@misc{9238749,
  abstract     = {{The loss of regulatory control over radioactive material and sources poses great risks to public safety. Such a situation necessitates the development of protocols and methods for effective and accurate localisation, characterisation and securement of the materials. Mobile gamma spectrometry, particularly using vehicle-borne detectors, has emerged as a viable method for in-situ characterisation of the gamma radiation field, and has been successfully used in searches for locating lost gamma sources. Traditional localisation methods rely on the peak count rate and full width at half maximum of the characteristic count rate curve as a vehicle-borne detector passes a source. However, assumptions required for these methods often fail due to real-world complexities. Bayesian search methods have been developed as a robust alternative, but further validation is needed to test its effectiveness and find the limiting cases.

This thesis presents PG-RAD (Primary Gamma RADiation simulator), a modular toolbox for simulating mobile search scenarios of gamma sources. PG-RAD generates synthetic counts that would be observed by a detector travelling along a path as it passes a gamma source. PG-RAD accounts for angular detector efficiency, air attenuation and counting statistics. PG-RAD is flexible in the definition of point sources and trajectory geometry. To demonstrate its applicability to research in source localisation methods, simulations of both HPGe and NaI(Tl) detectors were performed, simulating mobile search of Caesium-137 sources. PG-RAD was validated against existing reference codes and experimental data. It was also used to systematically test a two-source Bayesian localisation algorithm, assessing its performance as a function of source separation and difference in activity.

Results show that PG-RAD is able to generate representative count data, and can effectively be used for testing mobile search algorithms. The lack of shielding and Compton scattered photons likely account for the discrepancies found when comparing to some experimental data. However, because PG-RAD is developed as an open source toolbox, taking a modular and object-oriented approach, future implementation of these features is possible to enhance the realism of the generated data. Furthermore, other detectors or isotopes could be added in order to make PG-RAD useful for other research teams around the world.}},
  author       = {{Nelissen, Pim}},
  issn         = {{1404-6342}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Master’s Theses in Mathematical Sciences}},
  title        = {{PG-RAD: A Tool for Simulating Radiometric Data for Mobile Radioactive Source Searches and In Situ Measurements}},
  year         = {{2026}},
}