Knowing what a detector actually sees.

The question

A gamma-ray spectrometer counts photons, but only some of the photons a source emits end up in the full-energy peak of the spectrum: the rest miss the detector, pass through it, or deposit only part of their energy. The fraction that lands in the peak is the full-energy-peak efficiency. It depends on photon energy, on the size and shape of the detector crystal, and on where the source sits. Every quantitative gamma measurement, from environmental samples to reactor activation analysis, needs it. It is usually found by calibrating with standard sources at a few energies and geometries, then interpolating.

What he did

High-purity germanium (HPGe) detectors. His MSc thesis at Alexandria University (1999–2003) developed a direct statistical mathematical model to calculate the full-energy-peak efficiency of an HPGe detector. In 2011 it appeared at the 2nd International Workshop on Real Time Measurement, Instrumentation and Control at UOIT in Oshawa, in two papers: the model itself, and its validation across germanium detectors of different sizes.

Cadmium zinc telluride (CZT) detectors. For his MSc in the Physics and Technology of Nuclear Reactors at the University of Birmingham (2007–2008), his project studied the characteristics of the CZT detector. CZT is a semiconductor that works at room temperature, unlike germanium, which must be cooled; that makes it useful for portable and field instruments, at the cost of poorer energy resolution.

How it connects

Detector physics runs under the rest of his career. It is the measurement side of the same problem the Monte Carlo codes solve on the calculation side: how radiation moves through matter and where it deposits energy. It also underpins his radiation-safety work, including his Radiation Safety Officer and Transport of Dangerous Goods Officer training (Radiation Safety Institute of Canada, 2017), and his teaching: he taught Radiation Detection Techniques from 2005 to 2007, and Nuclear Radiation and Instrumentation is among the courses he is ready to teach.

The two strands meet in practice. A Monte Carlo model of a detector and its source geometry is a common way to compute efficiencies where calibration sources are hard to arrange, and a measured efficiency is a common check on such a model. His later work moved to reactor cores, but the habit is the same one his reactor papers show: a calculation is trusted when an independent method gives the same answer.