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Photocathodes are key elements in high-brightness electron sources and ubiquitous in the operation of large-scale accelerators, although their operation is often limited by their quantum efficiency and lifetime. Here, we propose to overcome these limitations by utilizing direct-laser nanostructuring techniques on copper substrates, improving their efficiency and robustness for next-generation electron photoinjectors. When the surface of a metal is nanoengineered with patterns and particles much smaller than the optical wavelength, it can lead to the excitation of localized surface plasmons that produce hot electrons, ultimately contributing to the overall charge produced. In order to quantify the performance of laser-produced plasmonic photocathodes, we measured their quantum efficiency in a typical electron gun setup. Our experimental results suggest that plasmon-induced hot electrons lead to a significant increase in quantum efficiency, showing an overall charge enhancement factor of at least 4.5 and up to 25. A further increase in their efficiency was observed when combined with semiconductor thin-films deposited over the laser processed surfaces, pointing at potential pathways for further optimization. We demonstrate that simple laser-produced plasmonic photocathodes outperform standard metallic photocathodes, and can be directly produced in-situ at the electron gun level in vacuum environments and without any disruptive intervention. This approach could lead to unprecedented efficient and continuous operation of electron sources, and is useful in many applications across scientific disciplines requiring high average and peak current electron beams.

Photocathodes are key elements in high-brightness electron sources and ubiquitous in the operation of large-scale accelerators, although their operation is often limited by their quantum efficiency and lifetime. Here, we propose to overcome these limitations by utilizing direct-laser nanostructuring techniques on copper substrates, improving their efficiency and robustness for next-generation electron photoinjectors. When the surface of a metal is nanoengineered with patterns and particles much smaller than the optical wavelength, it can lead to the excitation of localized surface plasmons that produce hot electrons, ultimately contributing to the overall charge produced. In order to quantify the performance of laser-produced plasmonic photocathodes, we measured their quantum efficiency in a typical electron gun setup. Our experimental results suggest that plasmon-induced hot electrons lead to a significant increase in quantum efficiency, showing an overall charge enhancement factor of at least 4.5 and up to 25. A further increase in their efficiency was observed when combined with semiconductor thin-films deposited over the laser processed surfaces, pointing at potential pathways for further optimization. We demonstrate that simple laser-produced plasmonic photocathodes outperform standard metallic photocathodes, and can be directly produced in-situ at the electron gun level in vacuum environments and without any disruptive intervention. This approach could lead to unprecedented efficient and continuous operation of electron sources, and is useful in many applications across scientific disciplines requiring high average and peak current electron beams. [ABSTRACT FROM AUTHOR]

Colorizing metals using micrometer and nanometer scale surface modifications has been vastly investigated and presents many advantages for applications across scientific and technological fields. By tuning the surface chemical composition or controlling its morphology, it is possible to produce a wide range of chromatic effects. Ultrafast laser processing presents here an interesting asset, as it allows to simultaneously provide chemical and morphological modifications at the micro‐scale in a single step. In this article, the composite colorization of copper surfaces with mW‐class average power deep ultraviolet (DUV) femtosecond laser pulses is demonstrated. The advantages of this setup are twofold: first, thanks to the increased absorption of copper in the DUV, the technique allows scaling down the requirement for laser power. Second, under ultrafast short‐wavelength illumination molecular oxygen bond‐breaks occur, enhancing the oxidation rate of the copper. The technique allows for highly controllable and efficient copper oxidation with the irradiation parameters. Taking these two effects into account, the generation of a wide spectrum of colors—from dark blue to shiny red—is demonstrated, and the role of the surface oxidation rate, the laser fluence, and laser scanning strategies in the colorization of copper surfaces employing DUV lasers is discussed. [ABSTRACT FROM AUTHOR]

Tunable single‐frequency lasers are the most prominent tool for high‐resolution spectroscopy, allowing for the study and exploitation of the electronic structure of atoms. A significant milestone relies on the demonstration of integrated laser technology for performing such a task. The device presented here is composed of a compact Fabry–Perot monolithic resonator capable of producing tunable and Fourier‐limited nanosecond pulses with a MHz‐class frequency stability without active cavity stabilization elements. It also has the remarkable capability of exploiting the Raman effect to funnel efficiently the broad spectrum of an input laser to a spectrally‐bright Stokes pulse at hard‐to‐access wavelength ranges. The targeted atom for the demonstrations is 152Sm, released as an atomic vapor in a hot cavity environment. Here, the Stokes field is tuned to a wavelength of 433.9 nm, while a crossed‐beams spectroscopy setup is used to minimize the Doppler broadened spectral features of the atoms. With this work, the suitability of integrated diamond Raman lasers as a high‐resolution in‐source spectroscopy tool is demonstrated, enabling many applications in atomic and nuclear physics. The integrated form‐factor and inherent simplicity makes such a laser an interesting prospect for quantum‐technology based sensing systems and related applications. [ABSTRACT FROM AUTHOR]

Author(s): Bruce Marsh[sup.1] Author Affiliations: (1) Earth and Planetary Sciences, Johns Hopkins University, 21218, Baltimore, MD, USA [Displayed Quote]Most of the sills described so far in this chapter [Palisades, Shiant, [...]

The age-old process of crystal fractionation leading to the diversity of the igneous rocks and Earth itself is an exceedingly well-understood chemical process in magmatism and physical chemistry. But the broader physical aspects of this and related processes have proven elusive on many fronts, especially in its relation to the spatial variations in rock composition, texture, and macroscopic features like layering. Magmatic systems, be they volcanic, dikes, sills, or plutons, are generally analyzed with a problem at hand and an end result in mind. The processes invoked to solve these problems, which are most often purely chemical, are often unique to each problem with few if any general principles emerging that are central to understanding the wider perspective of magmatic processes and problems. An attempt is made at the outset to provide a list of inviolate Magmatic First Principles that are relevant to analyzing most magmatic problems. These involve: initial conditions; critical crystallinity; solidification fronts; transport and emplacement fluxes; phenocrysts, xenocrysts, primocrysts; crystal size; layering and crystal sorting; thermal convection; magmatic processes are physical. Along with these principles, two reference magmatic systems are suggested where the initial conditions and outcome are unequivocal: the Sudbury impact melt sheet and the Hawaiian lava lakes. Sudbury formed in ~5 min by superheated magma crystallized to a near uniform sequence, while the tiny lava lakes, formed of crystal-laden slurries, form a highly differentiated layered sequence. The major difference is in the initial conditions of formation, especially the nature of the input materials. The challenge is to construct and analyze magmatic systems (i.e., magma chambers, sills, dikes, and lavas) using these reference end members and the suggested principles. The Hawaiian 500,000 year volcanic record exhibits what can be expected as input materials, namely a highly varied output of magma of an overall composition reflecting the abundance of entrained olivine primocrysts. The provenance of these crystals is varied, and within any single sample, the population may be highly heterogeneous in composition from crystal to crystal, yet the overall pattern of chemical fractionation is exceedingly regular and well defined. If similar inputs go to form large intrusions, these systems will undoubtedly be dominated by crystal-rich slurries, which provide a vast set of physical processes promoting exotic layering and, at the same time, given the effects of annealing and continued crystal growth, a final chemical record adhering to all the time-honored effects of crystal fractionation. The long assumed initial condition of instantaneously emplaced crystal-free magmas cannot reasonably produce the observed rock records. Keywords Magma * Magma chambers * Magmatic principles * Slurries, Introduction The sharp break in grain size between phenocrysts and groundmass is correlated with some corresponding change in conditions prevailing during freezing of the magma. Such a break occurs where [...]