Ion acceleration in electrostatic collisionless shock: on the optimal density profile for quasi-monoenergetic beams

• Published in: Plasma physics and controlled fusion 2018-02, Vol.60 (3), p.35010
• Main Authors: Boella, E, Fiúza, F, Novo, A Stockem, Fonseca, R, Silva, L O
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Collisionless shock wave acceleration; compact accelerators; electrostatic shocks; laser-driven shock acceleration; PARTICLE ACCELERATORS; PIC simulations
• ISSN: 0741-3335; 1361-6587
• DOI: 10.1088/1361-6587/aaa556

A numerical study on ion acceleration in electrostatic shock waves is presented, with the aim of determining the best plasma configuration to achieve quasi-monoenergetic ion beams in laser-driven systems. It was recently shown that tailored near-critical density plasmas characterized by a long-scale decreasing rear density profile lead to beams with low energy spread (Fiúza et al 2012 Phys. Rev. Lett. 109 215001). In this work, a detailed parameter scan investigating different plasma scale lengths is carried out. As result, the optimal plasma spatial scale length that allows for minimizing the energy spread while ensuring a significant reflection of ions by the shock is identified. Furthermore, a new configuration where the required profile has been obtained by coupling micro layers of different densities is proposed. Results show that this new engineered approach is a valid alternative, guaranteeing a low energy spread with a higher level of controllability.