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Dose enhancement near metal interfaces in synthetic diamond based x-ray dosimeters.

Alamoudi, Dalal (2016) Dose enhancement near metal interfaces in synthetic diamond based x-ray dosimeters. Doctoral thesis, University of Surrey.

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Diamond is an attractive material for medical dosimetry due to its radiation hardness, fast response, chemical resilience, small sensitive volume, high spatial resolution, near-tissue equivalence, and energy and dose rate independence. These properties make diamond a promising material for medical dosimetry compared to other semiconductor detector materials and wider radiation detection applications. This study is focused on one of the important factors to consider in the radiation detector; the influence of dose enhancement on the photocurrent performance at metallic interfaces in synthetic diamond radiation dosimeters with carbon based electrodes as a function of bias voltages. Monte Carlo (MC) simulations with BEAMnrc code were carried out to simulate the dose enhancement factor (DEF) and compared against the equivalent photocurrent ratio from experimental investigation. MC simulations show that the sensitive region for the absorbed dose distribution covers a few micrometers distances from the interface. Experimentally, two single crystal (SC) and one polycrystalline (PC) samples with carbon based electrodes were used. The samples were each mounted inside a tissue equivalent encapsulation design in order to minimize fluence perturbations. Copper, Gold and Lead have been investigated experimentally as generators of photoelectrons using 50 kVp and 100 kVp X-rays relevant for medical dosimetry. The results show enhancement in the detectors' photocurrent performance when different metals are butted up to the diamond detector. The variation in the photocurrent ratio measurements depends on the type of diamond samples, their electrode fabrication and the applied bias voltages indicating that the dose enhancement from diamond-metal interface modifies the electronic performance of the detector.

Item Type: Thesis (Doctoral)
Subjects : Medical and radiation physics
Divisions : Theses
Authors :
Date : 21 December 2016
Funders : King Saud bin Abdulaziz University for Health Science
Contributors :
Depositing User : Dalal Alamoudi
Date Deposited : 05 Jan 2017 09:09
Last Modified : 16 Jan 2019 17:10

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