1. A particle-beam projection processing apparatus for irradiating a target by means of a beam of energetic electrically charged particles, comprising an illumination system for generating and forming said energetic particles into an illuminating beam which is substantially tele/homocentric and whose diameter is greater by at least one order of magnitude than the length of the tele/homocentricity region of the illuminating beam, a pattern definition means located after the illumination system as seen along the direction of the beam, said pattern definition means being adapted to position an aperture pattern composed of apertures transparent to the energetic particles in the path of the illuminating beam, thus forming a patterned beam emerging from the aperture pattern, and a projection system positioned after the pattern definition means and adapted to project the patterned beam onto a target to be positioned after the projection system, further comprising at least one foil located across the path of the patterned beam, said at least one foil being positioned between the pattern definition means and the position of the target at a location close to a respective image of the aperture pattern formed by the projection system.