and must therefore be taken into account when conceiving the overall electrode arrangement which is customarily done by computer aided simulation of rf field distribution in the plasma discharge space of the reactor as in all embodiments described up to now and as was already addressed the dielectric spacing may be realized by dielectric solid material spacing and or by vacuum compartment spacing as further shown in fig6 the spacing between members 28 may be filled by dielectric material spacers 36 by such dielectric spacers 36 it becomes possible to ensure mutual floating operation of the metal members 28 even if the spacing w between neighboring metal tiles is selected to be larger than the addressed dark space distance further providing such dielectric spacers 36 filling the spaces between neighboring metal members 28 protects the dielectric spacing 12 i from ion and electron bombardment which may hardly be avoided even if at void spacings between neighboring metal members 28 the spacing w is selected to be smaller than the dark space distance further and with an eye on fig6 it might be possible to provide a unitary grid of dielectric spacers 36 which may be interposed into the spaces between the metal members 28 as a separate part and which thus may be exchanged easily thereby the.