Record proton energies from laser acceleration with cone targets

High-Energy, short-pulse lasers can be used to accelerate ion beams. Laser-driven acceleration promises to provide very compact ion sources suitable for a variety of applications such as ion beam tumor therapy.
Up until recently, however, the ion energies observed in experiments were too low to be useful for treating tumors.
Using a novel target design, we have broken a long-lasting record for maximum proton energy measured in a laser acceleration experiment, reaching for the first time proton energies suitable for radiation therapy of intraocular tumors.
We present realistic particle-in-cell simulations of the laser interacting with the target that can explain the increase in energy seen in our experiment. The results from these simulations will help to improve the target design, paving the way towards even higher proton energies.