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Patrick Knights

Publications and source records attributed to Patrick Knights.

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Materials Design for the Synthesis of High Strength Radiopure Copper Alloys for Rare Event Detection

Additive-free electroformed copper has emerged as the material of choice in exceptionally radiopure detectors for rare-event searches, based on its radiopurity, physical properties, and affordability. However, copper is ductile and of limited mechanical strength posing challenges for its use in future experiments. Electroformed copper-based alloys have been identified as a promising solution. However, their synthesis needs refining by exploring a complex parameter space of compositions and strengthening mechanisms. Here we show how a materials design approach may address current challenges and optimize alloy synthesis and processing. Alloy properties are predicted following thermal processing, using computational thermodynamics. The findings suggest a methodology to design high-performance, radiopure copper-based alloys suitable for next-generation rare-event experiments, while minimizing lengthy and expensive trial-and-error approaches. The impact on future experiments is exemplified through case-studies of the DarkSPHERE and XLZD experiments.

physics.ins-det

Searches for light Dark Matter with Spherical Proportional Counters

Elucidating the nature of dark matter is a key priority that would involve discovering new fundamental physics and is essential for understanding the structure and evolution of the universe. Despite the decades-long ever-more-sensitive searches, the particle content of dark matter remains elusive. Direct searches for dark matter candidates, to-date, focused mainly on candidates in the 10 GeV to 1 TeV, however, more recently lighter candidates with sub-GeV mass have been brought to the spotlight. This is an experimentally challenging mass region, which remains largely uncharted. The spherical proportional counter is a new type of gaseous detector which exhibits several features that make it ideally suited for the exploration of this mass range. In this article the invention and development of the spherical proportional counter are presented, its applications in the search for particle dark matter and beyond are reviewed, and possible future directions are discussed.

physics.ins-det

Ionisation quenching factors from W-values in pure gases for rare event searches

The effect of ionisation quenching for ions is critical for experiments relying on the measurement of low energy recoils, such as direct Dark Matter searches. We present ionisation quenching factor estimates over a range of energies for protons, $\alpha$-particles, and heavier ions in H$_{2}$, CH$_{4}$, N$_{2}$, Ar, CO$_{2}$, and C$_{3}$H$_{8}$ gases, estimated from the respective reference W-value measurements. The resulting ionisation quenching factors are compared with predictions from SRIM.

hep-ex

An undergraduate laboratory study of the polarisation of annihilation photons using Compton scattering

An experiment for the advanced undergraduate laboratory which allows students to study the effect of photon polarisation in Compton scattering and to explore q\ uantum entanglement is described. The quantum entangled photons are produced through electron-positron annihilation in the $S$-state, and their polarisations a\ re analysed using the Compton scattering cross-section dependence on the photon polarisation. The equipment necessary for this experiment is available at a typ\ ical undergraduate physics laboratory. Finite geometry effects are discussed and investigated with the use of a Geant4-based simulation.

physics.ed-ph