Abstract
The method of tracer-encapsulated solid pellet (TESPEL) is now flourishing in various fields. The original purpose to study impurity transport without giving substantial perturbation on the plasma is implemented successfully for years. In addition to this, TESPEL is being intensively applied to study thermal (especially non-local) transport, high energy particles with the use of TESPEL ablation cloud, and spectroscopy from the viewpoint of atomic data. It is now further growing up to the utilization of multiple tracer methods which was not planned at the initial phase of the project. The proof-of-principle experiment using triple tracers has been successfully implemented. This opens a way to compare the Z dependence or mass dependence of impurity transport. In this article, as TESPEL is used in a variety of fields, the TESPEL injection system is summarized together with the method of TESPEL production, TESPEL storage disk, TESPEL guide system, and the differential pumping system. Also, the observation system for TESPEL flight and TESPEL ablation is explained.
Highlights
Various researches on pellet fuelling and diagnostic applications of hydrogen and impurity pellet injection in tokamaks and helical systems have been done as described in some reviews.[1,2,3,4] In order to diagnose particle transport more accurately than the case with a simple impurity pellet injection, we have developed a method using a tracer-encapsulated solid pellet (TESPEL).[5,6,7,8,9] TESPEL consists of polystyrene (polymer: –CH(C6 H5 )CH2 –) as an outer part, and some tracers which are not intrinsic components in the plasma as the core part of TESPEL
The outer shell of TESPEL consists of polystyrene as stated above
TESPELs can be stored in the holes of the TESPEL storage disk made of stainless steel, while one empty hole is used for checking the precise matching of the hole position of the storage disk with the hole of the housing flange from outside
Summary
Various researches on pellet fuelling and diagnostic applications of hydrogen and impurity pellet injection in tokamaks and helical systems have been done as described in some reviews.[1,2,3,4] In order to diagnose particle transport more accurately than the case with a simple impurity pellet injection, we have developed a method using a tracer-encapsulated solid pellet (TESPEL).[5,6,7,8,9] TESPEL consists of polystyrene (polymer: –CH(C6 H5 )CH2 –) as an outer part, and some tracers which are not intrinsic components in the plasma as the core part of TESPEL. The radial localization of the tracers on a certain annular magnetic surface can be realized, which gives advantage for impurity transport study After injection of such a TESPEL into a plasma, the locally deposited “tracer”. Particles (originating from the core of TESPEL) will be immediately ionized and heated by the bulk electrons and ions These tracer particles move along magnetic field lines at first, and they fill the magnetic surface and diffuse radially outward (or inward by pinch effect in some cases). 0034-6748/2012/83(2)/023503/6/$30.00 new significant information about transport characteristics will be obtained With this method, the amount of the deposited particles in the plasma can be precisely identified because of the known amount of the tracer particles put in the core of TESPEL. The whole TESPEL injection system is described together with the method of TESPEL production, TESPEL storage disk, TESPEL guide system, and the differential pumping system
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