Nonlinear effects in the vibrating wire resonator

Abstract

The vibrating wire resonator has been extensively used as a viscometer for several years by many groups. Recently two experiments using a vibrating wire have shown typical nonlinear behaviors. In {sup 3}He-B below 0.2 {Tc} Guenault et al. observed a non-Lorentzian line shape for the wire resonance as well as hysteresis effects, namely a sharp rise on the low frequency side, a long tail towards higher frequencies and the resonance curve starting at a lower frequency when performing a downward frequency sweep. Nonlinear behaviors were also observed by Morishita et al. in their work on superfluid {sup 4}He in the long mean free path regime. In vacuum they noticed a resonance frequency shifting towards a lower frequency with increasing drive but no hysteresis. However in superfluid {sup 4}He, they observed similar results together with a clear hysteresis similar to the one observed by Guenault et al. Here preliminary experimental results are presented which exhibit the nonlinear behavior of a vibrating wire in air at room temperature. These results are discussed in the framework of a simple nonlinear phenomenological model.