Goal and Process

Our goal is to reach temperatures below those obtainable by boiling liquid helium under reduced vapor pressure (~1K).  We will do this using a paramagnetic salt. 

First, the lattice entropy of the salt will be brought to a negligible minimum by the boiling of liquid helium inside a vacuum can.   Using a 15000 Gauss superconducting magnet a field will be applied to uniformly align the dipoles in the direction of the magnetic field.  The salt will then be thermally isolated inside the vacuum can.  As the magnetic field is reduced the temperature will decrease through an isentropic process.  The temperature decreases because of the fact that the energy of the thermally isolated system is determined by the magnitude of the magnetic field.  This lower temperature, T, will then be measured using the relationship between magnetic susceptibility and temperature, found in Curie's Law: X = c/T.  Here X is the magnetic susceptibility and c is the Curie constant per unit volume which depends upon the particular salt used.  The temperature will therefore be measured by determining the magnetic susceptibility.  For an explanation of this see the following page: Temperature Measurement.