A diagnostic for measuring radial profile of visible continuum radiation from ADITYA-U Tokamak Plasmas

Abstract On ADITYA-U tokamak, a spectroscopic diagnostic has been developed to measure the radial profile of visible continuum radiation for determining the plasma effective charge, Zeff, to study the impurity transport and MHD driven instabilities. It consists of the collimating lenses, optical fibers, a multi-channel wavelength selection system, and photo multiplier tubes. The optical system allowing continuum radiation measurements around 536 nm (the wavelength selection system) consists of set of lenses, optical fibers and an interference filter with diameter of 5 cm and bandwidth of 3 nm. The spatial profile of radiation with a spatial resolution of ∼ 3 cm has been recorded from eight lines of sight viewing the plasma using an UHV compatible rectangular view port placed on the bottom port of the ADITYA-U tokamak. The centrally peaked spatial profile of visible continuum radiation has been recorded from the ADITYA-U tokamak plasmas. The chord averaged Zeff values estimated from the brightness measured along the central chord fall within 2.5 to 4.1 for the electron densities of 1.0 - 2.2 × 1019 m−3.