| Geant4 Cross Reference |
>> 1 $Id$
1 ---------------------------------------------- 2 -------------------------------------------------------------------
2 3
3 ========================================= 4 =========================================================
4 Geant4 - X-Ray Telescope Exampl 5 Geant4 - X-Ray Telescope Example
5 ========================================= 6 =========================================================
6 7
7 8
8 Introduction 9 Introduction
9 ------------ 10 ------------
10 XrayTel is an advanced Geant4 example based on 11 XrayTel is an advanced Geant4 example based on a realistic simulation of
11 an X-ray Telescope. It is based on work carri 12 an X-ray Telescope. It is based on work carried out by a team of Geant4
12 experts to simulate the interaction between X- 13 experts to simulate the interaction between X-ray Telescopes XMM-Newton
13 and Chandra with low energy protons present in 14 and Chandra with low energy protons present in the orbital radiation
14 background. The X-ray mirrors are designed to 15 background. The X-ray mirrors are designed to collect x-ray photons at
15 grazing-incidence angles and focus them onto d 16 grazing-incidence angles and focus them onto detectors at the focal plane.
16 However, this mechanism also seems to work for 17 However, this mechanism also seems to work for low energy protons which,
17 if they reach the detectors in sufficient numb 18 if they reach the detectors in sufficient numbers, can cause damage.
18 In this example, the geometry has been simplif 19 In this example, the geometry has been simplified by using a single mirror
19 shell and no baffles, but all the dimensions a 20 shell and no baffles, but all the dimensions and materials are realistic.
20 21
21 The aim of this advanced example is to illustr 22 The aim of this advanced example is to illustrate the use advanced
22 GUI, visualisation, particle generation and an 23 GUI, visualisation, particle generation and analysis schemes available
23 in Geant4: 24 in Geant4:
24 25
25 - macros are provided to display the geometry 26 - macros are provided to display the geometry and particle tracks with
26 OpenGL, DAWN Postscript or VRML visualisati 27 OpenGL, DAWN Postscript or VRML visualisation
27 28
28 - the generation of particles is done via the 29 - the generation of particles is done via the new General Particle Source
29 30
30 - histograming facilities are available throu 31 - histograming facilities are available through the G4AnalysisManager tools
31 32
32 In order to be able to use any of these packag 33 In order to be able to use any of these packages, prior installation is
33 necessary and a number of environment variable 34 necessary and a number of environment variables will have to be set.
34 35
35 36
36 NOTE: The geometry is refreshed on the viewer 37 NOTE: The geometry is refreshed on the viewer at the beginning of each run,
37 but the tracks are plotted only in case 38 but the tracks are plotted only in case an interesting event occurs.
38 This is the case only for about 1 every 39 This is the case only for about 1 every 10**4 events.
39 40
40 41
41 42
42 2. Run 43 2. Run
43 44
44 To execute a sample simulation with visualisat 45 To execute a sample simulation with visualisation of proton tracks
45 reaching the detector run: 46 reaching the detector run:
46 47
47 XrayTel 48 XrayTel
48 49
49 execute command "/control/execute test.mac" 50 execute command "/control/execute test.mac"
50 51
51 To enable visualisation, uncomment one line fr 52 To enable visualisation, uncomment one line from test.mac:
52 /control/execute vis.mac 53 /control/execute vis.mac
53 54
54 If the analysis options are set, histograms wi 55 If the analysis options are set, histograms will
55 automatically created and the corresponding fi 56 automatically created and the corresponding files will be created.
56 A 1D histogram will display the energy distrib 57 A 1D histogram will display the energy distribution of the protons
57 that reach the detector at the end of the run. 58 that reach the detector at the end of the run.
58 59
59 60
60 3. Detector description 61 3. Detector description
61 62
62 The telescope and detector geometry is defined 63 The telescope and detector geometry is defined in
63 XrayTelDetectorConstruction.cc 64 XrayTelDetectorConstruction.cc
64 65
65 66
66 4. Physics processes 67 4. Physics processes
67 68
68 The physics processes are in XrayTelPhysicsLis 69 The physics processes are in XrayTelPhysicsList.cc
69 The main process in this example is G4hMultipl 70 The main process in this example is G4hMultipleScattering for scattering of the protons
70 off the mirror surfaces. 71 off the mirror surfaces.
71 72
72 73
73 5. Event generation 74 5. Event generation
74 75
75 This is done using the new General Particle So 76 This is done using the new General Particle Source. Documentation for
76 this can be found in: 77 this can be found in:
77 78
78 http://reat.space.qinetiq.com/gps/ 79 http://reat.space.qinetiq.com/gps/
79 80
80 81
81 6. Analysis 82 6. Analysis
82 83
83 Relevant information from the simulation is pr 84 Relevant information from the simulation is processed in the XrayTelAnalysis
84 class and saved, through the G4AnalysisManager 85 class and saved, through the G4AnalysisManager interface, to Histograms and
85 Tuples. The output file is written in Root for << 86 Tuples. The output file is written in XML format, but one can easily switch to
86 No external software is required (apart from t << 87 ROOT (or Hbook) by changing the appropriate #include in XrayTelAnalysis.hh
>> 88 No external software is required (apart from the hbook case, in which the CERNLIB
>> 89 must be installed and a FORTRAN compiler must be present)
87 90