New Results for the Realization of the Superfluid Transition Temperature of Helium

A two-chamber sealed cell has been developed to realize the superfluid transition temperature of helium. A series of temperature plateaus are obtained while a series of small heat flows are applied to the capillary connecting the two chambers. The plateau temperatures are extrapolated to determine the transition temperature at zero heat flow. This paper reports the new results for the realization of the transition temperature of helium using seven cells. More than 30 measurements have been made in two laboratories since 2002, as five cells sealed in 2000 and two cells sealed in 2009 are used. The standard deviation of the measurements is ~0.02 mK.