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The interaction of ultra-intense high-power lasers with solid-state targets has been largely studied for the past 20 years as a future compact proton and ion source. Indeed, the huge potential established on the target surface by the escaping electrons provides accelerating gradients of TV/m. This process, called target normal sheath acceleration, involves a large number of phenomena and is very difficult to study because of the picosecond scale dynamics. At the SPARC_LAB Test Facility, the high-power laser FLAME is employed in experiments with solid targets, aiming to study possible correlations between ballistic fast electrons and accelerated protons. In detail, we have installed in the interaction chamber two different diagnostics, each one devoted to characterizing one beam. The first relies on electro-optic sampling, and it has been adopted to completely characterize the ultrafast electron components. On the other hand, a time-of-flight detector, based on chemical-vapour-deposited diamond, has allowed us to retrieve the proton energy spectrum. In this work, we report preliminary studies about simultaneous temporal resolved measurements of both the first forerunner escaping electrons and the accelerated protons for different laser parameters.

The divergent and broadband proton beams produced by the target normal sheath acceleration mechanism provide the unique opportunity to probe, in a point-projection imaging scheme, the dynamics of the transient electric and magnetic fields produced during laser-plasma interactions. Commonly such experimental setup entails two intense laser beams, where the interaction produced by one beam is probed with the protons produced by the second. We present here experimental studies of the ultra-fast charge dynamics along a wire connected to laser irradiated target carried out by employing a 'self proton probing arrangement i.e. by connecting the wire to the target generating the probe protons. The experimental data shows that an electromagnetic pulse carrying a significant amount of charge is launched along the wire, which travels as a unified pulse of 10s of ps duration with a velocity close to speed of light. The experimental capabilities and the analysis procedure of this specific type of proton probing technique are discussed. (C) 2016 Elsevier B.V. All rights reserved.

In this work, we present a novel realization of nanostructured targets suitable for improving laser-driven proton acceleration experiments, in particular with regard to the Target-Normal-Sheath Acceleration (TNSA) acceleration mechanism. The nanostructured targets, produced as films, are realized by a simpler and cheaper method than using conventional lithographic techniques. The growth process includes a two step approach for the production of the gold nanoparticle layers: 1) Laser Ablation in Solution and 2) spray-dry technique using a colloidal solution on target surfaces (Aluminum, Mylar and Multi Walled Carbon Nanotube). The obtained nanostructured films appear, at morphological and chemical analysis, uniformly nanostructured and the nanostructure distributed on the target surfaces without presence of oxides or external contaminants. The obtained targets show a broad optical absorption in all the visible region and a surface roughness that is two times greater than non-nanostructured targets, enabling a greater laser energy absorption during the laser-matter interaction experiments producing the laser-driven proton acceleration.

The construction of a novel Laser driven Light Ions Acceleration Line(L3IA) is progressing rapidly towards the operation, following the recent upgrade of the ILIL-PW laser facility. The Line was designed following the pilot experimental activity carried out earlier at the same facility to define design parameters and to identify main components including target control and diagnostic equipment, also in combination with the numerical simulations for the optimization of laser and target parameters. A preliminary set of data was acquired following the successful commissioning of the laser system >100 TW upgrade. Data include output from a range of different ion detectors and optical diagnostics installed for qualification of the laser-target interaction. An overview of the results is given along with a description of the relevant upgraded laser facility and features., 6 pages, 7 figures, 18 references, presented at the EAAC 2017

Laser-driven particle acceleration has become a growing field of research, in particular for its numerous interesting applications. One of the most common proton acceleration mechanism that is obtained on typically available multi-hundred TW laser systems is based on the irradiation of thin solid metal foils by the intense laser, generating the proton acceleration on its rear target surface. The efficiency of this acceleration scheme strongly depends on the type of target used. Improving the acceleration mechanism, i.e. enhancing parameters such as maximum proton energy, laminarity, efficiency, monocromaticy, and number of accelerated particles, is heavily depending on the laser-to-target absorption, where obviously cheap and easy to implement targets are best candidates. In this work, we present nanostructured targets that are able to increase the absorption of light compared to what can be achieved with a classical solid (non-nanostructured) target and are produced with a method that is much simpler and cheaper than conventional lithographic processes. Several layers of gold nanoparticles were deposited on solid targets (aluminum, Mylar and multiwalled carbon nanotube buckypaper) and allow for an increased photon absorption. This ultimately permits to increase the laser-to-particle energy transfer, and thus to enhance the yield in proton production. Experimental characterization results on the nanostructured films are presented (UV-Vis spectroscopy and AFM), along with preliminary experimental proton spectra obtained at the JLF-TITAN laser facility at LLNL.

International audience; Laser-driven ion acceleration by intense, ultra-short, laser pulse has received increasing attention inrecent years, and the availability of much compact and versatile ions sources motivates the study oflaser-driven sources of energetic neutral atoms. We demonstrate the production of a neutral anddirectional beam of hydrogen and carbon atoms up to 200 keV per nucleon, with a peak flow of 2.7 x10(13) atom s(-1). Laser accelerated ions are neutralized in a pulsed, supersonic argon jet with tunabledensity between 1.5 x 10(17) cm(-3) and 6 x 10(18) cm(-3). The neutralization efficiency has beenmeasured by a time-of-flight detector for different argon densities. An optimum is found, for whichcomplete neutralization occurs. The neutralization rate can be explained only at high areal densities (> 1x 10(17) cm(-2)) by single electron charge transfer processes. These results suggest a new perspectivefor the study of neutral production by laser and open discussion of neutralization at a lower density.

The development of high-intensity lasers has opened the field of nuclear reactions initiated by laser-accelerated particles. One possible application is the production of aneutronic fusion reactions for clean fusion energy production. We propose an innovative scheme based on the use of two targets and present the first results obtained with the ELFIE facility (at the LULI Laboratory) for the proton–boron-11 (p–11B) fusion reaction. A proton beam, accelerated by the Target Normal Sheat Acceleration mechanism using a short laser pulse (12 J, 350 fs, 1.056 µm, 1019 W cm−2), is sent onto a boron target to initiate fusion reactions. The number of reactions is measured with particle diagnostics such as CR39 track-detectors, active nuclear diagnostic, Thomson Parabola, magnetic spectrometer, and time-of-flight detectors that collect the fusion products: the α-particles. Our experiment shows promising results for this scheme. In the present paper, we discuss its principle and advantages compared with another scheme that uses a single target and heating mechanisms directly with photons to initiate the same p–11B fusion reaction.

Thin foils, 0.5–50 μm in thickness, have been irradiated in vacuum at Prague Asterix Laser System in Prague using 1015–16 W cm−2 laser intensity, 1315 nm wavelength, 300 ps pulse duration and different focal positions. Produced plasmas from metals and polymers films have been monitored in the forward and backward directions. Ion and electron accelerations have been investigated by using Thomson parabola spectrometer, x-ray streak camera, ion collectors and SiC semiconductor detectors, the latter employed in time-of-flight configuration. Ion acceleration up to about 3 MeV per charge state was measured in the forward direction. Ion and electron emissions were detected at different angles as a function of the irradiation conditions.

This paper presents the concept of transport and filtering of laser-accelerated proton pulses used for the first cell irradiation experiments performed with the Dresden 150 TW laser DRACO. Based on a simple non-focusing magnetic dipole equipped with two apertures the concept makes use of an energy dependent angular asymmetry of the proton spectra. For micron thin target foils protons of interest with energies above 7 MeV are observed to be significantly offset from target normal where low energy emission is dominantly centered. As the effect can be controlled via the target rotation with respect to the incoming light, it can be used to optimize the transport efficiency for high energy protons while simultaneously suppressing background radiation.