Chemical Vapour Deposition (CVD) diamond detectors were modelled for dosimetry
of radiotherapy beams. This was achieved by employing the EGSnrc Monte Carlo
(MC) method to investigate certain properties of the detector, such as size, shape
and electrode materials. Simulations were carried out for a broad 6 MV photon
beam, and water phantoms with both uniform and non-uniform voxel dimensions. A
number of critical MC parameters were investigated for the development of a model
that can simulate very small voxels. For a given number of histories (100 million),
combinations of the following parameters were analyzed: cross section data,
boundary crossing algorithm and the HOWFARLESS option, with the rest of the
transport parameters being kept at default values. The MC model obtained with the
optimized parameters was successfully validated against published data for a 1.25
MeV photon beam and CVD diamond detector with silver/carbon/silver structure with
thicknesses of 0.07/0.2/0.07 cm for the electrode/detector/electrode, respectively.
The interface phenomena were investigated for a 6 MV beam by simulating different
electrode materials: aluminium, silver, copper and gold for perpendicular and
parallel detector orientation with regards to the beam. The smallest interface
phenomena were observed for parallel detector orientation with electrodes made of
the lowest atomic number material, which was aluminium. The simulated
percentage depth dose and beam profiles were compared with experimental data.
The best agreement between simulation and measurement was achieved for the
detector in parallel orientation and aluminium electrodes, with differences of
approximately 1%.
In summary, investigations related to the CVD diamond detector modelling revealed
that the EGSnrc MC code is suitable for simulation of small size detectors. The
simulation results are in good agreement with experimental data and the model can
now be used to assist with the design and construction of prototype diamond
detectors for clinical dosimetry. Future work will include investigating the detector
response for different energies, small field sizes, different orientations other than
perpendicular and parallel to the beam, and the influence of each electrode on the
absorbed dose.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/3190 |
| Date | January 2009 |
| Creators | Baluti, Florentina |
| Publisher | University of Canterbury. Physics and Astronomy |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Florentina Baluti, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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