The invention relates to an arrangement for transporting radicals. An electron beam system is presented comprising a beamlet generator; a beamlet manipulator (204) comprising an array of apertures; a plasma generator comprising a chamber for forming a plasma, an inlet receiving input gas and outlets removing plasma or radicals created therein, the plasma generator further comprising outlets in flow connection with the plasma chamber outlets; and a hollow guiding body (309b) guiding radicals formed in the plasma towards the array of apertures for removing contaminant deposition. The hollow guiding body (309b) is removably connectable to an extended portion (307b) of the plasma generator outlet. A cover (400) can be placed over a connection between the hollow guiding body (309b) and the extended portion (307b). The extended portion (307b) of the plasma generator outlet and the hollow guiding body (309b) can be similarly formed as a slit.