Creation of Impurity Source inside Plasmas with Various Types of Tracer-Encapsulated Solid Pellet

A Tracer-Encapsulated Solid Pellet (TESPEL) was developed for promoting an impurity transport study in a magnetically-confined plasma. One of the advantages of the TESPEL is that it can make a three-dimensionally localized impurity source in the plasma. This enables us to inject the tracer impurity inside or in the vicinity of the region of interest. Recently, a new-type TESPEL with a thinner outer shell has been developed in order to achieve a shallower deposition of the tracer impurity. With the TESPEL having the thinner shell, we have achieved about 4 cm shallower deposition of the tracer impurity, compared with the case of the conventional thick-shell type TESPEL with the same outer diameter of about 700 µm. Moreover, for the achievement of the further shallower deposition of the tracer impurity, we also developed the TESPEL with a tracer-impurity-doped thin shell. After the injection of the TESPEL with the tracer-impurity-doped thin shell, the line emissions from the highly-ionized doped impurity are clearly observed with a vacuum ultraviolet spectrometer, which clearly demonstrates its ability to carry the impurity as a new tool.