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Our previously-reported observation of a disruptive prepulse on OMEGA, possibly as large as 1% of the extreme ultraviolet (euv) radiation measured from the main pulse, has recently been substantiated by the measurement of euv absorption spectra, prior to the main pulse. The absorption features have been identified with n=2 photoionization in aluminum atoms and ions up to Al5+. Cold aluminum is originally present as a 0.0125-um thick sealant coating applied to a neon-filled (10 atm) CH microballoon, with an euv transmission at the L-absorption edge of {approx}50%. The aluminum in turn is overcoated with 2 um of Mg. The spectra which show the absorption also include continua as well as line emissions from Mg9+ to Mg11+ ions. These occur prior to the onset of laser target irradiation by at least 10 ns, and imply a prepulse irradiance of about 10{sup 12} W/cm{sup 2}. Since the neon and CH are opaque to euv radiation from the rear, a likely scenario is early (prepulse) vaporization of the outer Mg layer, perhaps in hot spots, followed by laser radiation transmitted through the thin Al layer, thereby heating the CH surface. This could provide an euv continuum backlighter for the aluminum that leads to …

The Waste Encapsulation and Storage Facility (WESF) is located in the 200 East Area adjacent to B Plant on the Hanford Site north of Richland, Washington. The current WESF mission is to receive and store the cesium and strontium capsules that were manufactured at WESF in a safe manner and in compliance with all applicable rules and regulations. The scope of WESF operations is currently limited to receipt, inspection, decontamination, storage, and surveillance of capsules in addition to facility maintenance activities. The capsules are expected to be stored at WESF until the year 2017, at which time they will have been transferred for ultimate disposition. The WESF facility was designed and constructed to process, encapsulate, and store the extracted long-lived radionuclides, {sup 90}Sr and {sup 137}Cs, from wastes generated during the chemical processing of defense fuel on the Hanford Site thus ensuring isolation of hazardous radioisotopes from the environment. The construction of WESF started in 1971 and was completed in 1973. Some of the {sup 137}Cs capsules were leased by private irradiators or transferred to other programs. All leased capsules have been returned to WESF. Capsules transferred to other programs will not be returned except for the seven powder and …