2ND SOUND MEASUREMENTS NEAR THE TRICRITICAL POINT IN HE-3-HE-4 MIXTURES

In this paper we discuss a pulsed second sound experiment, aimed at de termining accurately the critical exponent zeta, and the predicted log arithmic correction to scaling, for the superfluid density along a tri critical path in the He-3-He-4 phase diagram. We present an accurate e stimate for the limits for closest approach to the tricritical point, as set by gravitationally induced sample inhomogeneities and finite si ze effects, and discuss some of the complications associated with meas urements close to the tricritical point.