A new small nano-Kelvin resolution thermometer for low temperature experiments

A small, high resolution paramagnetic susceptibility thermometer was developed using a GdCl₃ paramagnetic salt. The device uses a SQUID (Superconducting Quantum Interference Device) magnetometer to determine the temperature dependent magnetization of the salt in a magnetic field. The magnetic field is provided by a pair of small samarium cobalt permanent magnet disks situated inside the thermometer housing. This eliminates the need for a heavy, charging solenoid used in a conventional SQUID based magnetic thermometer system. This thermometer can resolve approximately 10^-9 K near the fluid-gas critical point of ³He (~3.31 K). The drift rate of the thermometer was measured to be <2×10^-13 K/s. This light weight thermometer (~7 g) is a candidate for use in future low temperature Space Shuttle and International Space Station experiments. The present thermometer design easily permits a variety of magnetic materials for use in other applications