[1230] | 1 | $Id: README,v 1.14 2009/11/20 18:08:53 santin Exp $ |
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[807] | 2 | ------------------------------------------------------------------- |
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| 3 | |
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| 4 | ========================================================= |
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| 5 | Geant4 - X-Ray Telescope Example |
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| 6 | ========================================================= |
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| 7 | |
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| 8 | |
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| 9 | Introduction |
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| 10 | ------------ |
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| 11 | XrayTel is an advanced Geant4 example based on a realistic simulation of |
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| 12 | an X-ray Telescope. It is based on work carried out by a team of Geant4 |
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| 13 | experts to simulate the interaction between X-ray Telescopes XMM-Newton |
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| 14 | and Chandra with low energy protons present in the orbital radiation |
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| 15 | background. The X-ray mirrors are designed to collect x-ray photons at |
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| 16 | grazing-incidence angles and focus them onto detectors at the focal plane. |
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| 17 | However, this mechanism also seems to work for low energy protons which, |
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| 18 | if they reach the detectors in sufficient numbers, can cause damage. |
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| 19 | In this example, the geometry has been simplified by using a single mirror |
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| 20 | shell and no baffles, but all the dimensions and materials are realistic. |
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| 21 | |
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| 22 | The aim of this advanced example is to illustrate the use advanced |
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| 23 | GUI, visualisation, particle generation and analysis schemes available |
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| 24 | in Geant4: |
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| 25 | |
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| 26 | - macros are provided to display the geometry and particle tracks with |
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| 27 | OpenGL, DAWN Postscript or VRML visualisation |
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| 28 | |
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| 29 | - the generation of particles is done via the new General Particle Source |
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| 30 | |
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| 31 | - histograming facilities are available through the AIDA 3.0 interfaces. |
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| 32 | |
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| 33 | - on-line visualisation of histograms is provided through the AIDA 3.0 interface. |
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| 34 | |
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| 35 | In order to be able to use any of these packages, prior installation is |
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| 36 | necessary and a number of environment variables will have to be set. |
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| 37 | |
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| 38 | |
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| 39 | NOTE: The geometry is refreshed on the viewer at the beginning of each run, |
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| 40 | but the tracks are plotted only in case an interesting event occurs. |
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| 41 | This is the case only for about 1 every 10**4 events. |
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| 42 | |
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| 43 | |
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| 44 | |
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| 45 | 2. Run |
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| 46 | |
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| 47 | To execute a sample simulation with visualisation of proton tracks |
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| 48 | reaching the detector run: |
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| 49 | |
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| 50 | XrayTel |
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| 51 | |
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| 52 | execute command "/control/execute xxxxx.mac" |
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| 53 | |
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| 54 | visualisation macros provided are |
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| 55 | - opengl.mac for OpenGL display |
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| 56 | - vrml.mac for VRML display and output file |
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| 57 | - dawn.mac for dawn display and PS output file |
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| 58 | |
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| 59 | To execute a run without visualisation use |
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| 60 | - test.mac |
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| 61 | |
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| 62 | |
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| 63 | If the analysis options are set, histograming windows will |
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| 64 | automatically open and the corresponding files will be created. |
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| 65 | A 1D histogram will display the energy distribution of the protons |
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| 66 | that reach the detector at the end of the run. |
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| 67 | |
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| 68 | |
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| 69 | 3. Detector description |
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| 70 | |
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| 71 | The telescope and detector geometry is defined in |
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| 72 | XrayTelDetectorConstruction.cc |
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| 73 | |
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| 74 | |
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| 75 | 4. Physics processes |
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| 76 | |
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| 77 | The physics processes are in XrayTelPhysicsList.cc |
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[1230] | 78 | The main process in this example is G4hMultipleScattering for scattering of the protons |
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| 79 | off the mirror surfaces. |
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[807] | 80 | |
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| 81 | |
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| 82 | 5. Event generation |
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| 83 | |
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| 84 | This is done using the new General Particle Source. Documentation for |
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| 85 | this can be found in: |
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| 86 | |
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| 87 | http://reat.space.qinetiq.com/gps/ |
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| 88 | |
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| 89 | |
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| 90 | 6. Analysis |
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| 91 | |
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| 92 | In case the variable G4ANALYSIS_USE is set: |
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| 93 | setenv G4ANALYSIS_USE 1 |
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| 94 | relevant information from the simulation is processed in the XrayTelAnalysis |
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| 95 | class and saved, through the AIDA interface, to Histograms and Tuples. |
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| 96 | |
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| 97 | Compilation and link flags to hook any AIDA compliant system are passed |
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| 98 | to the Geant4 GNUmakefile system by using the "aida-config" tool |
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| 99 | that should come with any AIDA compliant system. |
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| 100 | Specifically in the GNUmakefile you find the 2 lines: |
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| 101 | CPPFLAGS += `aida-config --include` |
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| 102 | LDFLAGS += `aida-config --lib` |
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| 103 | |
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[1230] | 104 | For more information about AIDA please look at: |
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[807] | 105 | http://aida.freehep.org/ |
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| 106 | |
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[1230] | 107 | Presently, tools |
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[807] | 108 | - OpenScientist (http://openscientist.lal.in2p3.fr/) |
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| 109 | - JAS (http://jas.freehep.org/jas3/) |
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[1230] | 110 | - iAIDA (http://iaida.dynalias.net/Intro.html) |
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[807] | 111 | provide an implementation of AIDA 3.2.1 |
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| 112 | |
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| 113 | To build and execute the example on platforms where there is no |
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| 114 | implementation of the analysis system, the environment variables |
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| 115 | must not be set. |
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| 116 | |
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