Clatterbridge: Difference between revisions
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The protons are generated using the G4ParticleGun class, and the physics list used is QGSP_BIC_HP, standard for simulating clinical proton beams. | The protons are generated using the G4ParticleGun class, and the physics list used is QGSP_BIC_HP, standard for simulating clinical proton beams. | ||
The energy of the beam after travelling through the beamline components is measured by tracking the energy deposition of individual protons within the water volume, using the | The energy of the beam after travelling through the beamline components is measured by tracking the energy deposition of individual protons within the water volume, using an implementation of the <code> G4VSensitiveDetector.cc </code> class. This simulation produces a post-beamline energy of 60.08 MeV and a Bragg peak at depth '''[insert depth]'''. | ||
'''[insert image of visualisation]''' | '''[insert image of visualisation]''' | ||
Revision as of 09:15, 27 July 2016
Simulation of the Clatterbridge beamline
This simulation models the monoenergetic 62.5 MeV proton beam at Clatterbridge Cancer Centre, as it traverses the components of the beamline and is then deposited into a volume of water. The beamline components are contained within a geometry modelling the Clatterbridge treatment room.
The protons are generated using the G4ParticleGun class, and the physics list used is QGSP_BIC_HP, standard for simulating clinical proton beams.
The energy of the beam after travelling through the beamline components is measured by tracking the energy deposition of individual protons within the water volume, using an implementation of the G4VSensitiveDetector.cc class. This simulation produces a post-beamline energy of 60.08 MeV and a Bragg peak at depth [insert depth].
[insert image of visualisation]
Running the simulation
Run macro proton.mac
This will run the simulation and produce the required output files.
[username@plus1 ProtonPB_build]$ ./protonPB proton.mac
Output files
The simulation code and proton.mac produce several output files:
kin.txt
This text file contains the output information from SteppingAction.cc , printed on a step-by-step basis for each proton (event). The first column contains the z position of the particle, relative to the position of the source at the inner room boundary. The second column contains the energy (MeV) of the proton at this z position.
300 62.3248 300 62.0776 300 62.2042 300 62.4347 300 62.2698 300 62.2164
Data Analysis
Open ROOT and run analysis file
The simulation analysis file reads the data in the output files and produces the associated plots.
[username@plus1 ProtonPB_build]$ root -l root [0] .x simulation_analysis.C
Proton energy deposition in water
Proton stopping distance in water
Proton flux along beamline
Kinetic energy of beam
Changing parameters
Initial beam parameters
Initial parameters of the proton beam can be modified in proton.mac
Beam radius
/gps/pos/radius 3 mm
Beam energy
This simulation models the proton beam source with a Gaussian distribution.
/gps/ene/type Gauss /gps/ene/mono 62.5 MeV /gps/ene/sigma 0.082 MeV
Source position
The proton source is positioned at z = -420 cm relative to the centre of the inner room (the mother volume), which translates as the wall surface of the inner room.
/gps/pos/type Plane /gps/pos/shape Circle /gps/pos/centre 0.0 0.0 -420 cm
Scoring mesh
Longitudinal scoring mesh
A longitudinal scoring mesh extends along the length of the beamline from the source to the water volume. The mesh utilises a filter to detect the flux of protons per cm2 and writes the data to the text file FluxLongitudinal.txt . The location of the mesh centre can be changed in proton.mac , in addition to the dimensions of the mesh and the number of bins.
/score/create/boxMesh waterMeshlongitudinal /score/mesh/boxSize 10. 10. 10. cm /score/mesh/nBin 1 1 400 /score/mesh/translate/xyz 0. 0. -226 cm
The filter can also be changed to observe the flux of particles other than protons:
/score/quantity/cellFlux protonFlux /score/filter/particle protonFilter proton
Lateral scoring mesh
A lateral scoring mesh is positioned at the end of the nozzle to record the dose distribution of the protons. The position, size and bin number of this mesh can be modified in the same way as the longitudinal mesh example above.
Beamline components
Components of the beamline can be added/removed in DetectorConstruction.cc .
Sensitive detectors
In this simulation, the water volume is assigned as a sensitive detector in DetectorConstruction.cc :
G4SDManager* SDman = G4SDManager::GetSDMpointer(); G4String name="SD"; DetectorSD = new SensitiveDetector(name); SDman->AddNewDetector(DetectorSD); logicWater->SetSensitiveDetector(DetectorSD);
Another beamline component may be used by setting its logical volume as a sensitive detector. The component should be chosen such that a significant proportion of the proton beam deposits energy, such as in the brass stopper, in order to produce enough data for plots.
SensitiveDetector.cc is derived from the G4VSensitiveDetector.cc base class. On a step-by-step basis, the energy deposited by the proton is recorded as a "hit" and added to a HitsCollection object. Other parameters may be retrieved at each step in the method ProcessHits .
G4bool SensitiveDetector::ProcessHits(G4Step* aStep, G4TouchableHistory* ROhist)
{
G4double edep = aStep->GetTotalEnergyDeposit();
if(aStep->GetTrack()->GetDefinition()->GetParticleName() == "proton"){
::Hit* newHit = new ::Hit();
newHit->SetEdep(edep);
HitID = detectorCollection->insert(newHit);
return true;
}
Physics list
Kinetic energy readings
[could go under data analysis section]