arXiv subjects

J. M. C. Brown

Publications and source records attributed to J. M. C. Brown.

5 recordsLinked to original sources

arXiv2026

In-situ suppression of surface radon emanation using an HDPE barrier at the Stawell Underground Physics Laboratory (SUPL)

Radon-induced backgrounds remain a limiting factor in low-background experiments conducted in underground laboratories. The enclosed nature of these laboratories can result in elevated radon levels, with emanation from the surrounding rock representing the primary source of radon. In this work, we present an in-situ study of radon emanation from the floor of the main experimental hall at the Stawell Underground Physics Laboratory (SUPL) and investigate the use of a high-density polyethylene (HDPE) barrier to suppress emanation. Surface emanation was measured using an AIRTHINGS Corentium Pro passive detector before and after installation of the barrier. The equilibrium radon concentration within the surface emanation setup was reduced from 5840 $\pm$ 50 Bq m $^{-3}$ to 259 $\pm$ 3 Bq m$^{-3}$, corresponding to a suppression of $\sim$96%. These results demonstrate the potential to retrofit radon barriers to suppress surface emanation under realistic underground conditions, supporting their use in planned low-background infrastructure at SUPL and future applications at other underground laboratories.

physics.ins-det↗

arXiv2023

A Geant4 Based Simulation Platform of the HollandPTC R&D Proton Beamline for Radiobiological Studies

A Geant4 based simulation platform of the Holland Proton Therapy Centre (HollandPTC, Netherlands) R&D beamline (G4HPTC-R&D) was developed to enable the planning, optimisation and advanced dosimetry for radiobiological studies. It implemented a six parameter non-symmetrical Gaussian pencil beam surrogate model to simulate the R&D beamline in both a pencil beam and passively scattered field configuration. Three different experimental proton datasets (70 MeV, 150 MeV, and 240 MeV) of the pencil beam envelope evolution in free air and depth-dose profiles in water were used to develop a set of individual parameter surrogate functions to enable the modelling of the non-symmetrical Gaussian pencil beam properties with only the ProBeam isochronous cyclotron mean extraction proton energy as input. This refined beam model was then benchmarked with respect to three independent experimental datasets of the R&D beamline operating in both a pencil beam configuration at 120 and 200 MeV, and passively scattered field configuration at 150 MeV. It was shown that the G4HPTC-R&D simulation platform can reproduce the pencil beam envelope evolution in free air and depth-dose profiles to within an accuracy on the order of $\pm$5% for all tested energies, and that it was able to reproduce the 150 MeV passively scattered field to the specifications need for clinical and radiobiological applications.

physics.med-ph↗

arXiv2023

Characterisation of the HollandPTC R&D proton beamline for physics and radiobiology studies

HollandPTC is an independent outpatient center for proton therapy, scientific research, and education. Patients with different types of cancer are treated with Intensity Modulated Proton Therapy (IMPT). In addition, the HollandPTC R&D consortium conducts scientific research into the added value and improvements of proton therapy. To this end, HollandPTC created clinical and pre-clinical research facilities including a versatile R&D proton beamline for various types of biologically and technologically oriented research. In this work, we present the characterization of the R&D proton beam line of HollandPTC. Its pencil beam mimics the one used for clinical IMPT, with energy ranging from 70 up to 240 MeV, which has been characterized in terms of shape, size, and intensity. For experiments that need a uniform field in depth and lateral directions, a dual ring passive scattering system has been designed, built, and characterized. With this system, field sizes between 2x2 cm2 and 20x20 cm2 with 98% uniformity are produced with dose rates ranging from 0.5 Gy/min up to 9 Gy/min. The unique and customized support of the dual ring system allows switching between a pencil beam and a large field in a very simple and fast way, making the HollandPTC R&D proton beam able to support a wide range of different applications.

physics.med-ph↗

arXiv2022

A new Standard DNA damage (SDD) data format

Our understanding of radiation induced cellular damage has greatly improved over the past decades. Despite this progress, there are still many obstacles to fully understanding how radiation interacts with biologically relevant cellular components to form observable endpoints. One hurdle is the difficulty faced by members of different research groups in directly comparing results. Multiple Monte Carlo codes have been developed to simulate damage induction at the DNA scale, while at the same time various groups have developed models that describe DNA repair processes with varying levels of detail. These repair models are intrinsically linked to the damage model employed in their development, making it difficult to disentangle systematic effects in either part of the modelling chain. The modelling chain typically consists of track structure Monte Carlo simulations of the physics interactions creating direct damages to the DNA; followed by simulations of the production and initial reactions of chemical species causing indirect damages. After the DNA damage induction, DNA repair models combine the simulated damage patterns with biological models to determine the biological consequences of the damage. We propose a new Standard data format for DNA Damage to unify the interface between the simulation of damage induction and the biological modelling of cell repair processes. Such a standard greatly facilitates inter model comparisons, providing an ideal environment to tease out model assumptions and identify persistent, underlying mechanisms. Through inter model comparisons, this unified standard has the potential to greatly advance our understanding of the underlying mechanisms of radiation induced DNA damage and the resulting observable biological effects.

q-bio.OT↗

arXiv2019

A High Count-Rate and Depth-of-Interaction Resolving Single Layered One-Side Readout Pixelated Scintillator Crystal Array for PET Applications

Organ-specific, targeted Field-of-View (FoV) Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI) inserts are viable solutions for a number of imaging tasks where whole-body PET/MRI systems lack the necessary sensitivity and resolution. To meet the required PET detector performance of these systems, high count-rates and effective spatial resolutions on the order of a few mm, a novel two-axis patterned reflector foil pixelated scintillator crystal array design is developed and its proof-of-concept illustrated in-silico with the Monte Carlo radiation transport modelling toolkit Geant4. It is shown that the crystal surface roughness and phased open reflector cross-section patterns could be optimised to maximise either the PET radiation detector's effective spatial resolution, or count rate before event pile up. In addition, it was illustrated that these two parameters had minimal impact on the energy and time resolution of the proposed PET radiation detector design. Finally, it is shown that a PET radiation detector with balance performance could be constructed using ground crystals and phased open reflector cross-section pattern corresponding to the middle of the tested range.

physics.ins-det↗