arXiv subjects

Lysander Miller

Publications and source records attributed to Lysander Miller.

3 recordsLinked to original sources

arXiv2026

Radioactive Source Seeking using Bayesian Optimisation with Movement Penalty

The use of mobile robotics in radioactive source seeking has become an important part of modern radiation-safety practices, supporting timely mitigation of contamination risks and helping protect public health. However, measuring radiation is often time-consuming, rendering traditional gradient-based source-seeking methods less effective due to lower sample efficiency. This paper proposes a sample-efficient Bayesian-Optimisation source-seeking strategy that utilises a heteroscedastic Gaussian process surrogate to balance exploration and exploitation. Excessive inter-sample travel is discouraged through a movement switching cost. The strategy is shown to generate sublinear regret in the source-seeking task, while simulations demonstrate its effectiveness in localising radioactive sources.

physics.app-ph↗

arXiv2025

Development and Flight Trial of a UAV-based Gamma Ray and Neutron Detection System for Large-Area Radioactivity Mapping and Source Activity Estimation

Advances in scintillation crystal and Silicon PhotoMultiplier (SiPM) technologies have enabled the development of compact, lightweight, and low-power radiation detectors that are suitable for integration with Unmanned Aerial Vehicles (UAVs). This integration enables efficient and cost-effective large-area radiation monitoring while minimising occupational exposure. In this work, a SiPM-based NaIL scintillation detection payload was developed, characterised, and mounted on a multirotor UAV for gamma ray and neutron source localisation and activity estimation applications. To support these capabilities, an analytic radionuclide detection efficiency model was developed and used to estimate radioactivity on the ground from aerial energy spectrum measurements. The analytic expression for the detection efficiency incorporated physical phenomena, including the branching ratio, detector solid angle, air attenuation, and intrinsic peak efficiency, leading to agreement within 10% of experimental radionuclide detection efficiencies. The UAV-based radiation detection system was physically validated through a controlled indoor live radioactive source demonstration at 1.5 m, 3 m, and 4.5 m flight heights. Using the developed ground-level radioactivity estimation method, Cs-137 and Co-60 sources were successfully localised within 0.5 m, and their activities were estimated with errors on the order of 10% or less.

physics.ins-det↗

arXiv2024

Material Properties of Popular Radiation Detection Scintillator Crystals for Optical Physics Transport Modelling in Geant4

Radiation detection is vital for space, medical imaging, homeland security, and environmental monitoring applications. In the past, the Monte Carlo radiation transport toolkit, Geant4, has been employed to enable the effective development of emerging technologies in these fields. Radiation detectors utilising scintillator crystals have benefited from Geant4; however, Geant4 optical physics parameters for scintillator crystal modelling are sparse. This work outlines scintillator properties for GAGG:Ce, CLLBC:Ce, BGO, NaI:Tl, and CsI:Tl. These properties were implemented in a detailed SiPM-based single-volume scintillation detector simulation platform developed in this work. It was validated by its comparison to experimental measurements. For all five scintillation materials, the platform successfully predicted the spectral features for selected gamma ray emitting isotopes with energies between 30 keV to 2 MeV. The full width half maximum (FWHM) and normalised cross-correlation coefficient (NCCC) between simulated and experimental energy spectra were also compared. The majority of simulated FWHM values reproduced the experimental results within a 2% difference, and the majority of NCCC values demonstrated agreement between the simulated and experimental energy spectra. Discrepancies in these figures of merit were attributed to detector signal processing electronics modelling and geometry approximations within the detector and surrounding experimental environment.

physics.ins-det↗