STUDY OF FAST ELECTRON TRANSPORT AND ENERGETIC PROTON GENERATION AT HIGH LASER INTENSITY AND APPLICATION TO FAST IGNITION

Fast Ignition is a very promising, alternative way to achieve energy gain in Inertial Confinement Fusion (ICF) research. It is based on the decoupling of the compression and heating stages of an equi-molar Deuterium-Tritium (DT) plasma, allowing to loose the very tight constraints of the classic central hot spot (CHS) ignition concept, and attaining higher energy gain. The compression of the DT capsule is performed by symmetrically focusing an array of energetic, long (ns) laser pulses on the capsule, inducing its implosion by ablation pressure driven convergent shocks. The heating of the compressed DT plasma is produced by energetic particle beams (electrons or protons), generated by an energetic, ultra-intense (I approx 10^20 W/cm2) short (approx 20 ps) laser pulse, focused at the instant of DT peak compression. The study of generation and transport of laser produced fast electrons and protons is therefore fundamental for the achievement of Fast Ignition ICF. In this work I present the experimental as well as modeling study of fast electron transport and proton beam generation, with application to Fast Ignition. In particular in this work I studied the fast electron transport in rapidly changing plasma density and temperature gradients, conditions expected in a full scale Fast Ignition experiment. In the second part of this work I demonstrated a method to improve the laser-to-proton energy conversion efficiency in a way very suitable for Fast Ignition as well as for medical application.