Plasma Diagnostics with Tracer-Encapsulated Solid Pellet

Abstract

The diagnostics method of a tracer-encapsulated solid pellet (TESPEL) has been developed. TESPEL consists of polystyrene as an outer shell and of specific material as a tracer in the core. Owing to the advantages of the TESPEL, the following results have been successfully obtained: (1) distinctive different feature of impurity transport between the plateau and Pfirsch-Schlüter regimes depending on the impurity source location which is analyzed with the STRAHL code, (2) specific feature of a non-local thermal transport such as abrupt increase of electron temperature in the plasma core in case of plasma cooling in the plasma periphery due to a small TESPEL injection, (3) spatially resolved energy distribution of the high energy particles obtained by a pellet charge exchange method, (4) longer impurity containment inside the magnetic island which is observed by depositing the tracers in the magnetic island by means of the TESPEL, and (5) identification of new spectral lines using interested atoms contained in the core of the TESPEL.

Development of TESPEL Configurations for Plasma Diagnostics

“…Shigeru SUDO 1,2) , Naoki TAMURA 1) , Chihiro SUZUKI 1) , Hisamichi FUNABA 1,2) , Masaru TAKAGI 3) and Nakahiro SATOH A Tracer-encapsulated Solid Pellet (TESPEL) injection method has been shown to be useful for many fields of plasma diagnostics. In order to provide more flexibility for such plasma diagnostics, we are developing various types of TESPELs.…”

“…Recently we reported two types of TESPEL configurations [1], namely, (i) thick-shell-type and (ii) thin-shelltype [2] for the accurate impurity transport diagnostics. In particular, it was shown that the impurity transport feature depends on the source location of the impurity and also on the collisionality (between impurities and bulk ions).…”

“…In Ref. [1], to enhance the difference of the tracer deposition, the outer diameter of the TESPEL is set as approximately 0.73 mm in case (i) and approximately 0.6 mm in case (ii). In this paper, we will report the new configuration of the TESPEL.…”

“…Based on the recent result [1], the shallower location of the tracer deposition compared to case (ii) is planned for investigating the impurity transport property more precisely. Therefore, we made (iii) a thin shell-type TESPEL whose shell is made of Poly-2,6-dichlorostyrene: (C 8 H 6 Cl 2 ) n .…”

“…This type of TESPEL is not only useful for impurity transport study but also for the neutron observation due to the transient increase of the deuterium in the local position in the plasma for the upcoming LHD D-D experiment. A Tracer-encapsulated Solid Pellet (TESPEL) injection method has contributed so far to the various fields of plasma diagnostics as reported [1]. However, we noticed that more detailed control of the tracer deposition location is necessary in particular for promoting the impurity transport study.…”