TESCAN

This study explores the excitation and ionization of an atomic beam as a pathway to optimize focused ion beams (FIBs) for high-precision applications. Leveraging the unique advantages of Rydberg excitation followed by field ionization-specifically its ability to minimize velocity and position dispersions-we present a method to generate ion beams with good performance at low energies. A custom LUA program, integrated into the simion simulation platform, models the intricate processes of particle distributions, laser excitation, and Rydberg ionization. This integrated approach incorporates essential parameters such as excitation and ionization rates, Stark shifts, Doppler effects, and electric fields, enabling a detailed analysis of ion-beam properties. Our simulations demonstrate the influence of critical factors such as the chosen Rydberg state, ionization region characteristics, and velocity dispersions on the final ion-beam quality. By optimizing these parameters, we achieve significant reduction of the axial energy spread and the longitudinal extent of the ionization region. This framework bridges theoretical modeling and experimental validation, offering a comprehensive toolkit for the development of next-generation ion sources and advancing FIB technologies across various scientific domains.

Coarse prior austenite grain (PAG) structures can sometimes be observed in high-strength steels, e.g., in parts produced by wire-arc additive manufacturing (WAAM), and are problematic as they are often associated with poor mechanical performance. In the case of WAAM, cyclic austenitisation can refine coarse PAG structures either during or after the building process. However, in this study we show that there can be a strong effect of heating rate during austenitisation on the resulting grain refinement. The heating rate effect was systematically studied in two steels—a low-alloy steel (300 M) and a maraging steel (Custom 465®)—from an as-WAAM’d state where both comprised coarse columnar PAGs. On heating, for all heating rates investigated and in both steels, the austenite ‘memory effect’ was first observed, which retained the columnar structure. This was then sometimes followed by autogenous recrystallisation (without applied external deformation), which greatly refined the PAGs. High-temperature in-situ electron backscatter diffraction was used to directly observe austenitisation in 300 M, revealing that the recrystallisation shifted from a continuous to a discontinuous mechanism with decreasing heating rate, and that a further decrease in rate suppressed recrystallisation altogether, leaving only a memory effect. Conversely, in Custom 465®, recrystallisation produced significant PAG refinement across all heating rates investigated. However, the recrystallised PAGs retained some crystallographic texture inherited from the columnar PAGs and twins in the as-built material. These findings provide mechanistic insight into grain refinement strategies for steels with coarse PAGs and highlight the importance of controlling heat rates during industrial processing.

The outcomes of a standard geochemical, geophysical and petrographical approach to exploration at Lead Trial, a small prospect in central Scotland, have been compared to the interpretation of a parallel gold compositional study describing 703 gold particles from local in situ and alluvial occurrences. Standard exploration approaches identified a 4.5 km2 zone hosting an array of numerous auriferous (to 17 g/t Au), vuggy, brecciated quartz-galena +/- sphalerite veins culminating in the identification of a drill target. The gold study identified three gold compositional types: two 23-32 wt.% Ag alloys with a Zn-Pb-Cu mineral inclusion assemblage differentiated by sphalerite abundance, and a 5-16 wt.% Ag alloy with a Mo-Bi-Pb-Cu-Fe inclusion signature, yet to be correlated with either float or outcrop. Spatial distribution of the gold types indicates lateral variation and probably vertical variation within a single magmatic hydrothermal system. Integration of gold particle studies with early stages of exploration offers rapid insights into the nature and distribution of mineralization when very limited information is available and is mutually supportive of standard exploration approaches.

The underlying geological processes responsible for germanium enrichment across various mineralization types remain elusive, posing a significant obstacle to the development of a comprehensive genetic models. The investigation of germanium-rich epigenetic sulfide-calcite veins from the Cu-Ag Kupferschiefer deposit in Lubin-Sieroszowice ore district in Poland provides new insights into the mechanisms of germanium concentration in sulfide ores. Petrographic observations at macro-and microscale levels suggest that this mineralization style is consistent with single or multiple brecciation episodes likely related to natural hydraulic fracturing by overpressured fluids. Electron microprobe microanalysis (EPMA), TESCAN Integrated Mineral Analyzer (TIMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) reveal that chalcopyrite, a predominant mineral in the veins, is also the primary host of germanium, containing up to 5 016 mg/kg of Ge. Typical associations include calcite, bornite, sphalerite, galena, and tennantite, with less common occurrences of luzonite, gersdorffite, betekhtinite, and anhydrite. Micro X-ray fluorescence (micro-XRF) mapping of massive chalcopyrite demonstrates that germanium distribution is inhomogeneous exhibiting two distinct spatial distribution patterns: dendrite-like and apparent oscillatory zoning. It is hypothesized that a rapid fluid pressure drop could be an important factor in formation of germanium-enriched sulphide ores.

Peculiar, tube-like features within the sandstone unit of the Kupferschiefer deposit have been found within the Lubin-Sieroszowice ore district in SW Poland. As they have not been previously reported in the literature, their general overview and features are described here. They occur in barren and mineralized sandstones and in some cases carry Cu-Ag and/or U mineralization typically consisting of chalcocite, chalcopyrite, bornite, native silver (0-19% Hg admixture), stromeyerite and U-bearing pyrobitumens. Studied features highlight the complex interaction between sedimentary features and fluids as well as between diagenetic and mineralizing processes.