89 lines
2.8 KiB
Markdown
89 lines
2.8 KiB
Markdown
\page Examplephasespace Example phasespace
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\author S. Incerti (a, *)\n
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a. LP2i, IN2P3 / CNRS / Bordeaux 1 University, 33175 Gradignan, France \n
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* e-mail: incerti@lp2ib.in2p3.fr \n
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## INTRODUCTION.
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The phasespace example shows how to simulate particle tracks in a cube of
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liquid water containing a scoring sphere, placed in its centre. The
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example creates two phase space files
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- one with the ROOT (psp.root) format,
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- one with the GRAS format (GRAS.csv),
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both scoring particles entering the sphere.
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## GEOMETRY SET-UP
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The geometry is a 100-micron side cube (World) made of liquid water (G4_WATER
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material), containing a sphere of 10-micron radius, placed in its center.
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Particles are shot along the Z axis (positive direction), starting at a
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Z = -12 microns from the center of the World.
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The World and sphere sizes and material can be changed directly
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in the phasespace.in macro file.
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The shooting is controled using GPS commands in phasespace.in.
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The variable density feature of materials is illustrated in
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DetectorConstruction. The material density can be changed directly in the
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phasespace.in macro file.
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## SET-UP
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Make sure $G4LEDATA points to the low energy electromagnetic data files.
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## HOW TO RUN THE EXAMPLE
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In interactive mode, run:
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```
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./phasespace
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```
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In batch, the macro phasespace.in can be used. It shows how to define dimensions
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and shoot different particle types.
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## PHYSICS
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The list of available Reference Physics Lists is shown when simulation starts.
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All Physics settings are done in the PhysicsList class.
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QGSP_BIC_HP is activated by default.
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At run time, tracks are killed inside the sphere,
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using in phasespace.in the command :
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```
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/step/killInsideScorer 1
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```
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## SIMULATION OUTPUT AND RESULT ANALYSIS
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The output results consists in a psp.root file, containing a ntuple, named
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"scorer".
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For each particle entering the sphere, when the PreStepPoint is located at
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the geometry boundary, it records :
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- the PDG encoding of the particle
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- the 3 PreStepPoint coordinates (in microns)
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- the 3 PreStepPoint momentum cosine (no unit)
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- the kinetic energy at PreStepPoint (in keV)
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This information is extracted from the SteppingAction class.
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The ROOT file can be easily analyzed using the provided ROOT macro file
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plot.C; to do so :
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* be sure to have ROOT installed on your machine
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* be sure to be in the directory containing the ROOT file created by phasespace
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* from there, launch ROOT by typing root
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* under your ROOT session, type in : .X plot.C to execute the macro file
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* alternatively you can type directly under your session : root plot.C
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The ROOT macro also writes a GRAS.csv file, following the format of GRAS (1).
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Such a file can for ex. be read with the moleculardna Geant4 advanced example (2).
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- (1) https://essr.esa.int/project/gras-geant4-radiation-analysis-for-space
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- (2) https://moleculardna.org
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