| Geant4 Cross Reference |
1 ---------------------------------------------- 1 -------------------------------------------------------------------
2 2
3 ========================================= 3 =========================================================
4 Geant4 - an Object-Oriented Toolkit for S 4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 ========================================= 5 =========================================================
6 6
7 TestEm13 7 TestEm13
8 -------- 8 --------
9 9
10 How to compute cross sections from the trans 10 How to compute cross sections from the transmition coefficient
11 ( see below, item Physics). 11 ( see below, item Physics).
12 12
13 1- GEOMETRY DEFINITION 13 1- GEOMETRY DEFINITION
14 14
15 It is a single box representing a layer of f 15 It is a single box representing a layer of finite thickness of
16 homogeneous material. 16 homogeneous material.
17 Two parameters define the geometry : 17 Two parameters define the geometry :
18 - the material of the box, 18 - the material of the box,
19 - the (full) size of the box. 19 - the (full) size of the box.
20 20
21 The default geometry (1 cm of water) is cons 21 The default geometry (1 cm of water) is constructed in
22 DetectorConstruction, but the above paramete 22 DetectorConstruction, but the above parameters can be changed
23 interactively via the commands defined in De 23 interactively via the commands defined in DetectorMessenger.
24 24
25 2- PHYSICS LIST 25 2- PHYSICS LIST
26 26
27 The physics list contains the standard elect 27 The physics list contains the standard electromagnetic processes.
28 In order not to introduce 'artificial' const 28 In order not to introduce 'artificial' constraints on the step size, the
29 multiple scattering is not instanciated, and 29 multiple scattering is not instanciated, and all processes are
30 registered as discrete : there is no continu 30 registered as discrete : there is no continuous energy loss.
31 31
32 3- AN EVENT : THE PRIMARY GENERATOR 32 3- AN EVENT : THE PRIMARY GENERATOR
33 33
34 The primary kinematic consists of a single p 34 The primary kinematic consists of a single particle starting at the edge
35 of the box. The type of the particle and its 35 of the box. The type of the particle and its energy are set in
36 PrimaryGeneratorAction (1 MeV gamma), and ca 36 PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4
37 build-in commands of ParticleGun class (see 37 build-in commands of ParticleGun class (see the macros provided with
38 this example). 38 this example).
39 39
40 4- PHYSICS 40 4- PHYSICS
41 41
42 An event is killed at the first step of the 42 An event is killed at the first step of the incident paticle.
43 Either the particle has interacted or is tra 43 Either the particle has interacted or is transmitted through the layer.
44 The cross section, also called absorption co 44 The cross section, also called absorption coefficient, is computed from
45 the rate of unaltered transmitted incident p 45 the rate of unaltered transmitted incident particles.
46 46
47 The result is compared with the 'input' data 47 The result is compared with the 'input' data, i.e. with the cross
48 sections stored in the PhysicsTables and use 48 sections stored in the PhysicsTables and used by Geant4.
49 49
50 A set of macros defining various run conditi 50 A set of macros defining various run conditions are provided.
51 The processes are actived/inactived in order 51 The processes are actived/inactived in order to survey the processes
52 individually. 52 individually.
53 53
54 54
55 6- VISUALIZATION 55 6- VISUALIZATION
56 56
57 The Visualization Manager is set in the main 57 The Visualization Manager is set in the main().
58 The initialisation of the drawing is done vi 58 The initialisation of the drawing is done via the commands
59 /vis/... in the macro vis.mac. To get visual 59 /vis/... in the macro vis.mac. To get visualisation:
60 > /control/execute vis.mac 60 > /control/execute vis.mac
61 61
62 The detector has a default view which is a l 62 The detector has a default view which is a longitudinal view of the
63 box. 63 box.
64 64
65 The tracks are drawn at the end of event, an 65 The tracks are drawn at the end of event, and erased at the end of run.
66 66
67 7- HOW TO START ? 67 7- HOW TO START ?
68 68
69 execute TestEm13 in 'batch' mode from macro 69 execute TestEm13 in 'batch' mode from macro files :
70 % TestEm13 compt.mac 70 % TestEm13 compt.mac
71 71
72 execute TestEm13 in 'interactive mode' with 72 execute TestEm13 in 'interactive mode' with visualization :
73 % TestEm13 73 % TestEm13
74 Idle> control/execute vis.mac 74 Idle> control/execute vis.mac
75 .... 75 ....
76 Idle> type your commands 76 Idle> type your commands
77 .... 77 ....
78 Idle> exit 78 Idle> exit
79 79
80 Macros provided in this example: <<
81 - anni.mac: e+ (10 MeV) on 5 cm Alumin <<
82 - compton.mac: gamma (300 keV) on 1 cm Alu <<
83 - conv.mac: gamma (20 MeV) on 5 mm Lead <<
84 - electron.mac: e- (100 MeV) on 1 cm Alumin <<
85 - gamma.mac: gamma (100 keV) on 1 cm Wat <<
86 - photoelec.mac: gamma (100 keV) on 1 cm Iro <<
87 - proton.mac: proton (1 GeV) on 1 cm Wate <<