Electron density profile measurements on LHD

Several kinds of density diagnostics have been developed and routinely operated to provide density profile information on the large helical device. A 13-channel far-infrared laser interferometer and a two-color millimeter-wave interferometer are used for monitoring the density profile. A C[O.sub.2] laser imaging interferometer has been developed for detailed profiled measurements of density and density fluctuations. A C[O.sub.2] laser densitometer measuring the Faraday rotation was developed for the long-pulse operations of large helical device. Details of each diagnostics and sample results are presented. Index Terms--Helical plasma, interferometer, plasma, plasma diagnostics, polarimeter.