Experimental study on temperature distribution measurement of an optical fiber encapsulated coil in liquid nitrogen

Fast quench detection technique is extremely important for high temperature superconducting (HTS) applications, especially HTS magnets. As one of potential candidates, the method based on distributed optical fiber sensors were suggested recently. To keep HTS tape structure intact and reduce thermal propagation time from HTS tape to optical fiber, a method that optical fiber is encapsulated in HTS tape edge along the length direction could be satisfied. In this paper, an optical fiber encapsulated tape (OF-tape) was successfully fabricated. To verify the feasibility of temperature measurement for this tape, a coil wound with OF-tape and a distributed temperature sensor (DTS) system were prepared. The main results show that temperature of the coil can be measured accurately in air and in liquid nitrogen. After suffering impulse currents with peak values of 570 A and durations of 1, 2, and 3 s, temperature rises of the coil are 98.5, 137.8, and 271.0 K, respectively. Moreover, the highest temperature appears from 3.6 m to 21.7 m of the coil when it suffers the impulse current of 460 A/3 s.