Study of nanostructured targets for plasma production via laser ablation

Metal nanowires (NWs) - nanostructures 20-100 nm in diameter and up to tens of micrometers long - behave as waveguides when irradiated with light with wavelength much greater than their diameter. This is due to collective excitations of free electrons (plasmons) in the metal which couple to light and travel on the surface of the nanowire. This effect can be used to efficiently absorb laser pulses to produce dense and hot plasma on special nanostructured targets with metal nanowires vertically aligned on the surface. In this thesis work, nanostructured targets with different parameters (length, diameter, metal and fabrication process) have been irradiated with infrared laser light. X-ray flux emitted by the cooling plasma is measured during irradiation, and the depth of craters formed on the target is measured later. This data is used to choose which target parameters are best for plasma production. Different targets are compared with each other and against a control, non-nanostructured (bulk) target. As will be shown, highly significant (> 5 sigma) differences are found between targets with different nanostructures, and between nanostructured and bulk target. This differences are very difficult to explain whithout accounting for the nanostructures in the targets. Therefore, data collected and analized in this thesis work supports the hypotesys that nanostructured targets perform better than bulk targets for laser plasma production purposes, and provides useful indications for optimization of NWS' parameters

Plasma Production via 6 ns Pulsed Laser at 1064 and 532 nm wavelengths on Nanostructured Targets

This thesis presents the result of a study, within the scope of the PLANETA experiment (an INFN research program), on the effect of nanostructures on laser-matter interaction. Specifically, the plasma created on targets containing metal nanowires when irradiated with a laser pulse 6 ns long, at 1064 and 532 nm wavelength, with a power density of about 1 · 1012 W/cm2 . Laser-produced plasma is of interest for a wide range of scientific and technological application, from using them as a source of X-rays to the possibility of nuclear fusion thanks to the high densities and temperatures which can be reached inside the plasma. However, most applications are constrained by the very limited penetration of laser energy into matter, due to the rapid formation of a reflective critical surface of dense plasma. PLANETA experiment was meant to investigate if targets with metal nanowires (thin cylinders with diameter < 100 nm, smaller than the laser’s wavelength) could lead to production of a hotter and/or longer lived plasma compared to bulk metal. The proposed mechanism would be a deeper penetration of laser light into the targets. This could lead to volumetric, instead of superficial heating, and thus to the production of a hotter and denser plasma compared to a bulk metal target. Targets were produced at the electron microscopy lab of INFN Bologna, with nanowires of different geometrical parameters and different metals. They were irradiated with a Nd-Yag laser at the INFN Laboratori Nazionali del Sud in Catania, and the resulting plasmas were observed with detectors of several kinds to compare them with plasmas from bulk metals. A different INFN facility at the Department of Physics, University of L’Aquila, equipped with a 532 nm wavelength laser was available to the PLANETA experiment

Spectrally tunable ultrashort monochromatized extreme ultraviolet pulses at 100 kHz

We present the experimental realization of spectrally tunable, ultrashort, quasimonochromatic extreme ultraviolet (XUV) pulses generated at 100 kHz repetition rate in a user-oriented gas high harmonic generation (GHHG) beamline of the Extreme Light Infrastructure - Attosecond Light Pulse Source (ELI ALPS) facility. Versatile spectral and temporal shaping of the XUV pulses are accomplished with a double-grating, time-delay compensated monochromator accommodating the two composing stages in a novel, asymmetrical geometry. This configuration supports the achievement of high monochromatic XUV flux (2.8e10+/-0.9e10 photons/s) combined with ultrashort pulse duration (4.0+/-0.2 fs using 12.1+/-0.6 fs driving pulses) and small spot size (sub-100 um). Focusability, spectral bandwidth, and overall photon flux of the produced radiation were investigated covering a wide range of instrumental configurations. Moreover, complete temporal (intensity and phase) characterization of the few-femtosecond monochromatic XUV pulses - a goal that is difficult to achieve by conventional reconstruction techniques - has been realized using ptychographic algorithm on experimentally recorded XUV-IR pump-probe traces. The presented results contribute to in-situ, time-resolved experiments accessing direct information on the electronic structure dynamics of novel target materials.Comment: 20 pages, 8 figure

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

Selezione dei fotomoltiplicatori per le misure di luminosita in atlas

Il rivelatore di luminosità LUCID di ATLAS, in LHC, deve cambiare fotomoltiplicatori durante il Long Shutdown I. Due modelli candidati per la sostituzione sono stati irradiati con raggi gamma per studiarne la resistenza alla radiazione. In questa tesi si riportano i risultati delle misure di dark current, guadagno relativo e risposta spettrale prima e dopo l'irraggiamento. L'unica differenza di rilievo dopo l'irraggiamento risulta essere l'aumento di dark current. All'interno dell'incertezza di misura, non ci sono variazioni negli altri parametri e non ci sono differenze sostanziali fra i due modelli

Nanostructured surfaces for nuclear astrophysics studies in laser-plasmas

The future availability of high-intensity laser facilities capable of delivering tens of petawatts of power (e.g. ELI-NP) into small volumes of matter at high repetition rates will give the unique opportunity to investigate nuclear reactions and fundamental interactions process under extreme plasma conditions [1]. In this context, use of targets with nanostructured surfaces is giving promising indications to reproduce plasma conditions suitable for measurements of thermonuclear reactions rates, in the domain of nanosecond laser pulses

Nanostructured surfaces for nuclear astrophysics studies in laser-plasmas

The future availability of high-intensity laser facilities capable of delivering tens of petawatts of power (e.g. ELI-NP) into small volumes of matter at high repetition rates will give the unique opportunity to investigate nuclear reactions and fundamental interactions process under extreme plasma conditions [1]. In this context, use of targets with nanostructured surfaces is giving promising indications to reproduce plasma conditions suitable for measurements of thermonuclear reactions rates, in the domain of nanosecond laser pulses