Plasma-Induced Arc and Its Plasma Response in a Toroidal Device

Abstract

A plasma-induced bi-polar arc and its plasma response were studied in a tokamak configuration, and a drastic change in the plasma potential near the arcing metal rod was found. Cylindrically concentric equi-potential surfaces are formed around the cathode spot, and a small change in the plasma potential observed at the plasma-wall interface breaks an ambipolarity there, forming a current channel across the toroidal plasma between the cathode spot and the vacuum chamber.

Characterization of gaseous carbon plasma in a low-temperature tokamak discharge

“…On the other hand it is found that the profile of V s becomes hollow, and a strong radial electric field E r (estimated to be 1.6 × 10 3 V m −1 ) is produced. E r can be generated by the arc current between the carbon rod and the vacuum chamber, because it is difficult for electrons and ions to traverse the strong magnetic field [7]. Figure 4(c) shows that T e at the plasma periphery is larger than that at the centre when the arc current flows, because Joule heating occurs more effectively at the periphery where E r is stronger that at the centre, as shown in figure 4(b).…”

“…Figure 1(b) shows the method of generating the gaseous carbon plasma. A plasma-assisted arc was ignited by applying a negative high voltage to the carbon rod inserted in the tokamak plasma with respect to the vacuum chamber [7,8]. A movable Langmuir probe is employed to measure the radial profiles of the plasma parameters.…”

“…We have proposed the generation of a gaseous plasma not from the volatile gas, but from the solid material by a plasma-assisted arc [5,6]. We apply this method to generating a high-density carbon plasma with a large volume in a low-temperature tokamak discharge [7,8]. For instance, one could consider applying this strongly ionized tokamak discharge to plasma processing, especially to the synthesis of thin films.…”