| Geant4 Cross Reference |
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2 Geant4 - an Object-Oriented Toolkit f 2 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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4 4
5 WLS 5 WLS
6 ---------- 6 ----------
7 7
8 This application simulates the propagation o 8 This application simulates the propagation of optical photons inside a
9 Wave Length Shifting (WLS) fiber. 9 Wave Length Shifting (WLS) fiber.
10 10
11 11
12 1- Geometry Definition 12 1- Geometry Definition
13 13
14 The default geometry is as follow: 14 The default geometry is as follow:
15 15
16 - A perfect, bare (or clad), PMMA fiber: 0.5mm 16 - A perfect, bare (or clad), PMMA fiber: 0.5mm radius, 2m length at
17 center (0,0,0) of the World. 17 center (0,0,0) of the World.
18 - A circular MPPC with 0.5mm radius at the +z 18 - A circular MPPC with 0.5mm radius at the +z end of the fiber
19 - World and coupling materials are G4_AIR 19 - World and coupling materials are G4_AIR
20 - Photons will always refracted out to couplin 20 - Photons will always refracted out to coupling material before
21 reaching MPPC 21 reaching MPPC
22 - There are many flexible parameters that the 22 - There are many flexible parameters that the user could specify.
23 They are under the /WLS directory of help. 23 They are under the /WLS directory of help.
24 24
25 25
26 2- Material Choices 26 2- Material Choices
27 27
28 There are several materials that the user ca 28 There are several materials that the user can use for the fiber core,
29 world and coupling. 29 world and coupling.
30 30
31 They are: 31 They are:
32 32
33 - Vacuum (G4_Galactic) 33 - Vacuum (G4_Galactic)
34 - Air (G4_AIR) 34 - Air (G4_AIR)
35 - PMMA, refractive index n = 1.60 35 - PMMA, refractive index n = 1.60
36 - Pethylene, n = 1.49 36 - Pethylene, n = 1.49
37 - FPethylene, n = 1.42 37 - FPethylene, n = 1.42
38 - Polystyrene, n = 1.60 38 - Polystyrene, n = 1.60
39 - Silicone, n = 1.46 39 - Silicone, n = 1.46
40 40
41 41
42 3- Photon Source 42 3- Photon Source
43 43
44 This program uses the General Particle Sourc 44 This program uses the General Particle Source (G4GeneralParticleSource)
45 provided by Geant4 for generating particles. 45 provided by Geant4 for generating particles. The energy of a primary
46 optical photon must be within the range 2.00 46 optical photon must be within the range 2.00 eV to 3.47 eV.
47 47
48 48
49 4- Hit 49 4- Hit
50 50
51 A hit is registered when an optical photon i 51 A hit is registered when an optical photon is absorbed on the MPPC
52 surface. Information stored in a hit includ 52 surface. Information stored in a hit includes the local coordinate of the
53 location the optical photon is absorbed on t 53 location the optical photon is absorbed on the MPPC, the global coordinate
54 where the optical photon left the fiber, the 54 where the optical photon left the fiber, the transit time of the optical
55 photon, and the energy of the optical photon 55 photon, and the energy of the optical photon.
56 56
57 57
58 5- Stepping Action 58 5- Stepping Action
59 59
60 The stepping action keeps track of the numbe 60 The stepping action keeps track of the number of bounces an optical photon has
61 gone through. In order to prevent infinite 61 gone through. In order to prevent infinite loop and extremely skewed
62 rays taking up computing time, there is a li 62 rays taking up computing time, there is a limit of the number of
63 bounces that an optical photon can go throug 63 bounces that an optical photon can go through before it is artificially killed.
64 The default limit is 100,000. The user can 64 The default limit is 100,000. The user can set his/her own limit using
65 the /stepping/setBounceLimit command. A val 65 the /stepping/setBounceLimit command. A value of 0 will turn off the
66 limit. All optical photons artificially kil 66 limit. All optical photons artificially killed will have murderee flag turned
67 on in their UserTrackInformation. 67 on in their UserTrackInformation.
68 68
69 69
70 6- Visualization 70 6- Visualization
71 71
72 To visualize particle trajectories, simply u 72 To visualize particle trajectories, simply use vis.mac macro in
73 interactive mode or in your own macro. 73 interactive mode or in your own macro.
74 74
75 75
76 7- main() 76 7- main()
77 77
78 - execute wls in 'batch' mode from macro file 78 - execute wls in 'batch' mode from macro files
79 - you can enter an optional integer seed for 79 - you can enter an optional integer seed for batch mode
80 % wls electron.mac (optional: enter a 80 % wls electron.mac (optional: enter an integer seed here)
81 81
82 - wls in 'interactive mode' with visualizatio 82 - wls in 'interactive mode' with visualization
83 % wls 83 % wls
84 .... 84 ....
85 Idle> /control/execute 85 Idle> /control/execute
86 Idle> /run/beamOn 1 86 Idle> /run/beamOn 1
87 .... 87 ....
88 Idle> exit 88 Idle> exit
89 89
90 8- Macros provided 90 8- Macros provided
91 91
92 - electron.mac: Sets up the geometry and conf 92 - electron.mac: Sets up the geometry and configures the particle source.
93 Primary particle is a 10 MeV 93 Primary particle is a 10 MeV electron.
94 - vis.mac: macro for visualization; called au 94 - vis.mac: macro for visualization; called automatically when no macro is
95 given on command line. 95 given on command line.