Rise time of proton cut-off energy in 2D and 3D PIC simulations

The Target Normal Sheath Acceleration (TNSA) regime for proton acceleration by laser pulses is experimentally consolidated and fairly well understood. However, uncertainties remain in the analysis of particle-in-cell (PIC) simulation results. The energy spectrum is exponential with a cut-off, but the maximum energy depends on the simulation time, following different laws in two and three dimensional (2D, 3D) PIC simulations, so that the determination of an asymptotic value has some arbitrariness. We propose two empirical laws for rise time of the cut-off energy in 2D and 3D PIC simulations, suggested by a model in which the proton acceleration is due to a surface charge distribution on the target rear side. The kinetic energy of the protons that we obtain follows two distinct laws, which appear to be nicely satisfied by PIC simulations. The laws depend on two parameters: the scaling time, at which the energy starts to rise, and the asymptotic cut-off energy. The values of the cut-off energy, obtained by fitting the 2D and 3D simulations for the same target and laser pulse, are comparable. This suggests that parametric scans can be performed with 2D simulations, since 3D ones are computationally very expensive. In this paper, the simulations are carried out for $a_0=3$ with the PIC code ALaDyn by changing the target thickness $L$ and the incidence angle $\alpha$. A monotonic dependence, on $L$ for normal incidence and on $\alpha$ for fixed $L$, is found, as in the experimental results for high temporal contrast pulses

Fusione nucleare: l’energia delle stelle

Intervengono Leonida Antonio Gizzi, Istituto Nazionale di Ottica del CNR, sede di Pisa, associato INFN Francesca Matteucci, docente di Astrofisica, Università di Trieste, accademico dei Lincei Modera Stefano Sandrelli, divulgatore e astrofisico, INAF-Osservatorio Astronomico di Brera E = mc2, diceva Einstein. Ovvero: la materia si può trasformare in energia e viceversa. Ma se per produrre energia bastasse solo un po’ di materia, non avremmo risolto ogni possibile crisi energetica? In che modo si realizza questa trasformazione in Natura? E a che punto è arrivata la ricerca per riprodurre questo fenomeno in laboratorio? Cercheremo di capirne di più, dialogando con Francesca Matteucci, docente di astrofisica presso l’Università di Trieste e Leonida Gizzi, Direttore del Laboratorio Laser Intensi dell’Istituto Nazionale di Ottica del CNR di Pisa. E scopriremo che le risposte a queste domande non solo ci illuminano sul nostro futuro prossimo, ma anche sul nostro passato remoto e sulla nostra origine cosmica

Laser-driven sources of high energy particles and radiation: lecture notes of the "Capri" Advanced Summer School

This volume presents a selection of articles based on inspiring lectures held at the “Capri” Advanced Summer School, an original event conceived and promoted by Leonida Antonio Gizzi and Ralph Assmann that focuses on novel schemes for plasma-based particle acceleration and radiation sources, and which brings together researchers from the conventional accelerator community and from the high-intensity laser-matter interaction research fields. Training in these fields is highly relevant for ultra-intense lasers and applications, which have enjoyed dramatic growth following the development of major European infrastructures like the Extreme Light Infrastructure (ELI) and the EuPRAXIA project. The articles preserve the tutorial character of the lectures and reflect the latest advances in their respective fields. The volume is mainly intended for PhD students and young researchers getting started in this area, but also for scientists from other fields who are interested in the latest developments. The content will also appeal to radiobiologists and medical physicists, as it includes contributions on potential applications of laser-based particle accelerators

Measurements of ultrafast ionisation dynamics from intense laser interactions with gas-jets,

Interaction of an intense, ultrashort laser pulse with a gas-jet target is investigated through femtosecond optical interferometry to study the dynamics of ionization of the gas. Experimental results are presented in which the propagation of the pulse in the gas and the consequent plasma formation is followed step by step with high temporal and spatial resolution. We demonstrate that, combining the phase shift with the measurable depletion of fringe visibility associated with the transient change of refractive index in the ionizing region and taking into account probe travel time can provide direct information on gas ionization dynamics

Laser-Plasma Acceleration with FLAME and ILIL Ultraintense Lasers

We report on the development of radiation and electron sources based on laser-plasma acceleration for biomedical and nuclear applications, using both the table top TW laser at ILIL and the 220 TW FLAME laser system at LNF. We use the ILIL laser to produce wakefield electrons in a self-focusing dominated regime in a mm scale gas-jet to generate large, uniform beams of MeV electrons for electron radiography and radiobiology applications. This acceleration regime is described in detail and key parameters are given to establish reproducible and reliable operation of this source. We use the FLAME laser to drive laser-plasma acceleration in a cm-scale gas target to obtain stable production of >100 MeV range electrons to drive a Thomson scattering ɣ-ray source for nuclear applications

Novel types of ionizing radiation sources at LNF-PLASMONX facility

The INFN Strategic Project PLASMONX (PLASma acceleration and MONochromatic X-ray production) deals with the creation of a High Intensity Laser Laboratory at LNF (HILL@LNF) beside the SPARC bunker, with which it will communicate via a channel for the propagation of laser beams. In this laboratory FLAME (Frascati Laser for Acceleration and Multidisciplinary Experiments), a 200TW, 30fs, 10Hz Ti:Sapphire Laser, will be setup. The main goals of this project are: 1) demonstration of high-gradient acceleration of relativistic electrons injected into electron plasma waves excited by ultra-short, super-intense laser pulses; 2) development of a monochromatic and tuneable X-ray source in the 20-1000 keV range, based on Thomson Scattering of laser pulses by the 20-200 MeV electrons of the LINAC of the SPARC project. One of the aims of the project consists in the realization of a pulsed source of ionizing radiation for R&D activity in different fields

Toward an effective use of laser-driven very high energy electrons for radiotherapy: Feasibility assessment of multi-field and intensity modulation irradiation schemes.

Radiotherapy with very high energy electrons has been investigated for a couple of decades as an effective approach to improve dose distribution compared to conventional photon-based radiotherapy, with the recent intriguing potential of high dose-rate irradiation. Its practical application to treatment has been hindered by the lack of hospital-scale accelerators. High-gradient laser-plasma accelerators (LPA) have been proposed as a possible platform, but no experiments so far have explored the feasibility of a clinical use of this concept. We show the results of an experimental study aimed at assessing dose deposition for deep seated tumours using advanced irradiation schemes with an existing LPA source. Measurements show control of localized dose deposition and modulation, suitable to target a volume at depths in the range from 5 to 10 cm with mm resolution. The dose delivered to the target was up to 1.6 Gy, delivered with few hundreds of shots, limited by secondary components of the LPA accelerator. Measurements suggest that therapeutic doses within localized volumes can already be obtained with existing LPA technology, calling for dedicated pre-clinical studies