Multiple pulse sheath acceleration: an optical approach to spectral control

Recent experimental results have shown that it is possible to produce laser-accelerated proton and ion beams with distinct quasi-monoenergetic features in the energy spectrum [1, 2]. As short-pulse ultraintense laser intensities exceed 1021Wcm−2, it may be possible to produce quasi-monoenergetic proton bunches with energies in the range of 100-200 MeV. This opens up the prospect of a new route to developing medical ion accelerators for oncology. In this paper we will briefly report on some of our recent work [3]. This showed that it is theoretically possible to produce laser-accelerated proton/ion beams with distinct spectral peaks by irradiating a solid target with two laser pulses that arrive in rapid succession. No special target composition or structure is required, unlike the other schemes that have been proposed [1, 2]. This may be advantageous for certain applications.