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Abstract

Collisionless shocks are of great interest in astrophysical scenarios as they are believed to be responsible for high energy cosmic rays and non-thermal particles. The field of laboratory astrophysics attempts to study astrophysical phenomena in a laboratory with the help of intense lasers. In view of laboratory-astrophysics experiments and laser-driven ion acceleration, collisionless shocks are studied semi-analytically and with numerical simulations. In particular, how the particle collisions in plasma can affect the laser-driven shock formation and subsequent ion acceleration is investigated. It is shown in this thesis, how resistive reorganisation of electromagnetic fields in a plasma target leads to significant improvement in the shock-accelerated ion-beam-profile without any additional need of target-tailoring (i.e. a known technique currently used to achieve a monoenergetic profile of the shock-accelerated ion-beam). This result is beneficial especially for medical science that requires therapeutic proton beams, particularly for the treatment of cancer. At ultra-high laser ntensities, the effect of radiative losses on particle's trajectory become important. These losses due to radiation emission have been shown to modify the shock's field structure. It is also demonstrated that exclusion of radiative losses can lead to overestimation of maximum ion-energy in a thin-target regime.