Fiber Optic Temperature Sensors for Long Cryogenic Thermal Paths

This SBIR Phase I proposal addresses damage prevention in high temperature superconducting power transmission lines, motors, generators and other specialized equipment that are now being deployed. Even though high temperature superconductors can operate up to 77K or higher, most equipment is operated at lower temperatures to obtain a safety factor to prevent overheating or magnetic field-induced quenching. Superconductor lengths from tens of meters to many km may be involved. If hot spots develop, causing the conductors to rapidly revert to their resistive states, the local heating increases and propagates the fault. This causes a rapid dissipation of the stored energy in the conductor or coil, with a significant probability of damaging the conductor if the quench is not detected in time. Fiber optic temperature sensors present the opportunity to detect hot spots at closely spaced points along a superconductor of arbitrary length in order to safely shut down the system before damage occurs. These sensors are all-dielectric, making them safe in even a very high voltage power system, and many sensing points, as close as a few cm to a meter, can be multiplexed on a single fiber, greatly simplifying the feedthrough requirements compared to electronic sensors.