High resolution visible spectrometer for divertor study in JT-60U

In JT-60U, a visible spectroscopic system with high wavelength resolution has been developed to observe Doppler broadening of spectral lines emitted from divertor plasmas. An echelle grating is used to obtain the high wavelength resolution and the nominal wavelength resolution is 5.3 pm. Using optical fibre arrays, the Littrow mounting and a charge-coupled device camera, it is possible to observe 10 sight lines simultaneously with a spatial resolution of 1.2 cm.