Various types of plasma discharge radiation sources have been proposed over the years. For example, capillary plasma discharge sources generate emissions in various wavelengths, that have include the EUV spectral ranges. The capillary discharge sources generally require a discharge occurring as a consequence of inducing electrical current into a gas located in a bore within a cavity. However, problems have occurred with these capillary discharge sources that have included but not limited to debris that also is emitted by the capillary discharge sources. The debris has the result of reducing the operating lifespan of these sources since the debris has been known to damage the surrounding optics such as lens, and other optical components that are used with the capillary discharge sources. In addition the interior walls of the capillary plasma discharge sources constantly wear down during operation which results in a limited lifespan for the sources. Various types of capillary discharge sources have included U.S. Pat. Nos. 6,232,613; 6,031,241 and 5,963,616 to Silfvast et al. by the same assignee as the subject invention, and are all incorporated by reference in the subject invention.
Various solutions have been proposed over the years. Such capillary discharge sources have included those by one of the subject inventors, and by the same assignee as that of the subject invention. For example, U.S. Pat. No. 6,232,613 to Silfvast et al. describes the use of debris blockers and collectors for capillary discharge sources. In the '613 patent, electrodes can be positioned to prevent and block debris generated from the capillary from being expelled into the optic components used with the discharge source. Other electrodes and components were used to collect the debris.
Although the '613 patent reduces the effects of the debris, it still does not reduce nor eliminate the actual generation of the debris from the plasma discharge sources.
Other known types of plasma discharge sources have included the use of wires. It has been shown by a group at Cornell University (David Hammer, Dept of Physics) that a discharge plasma created by evaporating a ‘cross’ of two metal wires between two electrodes, produces a bright, pinched plasma at the point at which the two wires cross. (one ref is “X-ray Source Characterization of Aluminum X-pinch Plasmas Driven by the 0.5 TW LION Accelerator,” N. Qi, D. A. Hammer, D. H. Kalantar, G. D. Rondeau, J. B. Workman, M. C. Richardson and Hong Chen, Proc. 2nd Int. Conf. on High Density Pinches, Los Angeles, pp. 71, (A.I.P.) April 1989, which is nonessential subject matter incorporated by reference), but there are many references to this work. However, exploding wires create other problems. For example, the wires are not reusable and can also generate debris.