| 1 | $Id: README,v 1.6 2006/03/31 14:02:13 maire Exp $
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| 2 | -------------------------------------------------------------------
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| 3 |
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| 4 | =========================================================
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| 5 | Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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| 6 | =========================================================
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| 7 |
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| 8 | ExampleN02
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| 9 | ----------
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| 10 |
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| 11 |
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| 12 | This example simulates a simplified fixe target experiment.
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| 13 |
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| 14 | 1- GEOMETRY DEFINITION
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| 15 |
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| 16 | The setup consists of a target followed by six chambers of increasing
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| 17 | transverse size. These chambers are located in a region called Tracker
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| 18 | region. Their shape are boxes, constructed as parametrised volumes
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| 19 | (ChamberParametrisation class).
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| 20 |
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| 21 | The default geometry is constructed in DetectorConstruction class.
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| 22 | One can change the material of the target and of the chambers
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| 23 | interactively via the commands defined in the DetectorMessenger class.
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| 24 |
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| 25 | In addition a transverse uniform magnetic field can be applied (see
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| 26 | N02MagneticField and DetectorMessenger classes).
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| 27 |
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| 28 |
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| 29 | 2- PHYSICS LIST
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| 30 |
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| 31 | The particle's type and the physic processes which will be available
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| 32 | in this example are set in PhysicsList class.
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| 33 |
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| 34 | In this example, all the so called 'electromagnetic processes' are
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| 35 | introduced for gamma, charged leptons, and charged hadrons (see the
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| 36 | method PhysicsList::ConstructEM()).
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| 37 |
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| 38 | An important data member of this class is the defaultCutValue which
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| 39 | defines the production threshold of secondary particles
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| 40 | (only Ionisation and Bremsstrahlung processes are concerned by this
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| 41 | CutValue).
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| 42 | Notice that the CutValue must be given in unit of length, corresponding
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| 43 | to the stopping range of the particle. It is automatically converted
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| 44 | in energy for each material, and a table is printed in the method
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| 45 | PhysicsList::SetCuts()
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| 46 |
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| 47 | In addition the build-in interactive command:
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| 48 | /process/(in)activate processName
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| 49 | allows to activate/inactivate the processes one by one.
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| 50 |
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| 51 |
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| 52 | 3- RUNS and EVENTS
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| 53 |
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| 54 | The primary kinematic consists of a single particle which hits the
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| 55 | target perpendicular to the input face. The type of the particle
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| 56 | and its energy are set in the PrimaryGeneratorAction class, and can
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| 57 | be changed via the G4 build-in commands of ParticleGun class.
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| 58 |
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| 59 | A RUN is a set of events.
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| 60 |
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| 61 | The user has control:
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| 62 | -at Begin and End of each run (class RunAction)
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| 63 | -at Begin and End of each event (class EventAction)
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| 64 | -at Begin and End of each track (class TrackingAction, not used here)
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| 65 | -at End of each step (class SteppingAction)
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| 66 |
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| 67 | The class SteppingVerbose prints some informations step per step,
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| 68 | under the control of the command: /tracking/verbose 1
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| 69 | It inherits from G4SteppingVerbose, and has been setup here in order
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| 70 | to illustrate how to extract informations from the G4 kernel during
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| 71 | the tracking of a particle.
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| 72 |
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| 73 |
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| 74 | 4- USER' LIMITS
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| 75 |
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| 76 | We illustrate how to introduce tracking constraints like maximum step
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| 77 | length, minimum kinetic energy ..etc.., via G4UserLimits class.
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| 78 | See DetectorConstruction and PhysicsList.
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| 79 |
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| 80 | 5- DETECTOR RESPONSE
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| 81 |
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| 82 | A HIT is a record, track per track (even step per step), of all the
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| 83 | informations needed to simulate and analyse the detector response.
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| 84 |
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| 85 | In this example the Tracker chambers are considered as the detector.
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| 86 | Therefore the chambers are declared 'sensitive detectors' (SD) in
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| 87 | the DetectorConstruction class.
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| 88 |
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| 89 | Then, a Hit is defined as a set of 4 informations per step, inside
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| 90 | the chambers, namely:
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| 91 | - the track identifier (an integer),
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| 92 | - the chamber number,
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| 93 | - the total energy deposit in this step,
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| 94 | - the position of the deposit.
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| 95 |
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| 96 | A given hit is an instance of the class TrackerHit which is created
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| 97 | during the tracking of a particle, step by step, in the method
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| 98 | TrackerSD::ProcessHits(). This hit is inserted in a HitsCollection.
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| 99 |
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| 100 | The HitsCollection is printed at the end of event (via the method
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| 101 | TrackerSD::EndOfEvent()), under the control of the command: /hits/verbose 1
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| 102 |
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| 103 |
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| 104 | 6- VISUALIZATION
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| 105 |
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| 106 | The Visualization Manager is set in the main().
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| 107 | The initialisation of the drawing is done via a set of /vis/ commands
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| 108 | in the macro vis.mac. This macro is automatically read from
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| 109 | the main when running in interactive mode.
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| 110 |
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| 111 | The tracks are automatically drawn at the end of event and erased at
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| 112 | the beginning of the next run.
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| 113 |
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| 114 | The visualization (with OpenGL driver) assumes two things:
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| 115 | 1- the visualisation & interfaces categories have been compiled
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| 116 | with the environment variable G4VIS_BUILD_OPENGLX_DRIVER.
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| 117 | 2- exampleN02.cc has been compiled with G4VIS_USE_OPENGLX.
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| 118 |
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| 119 | (The same with DAWNFILE instead of OPENGLX)
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| 120 |
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| 121 |
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| 122 | 7- USER INTERFACES
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| 123 |
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| 124 | The default command interface, called G4UIterminal, is done via
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| 125 | standart cin/G4cout.
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| 126 | On Linux and Sun-cc on can use a smarter command interface G4UItcsh.
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| 127 | It is enough to set the environment variable G4UI_USE_TCSH before
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| 128 | compiling exampleN02.cc
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| 129 |
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| 130 |
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| 131 | 8- HOW TO START ?
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| 132 |
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| 133 | - compile and link to generate an executable
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| 134 | % cd N02
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| 135 | % gmake
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| 136 |
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| 137 | - execute N02 in 'batch' mode from macro files (without visualization)
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| 138 | % exampleN02 run1.mac
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| 139 |
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| 140 | - execute N02 in 'interactive mode' with visualization
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| 141 | % exampleN02
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| 142 | ....
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| 143 | Idle> type your commands. For instance:
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| 144 | Idle> /run/beamOn 10
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| 145 | ....
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| 146 | Idle> /control/execute run2.mac
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| 147 | ....
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| 148 | Idle> exit
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| 149 |
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| 150 |
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