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Development of tissue-equivalent CVD-diamond radiation detectors with small interface effects
Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
Responsible organisation
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Due to its close tissue-equivalence, high radiation sensitivity, dose and dose-rate linearity, diamond is a very promising detector for radiation therapy applications. The present thesis focuses on the development of a chemical vapour deposited (CVD) diamond detector with special attention on the arrangement of the electrodes and encapsulation having minimal influence on the measured signal. Several prototype detectors were designed by using CVD-diamond substrates with attached silver electrodes.

Interface effects in the electrode-diamond-electrode structure are investigated using the Monte Carlo (MC) code PENELOPE. The studies cover a wide range of electrode and diamond thicknesses, electrode materials and photon beam energies. An appreciable enhancement of the absorbed dose to diamond was found for high-Z electrodes. The influence of the electrodes diminishes with decreasing atomic number difference and layer thickness, so that from this point of view thin graphite electrodes would be ideal. The effect of encapsulation, cable and electrical connections on the detector response is also addressed employing MC techniques. For Co-60, 6 and 18 MV photon beam qualities it is shown that the prototypes exhibit energy and directional dependence of about 3% and 2%, respectively. By modifying the geometry and using graphite electrodes the dependencies are reduced to 1%.

Although experimental studies disclose some limitations of the prototypes (high leakage current, priming effect and slow signal stabilisation), diamonds of higher quality, suitable for dosimetry, can be produced with better-controlled CVD process. With good crystals and a well-designed encapsulation, the CVD-diamond detector could become competitive for routine dosimetry. It is then important for correct dose determination to use a collision stopping power for diamond incorporating proper mean excitation energy and density-effect corrections. A new mean excitation energy of 88 eV has been calculated.

Place, publisher, year, edition, pages
Stockholm: Medicinsk strålningsfysik (tills m KI) , 2008. , 91 p.
Keyword [en]
CVD-diamond detector, tissue-equivalent encapsulation, dosimetry, Monte Carlo simulation
National Category
Physical Sciences
Research subject
Medical Radiation Physics
Identifiers
URN: urn:nbn:se:su:diva-8131ISBN: 978-91-7155-707-0 (print)OAI: oai:DiVA.org:su-8131DiVA: diva2:199634
Public defence
2008-09-12, föreläsningssalen, Radiumhemmet, Karolinska universitetssjukhuset, Solna, 10:00
Opponent
Supervisors
Available from: 2008-08-27 Created: 2008-08-27Bibliographically approved
List of papers
1. Influence of electrodes on the photon energy deposition in CVD-diamond dosimeters studied with the Monte Carlo code PENELOPE
Open this publication in new window or tab >>Influence of electrodes on the photon energy deposition in CVD-diamond dosimeters studied with the Monte Carlo code PENELOPE
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2006 In: Physics in Medicine and Biology, Vol. 51, 3607-3623 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25382 (URN)
Note
Part of urn:nbn:se:su:diva-8131Available from: 2008-08-27 Created: 2008-08-27Bibliographically approved
2. Design and characterization of a tissue-equivalent CVD-diamond detector for clinical dosimetry in high-energy photon beams
Open this publication in new window or tab >>Design and characterization of a tissue-equivalent CVD-diamond detector for clinical dosimetry in high-energy photon beams
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2008 In: Physica Medica, ISSN 1120-1797, Vol. 24, 158-167 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25383 (URN)
Note
Part of urn:nbn:se:su:diva-8131Available from: 2008-08-27 Created: 2008-08-27Bibliographically approved
3. Optimization of a tissue-equivalent CVD-diamond dosimeter for radiotherapy using the Monte Carlo code PENELOPE
Open this publication in new window or tab >>Optimization of a tissue-equivalent CVD-diamond dosimeter for radiotherapy using the Monte Carlo code PENELOPE
2008 In: Nuclear Instruments & Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, Vol. 593, 578-587 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25384 (URN)000259120700047 ()
Note
Part of urn:nbn:se:su:diva-8131Available from: 2008-08-27 Created: 2008-08-27Bibliographically approved
4. Collision stopping power of electrons in diamond
Open this publication in new window or tab >>Collision stopping power of electrons in diamond
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-25385 (URN)
Note
Part of urn:nbn:se:su:diva-8131Available from: 2008-08-27 Created: 2008-08-27 Last updated: 2010-01-13Bibliographically approved

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