Role of Helicon Waves on High-Density Plasma Production

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 them= -1 mode helicon wave propagates whereas them=+1 mode helicon wave is cut off. The produced helium plasma density in the case of them= -1 mode rf application is 1 ×1013cm-3, which is more than 5 times greater than in the case of them= +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 them= +1 mode rf is sustained by the antenna near field, while for them= -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 1012cm-3to 1013cm-3by efficient power deposition to electrons.