A method using a tracer-encapsulated solid pellet (TESPEL) has been developed to diagnose particle transport. TESPEL consists of polystyrene as the outer part and another material as the inner core. At first, it was confirmed at the compact helical system (CHS) that the tracer of lithium was deposited locally in the plasma. Moreover, the behaviour of the tracer particles was observed by charge exchange recombination spectroscopy. TESPEL was also injected into the large helical device (LHD). In this case, the Kα line of titanium was observed without the necessity of a neutral beam, and it was shown that this method is promising.
Impurity transport studies by means of tracer-encapsulated solid pellet injection in neutral beam heated plasmas on LHD