Gabriele Cosmo
165 lines
6.2 KiB
Plaintext
165 lines
6.2 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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Hadr07
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------
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Survey energy deposition and particle's flux from an hadronic cascade.
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Use PhysicsConstructor objects rather than predefined G4 PhysicsLists.
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Show how to plot a depth dose profile in a rectangular box.
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1- MATERIALS AND 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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A minimum of 4 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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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 absorber is surrounded by a World volume (vacuum)
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A function, and its associated UI command, allows to build a material
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directly from a single isotope.
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The default geometry is built in DetectorConstruction, but the above parameters
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can be changed interactively via commands defined in DetectorMessenger.
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To be identified by the ThermalScattering module, the elements composing a
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material must have a specific name (see G4ParticleHPThermalScatteringNames.cc)
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Examples of such materials are build in Hadr06/src/DetectorConstruction.
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2- PHYSICS LIST
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"Full" set of physics processes are registered, but via PhysicsConstructor
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objects rather than complete pre-defined G4 physics lists. This alternative
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way gives more freedom to register physics.
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Physics constructors are either constructors provided in Geant4 (with G4 prefix)
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or 'local'. They include : HadronElastic, HadronInelastic, IonsInelastic, GammaNuclear,
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RadioactiveDecay and Electomagnetic.
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(see geant4/source/physics_lists/constructors)
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HadronElasticPhysicsHP include a model for thermalized neutrons, under the control of a command
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defined in NeutronHPMesseger.
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GammmaNuclearPhysics is a subset of G4BertiniElectroNuclearBuilder.
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ElectromagneticPhysics is a simplified version of G4EmStandardPhysics.
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In perticular, no step constraint is imposed for energy loss mechanism (ionisation and brems).
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This is enough when spatial distribution of deposited energy do not need
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to be accurate (see param->SetStepFunction(1., 1*mm)).
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Several hadronic physics options are controlled by environment variables.
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To select them, see Hadr07.cc
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3- 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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4- PHYSICS
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The program computes the energy deposited in each absorber,
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and the flux of particles emerging in the world.
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Processes invoked and particles generated are listed.
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5- HISTOGRAMS
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The test has several built-in 1D histograms, which are managed by
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G4AnalysisManager and its Messenger. The histos can be individually
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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, etc..)
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(see the macros xxxx.mac).
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1 "total energy deposited in absorber 1
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2 "total energy deposited in absorber 2
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...........................................
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9 "total energy deposited in absorber 9
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10 "Edep (MeV/mm) profile along absorbers"
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One can control the name of the histograms file with the command:
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/analysis/setFileName name (default Hadr07)
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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 Hadr07)
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6- TRACKING and STEP MAX
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Hadr07 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 (histogram 10).
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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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histogram 10.
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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, via a physicsConstructor object (a builder).
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StepMax is evaluated in 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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7- 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 tracks are drawn at the end of event, and erased at the end of run.
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gamma green
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neutron yellow
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negative particles (e-, ...) red
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positive particles (e+, ions, ...) blue
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8- HOW TO START ?
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Execute Hadr07 in 'batch' mode from macro files :
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% Hadr07 run1.mac
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Execute Hadr07 in 'interactive mode' with visualization :
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% Hadr07
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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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- Na22.mac: multilayers. Radioactive source
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- alpha.mac: alpha (400 MeV). Limit the step size from histo 10
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- ionC12.mac: C12 (2.4 GeV). Limit the step size from histo 10
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- water.mac: e- (4 MeV) in Water
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Macros to be run interactively:
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- proton.mac: proton (1 GeV). Multilayers
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- vis.mac: To activate visualization
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