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This example simulates a simplified fixe target experiment. Read Example ParN02 for a description of how to run it in parallel.
The setup consists of a target followed by six chambers of increasing transverse size. These chambers are located in a region called Tracker region. Their shape are boxes, constructed as parametrised volumes (ChamberParametrisation class).
The default geometry is constructed in DetectorConstruction class. One can change the material of the target and of the chambers interactively via the commands defined in the DetectorMessenger class.
In addition a transverse uniform magnetic field can be applied (see N02MagneticField and DetectorMessenger classes).
The particle's type and the physic processes which will be available in this example are set in PhysicsList class.
In this example, all the so called 'electromagnetic processes' are introduced for gamma, charged leptons, and charged hadrons (see the method PhysicsList::ConstructEM()).
An important data member of this class is the defaultCutValue which defines the production threshold of secondary particles (mainly Ionisation and Bremsstrahlung processes are concerned by this CutValue). Notice that the CutValue must be given in unit of length, corresponding to the stopping range of the particle. It is automatically converted in energy for each material, and a table is printed in the method PhysicsList::SetCuts()
In addition the build-in interactive command:
/process/(in)activate processName
allows to activate/inactivate the processes one by one.
The primary kinematic consists of a single particle which hits the target perpendicular to the input face. The type of the particle and its energy are set in the PrimaryGeneratorAction class, and can be changed via the G4 build-in commands of ParticleGun class.
A RUN is a set of events.
The user has control: -at Begin and End of each run (class RunAction) -at Begin and End of each event (class EventAction) -at Begin and End of each track (class TrackingAction, not used here) -at End of each step (class SteppingAction)
The class SteppingVerbose prints some informations step per step, under the control of the command: /tracking/verbose 1 It inherits from G4SteppingVerbose, and has been setup here in order to illustrate how to extract informations from the G4 kernel during the tracking of a particle.
A HIT is a record, track per track (even step per step), of all the informations needed to simulate and analyse the detector response.
In this example the Tracker chambers are considered as the detector. Therefore the chambers are declared 'sensitive detectors' (SD) in the DetectorConstruction class.
Then, a Hit is defined as a set of 4 informations per step, inside the chambers, namely:
A given hit is an instance of the class TrackerHit which is created during the tracking of a particle, step by step, in the method TrackerSD::ProcessHits(). This hit is inserted in a HitsCollection.
The HitsCollection is printed at the end of event (via the method TrackerSD::EndOfEvent()), under the control of the command: /hits/verbose 1
The Visualization Manager is set in the main () (see exampleN02.cc). The initialisation of the drawing is done via a set of /vis/ commands in the macro vis.mac. This macro is automatically read from the main when running in interactive mode.
The tracks are automatically drawn at the end of event and erased at the beginning of the next run.
The visualization (with OpenGL driver) assumes two things: 1- the visualisation & interfaces categories have been compiled with the environment variable G4VIS_BUILD_OPENGLX_DRIVER. 2- ParN02.cc has been compiled with G4VIS_USE_OPENGLX.
(The same with DAWNFILE instead of OPENGLX)
The default command interface, called G4UIterminal, is done via standart cin/G4cout. On Linux and Sun-cc on can use a smarter command interface G4UItcsh. It is enough to set the environment variable G4UI_USE_TCSH before compiling ParN02.cc
1.9.8