  Theoretical investigations show that linearly and radially polarized
multiterawatt and petawatt laser beams, focused to subwavelength waist radii,
can directly accelerate protons and carbon nuclei, over micron-size distances,
to the energies required for hadron cancer therapy. Ions accelerated by
radially polarized lasers have generally a more favorable energy spread than
those accelerated by linearly polarized lasers of the same intensity.
