The boundary resistance between superfluid 4He near Tλ and a solid surface

We report high-resolution measurements of the singular contribution R-b to the thermal boundary resistance between a solid surface and superfluid helium near the superfluid-transition temperature T-lambda. The results confirm the observation by Murphy and Meyer that a gap between the cell end and the sidewall leads to an apparent finite-current contribution to R-b. In the absence of such a gap, overall agreement of R-b with theoretical predictions is very good. Remaining small differences require further investigations. Without a sidewall gap and within our resolution we found no finite-current effects over the range 3.9 mu W/cm(2)<Q <221 mu W/cm(2). (C) 1998 American Institute of Physics.