The Experimental Research on Uniformity of Argon Inductively Coupled Plasma at Different Cylinder Heights

Abstract

We report on the characteristics of argon inductively coupled plasma (ICP) for the ITER neutral beam injection system. In argon ICP, it was found by using Langmuir probe that the radial distribution of electronic density (Ne) was uniform while the radial distributions of both electron temperature (kTe ) and electric potential (VP) were non-uniform. The former depend on two factors: the variation of Ne was small, and the value of Ne was very large. The latter is owing to the generation and disappearance of the negative ions in the ICP, where the additional dynamic processes produce the instability. In addition, both kTe and VP profiles were very similar at the cylinder height H=14 cm, which proves the plasma sheath theory to some extent. Finally, both kTe and VP began flatter with the reduction of the cylinder height, which is owing to the decrease of the negative ions in the ICP.