AN OPTICAL FIBER CURRENT SENSOR FOR PLASMA DIAGNOSTICS

THIS PROJECT ADDRESSES THE NEED FOR MAGNETIC FIELD AND CURRENT MEASUREMENT DEVICES FOR FUSION PLASMA DIAGNOSTICS, ESPECIALLY IN THE COMPACT IGNITION TOKAMAK (CIT). FIBER OPTIC MAGNETIC FIELD SENSOR DEVELOPMENT IS PLANNED TO TAKE ADVANTAGE OF THE HIGH SENSITIVITY, HIGH TEMPERATURE, RADIATION RESISTANCE, AND DIELECTRIC PROPERTIES OF THE OPTICAL FIBER. THE HIGH SENSITIVITY AND LARGE DYNAMIC RANGEWILL BE ACHIEVED BY TWISTING LOW BIREFRINGENCE SINGLE MODE FIBER ENHANCED WITH A HIGH VERDET CONSTANT CORE MATERIAL. THE TWIST-INDUCED CIRCULAR BIREFRINGENCE QUENCHES THE ENVIRONMENTAL FLUCTUATIONS AND INCREASES DEVICE SENSITIVITY. TO MONITOR THE SPATIAL FIELD DISTRIBUTION, A POINT SENSOR WILL BE DEVELOPED EMPLOYING HIGH VERDET CONSTANT CRYSTALS. THE TEMPERATURE STABILITY OF THE OPTICALFIBER AND CRYSTAL WILL BE STUDIED AND OPTIMIZED. THE FEASIBILITY OF DISTRIBUTED POINT SENSING AROUND THE VACUUM VESSEL WILL BE ADDRESSED. OPTICAL FIBER SENSORS HAVE MANY DISTINCT ADVANTAGES OVER CONVENTIONAL TECHNIQUES; AMONG THEMARE SMALL SIZE AND DEPLOYMENT VERSATILITY, HIGH SENSITIVITY AND ACCURACY, RESISTANCE TO HIGH TEMPERATURE AND RADIATION ENVIRONMENT, AND INHERENT SAFETY AND IMMUNITY TO ELECTROMAGNETIC AND RADIO FREQUENCY INTERFERENCE. THESE SENSORS SHOULD PERFORM WELL IN HIGH RADIATION FIELDS, HIGH MAGNETIC FIELDS AND HIGH TEMPERATURE PLASMA ENVIRONMENTS. THE TECHNIQUE MEASURES CURRENT DIRECTLY, WHICH SIMPLIFIES DATA REDUCTION.