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1 -------------------------------------------------------------------
2
3 =========================================================
4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
5 =========================================================
6
7 TestEm16
8 --------
9 Simulate synchrotron radiation
10
11 1- GEOMETRY DEFINITION
12
13 The geometry consists of a single block of a homogenous material.
14
15 Two parameters define the geometry :
16 - the material of the box,
17 - the (full) size of the box.
18 The default is 500 m of vacuum.
19
20 A transverse uniform magnetic field can be applied.
21
22 The default geometry is constructed in DetectorConstruction class,
23 but all of the above parameters can be changed interactively via
24 the commands defined in the DetectorMessenger class.
25
26 2- PHYSICS LIST
27
28 The particle list include EM processes for gamma, e+, e-, mu+, mu-,
29 and protons, for the rest of particles only transportation.
30 Synchrotron radiation is added to all charged particles.
31 To make the synchrotron radiation easily visible, a very low
32 pressure "vaccuum" and a magnetic field of by default 1 Tesla
33 in z-direction is used.
34
35 3- AN EVENT : THE PRIMARY GENERATOR
36
37 The primary kinematic consists of a single particle which hits the
38 block perpendicular to the input face. The type of the particle
39 and its energy are set in the PrimaryGeneratorAction class, and can
40 changed via the G4 build-in commands of ParticleGun class (see
41 the macros provided with this example).
42 The default is an positron of 10 GeV.
43
44 In addition one can choose randomly the impact point of the incident
45 particle. The corresponding interactive command is built in
46 PrimaryGeneratorMessenger class.
47
48 A RUN is a set of events.
49
50
51 4- VISUALIZATION
52
53 The Visualization Manager is set in the main().
54 The initialisation of the drawing is done via the command
55 > /control/execute vis.mac
56 > /run/beamOn 1
57
58 The detector has a default view which is a longitudinal view of the box.
59
60 The tracks are drawn at the end of event, and erased at the end of run.
61 Optionaly one can choose to draw all particles, only the charged one,
62 or none. This command is defined in EventActionMessenger class.
63
64 5- PHYSICS DEMO
65
66 The particle's type and the physic processes which will be available
67 in this example are set in PhysicsList class.
68
69 In addition a build-in interactive command (/process/inactivate proname)
70 allows to activate/inactivate the processes one by one.
71
72 The threshold for producing secondaries can be changed.
73 eg: /run/setCut 100 micrometer
74 /run/initialize
75
76 To visualize the Synchrotron radiation :
77 /control/execute vis.mac
78
79 6- HOW TO START ?
80
81 - execute Test in 'batch' mode from macro files
82 % TestEm16 run01.mac
83
84 - execute Test in 'interactive mode' with visualization
85 % TestEm16
86 ....
87 Idle> type your commands
88 ....
89 Idle> exit
90
91 other Macros provided in this example:
92 - run01_prot.mac
93 Synchrotron radiation of 50 TeV protons in 20 T field
94 relevant for FCC-hh
95 - run02.mac
96 weak field long distance example
97 relevant for space applications
98 - TestReflection.mac
99 specular reflection of X-ray gammas on a block of
100 copper defined by Box_1m_Cu.gdml
101
102 7 - TRACKING : stepMax and setMaxStepLength
103
104 In order to control the accuracy of the deposition, the user can limit
105 'by hand' the maximum step size stepMax of charged particles.
106
107 The maximum tracking step length for computing of magnetic field lines
108 is by default set to 1 km.
109 Synchrotron radiation in very weak magnetic fields of the order of 1 Gauss
110 may require longer pathlength.
111 This can be achieved with using setMaxStepLength like
112 /testem/tracking/setMaxStepLength 100 km
113
114 8- HISTOGRAMS
115
116 TestEm16 produces 3 histograms which illustrate synchrotron radiation.
117 The photon energy spectrum (photons / energy bin) and the power spectrum
118 (photon spectrum weighted with the photon energy) and a histogram
119 of the path length between photon radiation is produced.
120
121 The histograms are managed by G4AnalysisManager and its Messenger.
122
123 The histos can be activated individually with the command :
124 /analysis/h1/set id nbBins valMin valMax unit
125 where 'unit' is the desired unit for the histo (MeV or KeV, cm or mm, etc..)
126
127 One can control the name of the histograms file with the command:
128 /analysis/setFileName name (default testem16)
129
130 It is possible to choose the format of the histogram file : root (default),
131 xml, csv, by using namespace in HistoManager.hh
132
133 It is also possible to print selected histograms on an ascii file:
134 /analysis/h1/setAscii id
135 All selected histos will be written on a file name.ascii (default testem16)
