We demonstrate laser-ion acceleration from a near-critical density plasma, using amplified
spontaneous emission (ASE) to convert a solid foil target into a lower-density target. In order
to investigate the target density dependence of the laser-ion acceleration, two cases were investigated for which the ASE
intensity differed by three orders of magnitude. In the low contrast case the beam centre for higher energy protons is shifted
closer to the laser-propagation direction of 45
○, while the centre of lower-energy beam remains near the target normal direction. We show that a near-critical density plasma
can be used to control proton beam direction based on its energy.
PACS 52.38.Kd Laser-plasma acceleration of electrons and ions - 52.59.-f Intense particle beams and radiation sources