The external electrical characteristics of Helicon plasma were measured over a wide range of RF power and magnetic field. External parameters, such as antenna voltage, current, phase shift, and internal parameter, electron density were measured. The equivalent discharge resistance and reactance, and the power transfer efficiency were calculated through these measurements. There are a helicon mode which produces high density plasma by helicon wave and a low-mode which produces low density plasma by capacitive electric field. In case of the helicon mode, voltage and current were lower than those of the low-mode. The phase difference between voltage and current decreases suddenly at the transition point from the low-mode to the helicon mode. Equivalent resistance and power efficiency increase and reactance decreases suddenly at the transition point.
