Patent ID: 8648536

Claim:
A plasma light source comprising: (a) a pair of coaxial electrodes that are arranged to face each other with respect to a symmetry plane, wherein each of the respective coaxial electrodes includes (i) a rod-shaped center electrode that extends on a single axis Z-Z, (ii) a guide electrode that surrounds a facing front end portion of the center electrode and has a predetermined gap between the guide electrode and the center electrode, and (iii) an insulation member that insulates the center electrode and the guide electrode from each other, wherein the symmetry plane is perpendicular to the axis Z-Z; (b) a discharge-environment-maintaining device that maintains a plasma medium inside the coaxial electrodes at a temperature and a pressure appropriate for the generation of plasma; and (c) a voltage-applying device that applies discharge voltages having reversed polarities to the respective coaxial electrodes; wherein a tubular discharge is formed between the pair of coaxial electrodes so as to confine the plasma in an axial Z-Z direction, wherein the insulation member is formed of partially porous ceramics that include an insulative dense portion that does not permit the continuous permeation of the liquefied plasma medium and a porous portion that permits the continuous permeation of the liquefied plasma medium, and wherein the insulative dense portion includes a reservoir that holds the plasma medium therein, and by the porous portion, the inner surface of the reservoir communicates with the gap between the center electrode and the guide electrode, through the inside of the insulative dense portion.