Spatially Modulated Emission of ECR Plasmas in Helium

Space modulation of the optical emission is observed in electron cyclotron resonance plasmas depending on the operating pressure. In contrast with low-pressure condition, where the plasma emission highlights a fairly homogeneous spatial structure, a spatial modulation appeared as the pressure increased: both color and intensity modulations were observed. This phenomenon is attributed to the establishment of a standing wave that modulate the plasma characteristics.