| 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 Example B2 7 Example B2
8 ---------- 8 ----------
9 9
10 This example simulates a simplified fixed tar 10 This example simulates a simplified fixed target experiment.
11 11
12 1- GEOMETRY DEFINITION 12 1- GEOMETRY DEFINITION
13 << 13
14 The setup consists of a target followed b 14 The setup consists of a target followed by six chambers of increasing
15 transverse size at defined instances from << 15 transverse size at defined instances from the target. These chambers are
16 located in a region called the Tracker re << 16 located in a region called the Tracker region.
17 Their shape are cylinders, constructed as 17 Their shape are cylinders, constructed as simple cylinders
18 (in B2a::DetectorConstruction) and as par << 18 (in B2aDetectorConstruction) and as parametrised volumes
19 (in B2b::DetectorConstruction), see also << 19 (in B2bDetectorConstruction), see also B2bChamberParameterisation class.
20 20
21 In addition, a global, uniform, and trans << 21 In addition, a global, uniform, and transverse magnetic field can be
22 applied using G4GlobalMagFieldMessenger, << 22 applied using G4GlobalMagFieldMessenger, instantiated in
23 B2[a,b]::DetectorConstruction::ConstructS << 23 B2[a,b]DetectorConstruction::ConstructSDandField with a non zero field value,
24 or via interactive commands. << 24 or via interactive commands.
25 For example: 25 For example:
26 26
27 /globalField/setValue 0.2 0 0 tesla 27 /globalField/setValue 0.2 0 0 tesla
28 << 28
29 An instance of the B2::TrackerSD class is << 29 An instance of the B2TrackerSD class is created and associated with each
30 logical chamber volume (in B2a) and with << 30 logical chamber volume (in B2a) and with the one G4LogicalVolume associated
31 with G4PVParameterised (in B2b). << 31 with G4PVParameterised (in B2b).
32 32
33 One can change the materials of the targe 33 One can change the materials of the target and the chambers
34 interactively via the commands defined in << 34 interactively via the commands defined in B2aDetectorMessenger
35 (or B2b::DetectorMessenger). For example: << 35 (or B2bDetectorMessenger). For example:
36 36
37 /B2/det/setTargetMaterial G4_WATER 37 /B2/det/setTargetMaterial G4_WATER
38 /B2/det/setChamberMaterial G4_Ar 38 /B2/det/setChamberMaterial G4_Ar
39 << 39
40 2- PHYSICS LIST 40 2- PHYSICS LIST
41 41
42 The particle's type and the physic proces 42 The particle's type and the physic processes which will be available
43 in this example are set in the FTFP_BERT << 43 in this example are set in the FTFP_BERT physics list. This physics list
44 requires data files for electromagnetic a 44 requires data files for electromagnetic and hadronic processes.
45 See more on installation of the datasets 45 See more on installation of the datasets in Geant4 Installation Guide,
46 Chapter 3.3: Note On Geant4 Datasets: 46 Chapter 3.3: Note On Geant4 Datasets:
47 http://geant4.web.cern.ch/geant4/UserDocu 47 http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/InstallationGuide/html/ch03s03.html
48 The following datasets: G4LEDATA, G4LEVEL 48 The following datasets: G4LEDATA, G4LEVELGAMMADATA, G4SAIDXSDATA and
49 G4ENSDFSTATEDATA are mandatory for this e 49 G4ENSDFSTATEDATA are mandatory for this example.
50 << 50
51 In addition, the build-in interactive com 51 In addition, the build-in interactive command:
52 /process/(in)activate processName 52 /process/(in)activate processName
53 allows the user to activate/inactivate th 53 allows the user to activate/inactivate the processes one by one.
54 54
55 3- ACTION INITALIZATION 55 3- ACTION INITALIZATION
56 56
57 A newly introduced class, B2::ActionInitial << 57 A newly introduced class, B2ActionInitialization,
58 instantiates and registers to Geant4 kernel 58 instantiates and registers to Geant4 kernel all user action classes.
59 << 59
60 While in sequential mode the action classes 60 While in sequential mode the action classes are instatiated just once,
61 via invoking the method: 61 via invoking the method:
62 B2::ActionInitialization::Build() << 62 B2ActionInitialization::Build()
63 in multi-threading mode the same method is 63 in multi-threading mode the same method is invoked for each thread worker
64 and so all user action classes are defined 64 and so all user action classes are defined thread-local.
65 65
66 A run action class is instantiated both thr << 66 A run action class is instantiated both thread-local
67 and global that's why its instance has is c 67 and global that's why its instance has is created also in the method
68 B2::ActionInitialization::BuildForMaster << 68 B2ActionInitialization::BuildForMaster()
69 which is invoked only in multi-threading mo 69 which is invoked only in multi-threading mode.
70 70
71 4- PRIMARY GENERATOR 71 4- PRIMARY GENERATOR
72 72
73 The primary generator action class employ << 73 The primary generator action class employs the G4ParticleGun.
74 The primary kinematics consists of a sing << 74 The primary kinematics consists of a single particle which starts at the world boundary
75 to the world boundary and hits the target << 75 and hits the target perpendicular to the entrance face. The type of the particle
76 face. The type of the particle and its en << 76 and its energy can be changed via the G4 built-in commands of
77 Geant4 built-in commands of the G4Particl << 77 the G4ParticleGun class.
78 << 78 Note that this particular case of starting a primary particle on the world boundary
>> 79 requires shooting in a direction towards inside the world.
>> 80
79 5- RUNS and EVENTS 81 5- RUNS and EVENTS
80 << 82
81 A run is a set of events. 83 A run is a set of events.
82 << 84
83 The user has control: 85 The user has control:
84 - at Begin and End of each run (class << 86 - at Begin and End of each run (class B2RunAction)
85 - at Begin and End of each event (clas << 87 - at Begin and End of each event (class B2EventAction)
86 - at Begin and End of each track (clas 88 - at Begin and End of each track (class TrackingAction, not used here)
87 - at End of each step (class SteppingAction, 89 - at End of each step (class SteppingAction, not used here)
88 << 90
89 The event number is written to the log fi << 91 The event number is written to the log file every requested number
90 of events in B2::EventAction::BeginOfEven << 92 of events in B2EventAction::BeginOfEventAction() and
91 B2::EventAction::EndOfEventAction(). << 93 B2EventAction::EndOfEventAction().
92 Moreover, for the first 100 events and ev << 94 Moreover, for the first 100 events and every 100 events thereafter
93 information about the number of stored tr << 95 information about the number of stored trajectories in the event
94 is printed as well as the number of hits << 96 is printed as well as the number of hits stored in the G4VHitsCollection.
95 << 97
96 The run number is printed at B2::RunActio << 98 The run number is printed at B2RunAction::BeginOfRunAction(), where the
97 G4RunManager is also informed how to SetR << 99 G4RunManager is also informed how to SetRandomNumberStore for storing
98 initial random number seeds per run or pe << 100 initial random number seeds per run or per event.
99 101
100 6- USER LIMITS 102 6- USER LIMITS
101 << 103
102 This example also illustrates how to intro 104 This example also illustrates how to introduce tracking constraints
103 like maximum step length, minimum kinetic 105 like maximum step length, minimum kinetic energy etc. via the G4UserLimits
104 class and associated G4StepLimiter and G4U << 106 class and associated G4StepLimiter and G4UserSpecialCuts processes.
105 See B2a::DetectorConstruction (or B2b::Det << 107 See B2aDetectorConstruction (or B2bDetectorConstruction).
106 108
107 The maximum step limit in the tracker regi 109 The maximum step limit in the tracker region can be set by the interactive
108 command (see B2a::DetectorMessenger, B2b:: << 110 command (see B2aDetectorMessenger, B2bDetectorMessenger classes).
109 For example: 111 For example:
110 112
111 /B2/det/stepMax 1.0 mm 113 /B2/det/stepMax 1.0 mm
112 114
113 7- DETECTOR RESPONSE 115 7- DETECTOR RESPONSE
114 << 116
115 A HIT is a step per step record of all th 117 A HIT is a step per step record of all the information needed to
116 simulate and analyse the detector respons 118 simulate and analyse the detector response.
117 << 119
118 In this example the Tracker chambers are 120 In this example the Tracker chambers are considered to be the detector.
119 Therefore, the chambers are declared 'sen 121 Therefore, the chambers are declared 'sensitive detectors' (SD) in
120 the B2a::DetectorConstruction (or B2b::De << 122 the B2aDetectorConstruction (or B2bDetectorConstruction) class.
121 They are associated with an instance of t << 123 They are associated with an instance of the B2TrackerSD class.
122 << 124
123 Then, a Hit is defined as a set of 4 info 125 Then, a Hit is defined as a set of 4 informations per step, inside
124 the chambers, namely: 126 the chambers, namely:
125 - the track identifier (an integer), 127 - the track identifier (an integer),
126 - the chamber number, 128 - the chamber number,
127 - the total energy deposit in this step, and 129 - the total energy deposit in this step, and
128 - the position of the energy deposit. 130 - the position of the energy deposit.
129 131
130 A given hit is an instance of the class B << 132 A given hit is an instance of the class B2TrackerHit which is created
131 during the tracking of a particle, step b 133 during the tracking of a particle, step by step, in the method
132 B2::TrackerSD::ProcessHits(). This hit is << 134 B2TrackerSD::ProcessHits(). This hit is inserted in a HitsCollection.
133 135
134 The HitsCollection is printed at the end 136 The HitsCollection is printed at the end of each event (via the method
135 B2::TrackerSD::EndOfEvent()), under the c << 137 B2TrackerSD::EndOfEvent()), under the control of the command:
136 /hits/verbose 2 138 /hits/verbose 2
137 139
138 The following paragraphs are common to all ba 140 The following paragraphs are common to all basic examples
139 141
140 A- VISUALISATION 142 A- VISUALISATION
141 143
142 The visualization manager is set via the G4 144 The visualization manager is set via the G4VisExecutive class
143 in the main() function in exampleB2a.cc (or << 145 in the main() function in exampleB2a.cc (or exampleB2b.cc).
144 The initialisation of the drawing is done v 146 The initialisation of the drawing is done via a set of /vis/ commands
145 in the macro vis.mac. This macro is automat 147 in the macro vis.mac. This macro is automatically read from
146 the main function when the example is used 148 the main function when the example is used in interactive running mode.
147 149
148 By default, vis.mac opens an OpenGL viewer 150 By default, vis.mac opens an OpenGL viewer (/vis/open OGL).
149 The user can change the initial viewer by c 151 The user can change the initial viewer by commenting out this line
150 and instead uncommenting one of the other / 152 and instead uncommenting one of the other /vis/open statements, such as
151 HepRepFile or DAWNFILE (which produce files 153 HepRepFile or DAWNFILE (which produce files that can be viewed with the
152 HepRApp and DAWN viewers, respectively). N 154 HepRApp and DAWN viewers, respectively). Note that one can always
153 open new viewers at any time from the comma 155 open new viewers at any time from the command line. For example, if
154 you already have a view in, say, an OpenGL 156 you already have a view in, say, an OpenGL window with a name
155 "viewer-0", then 157 "viewer-0", then
156 /vis/open DAWNFILE 158 /vis/open DAWNFILE
157 then to get the same view 159 then to get the same view
158 /vis/viewer/copyView viewer-0 160 /vis/viewer/copyView viewer-0
159 or to get the same view *plus* scene-modifi 161 or to get the same view *plus* scene-modifications
160 /vis/viewer/set/all viewer-0 162 /vis/viewer/set/all viewer-0
161 then to see the result 163 then to see the result
162 /vis/viewer/flush 164 /vis/viewer/flush
163 165
164 The DAWNFILE, HepRepFile drivers are always 166 The DAWNFILE, HepRepFile drivers are always available
165 (since they require no external libraries), 167 (since they require no external libraries), but the OGL driver requires
166 that the Geant4 libraries have been built w 168 that the Geant4 libraries have been built with the OpenGL option.
167 169
168 Since 11.1, the TSG visualization driver ca <<
169 file output in png, jpeg, gl2ps formats wit <<
170 It can be controlled via UI commands provid <<
171 demonstrated in the tsg_offscreen.mac macro <<
172 <<
173 For more information on visualization, incl 170 For more information on visualization, including information on how to
174 install and run DAWN, OpenGL and HepRApp, s 171 install and run DAWN, OpenGL and HepRApp, see the visualization tutorials,
175 for example, 172 for example,
176 http://geant4.slac.stanford.edu/Presentatio 173 http://geant4.slac.stanford.edu/Presentations/vis/G4[VIS]Tutorial/G4[VIS]Tutorial.html
177 (where [VIS] can be replaced by DAWN, OpenG 174 (where [VIS] can be replaced by DAWN, OpenGL and HepRApp)
178 175
179 The tracks are automatically drawn at the e 176 The tracks are automatically drawn at the end of each event, accumulated
180 for all events and erased at the beginning 177 for all events and erased at the beginning of the next run.
181 178
182 B- USER INTERFACES 179 B- USER INTERFACES
183 << 180
184 The user command interface is set via the G 181 The user command interface is set via the G4UIExecutive class
185 in the main() function in exampleB2a.cc << 182 in the main() function in exampleB2a.cc
186 << 183 The selection of the user command interface is then done automatically
187 The selection of the user command interface << 184 according to the Geant4 configuration or it can be done explicitly via
188 according to the Geant4 configuration or it << 185 the third argument of the G4UIExecutive constructor (see exampleB4a.cc).
189 the third argument of the G4UIExecutive con << 186
190 <<
191 The gui.mac macros are provided in examples <<
192 is automatically executed if Geant4 is buil <<
193 It is also possible to customise the icons <<
194 demonstrated in the icons.mac macro in exam <<
195 <<
196 C- HOW TO RUN 187 C- HOW TO RUN
197 << 188
198 - Execute exampleB2a in the 'interactive m 189 - Execute exampleB2a in the 'interactive mode' with visualization
199 % exampleB2a 190 % exampleB2a
200 and type in the commands from run1.mac l << 191 and type in the commands from run1.mac line by line:
201 Idle> /tracking/verbose 1 << 192 Idle> /tracking/verbose 1
202 Idle> /run/beamOn 1 193 Idle> /run/beamOn 1
203 Idle> ... 194 Idle> ...
204 Idle> exit 195 Idle> exit
205 or 196 or
206 Idle> /control/execute run1.mac or ru << 197 Idle> /control/execute run1.mac or run2.mac
207 .... 198 ....
208 Idle> exit 199 Idle> exit
209 200
210 - Execute exampleB2a in the 'batch' mode f << 201 - Execute exampleB2a in the 'batch' mode from macro files
211 (without visualization) 202 (without visualization)
212 % exampleB2a run2.mac 203 % exampleB2a run2.mac
213 % exampleB2a exampleB2.in > exampleB2. 204 % exampleB2a exampleB2.in > exampleB2.out
214 << 205