The invention relates to a charged particle lithography system for exposing a target. The system includes a charged particle beam generator for generating a charged particle beam; an aperture array (6) for forming a plurality of beamlets from the charged particle beam; and a beamlet projector (12) for projecting the beamlets onto a surface of the target. The charged particle beam generator includes a charged particle source (3) for generating a diverging charged particle beam; a collimator system (5a,5b,5c,5d; 72;300) for refracting the diverging charged particle beam; and a cooling arrangement (203) for removing heat from the collimator system, the cooling arrangement comprising a body surrounding at least a portion of the collimator system.