Approach towards quasi-monoenergetic laser ion acceleration with doped target

Ion acceleration by using a laser pulse irradiating a disk target which includes hydrogen and carbon is examined using three-dimensional particle-in-cell simulations. It is shown that over $200$ MeV protons can be generated by using a $620$TW, $5\times10^{21}$ W/cm$^2$ laser pulse. In a polyethylene (CH$_2$) target, protons and carbon ions separate and form two layers by radiation pressure acceleration. A strong Coulomb explosion in this situation and Coulomb repulsion between each layer generates high energy protons. A doped target, low density hydrogen within a carbon disk, becomes a double layer target which is comprised of a thin and low density hydrogen disk on the surface of a high-$Z$ atom layer. This then generates a quasi-monoenergetic proton beam.