HE-3 MELTING PRESSURE THERMOMETRY

High-precision measurements of the He-3 melting pressure versus temper ature have been made from 500 mu K to 25 mK using a Co-60 nuclear orie ntation primary thermometer and a Pt NMR susceptibility secondary ther mometer. Temperatures for the fixed points on the melting curve are: t he superfluid A transition T-A = 2.505 mK the A-B transition T-AB = 1. 948 mK, and the solid ordering temperature T-N = 0.934 mK. These fixed points and a functional form for P(T) constitute a convenient tempera ture scale, based on a primary thermometer, usable to well below 1 mK.