173 lines
7.4 KiB
Plaintext
173 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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Example B1
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-----------
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This example demonstrates a very simple application where an energy
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deposit is accounted in user actions and their associated objects
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and a dose in a selected volume is calculated.
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1- GEOMETRY DEFINITION
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The geometry is constructed in the B1::DetectorConstruction class.
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The setup consists of a an envelope of box shape containing two
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volumes: a spherical cone and a trapezoid.
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In this example we use some common materials materials for medical
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applications. The envelope is made of water and the two inner volumes
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are made from tissue and bone materials.
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The materials are created with the help of the G4NistManager class,
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which allows to build a material from the NIST database using their
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names. All available materials can be found in the Geant4 User's Guide
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for Application Developers, Appendix 10: Geant4 Materials Database.
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2- PHYSICS LIST
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The particle's type and the physic processes which will be available
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in this example are set in the QBBC physics list. This physics list
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requires data files for electromagnetic and hadronic processes.
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See more on installation of the datasets in Geant4 Installation Guide,
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Chapter 3.3: Note On Geant4 Datasets:
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http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides
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/InstallationGuide/html/ch03s03.html
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The following datasets: G4LEDATA, G4LEVELGAMMADATA, G4NEUTRONXSDATA,
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G4SAIDXSDATA and G4ENSDFSTATEDATA are mandatory for this example.
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In addition the build-in interactive command:
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/process/(in)activate processName
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allows to activate/inactivate the processes one by one.
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3- ACTION INITALIZATION
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A newly introduced class, B1::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 instatiated just once,
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via invoking the method:
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B1::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 is instantiated both thread-local
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and global that's why its instance is created also in the method
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B1::ActionInitialization::BuildForMaster()
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which is invoked only in multi-threading mode.
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4- PRIMARY GENERATOR
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The primary generator is defined in the B1::PrimaryGeneratorAction class.
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The default kinematics is a 6 MeV gamma, randomly distributed in front
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of the envelope across 80% of the transverse (X,Y) envelope size.
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This default setting can be changed via the Geant4 built-in commands
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of the G4ParticleGun class.
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5- DETECTOR RESPONSE
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This example demonstrates a simple scoring implemented directly
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in the user action classes. Alternative ways of scoring via Geant4 classes
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can be found in the other examples.
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The energy deposited is collected step by step for a selected volume
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in B1::SteppingAction and accumulated event by event in B1::EventAction.
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At end of event, the value acummulated in B1::EventAction is added in B1::RunAction
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and summed over the whole run (see B1::EventAction::EndOfevent()).
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Total dose deposited is computed at B1::RunAction::EndOfRunAction(),
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and printed together with informations about the primary particle.
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In multi-threading mode the energy accumulated in G4Accumulable objects per
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workers is merged to the master in B1::RunAction::EndOfRunAction() and the final
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result is printed on the screen.
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G4Parameter<G4double> type instead of G4double type is used for the B1::RunAction
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data members in order to facilitate merging of the values accumulated on workers
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to the master. Currently the accumulables have to be registered to G4AccumulablesManager
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and G4AccumulablesManager::Merge() has to be called from the users code. This is planned
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to be further simplified with a closer integration of G4Accumulable classes in
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the Geant4 kernel next year.
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An example of creating and computing new units (e.g., dose) is also shown
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in the class constructor.
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The following paragraphs are common to all basic examples
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A- VISUALISATION
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The visualization manager is set via the G4VisExecutive class
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in the main() function in exampleB1.cc.
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The initialisation of the drawing is done via a set of /vis/ commands
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in the macro vis.mac. This macro is automatically read from
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the main function when the example is used in interactive running mode.
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By default, vis.mac opens an OpenGL viewer (/vis/open OGL).
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The user can change the initial viewer by commenting out this line
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and instead uncommenting one of the other /vis/open statements, such as
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HepRepFile or DAWNFILE (which produce files that can be viewed with the
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HepRApp and DAWN viewers, respectively). Note that one can always
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open new viewers at any time from the command line. For example, if
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you already have a view in, say, an OpenGL window with a name
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"viewer-0", then
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/vis/open DAWNFILE
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then to get the same view
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/vis/viewer/copyView viewer-0
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or to get the same view *plus* scene-modifications
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/vis/viewer/set/all viewer-0
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then to see the result
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/vis/viewer/flush
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The DAWNFILE, HepRepFile drivers are always available
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(since they require no external libraries), but the OGL driver requires
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that the Geant4 libraries have been built with the OpenGL option.
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From Release 9.6 the vis.mac macro in example B1 has additional commands
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that demonstrate additional functionality of the vis system, such as
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displaying text, axes, scales, date, logo and shows how to change
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viewpoint and style. Consider copying these to other examples or
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your application. To see even more commands use help or
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ls or browse the available UI commands in the Application
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Developers Guide, Section 7.1.
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For more information on visualization, including information on how to
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install and run DAWN, OpenGL and HepRApp, see the visualization tutorials,
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for example,
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http://geant4.slac.stanford.edu/Presentations/vis/G4[VIS]Tutorial/G4[VIS]Tutorial.html
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(where [VIS] can be replaced by DAWN, OpenGL and HepRApp)
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The tracks are automatically drawn at the end of each event, accumulated
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for all events and erased at the beginning of the next run.
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B- USER INTERFACES
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The user command interface is set via the G4UIExecutive class
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in the main() function in exampleB1.cc
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The selection of the user command interface is then done automatically
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according to the Geant4 configuration or it can be done explicitly via
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the third argument of the G4UIExecutive constructor (see exampleB4a.cc).
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C- HOW TO RUN
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- Execute exampleB1 in the 'interactive mode' with visualization:
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% ./exampleB1
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and type in the commands from run1.mac line by line:
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Idle> /control/verbose 2
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Idle> /tracking/verbose 1
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Idle> /run/beamOn 10
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Idle> ...
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Idle> exit
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or
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Idle> /control/execute run1.mac
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....
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Idle> exit
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- Execute exampleB1 in the 'batch' mode from macro files
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(without visualization)
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% ./exampleB1 run2.mac
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% ./exampleB1 exampleB1.in > exampleB1.out
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