Browsing by Author "Krause, Philip George"

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    Advances in design of high-performance heterostructured scintillators for time-of-flight positron emission tomography
    (Wiley, 2023-10-10) Krause, Philip George; Rogers, Edith; Bizarri, Gregory
    Core to advancing time-of-flight positron emission tomography (ToF-PET) toward a less invasive, more flexible procedure with a higher diagnostic power is the development of enhanced radiation detector materials. One promising avenue is the development of heterostructured scintillators where multiple materials work in synergy to exceed the performance of each individual component. Applied to ToF-PET detectors, one component contributes predominantly to the absorption of gamma rays and the other to the creation of ultra-fast photons. Whilst other authors have proposed various concepts, heterostructured scintillators are still in their infancy and scientifically guiding their development remains a challenge. Toward this aim and based on simulation and modeling developments, heterostructure properties are directly linked to ToF-PET performance. This is made possible by redefining the notions of detector photo-peak efficiency and timing response, as defined for monolithic detectors, in the context of heterostructured scintillators. Their overall potential is then discussed as a function of the materials and design used. This provides a quantitative framework to rapidly and efficiently support the advancement of heterostructured detectors for ToF-PET technology.
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    Design rules for time of flight Positron Emission Tomography (ToF-PET) heterostructure radiation detectors
    (Elsevier, 2022-06-27) Krause, Philip George; Rogers, Edith; Birowosuto, Muhammad Danang; Pei, Qibing; Auffray, Etiennette; Vasil'ev, Andrey N.; Bizarri, Gregory
    Despite the clinical acceptance of ToF-PET, there is still a gap between the technology's performance and the end-user's needs. Core to bridging this gap is the ability to develop radiation detectors combining a short attenuation length and a sub-nanosecond time response. Currently, the detector of choice, Lu2SiO5:Ce3+ single crystal, is not selected for its ability to answer the performance needs, but as a trade-off between requirements and availability. To bypass the current performance limitations, in particular restricted time response, the concept of the heterostructured detector has been proposed. The concept aims at splitting the scintillation mechanisms across two materials, one acting primarily as an absorber and one as an ultra-fast emitter. If the concept has attracted the interest of the medical and material communities, little has been shown in terms of the benefits/limitations of the approach. Based on Monte Carlo simulations, we present a survey of heterostructure performance versus detector design. The data allow for a clear understanding of the design/performance relationship. This, in turn, enables the establishment of design rules toward the development and optimization of heterostructured detectors that could supersede the current detector technology in the medical imaging field but also across multiple sectors (e.g. high-energy physics, security).
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    Oxidation resistant flexible transparent conductive electrodes by synthesising CuNi nanowires.
    (2018-08) Krause, Philip George; Huang, Zhaorong; Endrino, José L.
    This research attempts to find a replacement for ITO that is flexible and doesn’t oxidise by synthesising CuNi nanowires in a single pot process. Indium is scarce, expensive, and non-flexible so has to be printed on solid substrates such as glass. It involved costly and wasteful processes to apply and cure and is running out. Copper nanowires are a cheap alternative but they oxidise. The simple difference between synthesising Cu NW’s and CuNi NW’s is the addition of glucose which is low cost. The nickel inhibits oxidation so no extra processes are required to protect them. Copper-nickel nanowires have rarely been synthesised and this research explains how to and shows that copper-nickel nanowires could directly replace ITO. This research shows a systematic approach to solving the problem, by varying the glucose and heat cycle to maximise the aspect ratio and achieve a nickel content of 5 > 20%. Once the best nanowires were synthesised, the ink concentration and thickness was varied to optimise the optoelectronic properties. Many CuNi NW’s were grown with >700 aspect ratio and Ni content 5 > 20% by adjusting the glucose content. The aspect ratio increases when the synthesis temperature is lowered as low as 160 °C while maintaining the Ni content range. A compromise is necessary as higher nickel content reduces the aspect ratio. A synthesis of 8.9% Ni was found to be as conductive after 112 days, as it was when it was made, thus showing that CuNi alloy does inhibit oxidation. This research has shown that CuNi NW’s can replace ITO in every area while being over 100 times less expensive and easier to make, apply and cure, enabling more uses of this technology in the future. They are also flexible which will allow even more areas of use.
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    Two-dimensional perovskite functionalized fiber-type heterostructured scintillators
    (AIP Publishing, 2023-02-21) Rogers, Edith; Birowosuto, Muhammad Danang; Maddalena, Francesco; Dujardin, Christophe; Pagano, Fiammetta; Kratochwil, Nicolaus; Auffray, Etiennette; Krause, Philip George; Bizarri, Gregory
    A fiber-type heterostructured scintillator based on bismuth germanate (Bi4Ge3O12) functionalized with the 2D-perovskite butylammonium lead bromide ((BA)2PbBr4) has been fabricated, and its scintillation performance analyzed toward its use for fast timing applications such as time-of-flight Positron Emission Tomography. The pixel shows energy sharing between the matrix and filler component, confirming that the two components are in synergy.