a design study for a cobra upgrade to - Institut für Kern- und ...

98 B SECOND APPENDIX
B.2 Geant4
Geant4 is an object-oriented toolkit for the simulation of the passage of
particles through matter, written in C++. It provides a realistic reproduction
of physical processes for an energy region from 250 eV up to
a few GeV. The necessary cross sections for the simulations are interpolated
from stored values in evaluated databases. The final state depends
on the angle and energy distributions and will be calculated with
the corresponding theoretical model or interpolated from the database
[44].
A main method with two toolkit classes (G4Runmanager and
G4UImanager) and three classes, which are derived from
toolkit classes (G4Detectorconstruction, G4PhysicsList and
G4PrimaryGeneratorAction) are required for building a simulation.
The G4Runmanager controls the flow of the program. It manages
the initialisation procedures like detector construction, definition of
particles and physics processes or initialisation of primary particles.
In the user initialised class DetectorConstruction, the geometry and
material of the detector are defined by the user.
In the PhysicsList, the user defines the particles and physical processes,
which shall be regarded. The initial state of the event is defined with
the PrimaryGeneratorAction. This implies the particle type, energy, position,
direction and number of initialised particles. A RUN is defined
as a set of events. The user has control at the Begin and End of each run
(class RunAction), the Begin and End of each event (class EventAction),
the begin and End of each track (class TrackingAction) and at the End
of each step (class SteppingAction). A HIT is a record, track per track
(and even step per step), of a set of user defined information needed to
simulate and analyse the detector response. Only interactions in volumes,
specified as sensitive detectors can be handled as hits and be
stored in the HitsCollection. The HitsCollection is printed at the end of
event (via the method TrackerSD::EndOfEvent()), under the control of
the command:/hits/verbose 1. A visualisation of the event is possible
with the G4VisManager. Used visualisation systems are OpenGL,
Heprep or Dawn. Geant4 applications can run in batch mode, where
macro commands, being read at the beginning of a run, can be used.
An interactive mode, driven by command lines or via a graphical user
interface is also possible. [48]
VENOM is the Cobra simulation framework, first developed by H.
Kiel [8] and redesigned by J. Wilson and B. Morgan [53]. It is a