| Geant4 Cross Reference |
1
2 =========================================
3 Geant4 - an Object-Oriented Toolkit for S
4 =========================================
5
6
7
8 field04 Example
9 ---------------
10
11 This example shows how to define/use OVER
12 in Geant4. Fields might be either magneti
13
14 Credit goes to Tom Roberts and Muons Inc.
15 and ideas were taken at liberty from the
16 G4BEAMLINE release 1.12.
17
18 http://g4beamline.muonsinc.com
19
20 **************
21 *Classes Used*
22 **************
23
24 1 - main()
25
26 See field04.cc.
27
28 The example can be run with the follow
29
30 % field04 [-m macro ] [-p physicsList]
31
32 If a macro is provided with the option
33 otherwise the program open the interac
34 default initialization macro init_vis.
35 to start the program without initializ
36
37 For example:
38 to assign the F04PhysicsList:
39 % field04 -p QGSP_BERT
40
41 an initial random number seed with:
42 % field04 field04.in -r 12345
43
44 to start with a macro file and an init
45 % field04 -m field04.in -r 12345
46
47
48 2- GEOMETRY DEFINITION
49
50 The geometry consists of two solenoida
51 followed by a (blue-colored "TransferM
52 axis and center of the "CaptureMgnt" c
53 position of the "TransferMgnt" relativ
54 "CaptureMgnt", as well as its axis ang
55 "Target" is positioned inside the "Cap
56 from 0 to 180 deg, and hence also the
57 proton beam wrt the "CaptureMgnt"'s ax
58 inside the "TransferMgnt", its default
59 upstream end of the "TransferMgnt". Fi
60 located inside the "TransferMgnt", by
61
62
63 The "World" consists of a solid cylind
64 (It is the responsibility of the use
65 large enough to contain the rest of
66
67 Three parameters define the world :
68 - the material of the world,
69 - the world radius,
70 - the world length.
71
72 Example (default values):
73 /field04/SetWorldMat G4_AIR
74 /field04/SetWorldR 5.0 m
75 /field04/SetWorldZ 50.0 m
76
77
78 The "Target" is a solid cylinder made
79
80 Five parameters define the target:
81 - the material of the target,
82 - the target radius,
83 - the target thickness,
84 - the target position inside the "Capt
85 - the target axis angle relative to th
86
87 Example (default values):
88 /field04/SetTgtMat G4_W
89 /field04/SetTgtRad 0.4 cm
90 /field04/SetTgtThick 16.0 cm
91 /field04/SetTgtPos 0.0 cm
92 /field04/SetTgtAng 170
93
94
95 The "Degrader" is a solid cylinder ma
96
97 Four parameters define the degrader:
98 - the material of the degrader,
99 - the degrader radius,
100 - the degrader thickness,
101 - the degrader position relative to th
102
103 Example (default values):
104 /field04/SetDgrMat G4_Pb
105 /field04/SetDgrRad 30.0 cm
106 /field04/SetDgrThick 0.1 cm
107 #/field04/SetDgrPos -7.4 m
108
109
110 The "CaptureMgnt" is a solenoid (vacuu
111 a two-sided or a one-sided magnetic bo
112 varying linearly from the center value
113 The one-sided F04FocusSolenoid has the
114 on the z < 0 side.
115
116 Four parameters define the "CaptureMgn
117 - the magnet radius,
118 - the magnet length,
119 - the weaker magnetic field at the cen
120 - the stronger magnetic field at the e
121
122 Example (default values):
123 /field04/SetCaptureR 0.6 m
124 /field04/SetCaptureZ 4.0 m
125 /field/SetCaptureB1 2.5 tesla
126 /field/SetCaptureB2 5.0 tesla
127
128
129 The "TransferMgnt" is a solenoid (vacu
130 constant B-field. When the "TransferMg
131 the "CaptureMgnt", its relative positi
132
133 Four parameters define the "TransferMg
134 - the magnet radius,
135 - the magnet length,
136 - the magnet field,
137 - the magnet relative position
138 (its upstream face wrt the downstrea
139
140 Example (default values):
141 /field04/SetTransferR 0.3 m
142 /field04/SetTransferZ 15.0 m
143 /field/SetTransferB 5.0 tesla
144 /field04/SetTransferP 0.0 m
145
146 The default geometry is constructed in
147 but all the parameters can be changed
148 the F04DetectorMessenger class.
149
150
151 3- MATERIAL DEFINITION
152
153 Material definitions are done through
154 which keeps a pointer to the G4NistMan
155 GetMaterial by name (G4String) which i
156 G4NistManager::FindOrBuildMaterial, an
157 methods. It has also a method CreateMa
158 absent from the NIST data base, shows
159 G4NistManager::ConstructNewMaterial me
160
161
162 4- AN EVENT: THE PRIMARY GENERATOR
163
164 The primary kinematic consists of a si
165 target perpendicular to its upstream f
166 and its energy are set in the F04Prima
167 be changed via the G4 build-in command
168 In addition, there is a fRndmFlag, whi
169 explore randomly the whole cross secti
170 beam consists of 500 MeV protons, star
171 the target, directed along dx = dy = 0
172 The default direction should NOT be ch
173 x/y/zvertex commands are relative to t
174
175 Example:
176 /gun/random on
177 #/gun/xvertex 0 mm
178 #/gun/yvertex 0 mm
179 #/gun/zvertex -100 mm
180
181
182 5- DETECTOR RESPONSE
183
184 Information is extracted from the prog
185 at the TestPlane.
186
187
188 6- PHYSICS
189
190 The F04PhysicsList extends a selected
191 The base physics list name is provided
192 constructor.
193
194 In addition to processes defined in th
195 there is added the F04StepMax process
196 via dedicated commands in F04PhysicsLi
197
198 The command to define maximum step:
199 /exp/phys/stepMax value unit
200
201 The decay of pions can be assigned via
202
203 /decay/pienu
204 /decay/pimunu
205
206 The pienu assignment includes a small
207 e nu gamma (G4PionRadiativeDecayChanne
208
209 The standard/default muon decay chain
210 G4MuonDecayChannelWithSpin and 1.4% G4
211 in ConstructParticle().
212
213 The pion decay process G4PolDecay inhe
214 the virtual method - empty in the base
215
216 The muon decay process is G4DecayWithS
217
218 Furthermore, the following commands ar
219 may only be used AFTER /run/initialize
220
221 /process/inactivate msc
222 /process/activate msc
223
224 7- Overlapping Fields
225
226 The F04GlobalField (a singleton) is in
227 F04DetectorConstruction() and assigned
228 in UpdateField():
229
230 fFieldManager = GetGlobalFieldManager(
231 fFieldManager->SetDetectorField(this);
232
233 The F04GlobalField has a std::vector<E
234
235 The field from each individual beamlin
236 F04ElementField object. Any number of
237 objects can be added to the F04GlobalF
238 represents an element with an EM field
239 F04ElementField to the global F04Globa
240
241 Of course, the F04GlobalField has the
242
243 Before /run/initialize in the macro fi
244 field command must have been issued if
245 field commands was employed:
246
247 /field/update
248
249 Other options are:
250
251 /field/setStepperType 4
252 /field/setMinStep 10 mm
253 /field/setDeltaChord 3.0 mm
254 /field/setDeltaOneStep 0.01 mm
255 /field/setDeltaIntersection 0.1 mm
256 /field/setEpsMin 2.5e-7 mm
257 /field/setEpsMax 0.05 mm
258
259 Each field element has a rectilinear b
260 coordinate space which is checked befo
261 actually be inside the F04ElementField
262 SetGlobalPoint is called 8 times for t
263 bounding box, after a local->global co
264
265 The F04ElementField is the interface c
266 compute the field value at a given poi
267
268 A beamline element, for example the F0
269 from F04ElementField and implement the
270
271 simpleSolenoid
272 = new F04SimpleSolenoid(B, l, logicT
273
274 Besides the magnetic field and the len
275 the constructor needs the knowledge of
276 the beamline element and where its cen
277 'World'.
278
279 The F04ElementField has a G4AffineTran
280 allows the quick computation of coordi
281 only be determined by knowing the elem
282 the global frame and after all of the
283 For this reason, the object is prepare
284 constructor providing it with the coor
285 to the G4LogicalVolume. Later the Cons
286 calculate the fGlobal2local and the bo
287 from the F04RunAction::BeginOfRunActio
288 certain that the geometry has been com
289
290 FieldList* fields = F04GlobalField::Ge
291
292 if (fields) {
293 if (fields->size()>0) {
294 FieldList::iterator i;
295 for (i=fields->begin(); i!=field
296 }
297 }
298
299 The F04ElementField constructor will a
300 F04GlobalField. Finally, its AddFieldV
301 for this element to field[].
302
303
304 8- User Action Classes
305
306 F04RunActionMessenger:
307
308 /rndm/save freq - to save
309 0 not saved
310 >0 saved on: b
311 1 saved on:
312 2 saved on: e
313 /rndm/read random/run0evt
314
315 F04RunAction:
316 BeginOfRunAction: Deal wi
317 initialization etc. Call
318 F04ElementFields in the F
319 EndOfRunAction: random nu
320
321 F04EventActionMessenger:
322 /event/setverbose
323
324 F04EventAction(RunAction* RA):
325 Customized BeginOfEvent p
326 EndofEvent:
327 saveEngingStatus and show
328 in F04RunAction
329
330 F04TrackingAction:
331 PreUserTrackingAction: In
332 and set the application T
333 PostUserTrackingAction: R
334 and decide to save random
335
336 F04SteppingActionMessenger:
337
338 F04SteppingAction:
339 UserSteppingAction: Kill
340 volume. Diagnostic/histog
341 TestPlane. Find decay pos
342 FIRST reverses z-momentum
343 F04UserTrackInformation o
344
345 F04StackingAction:
346 Track only primaries, pi+
347
348 F04UserTrackInformation:
349 Keep an application F04Tr
350 undefined, left, rig
351
352 F04SteppingVerbose:
353 Only print track header an
354 pi+ and mu+.
355 Note: the information for
356
357 F04Trajectory, TrajectoryPoint:
358 Example of application spe
359
360 9- HOW TO START ?
361
362 - Execute field04 in 'batch' mode from
363 % field04 -m field04.in
364
365 - Execute field04 in 'interactive' mod
366 % field04
367 ....
368 Idle> type your commands
369 ....
370
371 - Execute field04 in 'interactive' mod
372 % field04 -s preinit
373 ....
374 Idle> type your commands, then
375 Idle> /run/initialize
376 Idle> /control/execute vis.mac
377 ....