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 jield. The magnetic jield 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 lO-'K near the liquid-gas critical point of H e (3.31 K). The drlft rate of the thermometer was measured to be < 2 X 10-13K/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.