Ja. Lipa et al., PRELIMINARY-RESULTS FROM A SHUTTLE MISSION TO MEASURE THE HEAT-CAPACITY OF CONFINED HELIUM NEAR THE LAMBDA-POINT, Journal of low temperature physics, 113(5-6), 1998, pp. 849-860
We describe the preliminary results from a Shuttle mission to measure
the heat capacity of helium confined within a stack of evenly spaced s
ilicon plates at temperatures very close to the superfluid transition.
Recently developed high resolution thermometry has substantially impr
oved our ability to study dimensional cross-over effects in well-defin
ed geometries. These effects have been of interest to theorists and ex
perimentalists for decades. The main part of the apparatus consists of
a high purity copper calorimeter containing a stack of 408 silicon pl
ates spaced 57 microns apart, and a pair of high resolution, fast resp
onse, paramagnetic salt thermometers with a noise level of < 10(-10) K
in a 1 Hz bandwidth. The resolution of the heat capacity measurements
was about 5 x 10(-9) K, allowing the finite size peak to be mapped in
detail. In addition, wide range data containing information on the be
havior of the surface specific heat was collected. The preliminary ana
lysis shows fair agreement with theory. The results can also be combin
ed with supplementary ground measurements on smaller length scales to
perform additional tests of scaling predictions for cross-over to lowe
r dimensional behavior.