in the DetectorMessenger class.
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2- PHYSICS LIST
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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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The following options for EM physics using builders from physics_lists
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sub-package are available:
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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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- "emstandardGS" standard EM physics and Goudsmit-Saunderson multiple scatt.
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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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- "emstandardMP" standard EM physics where for e- a new model
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G4DiscreteScatteringModel is applied; for this model
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a data set G4GBFPDATA should be requested from EM group
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A local builder, PhysListEmStandard "local" (similar to opt3) is also
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available.
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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- ACTION INITIALIZATION
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A newly introduced class, ActionInitialization, instantiates and registers
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to Geant4 kernel all user action classes.
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While in sequential mode the action classes are instantiated just once,
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via invoking the method:
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ActionInitialization::Build()
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in multi-threading mode the same method is invoked for each thread worker
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and so all user action classes are defined thread-local.
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A run action class (if present) has to be instantiated both thread-local
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and global, which is why its instance has to be created also in the method
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ActionInitialization::BuildForMaster()
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which is invoked only in multi-threading mode.
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4- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle starting at the
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left face of the box. The type of the particle and its energy are set
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in the PrimaryGeneratorAction class, and can be changed via the G4
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build-in commands of G4ParticleGun class (see the macros provided with
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this example).
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In addition one can choose randomly the impact point of the incident
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particle. The corresponding interactive command is built in
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PrimaryGeneratorMessenger class.
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A RUN is a set of events.
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5- 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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Optionally one can choose to draw all particles, only the charged one,
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or none. This command is defined in EventActionMessenger class.
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6- HOW TO START ?
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- Execute TestEm11 in 'batch' mode from macro files
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% TestEm11 run01.mac
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- Execute TestEm11 in 'interactive mode' with visualization
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% TestEm11
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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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- alpha.mac: alpha (400 MeV) on water
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- ionC12.mac: ion C12 (2.4 GeV) on water
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- multiLayers.mac: gamma (6 MeV) on multi layers
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- radioactive.mac: radioactive ion on multi layers
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- range.mac: compute csda range of primary particle
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- run01.mac: e- (500 keV) on silicon. Step max from histo 1
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- run02.mac: e- (500 keV) on silicon. Step max from geometry
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- sandia.mac: to compare with Sandia data
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- water.mac: e- (4 MeV) on water. No constraint on tracking step
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Macros to be run interactively:
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- vis.mac: To activate visualization
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7- TRACKING and STEP MAX
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TestEm11 computes the distribution of energy deposited along the trajectory of
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the incident particle : the so-called longitudinal energy profile,
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or depth dose distribution.
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The energy deposited (edep) is randomly distribued along the step (see
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SteppingAction).
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In order to control the accuracy of the deposition, the maximum step size
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of charged particles is computed automatically from the binning of
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histograms 1 and 8 (see RunAction).
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As an example, this limitation is implemented as a 'full' process :
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see StepMax class and its Messenger. The 'StepMax process' is registered
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in the Physics List.
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StepMax is evaluated at RunAction::BeginOfRun(),
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and passed to the StepMax process.
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A boolean UI command allows to deactivate this mechanism.
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Another UI command allows to define directly a stepMax value.
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8- HISTOGRAMS
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TestEm11 has several predefined 1D histograms :
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1 : longitudinal energy profile (in MeV/mm and per event)
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2 : total energy deposited in all absorbers
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3 : total track length of the primary track
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4 : step size of the primary track
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5 : projected range of the primary track
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6 : total track length of charged secondary tracks
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7 : step size of charged secondary tracks
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8 : longitudinal energy profile (in MeV.cm2/g), as a function of x/r0
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where r0 is the range of the primary particle
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11 : energy deposited in absorber 1
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12 : energy deposited in absorber 2
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...etc........
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The histograms are managed by G4Analysis classes.
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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 testem11)
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It is possible to choose the format of the histogram file : root (default),
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hbook, 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 testem11)
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