The invention relates to a charged particle system for processing a target surface with at least one charged particle beam. The system comprises an optical column with a beam generator module for generating a plurality of charged particle beams, a beam modulator module for switching on and off said plurality of beams and a beam projector module for projecting beams or subbeams on said target surface. The system further comprises a frame supporting each of said modules in a fixed position and alignment elements for aligning at least one of beams and/or subbeams with a downstream module element.