Frequency and surface dependence of the mechanical loss in fused silica

We have compiled measurements of the mechanical loss in fused silica from samples spanning a wide range of geometries and resonant frequency in order to model the known variation of the loss with frequency and surface-to-volume ratio. This improved understanding of the mechanical loss has contributed significantly to the design of advanced interferometric gravitational wave detectors, which require ultra-low loss materials for their test mass mirrors.Comment: 5 pages, 3 figure but 5 figure file

Low energy p-Be nuclear reactions for depth-profiling Be in alloys. [Segregation induced by Ni-ion bombardment]

Beryllium distributions within the first micron of the surface of nickel- or copper-based alloys were investigated with a 300-keV proton probe utilizing low energy nuclear reactions. Be was segregated in Ni by point defect flows to the surface of the specimen during Ni-ion bombardment of elevated temperatures. The nuclear reactions used are /sup 9/Be(p,d)/sup 8/Be and /sup 9/Be(p,..cap alpha..)/sup 6/Li. The deuteron and alpha groups are simultaneously observable using a standard surface barrier detector. Observations were made at a 150/sup 0/ scattering angle; a 2.5 ..mu.. mylar filter in front of the detector was used for observing the deuteron yields. The alpha group may be observed with or without the filter depending on whether counting statistics or energy resolution are the more important constraints. Significant Be segregation toward the surface was observed in specimens after irradiation at 625/sup 0/C to 23 dpa with 3.2-MeV Ni ions. Concentrations of Be were nearly doubled within 500 A of the surface and a region depleted of Be extended below the surface layer to a depth of about 3000 A. These results are in agreement with predictions