  Vibrating probes when immersed in a fluid can provide powerful tools for
characterising the surrounding medium. In superfluid 3He-B, a condensate of
Cooper pairs, the dissipation arising from the scattering of quasiparticle
excitations from a mechanical oscillator provides the basis of extremely
sensitive thermometry and bolometry at sub-millikelvin temperatures. The unique
properties of the Andreev reflection process in this condensate also assist by
providing a significantly enhanced dissipation. While existing models for such
damping on an oscillating cylinder have been verified experimentally, they are
valid only for flows with scales much greater than the coherence length of 3He,
which is of the order of a hundred nanometres. With our increasing proficiency
in fabricating nanosized oscillators which can be readily used in this
superfluid there is a pressing need for the development of new models that
account for the modification of the flow around these smaller oscillators. Here
we report preliminary results on measurements of the damping in superfluid
3He-B of a range of cylindrical nano-sized oscillators with radii comparable to
the coherence length, and outline a model for calculating the associated drag.
