optical/wls/README.md

0001 \page Examplewls Example wls
0002
0003 This application simulates the propagation of optical photons inside a
0004 Wave Length Shifting (WLS) fiber.
0005
0006
0007 ## Geometry Definition
0008
0009   The default geometry is as follow:
0010
0011 - A perfect, bare (or clad), PMMA fiber: 0.5mm radius, 2m length at
0012   center (0,0,0) of the World.
0013 - A circular MPPC with 0.5mm radius at the +z end of the fiber
0014 - World and coupling materials are G4_AIR
0015 - Photons will always refracted out to coupling material before
0016   reaching MPPC
0017 - There are many flexible parameters that the user could specify.
0018   They are under the /WLS directory of help.
0019
0020
0021 ## Material Choices
0022
0023   There are several materials that the user can use for the fiber core,
0024   world and coupling.
0025
0026 They are:
0027
0028 - Vacuum (G4_Galactic)
0029 - Air (G4_AIR)
0030 - PMMA, refractive index n = 1.60
0031 - Pethylene, n = 1.49
0032 - FPethylene, n = 1.42
0033 - Polystyrene, n = 1.60
0034 - Silicone, n = 1.46
0035
0036
0037 ## Photon Source
0038
0039   This program uses the General Particle Source (G4GeneralParticleSource)
0040   provided by Geant4 for generating particles. The energy of a primary
0041   optical photon must be within the range 2.00 eV to 3.47 eV.
0042
0043
0044 ## Hit
0045
0046   A hit is registered when an optical photon is absorbed on the MPPC
0047   surface.  Information stored in a hit includes the local coordinate of the
0048   location the optical photon is absorbed on the MPPC, the global coordinate
0049   where the optical photon left the fiber, the transit time of the optical
0050   photon, and the energy of the optical photon.
0051
0052
0053 ## Stepping Action
0054
0055   The stepping action keeps track of the number of bounces an optical photon has
0056   gone through.  In order to prevent infinite loop and extremely skewed
0057   rays taking up computing time, there is a limit of the number of
0058   bounces that an optical photon can go through before it is artificially killed.
0059   The default limit is 100,000.  The user can set his/her own limit using
0060   the /stepping/setBounceLimit command.  A value of 0 will turn off the
0061   limit.  All optical photons artificially killed will have murderee flag turned
0062   on in their UserTrackInformation.
0063
0064
0065 ## Visualization
0066
0067   To visualize particle trajectories, simply use vis.mac macro in
0068   interactive mode or in your own macro.
0069
0070
0071 ## main()
0072
0073  - Execute wls in 'batch' mode from macro files; \n
0074    you can enter an optional integer seed for batch mode
0075 ```
0076 % ./wls electron.mac (optional: enter an integer seed here)
0077 ```
0078
0079  - wls in 'interactive mode' with visualization
0080 ```
0081 % ./wls
0082 ....
0083 Idle> /control/execute vis.mac
0084 Idle> /run/beamOn 1
0085 ....
0086 Idle> exit
0087 ```
0088
0089 ## Macros provided
0090
0091  - electron.mac: Sets up the default geometry and configures the particle source.
0092                  Primary particle is a 10 MeV electron.
0093  - vis.mac: macro for visualization; called automatically when no macro is
0094             given on command line.