Investigation of helicon-wave discharge in a low magnetic field using molecular and rare gases

The helicon-wave discharge is performed in a low magnetic field B-0 < 100 G using phased multiple helical antennas, where the phase difference among radio-frequency (RF) currents applied to each antenna is externally controlled. When an argon plasma is produced by the helical antennas, the electron density has a maximum value at B-0 similar to 30 G, which is an order of magnitude larger than that at 0 G. The helicon wave with the azimuthal mode number of m = + 1 is excited at B-0 yielding the density peak. In the molecular gas, such as nitrogen and oxygen, the density peaks are also observed at B-0 similar to 30 G and reaches 2 x 10(11) cm(-3) for the RF power of 1000 W and the gas pressure of 5 x 10(-2) Pa. In this case components of the plasma including ions and radicals are analyzed by an optical emission spectroscopy.