and the orientation of the grooves 148 are configured such that cooling gas flows 126 d travel through each groove 148 to the region 46 aft of the electrode 122 the grooves 148 are dimensioned to produce a substantial pressure drop in the gas flow passing through the groove passages the velocity of the cooling gas flows 126 d decreases as the gas flows into grooves 148 past the ribs 122 c toward the second end of the electrode 122 e the plurality of ribs 122 c act as heat transfer surfaces for cooling the electrode 122 as such an increased the surface area of the electrode is exposed to the cooling gas flows 126 d resulting in more effective cooling of the electrode 122 the plurality of grooves 148 allow multiple cooling gas flows 126 d to flow through the shoulder 122 b of the electrode 122 because there is a substantial pressure drop through the grooves 148 and because of the large surface area of the imperforate face 122 f the gas flow 26 c pressurizes the chamber 36 rapidly with only a small pressure acting on the opposite surfaces of the electrode in the region above the electrode 46 this pressurization u201c blows back u201d the electrode against the force of the spring 16 allowing the flow 26 c in the plasma chamber to assume an unrestricted swirling pattern which is conducive to the formation of a stable plasma arc the electrode.