Size effects in superfluid He3

The superfluid density and the transition temperature of He3 filling the pores of packed powders of 3 different sizes, nominally 1.0, 0.3, and 0.05 m, have been measured using fourth sound. Progressively larger depressions are observed for both the superfluid density and the transition temperature as the powder size is decreased. The depression in the transition temperature has been measured as a function of pressure and is found to be consistent with theoretical estimates of the superfluid coherence length. © 1980 The American Physical Society.