Spectral measurements of inductively coupled and m = +1, - 1 helicon discharge modes of the constructed plasma source

In the present context, the industrial type of Amirkabir helicon plasma source has been introduced that was designed and constructed at the Helicon Plasma Laboratory of Amirkabir University of Technology with the aim of using it in material processing applications. Helicon plasma in two m = +1 and m = -1 modes of operation was studied, and also its application was compared with the inductively coupled plasma (ICP) mode in this experimental work. This study was performed by employing two techniques including optical emission spectroscopy and imaging using a camera with polarizing filters, in which the images and spectra of ICP and m = +1, -1 helicon plasma modes were recorded under the experimental conditions. The effects of the device operational parameters on the argon plasma emission spectra were investigated in the wavelength range of 350-950 nm. It was observed from the comparison of the plasma spectra that the ionization rate increases significantly for the plasma helicon mode than ICP and also for m = +1 helicon mode of operation than m = -1. In this work, the values of device operational parameters such as the RF power delivered to the half-helix antenna, external magnetic field intensity, and the injected gas flow rate were varied in the range of 400-900 W, 100-300 mT, and 1-10 SCCM in the experiment, respectively. In addition, the optimum values of RF power, magnetic field intensity, and the injected gas flow rate for achieving the maximum ionization rate were, respectively, obtained as 900 W, 300 mT, and 3 SCCM.