Speaker
Dr
Yusuf Zakari
(DST/NRF Centre of Excellence in strong Materials and School of Physics, University of the Witwatersrand. Private Bag 3, PO Wits 2050, Johannesburg, Republic of South Africa)
Description
The exceptional and unique physical properties of diamond have made the mineral a choice material in radiation measurement. Diamond detectors are currently used extensively in high-energy physics. The tissue equivalence of diamond allows for accurate radiation dose determination without large corrections for different attenuation values in biological tissue. The low Z value limits this advantage however to the lower energy photons such as for example in Mammography X-ray beams.
This paper assays the performance of nine Chemical Vapor Deposition (CVD) diamonds for use as radiation sensing material. The specimens fabricated in wafer form are classified as detector grade, optical grade and single crystals.
It is well known that the presence of defects in diamonds, including CVD specimens, not only dictates but also affects the responds of diamond to radiation in different ways. In this investigation, tools such as electron spin resonance (ESR), thermolumniscence
(TL) Raman spectroscopy and ultra violet (UV) spectroscopy were used to probe each of the samples. The specimen was spectroscopically analyzed with α-particles for a choice of detector sample and for linearity, sensitivity and other characteristics of a detector to photon interaction.
The resistivity of each of the diamond grade is calculated from the I-V characteristics of the samples.
The diamonds categorized into four each, of the so called Detector and Optical grades, and a single crystal CVD were exposed to low X-ray peak voltage range (22 to 27 KVp) with a trans-crystal polarizing fields of 0.4kV.cm-1, 0.66kV.cm-1 and 0.8kV.cm-1.
The presentation discusses the presence of defects identifiable by the techniques used and correlates the radiation performance of the three types of crystals to their presence. The choice of a wafer as either a sensitive alpha detector, spectrometer or as X-ray dosimeter within the selected energy range was made. The analyses was validated with Monte- Carlo code (PENELOPE)
Author
Dr
Yusuf Zakari
(DST/NRF Centre of Excellence in strong Materials and School of Physics, University of the Witwatersrand. Private Bag 3, PO Wits 2050, Johannesburg, Republic of South Africa)
