Heat capacity measurements of He-4 at constant heat flux near T-lambda

The heat capacity, C-Q, of superfluid He-4 in the presence of a constant he at flux, Q, is expected to diverge at a depressed transition temperature, T -c(Q). We have taken preliminary measurements of C-Q at various heat flux v alues in the range 1 mu W/cm(2) less than or equal to Q less than or equal to 4 mu W/Cm-2. We observe that at sufficiently small reduced temperatures, C-Q is enhanced as a function of Q, and that the enhancement is larger tha n theoretical predictions by Chui et al. and Hausmann and Dohm (Phys. Rev. Lett 77 (1996) 980, 1793; preprint). (C) 2000 Elsevier Science B.V. All rig hts reserved.