Advanced Fiber Optic Sensor for Superconducting Magnets

High temperature superconductors are becoming increasingly more viable candidates for plasma fusion, high-energy accelerators, and industrial/medical applications. Due to defects within the high temperature superconducting materials during the manufacturing and assembly process, quenching is still an important problem. Quench detection needs to be fast and, ideally, should identify the location of the quenching site. Currently, there are no means for identifying the location of the quenching site inside the magnet. Optical fibers have been used inside superconducting magnets, but thus far only to measure temperature and strain. HOW PROBLEM IS BEING ADDRESSED: We have demonstrated a new technique of using optical fibers to measure the magnet field characteristics within a room-temperature magnet. We will apply this same technique to measure the magnetic field characteristics inside a superconducting magnet with the aim of using these measurements to detect the onset of quenching and to identify the location of the quenching site. During Phase I we will 1) perform a proof-of-principle experiment to demonstrate the ability of our fiber diagnostic to measure the magnetic field characteristics of a superconducting wire during normal and quenching operation and 2) develop the design for a prototype fiber diagnostic that will be tested on a high temperature superconducting magnet during Phase II. COMMERCIAL APPLICATIONS AND OTHER BENEFITS: Superconducting magnets are major components for plasma fusion devices and high energy accelerators where there is a keen interest to be able to use high temperature superconductors because of the much lower cost to cool them. Superconductors are also used extensively in nuclear magnetic resonance and magnetic resonance imaging medical diagnostic machines. Superconducting power cables, superconducting generators, magnetic levitation, and railguns are other technologies that rely on superconductors. Our fiber diagnostic will help all these technologies by facilitating the assembly, shakedown and operation of these devices. KEY WORDS: Superconductors, high temperature superconductors, magnetic field diagnostic, quench detection.