The acceleration of ions from ultrathin foils has been investigated by using 250 TW, subpicosecond laser pulses, focused to intensities of up to 3 X 10(20) W cm(-2). The ion spectra show the appearance of narrow-band features for protons and carbon ions peaked at higher energies (in the 5-10 MeV/nucleon range) and with significantly higher flux than previously reported. The spectral features and their scaling with laser and target parameters provide evidence of a multispecies scenario of radiation pressure acceleration in the light sail mode, as confirmed by analytical estimates and 2D particle-in-cell simulations. The scaling indicates that monoenergetic peaks with more than 100 MeV/nucleon are obtainable with moderate improvements of the target and laser characteristics, which are within reach of ongoing technical developments.
Bibliographical noteThe authors acknowledge funding from EPSRC [EP/
E035728/1-LIBRA consortium, EP/E048668/1 and EP/
J002550/1-Career Acceleration Fellowship held by S. K.],
Leverhulme Trust (Fellowship ECF-2011-383 held by
G. S.), MIUR (Italy) via the FIRB project ‘‘SULDIS,’’
projects ELI (Grant No. CZ.1.05/1.1.00/483/02.0061) and
OPVK 3 (Grant No. CZ.1.07/2.3.00/20.0279), and DFG
programs TR18 and GK1203. The authors also
acknowledge support from the target fabrication group
and e-Science facility of RAL-STFC.