Dottorato in FISICA DEGLI ACCELERATORI

Titolo della tesi: Advanced time-of-flight diagnostics for real-time characterization of ions accelerated by high energy lasers

Time-Of-Flight (TOF) methods are very effective to detect ions accelerated in laserplasma interactions, but they show significant limitations when used in experiments with high energy and intensity lasers, where both high-energy ions and remarkable levels of ElectroMagnetic Pulses (EMPs) in the radiofrequency-microwave range are generated. In this joined-doctoral thesis, performed at the La Sapienza University in Rome, at the institut national de la recherche scientifique (INRS) in Montréal and at ENEA Centro Ricerche Frascati, an advanced diagnostic technique for the characterization of protons accelerated by intense laser-matter interactions with high-energy and high-intensity lasers has been implemented. The proposed method exploits and improves the advantages given by TOF technique coupled to Chemical Vapor Deposition diamond detectors and features high sensitivity, high energy resolution and high radiation hardness. Thanks to the optimization of the acquisition system and to the careful setup of the TOF line, high signal-to-noise ratios in environments heavily affected by remarkable EMP fields have been achieved. In the first part of the work a brief overview of laser-matter interaction is given, with particular emphasis to processes leading to particle acceleration. Then, the main diagnostic techniques available for the characterization of secondary sources produced by laser-matter interaction are presented. Here the TOF technique is introduced and analyzed when coupled with different kinds of detectors, including diamonds. The choice of the latter is justified by their physical properties. Various types of diamond structures and electrode layouts have been tested and their performances characterized for application as detectors to be employed in TOF lines. The second part of the work is dedicated to a detailed description of the proposed advanced technique and to examples of its effectiveness in reducing the EMP noise and in enhancing the dynamic range, when employed in real experimental scenarios. A novel procedure to retrieve a calibrated proton spectrum from the performed measurements is here also proposed and discussed. Eventually, the developed technique is applied for detecting laser-plasma accelerated particles produced in different application scenarios and in the most variable laser-matter interaction conditions and the concept of a new multi-layer detector is also described.