Infrared laser polarimetry for electron density measurement in tokamak plasmas

The infrared CO2 laser polarimetry for electron density measurement based o n the tangential Faraday rotation has been progressed in JT-60U tokamak. Th e reliability of polarimetry in a pellet-injected plasma was confirmed. The Faraday rotation was measured with good angle resolution of similar to0.01 degrees under the sufficiently fast temporal resolution of 4 ms. Electron density evaluated from the tangential Faraday rotation measured by polarime try shows good agreement with that measured by interferometry for an identi cal probing laser beam. The long-time continuous measurement was successful with good stability and accuracy. The basic feasibility of the infrared CO 2 laser polarimetry for electron density measurement in long-time and stead y-state operation in large fusion devices was demonstrated. (C) 2001 Americ an Institute of Physics.