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Collision stopping power of electrons in diamond
Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
Responsible organisation
Manuscript (Other academic)
URN: urn:nbn:se:su:diva-25385OAI: diva2:199633
Part of urn:nbn:se:su:diva-8131Available from: 2008-08-27 Created: 2008-08-27 Last updated: 2010-01-13Bibliographically approved
In thesis
1. Development of tissue-equivalent CVD-diamond radiation detectors with small interface effects
Open this publication in new window or tab >>Development of tissue-equivalent CVD-diamond radiation detectors with small interface effects
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.
CVD-diamond detector, tissue-equivalent encapsulation, dosimetry, Monte Carlo simulation
National Category
Physical Sciences
Research subject
Medical Radiation Physics
urn:nbn:se:su:diva-8131 (URN)978-91-7155-707-0 (ISBN)
Public defence
2008-09-12, föreläsningssalen, Radiumhemmet, Karolinska universitetssjukhuset, Solna, 10:00
Available from: 2008-08-27 Created: 2008-08-27Bibliographically approved

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