BREAKING THE 70 MeV PROTON ENERGY THRESHOLD IN LASER PROTON ACCELERATION AND GUIDING BEAMS TO APPLICATIONS

摘要

The acceleration of protons and light ions such as carbon by the interaction of intense laser beams with solid targets has been studied for more than 10 years. Since the discovery of the Target Normal Sheath Acceleration (TNSA) mechanism in 2000 by Snavely et al. [1] a lot of experiments and theoretical models have been used to understand the physical details underlying this mechanism and to characterize the resulting ion beam in terms of spatial and spectral energy distribution. While the required energy of the laser has been reduced by an order of magnitude and the targets have been optimized no experiment has exceeded energies around 70 MeV for protons in such experiments. With respect to the outstanding qualities of those laser accelerated ion beams, especially the low emittance, which allows for transport and focusing, many applications have been proposed. Recently new accelerating mechanisms have been proposed relying on the increasing laser intensity available with modern systems. Among them is the BOA (Break Out Afterburner) mechanism [2] first discovered at LANL in extensive computer simulations. The mechanism relies on the relativistic transparency of solids and has been first discovered experimentally at the LANL Trident laser system. Most of the possible future applications also require the selection of a specific particle energy with ΔE=E < 1% and a focused or low-divergent beam. Here, several attempts have been taken in the past and the most promising results obtained with the use of small permanent-magnetic quadrupole devices [3,4] or pulsed high-field solenoids [5,6].