Electrode structure for generating electrical discharge plasma

A method of treating a moving substrate with an electrical discharge plasma, which comprises passing said substrate along a plurality of different paths of travel through an electrode means comprising at least two electrode structures, each electrode structure comprising at least one row of a plurality of elongated, tubular electrodes, the rows of one electrode structure alternating with the rows of the other electrode structure to form a stacked array of rows transverse to the said paths of travel of said substrate;

• maintaining the electrode structures at opposite polarity;
• the tubular electrodes being arranged to provide a plurality of different paths of travel of said substrate through said stacked array;
• each said path being substantially tangent to a plurality of said tubular electrodes arranged alternately of one polarity and then the opposite polarity;
• establishing an electrical plasma discharge such that the flow of plasma current is at least substantially parallel to a major surface of the substrate during each said path of travel of said substrate, said tubular electrodes being so arranged as to be operable to generate an electrical plasma discharge between adjacent tubular electrodes of opposite polarity;
• and cooling the tubular electrodes during the electrical discharge by flowing coolant therethrough.