Plasma production studies excited by the radio frequency (RF) wave were carried out using various antenna configurations. Six types of side antennae, located outside the large cylindrical chamber, and two types of internal loop antennae were tested. The ion saturation current of a probe and the plasma emission were measured as a function of the filling pressure, the RF power and the magnetic field. With the increase in the power and the magnetic field, increased in most cases, while some of the antennae showed the maximum values under low magnetic field. Among the side antennae, a spiral antenna produced the highest value of in a wide operational window. For the case of the internal loop antennae, the electric field parallel to the magnetic field did not show a significant contribution to plasma production. These results suggest the importance of the loop-like RF-induced electric field. When an external magnetic field was applied, the uniformity of the plasma produced by the internal loop antennae in both the radial and axial directions was improved.
The propagation characteristics of electromagnetic waves through plasma in the near-field region of low-frequency loop antenna