(3)He specific-heat and thermometry at Millikelvin Temperatures.
01 January 1987
High-precision specific-heat measurements were made on pure liquid (3)He in both the normal and superfluid phases for temperatures between 0.6 and 5mK and for pressures between 0 and 34bar. The data were obtained using a magnetic susceptibility thermometer which was calibrated against the NBS scale near 15 mK and at lower temperatures principally by the condition that the zero- pressure normal-phase specific heat be linear in temperature. The (3)He phase diagram based on this scale is presented. In particular we find that T(A)=2.49 mK which differs quite substantially from the currently accepted value of about 2. 7mK. Multiplying the Helsinki Pt NMR temperatures by a factor of 0.89 or subtracting 0.13mK from the La Jolla magnetic temperatures brings both of these scales into excellent agreement with the new scale.