INDUCTIVE BROAD-BAND SENSORS FOR ELECTROMAGNETIC WAVES

A broad-band sensor for a radio frequency plasma processing system that includes a reaction chamber housing an electrode within a vacuum processing environment. The sensor includes an inductive pickup positioned in the vacuum processing environment proximate to the electrode. The inductive pickup includes a wire formed into a loop extending in an azimuthal direction about a symmetry axis of the reaction chamber. A lead carrying an electric signal from the inductive pickup extends through a vacuum wall of the reaction chamber outside the vacuum processing environment. An attenuator circuit including an electrical resistance bridge couples the lead to a signal carrier extending outside the vacuum processing environment. The broad-band sensor has radio frequency detection capability for measuring electromagnetic surface modes within the plasma chamber and coupling the measured electromagnetic surface modes to the signal carrier.