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Exploring the New Science and engineering unveiled by Ultraintense ultrashort Radiation interaction with mattEr

Periodic Reporting for period 3 - ENSURE (Exploring the New Science and engineering unveiled by Ultraintense ultrashort Radiation interaction with mattEr)

Reporting period: 2018-09-01 to 2020-02-29

The aim of the ENSURE project is the theoretical, numerical and experimental investigation of novel ion acceleration mechanisms in the interaction of ultrashort (10^-12 to 10^-14 s), superintense (10^19-10^23 W/cm2) laser pulses with solid targets whose properties (composition, thickness, density profile) are controlled down to the nanoscale.
The topic of ion acceleration by intense laser pulses has attracted an impressive amount of experimental and theoretical work and can now be considered as one of the most active and innovative areas of laser and plasma physics. The appealing features of laser-driven ion beams (e.g. the extremely short acceleration length, high collimation, very low emittance, picosecond duration of the ion bunch), not found for conventional ion sources, are promising for several scientific, technological and societal applications which are based on the unique properties of localized energy deposition by ion beams in dense matter.
The ENSURE project has a strong focus towards the use of these beams for novel key applications in materials (material irradiation and advanced characterization) & nuclear (ion-driven secondary particle/exotic nuclei sources) science and engineering. These goals are pursued integrating in an unprecedented way advanced expertise and methods from materials science and engineering, laser-plasma physics and computational science into a single team.
"Period 1-30 months.

At the mid-term reporting period, the implementation of the project is successful and globally on time. Our achievements in the context of these activities are reported below.

WP1: Experimental production of innovative solid targets with properties, controlled at a nanometric scale, optimized for the achievement of novel and improved ion acceleration regimes and laser-ion beams.
The main scope of the task is the development of materials with desired and often unconventional properties (such as ultra-low density, controlled nanostructure, etc) to be used in laser-driven acceleration experiments in combination with ""standard"" targets to enhance their performance. During the first half of the project, the experimental activities related to target preparation have mainly relied on the exploitation of the Pulsed Laser Deposition techniques with a nanosecond laser source (ns-PLD), available at the Host Institution (HI). Ultra-low density foams with controlled nanostructure and thickness are deposited on the surface of micrometric-thick foils, to increase the coupling with the laser radiation, potentially leading to an overall enhancement of the laser-driven acceleration performance. We have demonstrated the viability of this solution, along with its flexibility and adaptability to different target solution. We investigated, both theoretically and experimentally, the growth dynamics of ultra-low density carbon (C) foams in PLD experiments. Besides its novelty and intrinsic interest from a fundamental point of view, a deeper understanding of the foam growth process is required for a better control of the foam properties (e.g. high uniformity also for reduced thicknesses) which in turn is instrumental for a full exploitation of the possibilities offered by non-conventional target solutions. We have also worked on the development of advanced techniques for the characterization of nanostructured materials. In addition, other kinds of films and coatings have been developed, mostly in the light of the interest on the experimental investigation of the behavior of nanostructured materials under plasma, electromagnetic and ion beams (see WP2). In this frame high density tungsten films and compact boron films have been prepared and characterized for exposure to plasmas and ion beams. To achieve the ENSURE goals related to the experimental activities, new research laboratories have also been established at the HI, equipped with advance instrumentation:
- A new fs-PLD deposition system, based on a Ti:sapphire Laser system, whose properties (pulse duration < 100 fs, pulse energy > 5mJ) are qualifying as a source for Pulsed Laser Deposition experiments as well as a versatile tool for material modification and processing. A specifically designed interaction chamber, which is an essential part of the new fs-PLD deposition system, has been acquired. The chamber can work in two configurations: i) as a fs-PLD deposition chamber, when the laser is focused on the target, ii) as an interaction chamber for material processing, when the laser is directed on the substrate. For both configurations, a dedicated software manages the machine operation and control.
- A Magnetron Sputtering deposition system based on the HiPIMS (High Pulse Intensity Magnetron Sputtering) technology, which has been developed at the beginning of the past decade. This system differs from conventional Magnetron Sputtering with respect to the very high ionization degree of the plasma produced during the sputtering process. This characteristic will be exploited to produce novel materials with advanced features, such as excellent mechanical properties also in the form of a free-standing film, which are of great interests for the aims of ENSURE. The experimental activities of this WP1 in the future will be mainly focused on the production of more complex material configurations: ultra-thin targets and targets with variable density and with heterogeneous controlled"
The results of the ENSURE project can determine a unique impact in the research on laser-driven ion acceleration in Europe, providing new directions to support the attainment, in the next future, of concrete applications of great societal relevance, in medical, energy and materials areas. ENSURE will also sustain the development of some of the major research European infrastructures of the next decades, like ELI and HiBEF@XFEL. Together with its aims and adopted methodology, these results and impact enlighten the ground-breaking, non-conventional, interdisciplinary, high-risk/high-gain nature of the ENSURE project.
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