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0004 Geant4 - X-Ray Telescope Example
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0006
0007
0008 Introduction
0009 ------------
0010 XrayTel is an advanced Geant4 example based on a realistic simulation of
0011 an X-ray Telescope. It is based on work carried out by a team of Geant4
0012 experts to simulate the interaction between X-ray Telescopes XMM-Newton
0013 and Chandra with low energy protons present in the orbital radiation
0014 background. The X-ray mirrors are designed to collect x-ray photons at
0015 grazing-incidence angles and focus them onto detectors at the focal plane.
0016 However, this mechanism also seems to work for low energy protons which,
0017 if they reach the detectors in sufficient numbers, can cause damage.
0018 In this example, the geometry has been simplified by using a single mirror
0019 shell and no baffles, but all the dimensions and materials are realistic.
0020
0021 The aim of this advanced example is to illustrate the use advanced
0022 GUI, visualisation, particle generation and analysis schemes available
0023 in Geant4:
0024
0025 - macros are provided to display the geometry and particle tracks with
0026 OpenGL, DAWN Postscript or VRML visualisation
0027
0028 - the generation of particles is done via the new General Particle Source
0029
0030 - histograming facilities are available through the G4AnalysisManager tools
0031
0032 In order to be able to use any of these packages, prior installation is
0033 necessary and a number of environment variables will have to be set.
0034
0035
0036 NOTE: The geometry is refreshed on the viewer at the beginning of each run,
0037 but the tracks are plotted only in case an interesting event occurs.
0038 This is the case only for about 1 every 10**4 events.
0039
0040
0041
0042 2. Run
0043
0044 To execute a sample simulation with visualisation of proton tracks
0045 reaching the detector run:
0046
0047 XrayTel
0048
0049 execute command "/control/execute test.mac"
0050
0051 To enable visualisation, uncomment one line from test.mac:
0052 /control/execute vis.mac
0053
0054 If the analysis options are set, histograms will
0055 automatically created and the corresponding files will be created.
0056 A 1D histogram will display the energy distribution of the protons
0057 that reach the detector at the end of the run.
0058
0059
0060 3. Detector description
0061
0062 The telescope and detector geometry is defined in
0063 XrayTelDetectorConstruction.cc
0064
0065
0066 4. Physics processes
0067
0068 The physics processes are in XrayTelPhysicsList.cc
0069 The main process in this example is G4hMultipleScattering for scattering of the protons
0070 off the mirror surfaces.
0071
0072
0073 5. Event generation
0074
0075 This is done using the new General Particle Source. Documentation for
0076 this can be found in:
0077
0078 http://reat.space.qinetiq.com/gps/
0079
0080
0081 6. Analysis
0082
0083 Relevant information from the simulation is processed in the XrayTelAnalysis
0084 class and saved, through the G4AnalysisManager interface, to Histograms and
0085 Tuples. The output file is written in Root format, but one can easily switch to Xml (or Csv, Hdf5) by changing the G4AnalysisManager default file type in XrayTelAnalysis::book().
0086 No external software is required (apart from the Hdf5 case).
0087
