Gabriele Cosmo
92 lines
2.7 KiB
Plaintext
92 lines
2.7 KiB
Plaintext
=========================================================
|
|
Geant4 - an Object-Oriented Toolkit for Simulation in HEP
|
|
=========================================================
|
|
|
|
WLS
|
|
----------
|
|
|
|
This application simulates the propagation of photons inside a Wave Length
|
|
Shifting (WLS) fiber.
|
|
|
|
|
|
1- Geometry Definition
|
|
|
|
The default geometry is as follow:
|
|
|
|
- A perfect, bare, PMMA fiber: 0.5mm radius, 2m length at center(0,0,0)
|
|
of the World.
|
|
- A circular MPPC with 0.5mm radius at the +z end of the fiber
|
|
- World and coupling materials are G4_AIR
|
|
- Photons will always refracted out to coupling material before
|
|
reaching MPPC
|
|
- There are many flexible parameters that the user could specify.
|
|
They are under the /WLS directory of help.
|
|
|
|
|
|
2- Material Choices
|
|
|
|
There are several materials that the user can use for the fiber core,
|
|
world and coupling.
|
|
|
|
They are:
|
|
|
|
- Vacuum (G4_Galactic)
|
|
- Air (G4_AIR)
|
|
- PMMA, n = 1.60
|
|
- Pethylene, n = 1.49
|
|
- FPethylene, n = 1.42
|
|
- Polystyrene, n = 1.60
|
|
- Silicone, n = 1.46
|
|
|
|
|
|
3- Photon Source
|
|
|
|
This program uses the General Particle Source (G4GeneralParticleSource)
|
|
provided by GEANT4 for
|
|
generating photons. The energy of the photon must be within 2.00 eV
|
|
to 3.47 eV. For detail instruction on how to use the General Particle
|
|
Source, please visit their home page at:
|
|
|
|
http://reat.space.qinetiq.com/gps/
|
|
|
|
|
|
4- Hit
|
|
|
|
A hit is registered when the photon is absorbed on the MPPC surface.
|
|
Information stored in hit includes the local coordinate of the location
|
|
the photon is absorbed on the MPPC, the global coordinate where the
|
|
photon left the fiber and the transit time of the photon.
|
|
|
|
|
|
5- Stepping Action
|
|
|
|
The stepping action keeps track of the number of bounces a photon has
|
|
gone through. In order to prevent infinite loop and extremely skewed
|
|
rays taking up computing time, there is a limit of the number of
|
|
bounces that a photon can go through before it is artificially killed.
|
|
The default limit is 100,000. The user can set his/her own limit using
|
|
the /stepping/setBounceLimit command. A value of 0 will turn off the
|
|
limit. All photons artificially killed will have murderee flag turned
|
|
on in their UserTrackInformation.
|
|
|
|
|
|
6- Visualization
|
|
|
|
To visualize a photon's trajectory, simply use vis.mac macro in
|
|
interactive mode or in your own macro.
|
|
|
|
|
|
7- main()
|
|
|
|
- execute wls in 'batch' mode from macro files
|
|
- you can enter an optional integer seed for batch mode
|
|
% wls wls.in (optional: enter an integer seed here)
|
|
|
|
- wls in 'interactive mode' with visualization
|
|
% wls
|
|
....
|
|
Idle> /control/execute vis.mac
|
|
Idle> /run/beamOn 1
|
|
....
|
|
Idle> exit
|