Measurements of superfluid densities and critical superfluid mass currents of pure 4He and 3He/4He mixtures in nuclepore near the lambda transition

Abstract

Measurements have been made of the relative superfluid density psp/ p and the critical mass currentIsc for the onset of dissipation in the superfluid flow of pure 4He and 3He/4He mixtures in the circular cylindrical pores of Nuclepore near the h transition, using a double-ended Helmholtz resonator. Pore diameters of O. 03, O. 1, and 0.4 tzm were studied using 3He mole fractions of O. O, ~ 0.2, and 0.4. For each pore diameter dp and mole fraction x our results for psp/ p were • 0 675 fitted relattvely well by the form C(t-to1) " and those for Isc by the form I~co(t-to~) g, where t=-[Tx -T]/Tx. For each combination of dp and x the reduced onset temperatures to1 and toc are in rough agreement with each other but somewhat larger than values found by others for Nuclepore. For the smaller two pore diameters, these onset temperatures are consistent with the unithat near Tx, h p~b~/m4kBT should be a constant versality hypothesis 2 e independent of T and x. Here h is the reduced Planck constant, P~b is the bulk superfluid density, ~ is the coherence length, m4 is the 4He atom mass, kB is Boltzmann ' s constant, and T is the absolute temperature. At each value of x the amplitudes C agree well with the corresponding amplitude for Psb/P, and g equals 1.17 + 0.04 for all cases. Measurements of the velocity of second sound at x = 0. 000, 0.190, 0.401, and 0.450 are also reported.

Superfluid Fraction ofH3e−H4Kimball1, Gasparini2 2001Phys. Rev. Lett.17050View full textAdd to dashboardCite

“…This is done far from the transition where the data match the behavior of unconfined helium. We have used the data from [21]. We show the result of this in Fig.…”

“…j 0 ͑0͒. For the concentrations we have studied, x 0, 0.15, 0.24, 0.36 we have j 0 ͑x͒ 3.57, 4.53, 5.31, 6.72 [21]. The data plotted according to Eq.…”

“…Measurements of the superfluid fraction for cylindrical confinement have been done; however, these data have not yielded an overall scaling [21]. To achieve confinement, we have used a technique whereby two wafers of silicon are bonded at a separation determined by a lithographically formed pattern of SiO 2 [22,23].…”