A high density (>10¹²cm^-3) multi-dipole confinement hot cathode discharge and its characteristics of plasma parameters formation

A high density multi-dipole confined hot cathode discharge has been developed using a large area DC heated LaB₆ hot cathode. This device facilitates the investigation of a gradual transition of an unmagnetized discharge from a partial ionized discharge to a fully ionized discharge. Evolution of electron temperature, electron density, and optical emission characteristics with the discharge transition is measured and compared to the evolution of these parameters in abruptly transited helicon discharges. Due to the lack of coupling between the discharge characteristics (i.e. plasma conductivity) and the RF-power coupling mechanisms, this discharge is expected to provide a unique opportunity to investigate previous claims of known phenomena in helicon plasmas and other fully ionized discharges. These phenomena include neutral depletion, transition of optical emission characteristics, and temperature evolution. Preliminary of these investigations will be presented in this oral report. Issues in plasma diagnostics in these unmagnetized, high density discharges are also presented.