Gabriele Cosmo
141 lines
5.7 KiB
Plaintext
141 lines
5.7 KiB
Plaintext
$Id: README 69174 2013-04-21 20:38:15Z maire $
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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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NeutronSource
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-------------
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NeutronSource is an example of neutrons production. It illustrates the cooperative work
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of nuclear reactions and radioactive decay processes.
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It survey energy deposition and particle's flux.
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It uses PhysicsConstructor objects.
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1- MATERIALS AND GEOMETRY DEFINITION
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The geometry is a cylinder (absorber) of an homogenous material (default : Beryllium oxide).
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This absorber is within a container (default : stainless-steel).
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Five parameters define the geometry :
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- the material of the absorber
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- the radius and length of the absorber
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- the material of the container
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- the thickness of the container
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The default geometry is built in DetectorConstruction, but the above
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parameters can be changed interactively via commands defined in DetectorMessenger.
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The container is surrounded by a World volume (air)
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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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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 DetectorConstruction of Hadr04,06,07.
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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 trigger them, an envHadronic.csh has been added in this example.
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One must select the options wished, and do
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source envHadronic.csh (or sh)
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3- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic is a single particle uniformly shooted within the absorber.
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The type of the particle and its energy are set in PrimaryGeneratorAction (Am241, at rest),
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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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4- PHYSICS
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The program computes and plots energy deposited in the interaction volume
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(absorber + container) and the flux of particles leaving this volume.
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Processes invoked and particles generated during hadronic cascade are listed.
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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. 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 deposit"
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2 "dummy"
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3 "total kinetic energy flow"
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4 "energy spectrum of emerging gamma"
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5 "energy spectrum of emerging e+-"
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6 "energy spectrum of emerging neutrons"
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7 "energy spectrum of emerging protons"
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8 "energy spectrum of emerging deuterons"
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9 "energy spectrum of emerging alphas"
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10 "energy spectrum of all others emerging ions"
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11 "energy spectrum of all others emerging baryons"
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12 "energy spectrum of all others emerging mesons"
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13 "energy spectrum of all others emerging leptons (neutrinos)"
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The histograms are managed by the HistoManager class and its Messenger.
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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 NeutronSource)
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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 NeutronSource)
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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 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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7- HOW TO START ?
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Execute NeutronSource in 'batch' mode from macro files :
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% NeutronSource run1.mac
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Execute NeutronSource in 'interactive mode' with visualization :
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% NeutronSource
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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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