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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. [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]

This article, titled "In-Source High-Resolution Spectroscopy Using an Integrated Tunable Raman Laser," discusses the use of integrated tunable diamond Raman lasers in accessing the hyperfine structure of atoms. These lasers produce spectrally-bright tunable Stokes pulses, offering MHz-class resolution without active cavity stabilization. The study demonstrates the effectiveness of these lasers for high-resolution in-source spectroscopy, with potential applications in the fields of atomic and nuclear physics. The authors of the article are Eduardo Granados, Georgios Stoikos, Cyril Bernerd, Katerina Chrysalidis, Daniel T. Echarri, Valentin N. Fedosseev, Reinhard Heinke, and Bruce A. Marsh. [Extracted from the article]

In the centres of stars where the temperature is high enough, threea-particles (helium nuclei) are able to combine to form12C because of a resonant reaction leading to a nuclear excited state. (Stars with masses greater than~0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed.) Although the reaction rate is of critical significance for determining elemental abundances in the Universe, and for determining the size of the iron core of a star just before it goes supernova, it has hitherto been insufficiently determined. Here we report a measurement of the inverse process, where a12C nucleus decays to threea-particles. We find a dominant resonance at an energy of~11?MeV, but do not confirm the presence of a resonance at 9.1?MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-arate for temperatures from 107?K to 1010?K and find significant deviations from the standard rates. Our rate below~5×107?K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed. At temperatures above 109?K, our rate is much less, which modifies predicted nucleosynthesis in supernovae. [ABSTRACT FROM AUTHOR]