| Geant4 Cross Reference |
>> 1 $Id: README 66241 2012-12-13 18:34:42Z gunter $
1 ---------------------------------------------- 2 -------------------------------------------------------------------
2 3
3 ========================================= 4 =========================================================
4 Geant4 - an Object-Oriented Toolkit for S 5 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 ========================================= 6 =========================================================
6 7
7 TestEm13 8 TestEm13
8 -------- 9 --------
9 10
10 How to compute cross sections from the trans 11 How to compute cross sections from the transmition coefficient
11 ( see below, item Physics). 12 ( see below, item Physics).
12 13
13 1- GEOMETRY DEFINITION 14 1- GEOMETRY DEFINITION
14 15
15 It is a single box representing a layer of f 16 It is a single box representing a layer of finite thickness of
16 homogeneous material. 17 homogeneous material.
17 Two parameters define the geometry : 18 Two parameters define the geometry :
18 - the material of the box, 19 - the material of the box,
19 - the (full) size of the box. 20 - the (full) size of the box.
20 21
21 The default geometry (1 cm of water) is cons 22 The default geometry (1 cm of water) is constructed in
22 DetectorConstruction, but the above paramete 23 DetectorConstruction, but the above parameters can be changed
23 interactively via the commands defined in De 24 interactively via the commands defined in DetectorMessenger.
24 25
25 2- PHYSICS LIST 26 2- PHYSICS LIST
26 27
27 The physics list contains the standard elect 28 The physics list contains the standard electromagnetic processes.
28 In order not to introduce 'artificial' const 29 In order not to introduce 'artificial' constraints on the step size, the
29 multiple scattering is not instanciated, and 30 multiple scattering is not instanciated, and all processes are
30 registered as discrete : there is no continu 31 registered as discrete : there is no continuous energy loss.
31 32
32 3- AN EVENT : THE PRIMARY GENERATOR 33 3- AN EVENT : THE PRIMARY GENERATOR
33 34
34 The primary kinematic consists of a single p 35 The primary kinematic consists of a single particle starting at the edge
35 of the box. The type of the particle and its 36 of the box. The type of the particle and its energy are set in
36 PrimaryGeneratorAction (1 MeV gamma), and ca 37 PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4
37 build-in commands of ParticleGun class (see 38 build-in commands of ParticleGun class (see the macros provided with
38 this example). 39 this example).
39 40
40 4- PHYSICS 41 4- PHYSICS
41 42
42 An event is killed at the first step of the 43 An event is killed at the first step of the incident paticle.
43 Either the particle has interacted or is tra 44 Either the particle has interacted or is transmitted through the layer.
44 The cross section, also called absorption co 45 The cross section, also called absorption coefficient, is computed from
45 the rate of unaltered transmitted incident p 46 the rate of unaltered transmitted incident particles.
46 47
47 The result is compared with the 'input' data 48 The result is compared with the 'input' data, i.e. with the cross
48 sections stored in the PhysicsTables and use 49 sections stored in the PhysicsTables and used by Geant4.
49 50
50 A set of macros defining various run conditi 51 A set of macros defining various run conditions are provided.
51 The processes are actived/inactived in order 52 The processes are actived/inactived in order to survey the processes
52 individually. 53 individually.
53 54
54 55
55 6- VISUALIZATION 56 6- VISUALIZATION
56 57
57 The Visualization Manager is set in the main 58 The Visualization Manager is set in the main().
58 The initialisation of the drawing is done vi 59 The initialisation of the drawing is done via the commands
59 /vis/... in the macro vis.mac. To get visual 60 /vis/... in the macro vis.mac. To get visualisation:
60 > /control/execute vis.mac 61 > /control/execute vis.mac
61 62
62 The detector has a default view which is a l 63 The detector has a default view which is a longitudinal view of the
63 box. 64 box.
64 65
65 The tracks are drawn at the end of event, an 66 The tracks are drawn at the end of event, and erased at the end of run.
66 67
67 7- HOW TO START ? 68 7- HOW TO START ?
68 69
69 execute TestEm13 in 'batch' mode from macro 70 execute TestEm13 in 'batch' mode from macro files :
70 % TestEm13 compt.mac 71 % TestEm13 compt.mac
71 72
72 execute TestEm13 in 'interactive mode' with 73 execute TestEm13 in 'interactive mode' with visualization :
73 % TestEm13 74 % TestEm13
74 Idle> control/execute vis.mac 75 Idle> control/execute vis.mac
75 .... 76 ....
76 Idle> type your commands 77 Idle> type your commands
77 .... 78 ....
78 Idle> exit 79 Idle> exit
79 80
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 <<