A Tracer-Encapsulated Solid PELlet (TESPEL) injection is one of the simplest and new idea to study the confinement of impurity and the other plasma properties [1]. A TESPEL ball consists of polystyrene polymer as an outer shell, the diameter of which ranges from 300 to 900 μm, and tracer particles as an inner core. The special features of this method are: (a) local deposition inside the plasma, (b) the deposited amount of the tracer in the plasma can be known precisely, (c) relatively wide selection of tracer material is possible. The achievements of this multi-functional diagnostic method with TESPEL injection on LHD are: (a) impurity transport properties such as diffusion coefficient D and inward pinch velocity V are obtained with the temporal evolution of Ti Kα (He-like; E = 4.7 keV) and Ti XIX (λ =16.959 nm) measured by a soft x-ray pulse height analyzer and a vacuum ultraviolet spectrometer, respectively, (b) from the cold pulse propagation due to TESPEL injection, heat diffusivity was obtained, and the remarkable difference of the diffusivity in the magnetic island and outside of that was observed, (c) TESPEL injection suggested that particle flow feature was found to be different in and outside of the magnetic island, (d) TESPEL gives the reference for the absolute intensity of spectroscopic light, (e) through pellet charge exchange process, high energy particles have been observed, (f) the cloud density of TESPEL is estimated from the observed Stark broadening of the ablation light spectrum in the region of H_β. The advanced application of TESPEL to particle transport study is to observe light emission due to charge exchange recombination of a tracer with a heating neutral beam. For the first experiments, a clear Mg contribution (H-like n = 2-3, λ = 4.5 nm) after the TESPEL injection has been observed. This experimental result suggests that the TESPEL technique would be a powerful tool for local transport measurement on LHD.

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