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1 -------------------------------------------------------------------
2
3 =========================================================
4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 =========================================================
6
7 TestEm14
8 --------
9
10 How to compute cross sections from the direct evaluation of the mean
11 free path ( see below, item Physics).
12 How to plot final state of a process.
13
14 1- GEOMETRY DEFINITION
15
16 It is a single box representing a 'semi infinite' homogeneous medium.
17 Two parameters define the geometry :
18 - the material of the box,
19 - the (full) size of the box.
20
21 The default geometry (100 m of water) is constructed in
22 DetectorConstruction, but the above parameters can be changed
23 interactively via the commands defined in DetectorMessenger.
24
25 2- PHYSICS LIST
26
27 The physics list contains the standard electromagnetic processes.
28 In order not to introduce 'artificial' constraints on the step size, the
29 multiple scattering is not instanciated, and all processes are
30 registered as discrete : there is no continuous energy loss.
31
32 3- AN EVENT : THE PRIMARY GENERATOR
33
34 The primary kinematic consists of a single particle starting at the edge
35 of the box. The type of the particle and its energy are set in
36 PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4
37 build-in commands of ParticleGun class (see the macros provided with
38 this example).
39
40 4- PHYSICS
41
42 An event is killed at the first interaction of the incident paticle.
43 The absorption length, also called mean free path, is computed as
44 the mean value of the track length of the incident particle.
45 This is why the medium must be 'infinite' : to be sure that interaction
46 occurs at any events.
47
48 The result is compared with the 'input' data, i.e. with the cross
49 sections stored in the PhysicsTables and used by Geant4.
50
51 The energy spectrum and the angular distribution of the scattered
52 particle (if any) and of the created secondaries are plotted (see
53 SteppingAction).
54
55 A set of macros defining various run conditions are provided.
56 The processes are actived/inactived in order to survey the processes
57 individually.
58
59 5- HISTOGRAMS
60
61 The test contains 6 built-in 1D histograms, which are managed by the
62 HistoManager class and its Messenger. The histos can be individually
63 activated with the command :
64 /analysis/h1/set id nbBins valMin valMax unit
65 where unit is the desired unit for the histo (MeV or keV, etc..)
66 (see the macros xxxx.mac).
67
68 1 "scattered primary particle: energy spectrum"
69 2 "scattered primary particle: costheta distribution"
70 3 "charged secondaries: energy spectrum"
71 4 "charged secondaries: costheta distribution"
72 5 "neutral secondaries: energy spectrum"
73 6 "neutral secondaries: costheta distribution"
74
75 The histograms are managed by the HistoManager class and its Messenger.
76 The histos can be individually activated with the command :
77 /analysis/h1/set id nbBins valMin valMax unit
78 where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
79
80 One can control the name of the histograms file with the command:
81 /analysis/setFileName name (default testem14)
82
83 It is possible to choose the format of the histogram file : root (default),
84 hdf5, xml, csv, by changing the default file type in HistoManager.cc
85
86 It is also possible to print selected histograms on an ascii file:
87 /analysis/h1/setAscii id
88 All selected histos will be written on a file name.ascii (default testem14)
89
90 6- VISUALIZATION
91
92 The Visualization Manager is set in the main().
93 The initialisation of the drawing is done via the commands
94 /vis/... in the macro vis.mac. To get visualisation:
95 > /control/execute vis.mac
96
97 The detector has a default view which is a longitudinal view of the
98 box.
99
100 The tracks are drawn at the end of event, and erased at the end of run.
101
102 7- HOW TO START ?
103
104 execute TestEm14 in 'batch' mode from macro files :
105 % TestEm14 compt.mac
106
107 execute TestEm14 in 'interactive mode' with visualization :
108 % TestEm14
109 Idle> control/execute vis.mac
110 ....
111 Idle> type your commands
112 ....
113 Idle> exit
114
115 Macros provided in this example:
116 - anni.mac: e+ (100 MeV) on Aluminium
117 - atomicDeexcitation: gamma (80 keV) on Tellurium
118 - compton.mac: gamma (300 keV) on Aluminium
119 - conv.mac: gamma (20 MeV) on Lead
120 - convtomu.mac: gamma (100 TeV) on Iron
121 - electron.mac: e- (100 MeV) on Aluminium
122 - gamma.mac: gamma (100 keV) on Water
123 - photoelec.mac: gamma (80 keV) on Gold
124 - proton.mac: proton (100 MeV) on Water
