A particle-beam column comprising a needle-type ions source such as a liquid metal ion source, one or more round lenses, and a plurality of interleaved quadrupole lenses, by means of which the chromatic aberration of the column may be reduced or entirely compensated. Also an ion-beam column comprising a liquid alloy ion source, interleaved quadrupole lenses, and a Wien velocity filter, whereby a focused beam of ions of a single atomic number may be produced. Such columns produce a more finely focused beam than columns based only on electrostatic lenses, and allow increased lens apertures and larger beam currents.