Analysis of diffusive coefficient of electron heat pulse based on singular value decomposition in HT-7 tokamak

In this paper, singular value decomposition (SVD) as a filter-noise method is applied to electron cyclotron emission (ECE) diagnostic signals. The decomposed vectors contain the information about sawtooth such as the temporal vectors that show the sawtooth period and the spatial vectors that indicate the inverse radius. The propagation of electron heat pulse is investigated from electron cyclotron emission signals by using the perturbation method in HT-7 tokamak. The heat diffusivities are obtained at different densities in ohmic plasmas. The special result is that the heat diffusivity becomes larger as the heat pulse propagates outwards from the outside of the inverse radius.