FARADAY PLASMA CURRENT SENSOR WITH COMPENSATION FOR RECIPROCAL BIREFRINGENCE INDUCED BY MECHANICALPERTURBATIONS

A Faraday fiber-optic current sensor was employed to measure the tokamak plasma current. In order to decrease the influence of mechanical perturbations on the sensor sensitivity, a two-pass optical scheme with a variable Faraday mirror at the fiber end is proposed. A decrease, by two orders of magnitude, in the influence of the linear birefringence produced by an external piezoceramic fiber modulator was experimentally observed. RESUMEN Se utilizó un sensor de corriente hecho de fibra óptica empleando el efecto Faraday, para medir la corriente en el plasma de un tokamak. Para reducir la influencia de ruido mecánico en la sensitividad del sensor, se propone un arreglo óptico de dos pasos con un espejo variable de Faraday colocado en un extremo de la fibra. Experimentalmente se observo una disminución, de dos ordenes de magnitud, en la influencia de la birefringencia lineal producida externamente por un modulador piezocerámico de fibra