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1
2 =========================================================
3 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
4 =========================================================
5
6 Hadr03
7 ------
8
9 How to compute total cross section from the direct evaluation of the
10 mean free path ( see below, item Physics).
11 How to identify nuclear reactions.
12 How to plot energy spectrum of secondary particles.
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 (10 m of molybdenum) is built in DetectorConstruction,
22 but the above parameters can be changed interactively via commands defined
23 in DetectorMessenger.
24
25 2- PHYSICS LIST
26
27 The PhysicsList contains builders for hadronic interactions.
28 Predefined G4 PhysicsConstructors or 'local' PhysicsConstructors can be used
29 (see geant4/source/physics_lists or example runAndEvent/RE04).
30
31 In order not to introduce 'artificial' constraints on the step size,
32 electromagnetic processes are not registered: there is no continuous energy
33 loss.
34
35 Several hadronic physics options are controlled by environment variables.
36 To select them, see Hadr03.cc.
37
38 3- AN EVENT : THE PRIMARY GENERATOR
39
40 The primary kinematic consists of a single particle starting at the edge
41 of the box. The type of the particle and its energy are set in
42 PrimaryGeneratorAction (neutron 1 MeV), and can be changed via the G4
43 build-in commands of ParticleGun class (see the macros provided with
44 this example).
45
46 4- PHYSICS
47
48 An event is killed at the first interaction of the incident particle.
49 The absorption length, also called mean free path, is computed as
50 the mean value of the track length of the incident particle.
51 This is why the medium must be 'infinite' : to be sure that interaction
52 occurs at any events.
53
54 The result is compared with the 'input' value, i.e. with the cross sections
55 given by G4HadronicProcessStore and used by Geant4.
56
57 The list of nuclear reactions that occured is printed.
58 (the number of gamma of deexcitation is not printed).
59
60 Then, comes the total list of generated particles and ions.
61 The energy spectrum of the scattered particle (if any) and of the created
62 secondaries are plotted (see SteppingAction).
63
64 Momentum conservation is checked as :
65 momentum balance = modulus(P_out - P_in)
66
67 A set of macros defining various run conditions are provided.
68 The processes can be actived/inactived in order to survey the processes
69 individually.
70
71 5- HISTOGRAMS
72
73 The test contains 12 built-in 1D histograms, which are managed by
74 G4AnalysisManager and its Messenger. The histos can be individually
75 activated with the command :
76 /analysis/h1/set id nbBins valMin valMax unit
77 where unit is the desired unit for the histo (MeV or keV, etc..)
78 (see the macros xxxx.mac).
79
80 1 "kinetic energy of scattered primary particle"
81 2 "kinetic energy of gamma"
82 3 "kinetic energy of e-"
83 4 "kinetic energy of neutrons"
84 5 "kinetic energy of protons"
85 6 "kinetic energy of deuterons"
86 7 "kinetic energy of alphas"
87 8 "kinetic energy of nuclei"
88 9 "kinetic energy of mesons"
89 10 "kinetic energy of baryons"
90 11 "Q = Ekin out - Ekin in"
91 12 "Pbalance = mag(P_out - P_in)"
92 13 "atomic mass of nuclei"
93
94 The histograms are managed by the HistoManager class and its Messenger.
95 The histos can be individually activated with the command :
96 /analysis/h1/set id nbBins valMin valMax unit
97 where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..)
98
99 One can control the name of the histograms file with the command:
100 /analysis/setFileName name (default Hadr03)
101
102 It is possible to choose the format of the histogram file : root (default),
103 xml, csv, by using namespace in HistoManager.hh
104
105 It is also possible to print selected histograms on an ascii file:
106 /analysis/h1/setAscii id
107 All selected histos will be written on a file name.ascii (default Hadr03)
108
109 6- VISUALIZATION
110
111 The Visualization Manager is set in the main().
112 The initialisation of the drawing is done via the commands
113 /vis/... in the macro vis.mac. To get visualisation:
114 > /control/execute vis.mac
115
116 The detector has a default view which is a longitudinal view of the box.
117 The tracks are drawn at the end of event, and erased at the end of run.
118
119 7- HOW TO START ?
120
121 Execute Hadr03 in 'batch' mode from macro files :
122 % Hadr03 inelastic.mac
123
124 Execute Hadr03 in 'interactive mode' with visualization :
125 % Hadr03
126 Idle> control/execute vis.mac
127 ....
128 Idle> type your commands
129 ....
130 Idle> exit
131
132 Macros provided in this example:
133 - hadr03.in: macro used in Geant4 testing
134 - Au196.mac: neutron (1 MeV) on Au195
135 - elastic.mac: proton (10 MeV) on Mo100. Elastic collisions alone
136 - fusion.mac: deuteron (400 keV) on tritium
137 - gamma.mac: gamma (10 MeV) on Au196
138 - inelastic.mac: proton (10 MaV) on Mo98. Inelastic interactions alone
139 - ion.mac: Li7 (140 MeV) on Be9
140 - nCapture.mac: neutron (1 eV) on Boron. Capture process alone
141 - nFission.mac: neutron (1 eV) on U235. Fission process alone
142 - neutron.mac: neutron (1 MeV) on Boron
143
144 Macros to be run interactively:
145 - debug.mac: proton (10 MeV) on Boron
146 - vis.mac: To activate visualization
