Gabriele Cosmo
88 lines
3.0 KiB
Plaintext
88 lines
3.0 KiB
Plaintext
-------------------------------------------------------------------
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=========================================================
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Geant4 - X-Ray Telescope Example
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=========================================================
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Introduction
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------------
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XrayTel is an advanced Geant4 example based on a realistic simulation of
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an X-ray Telescope. It is based on work carried out by a team of Geant4
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experts to simulate the interaction between X-ray Telescopes XMM-Newton
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and Chandra with low energy protons present in the orbital radiation
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background. The X-ray mirrors are designed to collect x-ray photons at
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grazing-incidence angles and focus them onto detectors at the focal plane.
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However, this mechanism also seems to work for low energy protons which,
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if they reach the detectors in sufficient numbers, can cause damage.
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In this example, the geometry has been simplified by using a single mirror
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shell and no baffles, but all the dimensions and materials are realistic.
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The aim of this advanced example is to illustrate the use advanced
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GUI, visualisation, particle generation and analysis schemes available
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in Geant4:
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- macros are provided to display the geometry and particle tracks with
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OpenGL, DAWN Postscript or VRML visualisation
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- the generation of particles is done via the new General Particle Source
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- histograming facilities are available through the G4AnalysisManager tools
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In order to be able to use any of these packages, prior installation is
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necessary and a number of environment variables will have to be set.
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NOTE: The geometry is refreshed on the viewer at the beginning of each run,
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but the tracks are plotted only in case an interesting event occurs.
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This is the case only for about 1 every 10**4 events.
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2. Run
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To execute a sample simulation with visualisation of proton tracks
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reaching the detector run:
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XrayTel
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execute command "/control/execute test.mac"
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To enable visualisation, uncomment one line from test.mac:
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/control/execute vis.mac
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If the analysis options are set, histograms will
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automatically created and the corresponding files will be created.
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A 1D histogram will display the energy distribution of the protons
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that reach the detector at the end of the run.
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3. Detector description
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The telescope and detector geometry is defined in
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XrayTelDetectorConstruction.cc
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4. Physics processes
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The physics processes are in XrayTelPhysicsList.cc
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The main process in this example is G4hMultipleScattering for scattering of the protons
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off the mirror surfaces.
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5. Event generation
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This is done using the new General Particle Source. Documentation for
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this can be found in:
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http://reat.space.qinetiq.com/gps/
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6. Analysis
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Relevant information from the simulation is processed in the XrayTelAnalysis
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class and saved, through the G4AnalysisManager interface, to Histograms and
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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().
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No external software is required (apart from the Hdf5 case).
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