Isolated bulk damage centers are produced when KDP crystals are irradiated by 1-ns 1064-nm pulses. We have tested about 100 samples and find the median threshold to be 7 J/cm/sup 2/ when the samples are irradiated only once at each test volume (1-on-1 tests). The median threshold increased to 11 J/cm/sup 2/ when the test volumes were first subjected to subthreshold laser irradiation (n-on-1 tests). We baked several crystals at temperatures from 110 to 165/sup 0/C and remeasured their thresholds. Baking increased thresholds in some crystals, but did not change thresholds of others. The median threshold of baked crystals ranged from 8 to 10 J/cm/sup 2/ depending on the baking temperature. In crystals that had been baked, subthreshold irradiation produced a large change in the bulk damage threshold, and reduced the volume density of damage centers relative to the density observed in unbaked crystals. The data are summarized in the table.

The objective of the proposed research is to evaluate hypersaline brines from geothermal sources and salt domes as possible sources for some strategic metals. This research is suggested because several previous analyses of brine from geothermal wells in the Imperial Valley, California, and from Gulf Coast salt domes, indicate near commercial values for platinum as well as other metals (i.e., gold, silver). Extraction of the platinum should be technically feasible. A research program should include more complete systematic sampling and analysis for resource delineation, followed by bench-scale investigation of several potential extraction processes. This could be followed by engineering feasibility and design studies, for extraction of the metals either as a by-product of other operations or in a stand-alone process.