positively charged particles downward away from the reticle 36 the electric field 78 is localized near the reticle 36 to minimize the possibility of positively charged particles below the electrodes 68 a 68 b from being attracted toward the reticle any particles in the space 46 have been assumed to be electrically neutral some particles may become positively charged by the photoelectric effect notably from euv radiation that has scattered from the surface of the reticle 36 into the space 46 these particles would be attracted even more efficiently to the electrodes 68 a 68 b although a mechanism is not currently known if some particles do acquire a negative charge in the space 46 and are conveyed by the gas flow near the electrodes 68 a 68 b they undesirably will be driven by the electric field toward the surface of the reticle 36 a means of avoiding this situation is to provide a flow of positive gas ions from the nozzle manifolds 52 a 52 b into the space 46 these ions can neutralize any negatively charged particles in the space 46 and prevent them from being driven toward the surface of the reticle 36 by the electrodes 68 a 68 b these ions may be produced by e g a positive corona discharge whereby a positively charged set of sharp conductive points removes electrons from adsorbed gas atoms giving them a positive charge and repelling them from the points referring now to fig5 an embodiment of an euvl system 900 is shown the depicted system 900 comprises a vacuum chamber 902 including vacuum pumps 906 a 906 b that are arranged to enable desired vacuum levels to be established and maintained within respective.