Selective ion acceleration by intense radiation pressure

McIlvenny, A. and Doria, D. and Romagnani, L. and Ahmed, H. and Booth, N. and Ditter, E. J. and Ettlinger, O. C. and Hicks, G. S. and Martin, P. and Scott, G. G. and Williamson, S. D. R. and Macchi, A. and McKenna, P. and Najmudin, Z. and Neely, D. and Kar, S. and Borghesi, M. (2021) Selective ion acceleration by intense radiation pressure. Physical Review Letters, 127 (19). 194801. ISSN 1079-7114 (https://doi.org/10.1103/PhysRevLett.127.194801)

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Abstract

We report on the selective acceleration of carbon ions during the interaction of ultrashort, circularly polarized and contrast-enhanced laser pulses, at a peak intensity of 5.5×1020 W/cm2, with ultrathin carbon foils. Under optimized conditions, energies per nucleon of the bulk carbon ions reached significantly higher values than the energies of contaminant protons (33 MeV/nucleon vs 18 MeV), unlike what is typically observed in laser-foil acceleration experiments. Experimental data, and supporting simulations, emphasize different dominant acceleration mechanisms for the two ion species and highlight an (intensity dependent) optimum thickness for radiation pressure acceleration; it is suggested that the preceding laser energy reaching the target before the main pulse arrives plays a key role in a preferential acceleration of the heavier ion species.