Jeudi 12 janvier 2017, 14h
par Satya Kar, School of Mathematics and Physics, Queen’s University Belfast
Salle Christian Harel, Laboratoire CELIA, Domaine du Haut Carré
43 rue Pierre Noailles, 33405 Talence cedex
In the context of developing a compact, high current ion accelerator, the study of intense laser driven acceleration mechanisms and their optimisation of the ion beams produced, have been, over the past decade, very active areas of research . An appealing beam of ions will not only be useful for their direct application in science, industry and healthcare; it can be beneficial towards development of secondary radiation sources, such as neutrons. An ultra-short, directional burst of fast neutrons, produced by high power laser driven compact ion accelerators, would have a wide ranging applications, including material testing for fusion energy research, fast neutron radiography, neutron resonance spectroscopy etc.
Several aspects of this area have been the research focus of our group at the Queen’s university Belfast. While we sought out exploring the possibility of ion acceleration from ultra-thin targets at the onset of radiation pressure effects , significant efforts have been made to control and optimize the ion beam parameters produced by the well-known Target Normal Sheath Acceleration mechanism. A recently developed concept of a versatile, miniature linear accelerating module to achieve simultaneous focusing, energy selection and post-acceleration of the proton beams will be discussed. After a proof-of-principle demonstration of the technique at university-scale laser, achieving post-acceleration of ~10^8 protons by ~5 MeV over less than a cm of propagation  – i.e. an accelerating gradient of ~ 0.5 GeV/m, already beyond what can be sustained by conventional accelerator technologies, the technique was recently employed at the Vulcan Petawatt, UK and Titan laser, LLNL, USA, which produced narrow band pencil beams of up to 50 MeV. Where preliminary analysis indicates a fast scaling of the post-acceleration gradient with laser power, deploying this modular device in a multi-stage scenario will open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications. Recent progress in the development of laser-driven neutron source will also be presented , which not only paved the way towards increasing neutron flux by improving its anisotropicity, measuring neutrons itself proved to be an extremely useful diagnostic to characterize and optimize the acceleration mechanism of their parent ions.
 A. Macchi et. al., Rev. Mod. Phys. 85, 751 (2013).
 S. Kar et. al., Phys. Rev. Lett., 109, 185006 (2012)
 S. Kar et. al., Nature communication, 7, 10792 (2016)
 S. Kar et. al., New J. Phys., 18, 053002 (2016)