Laser-plasma acceleration of quasi-monoenergetic protons from microstructured targets

Particle acceleration based on high intensity laser systems ( a process known as laser - plasma acceleration) has achieved high quality particle beams that compare favourably with conventional acceleration techniques in terms of emittance, brightness and pulse duration(1-4). A long-term difficulty associated with laser - plasma acceleration - the very broad, exponential energy spectrum of the emitted particles - has been overcome recently for electron beams(5-7). Here we report analogous results for ions, specifically the production of quasi-monoenergetic proton beams using laser - plasma accelerators. Reliable and reproducible laser-accelerated ion beams were achieved by intense laser irradiation of solid microstructured targets. This proof-of-principle experiment serves to illuminate the role of laser-generated plasmas as feasible particle sources. Scalability studies show that, owing to their compact size and reasonable cost, such table-top laser systems with high repetition rates could contribute to the development of new generations of particle injectors that may be suitable for medical proton therapy(8-10).