Observation of a Forbidden Line of Fe xx and Its Application for Ion Temperature Measurements in the Princeton Large Torus Tokamak

A spectrum line in the Princeton Large Torus (PLT) tokamak discharges, with wave-length measured as 2665. 1 0. 3, has been identified as the 2s^22p^3^2D₅₂^2D₃₂ magnetic dipole transition in Fe xx ground configuration. A variety of localized spectroscopic diagnostics, e. g. , ion temperature and density distribution measurements in the high-temperature interior of the plasma, are feasible by means of forbidden lines of this type. The 2665- line has been used to measure near-central ion temperature in a discharge with auxiliary neutral-beam heating.