Abstract
Plasma production by rf fields in the helicon wave frequency range is investigated by using the rotating field antenna which can select the azimuthal mode number of the applied rf. The calculated dispersion relation shows that the m = -1 mode helicon wave propagates whereas the m =+1 mode helicon wave is cut off. The produced helium plasma density in the case of the m = -1 mode rf application is 1 ×1013 cm-3, which is more than 5 times greater than in the case of the m = +1 mode rf application. The two-dimensional numerical simulation of the rf plasma production also qualitatively gives the same result as in the experiment. The plasma for the m = +1 mode rf is sustained by the antenna near field, while for the m = -1 mode rf, it is sustained by the power absorption from the propagating helicon wave. From both the experiment and the simulation, the helicon wave is revealed to increase the plasma density from the order of 1012 cm-3 to 1013 cm-3 by efficient power deposition to electrons.