Fourth sound, size effects, and healing length in superfluid He3

Fourth sound was used to measure the depressions of the superfluid component density and the transition temperature of superfluid He3 confined in resonators filled with packed powders. The observed magnitude of the size effects in He3 is much greater than that in He4 [M. Kriss and I. Rudnick, J. Low Temp. Phys. 3, 339 (1970)]. The depression in transition temperature was measured as a function of pressure (12–30 bar) and pore size (0.1–5 μm) and it is found to be consistent with theoretical estimates of healing length. The Q of a fourth sound resonance was also measured as a function of temperature over a limited range. The maximum Q observed was 40. The magnitude of Q appears to be too small to be accounted for by the normal component motion alone. [Work supported by NSF.]