Heat capacity experiment for very high resolution tests of the theory of confined materials

Abstract

We report the current status of an experiment to measure the heat capacity of helium confined within a stack of evenly spaced silicon plates at temperatures very close to the superfluid transition. Newly developed high-resolution thermometry has substantially improved our ability to look into regions where three-dimensional crosses over to two-dimensional behaviour and where two-dimensional behaviour dominates. These regions have been of interest to theorists and experimentalists for decades. The main part of the apparatus consists of a high-purity copper calorimeter containing a stack of 408 silicon plates spaced 57 μm apart and a pair of high-resolution, fast response, paramagnetic salt thermometers. The thermometers have been shown to have a noise level of 10-10 K with 1 Hz bandwidth. The expected resolution of the heat capacity measurements is 10-9 K. To avoid the smearing effects of gravity in the 4.5-cm high helium sample, the measurements will be performed on the Space Shuttle. The results from the experiment can be combined with supplementary ground measurements on smaller length scales to perform additional tests of the renormalization group predictions for crossover to lower-dimensional behaviour. © 1996 Elsevier Science Limited.