Vibrating Wire Thermometry in Superfluid 3He

We report systematic measurements of the response of a Vibrating Wire Resonator (VWR) in normal and superfluid liquid ³He. Special attention has been paid to the hydrodynamic regime of the superfluid B-phase, where the response parameters of the VWR do not follow a simple law. We show that a simple interpolation between the region where first order slip-corrections can be applied and the ballistic regime is insufficient. Measuring an empirical effective viscosity, we propose a temperature calibration method which allows the use of VWRs as a secondary thermometer at intermediate and high pressures in the temperature range 0.2 T _c < T < 50 mK.     

Repulsive Flux Pinning Force in NbTi/Nb Superconductor/Superconductor Multilayers

Flux pinning characteristics have been investigated for the Nb _x Ti_100-x /Nb(x = 65, 50 and 28) and Nb ₂₈ Ti ₇₂/Nb ₆₅ Ti ₃₅ superconductor(S)/superconductor(S^′) multilayers. The maximum of the pinning force F _{p⊥ max} perpendicular to the layer plane as a function of the structure modulation length λ has a peak in the quasi-two-dimensional region (λ～20 nm). The maximum. values of the F _{p⊥ max} versus λ curve are proportional to the difference of the GL coherence length (ξ _GL ) between the superconductive sublayers S and S^′. The results suggest that the large F _{p⊥ max} in the S/S^′ multilayer is caused by the repulsive pinning force due to Nb layers with larger ξ _GL .     

The mechanochemical processing of aerospace metals

The status of mechanochemical processing of aerospace metals (aluminum and titanium) is reviewed. It is demonstrated that the activation of chemical reactions by mechanical energy can lead to many interesting applications including production of advanced materials with novel constitutional and microstructural effects leading to enhanced mechanical properties.