outside the laser tube to the edge surface of the hot electrode so that springs 1 and 2 are compressed against the edge surface of the hot electrode to provide a good rf contact as shown in fig1 another modification that was made to this standard part was to have a u201c lip u201d 13 machined in the stainless steel flange 9 that also protrudes past the inside surface of the laser tube housing an u201c o u201d ring recess 10 is provided to maintain the hermetically sealed condition of the laser tube housing when the rf feed through metal to ceramic flange assembly is bolted onto an outside surface of the laser tube housing a nickel plated aluminum rf shield 12 is press fitted over the stainless steel lip 13 to ensure a good electric contact between the shield 12 and the lip 13 the rf shield 12 serves as the outer ground conductor of a short co axial transmission line the characteristic impedance of which is designed to match the input impedance of the laser discharge as well as the output impedance of the impedance matching network that feeds rf power from external to the laser tube housing to the laser discharge within the hermetically sealed laser housing this.