Integration of Optical Sensors for Quench Detection in HTS Stacks and Cables for Fusion Applications

The high environmental electromagnetic noise characteristic of fusion reactors and low quench propagation velocity of HTS conductors designed for such applications drive the quest for quench detection solutions alternative to voltage methods. Techniques based on optical fiber sensors represent a promising solution, but their integration in cables is not straightforward due to their intrinsic fragility. In this work, we report on the production and testing of an HTS aluminum slotted core cable exploiting a BRAided STack (BRAST) of REBCO tapes. The braid also encloses two stainless steel capillaries containing fiber-optic sensors responsible for monitoring the stack temperature. The sample was subjected to quench experiments at liquid nitrogen temperature, evaluating its electrical and thermal response. The experimental results demonstrate that the integration of optical sensors within the BRAST enables monitoring of stack temperature and detection of quench events, highlighting the greater sensitivity achieved by detecting temperature changes directly on the superconducting stack compared with sensors placed on the outer jacket. This approach represents thus a simple and effective solution for the integration of optical sensors in fusion cables.