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Plasma mirrors have become the preferred method for electron injection to laser-based accelerators, but the optimal configuration is difficult to achieve. Here, an alternative injection method employing a low-density foam target and a helical laser pulse is investigated numerically.

The recent development of petawatt-class laser systems sets a focus on the development of ultra-thin free-standing targets to access enhanced particle acceleration schemes vital for future applications, such as, medical and laser-driven nuclear physics. Specific strategies are required to improve the laser-to-particle energy conversion efficiency and increase the maximum particle energy. One of the promising approaches is based on the target design optimization; either by tuning key parameters which will strongly affect the laser-matter interaction process (e.g., material, composition, density, thickness, lateral dimensions, and shape) or by using micro/nanostructures on the target surface. At ELI-NP, considerable efforts are dedicated to extend the target capabilities beyond simple planar target design and develop complex targets with tailored properties suitable for high-power laser-plasma interaction experiments, as well as for studies with gamma and positrons beams. The paper provides an overview of the manufacturing capabilities currently available within ELI-NP Targets Laboratory for providing users with certain types of solid targets, specifically micro/nanostructured gold and copper foils and microns thick, porous anodized alumina. Also, optimization studies of alternative patterns (micro/nanodots) on silicon substrate are presented for future implementation on metallic free-standing thin foils.

Laser wakefield acceleration is able to provide electron beams of GeV energy and continuously evolves toward higher energies. These beams have broad energy spectrum; hence, their measurements require diagnostics with wide energy acceptance. Here, we present a design of an electron spectrometer to characterize the beams in the energy range of 100 MeV–10 GeV, in a single shot. The design consists of 1-m long permanent dipole magnets and has a variable gap opening to accommodate different divergences and pointings of the electron beams. The design is backed by simulations, which are used to optimize the positions of imaging plates. The use of a collimator to improve the energy resolution in the case of large beam divergences and beam pointing is presented. We also present the Monte Carlo simulations to evaluate the signal to noise ratio, with and without a collimator.

The emergence of a new era reaching beyond current state-of-the-art ultrashort and ultraintense laser technology has been enabled by the approval of around € 850 million worth of structural funds in 2011–2012 by the European Commission for the installation of Extreme Light Infrastructure (ELI). The ELI project consists of three pillars being built in the Czech Republic, Hungary, and Romania. This challenging proposal is based on recent technical progress allowing ultraintense laser fields in which intensities will soon be reaching as high as I0 ∼ 1023 W cm−2. This tremendous technological advance has been brought about by the invention of chirped pulse amplification by Mourou and Strickland. Romania is hosting the ELI for Nuclear Physics (ELI-NP) pillar in Măgurele near Bucharest. The new facility, currently under construction, is intended to serve the broad national, European, and international scientific community. Its mission covers scientific research at the frontier of knowledge involving two domains. The first is laser-driven experiments related to NP, strong-field quantum electrodynamics, and associated vacuum effects. The second research domain is based on the establishment of a Compton-backscattering-based, high-brilliance, and intense γ beam with Eγ ≲ 19.5 MeV, which represents a merger between laser and accelerator technology. This system will allow the investigation of the nuclear structure of selected isotopes and nuclear reactions of relevance, for example, to astrophysics with hitherto unprecedented resolution and accuracy. In addition to fundamental themes, a large number of applications with significant societal impact will be developed. The implementation of the project started in January 2013 and is spearheaded by the ELI-NP/Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH). Experiments will begin in early 2020.

Electron transport in a nanowire exhibits a distinct behavior following the irradiation of intense laser pulse. Using particle-in-cell simulation, we observe a large-amplitude particle-driven wakefield excitation followed by electron acceleration in the solid density. Besides, we observed the quiver of the electrons across the nanowire under the action of the surrounding laser electric field facilitating deeper wakefield propagation in the nanowire with 2.5× energy gain over a flat target. These results open insights into the laser-energy coupling with nanostructure targets and radiation sources, and motivate the wakefield acceleration in solid density plasma.

High-power PW laser systems (HPLS) provide intense beams of accelerated reaction-driving protons simultaneously with spatially localized keV-plasmas. We herein depict our groundwork and strategy to use these unique features of the HPLS at the Extreme Light Infrastructure (ELI-NP) by exposing the long-lived nuclear isomer 93 m Mo at 2.425 MeV ( t 1 / 2 = 6.85 h) to plasma facilitating the local petawatt beamlines. An intermediate short-lived ( t 1 / 2 = 3.52 ns) state situated only 4.85 keV above 93 m Mo constitutes a gateway to allow for its prompt release. The controllable release of the nuclear isomer energy will henceforth enable harvesting energy densities in the nuclear regime of GJkg - 1 (‘Nuclear Battery’). The campaign was inspired by the observation of the triggered release of 93 m Mo via the intermediate state by Chiara et al. [1] published in Nature. They assigned the hitherto elusive Nuclear Excitation by Electron Capture (NEEC) as the driving process and claimed a very high probability of P NEEC exp = 0.010 (3) . However, these claims are challenged by experimentalists [2-3] and theory [4]. We herein outline our strategy following bespoke theoretical guidance in the quest to unambiguously and independently demonstrate the onset of NEEC in 93 m Mo . With the yield estimations derived for our forthcoming HPLS experiment at ELI-NP, we draw optimism to resolve the current conundrum between the conflicting experimental observations and theoretical interpretations as discussed in world-leading journals and to pave the way for the future utilization of isomer depopulation in applied physics. [ABSTRACT FROM AUTHOR]