High density central cell plasma production and ion heating by helicon wave damping and its mode conversion into a slow Alfven wave

A new scheme of plasma production and ion heating in the central cell of the tandem mirror is demonstrated. Helicon mode plasma production in combination with two ion species plasma heating by mode conversion of a fast Alfven wave into a slow Alfven wave realizes ion heating of a high density plasma, and could remove the density limitation caused by the conventional scheme using slow ion cyclotron waves. The achieved value of products of electron density and average ion temperature is 9 x 1020 eV · m-3 for an RF power of 165 kW. Analysis of wave damping indicates that matching the radiation spectrum of the antenna with the damping spectrum results in efficient plasma production. The phased dual double-half-turn antenna is suitable for helicon wave spectrum control. (author). 20 refs, 14 figs