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1 -------------------------------------------------------------------
2
3 =========================================================
4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 =========================================================
6
7 TestEm1
8 -------
9 How to count processes.
10 How to activate/inactivate processes.
11 How to survey the tracking, in particular the range of charged particles.
12 How to define a maximum step size.
13
14 1 - GEOMETRY DEFINITION
15
16 It is a simple box which represents a 'semi infinite' homogeneous medium.
17
18 Two parameters define the geometry :
19 - the material of the box,
20 - the full size of the box.
21
22 In addition a transverse uniform magnetic field can be applied.
23 e.g. /globalField/setValue 0 0 5 tesla
24
25 The default geometry is constructed in DetectorConstruction class, but all of
26 the above parameters can be changed interactively via the commands defined in
27 the DetectorMessenger class.
28
29 2 - PHYSICS LIST
30
31 Physics lists are based on modular design. Several modules are instantiated:
32 1. Transportation
33 2. EM physics
34 3. Decays
35 4. StepMax - for step limitation
36
37 EM physics builders can be local (eg. in this example) or from G4 kernel
38 physics_lists subdirectory.
39
40 Local physics builder:
41 - "local" standard EM physics with current 'best' options setting.
42 these options are explicited in PhysListEmStandard
43
44 From geant4/source/physics_lists/builders:
45 - "emstandard_opt0" recommended standard EM physics for LHC
46 - "emstandard_opt1" best CPU performance standard physics for LHC
47 - "emstandard_opt2" similar fast simulation
48 - "emstandard_opt3" best standard EM options - analog to "local" above
49 - "emstandard_opt4" best current advanced EM options standard + lowenergy
50 - "emstandardSS" standard EM physics and single scattering model
51 - "emlivermore" low-energy EM physics using Livermore data
52 - "empenelope" low-energy EM physics implementing Penelope models
53 - "emlowenergy" low-energy EM physics implementing experimental
54 low-energy models
55
56 Physics lists and options can be (re)set with UI commands
57
58 A few commands have been added to PhysicsList, in order to set the production
59 threshold for secondaries for gamma and e-/e+.
60
61 3 - AN EVENT : THE PRIMARY GENERATOR
62
63 The primary kinematic consists of a single particle starting at the left face
64 of the box. The type of the particle and its energy are set in the
65 PrimaryGeneratorAction class, and can be changed via the G4 build-in commands
66 of G4ParticleGun class (see the macros provided with this example).
67
68 In addition one can choose randomly the impact point of the incident particle.
69 The corresponding interactive command is built in PrimaryGeneratorMessenger.
70
71 4 - VISUALIZATION
72
73 The Visualization Manager is set in the main () (see TestEm1.cc).
74 The initialisation of the drawing is done via the commands /vis/... in the
75 macro vis.mac. To get visualisation:
76 > /control/execute vis.mac
77
78 The detector has a default view which is a longitudinal view of the box.
79
80 The tracks are drawn at the end of event, and erased at the end of run.
81
82 5 - PHYSICS SURVEY
83
84 The particle's type and the physics processes which will be available in this
85 example are set in PhysicsList class.
86
87 A set of macros defining various run conditions are provided. The processes
88 are actived/inactivated together with differents cuts, in order to survey the
89 processes one by one.
90
91 The number of produced secondaries are counted, the number of steps, and the
92 number of process calls responsible of the step.
93
94 6 - HOW TO START ?
95
96 - execute TestEm1 in 'batch' mode from macro files
97 % TestEm1 runs.mac
98
99 - execute TestEm1 in 'interactive mode' with visualization
100 % TestEm1
101 ....
102 Idle> type your commands
103 ....
104 Idle> exit
105
106 Macros provided in this example:
107 - brems.mac: Bremsstrahlung only
108 - erange.mac: compute the csda range of primary particle
109 - geantino.mac: geantino as primary particle
110 - ionis.mac: Ionisation only
111 - photoelec.mac: 100 keV photon photoelectric effect
112 - radioactive.mac: use radioactive ion as primary particle
113 - range.mac: compute the csda range of the primary particle
114 with or without fluctuations
115 - erange.mac, pRange.mac, alphaRange.mac, ionRange.mac: variants of range.mac
116 to play with StepFunction()
117 - runs.mac: electron 100 MeV; all processes
118
119 Macros to be run interactively:
120 - annihil.mac: To visualise 100 MeV e+ annihilation
121 - decayinfly.mac: To visualise decay in fly of N16
122 - etaDecay.mac: to visualise decay of eta particle
123 - gammaconversion.mac: To visualise gamma conversion and e+ annihilation
124 - photon.mac: To visualiza p300 keV photon beam
125 - stepMax.mac: to test command /testem/stepMax
126 - vis.mac: To activate visualization
127
128 7 - TRACKING : StepMax
129
130 In order to control the accuracy of the deposition, the user can limit
131 'by hand' the maximum step size of charged particles.
132 As an example, this limitation is implemented as a 'full' process :
133 see StepMax class and its Messenger. The 'StepMax process' is registered
134 in the Physics List.
135
136 8 - HISTOGRAMS
137
138 Testem1 produces several histo which are saved as testem1.root by default.
139 Content of these histo:
140 1 : track length of primary particle
141 2 : number of steps primary particle
142 3 : step size of primary particle
143 4 : total energy deposit
144 5 : energy of charged secondaries at creation
145 6 : energy of neutral secondaries at creation
146 7 : NIEL energy
147 8 : energy leakage
148 9 : energy deposit + leakage
149
150 The histograms are managed by G4AnalysisManager class and its Messenger.
151 The histos can be individually activated with the command :
152 /analysis/h1/set id nbBins valMin valMax unit
153 where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
154
155 One can control the name of the histograms file with the command:
156 /analysis/setFileName name (default testem1)
157
158 It is possible to choose the format of the histogram file : root (default),
159 hdf5, xml, csv, by changing the default file type in HistoManager.cc
160
161 It is also possible to print selected histograms on an ascii file:
162 /analysis/h1/setAscii id
163 All selected histos will be written on a file name.ascii (default testem1)
