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 CO{sub}2 laser imaging interferometer has been developed for detailed profiled measurements of density and density fluctuations. A CO{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.
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