A plasma processing apparatus includes a toroidal-shape plasma vessel comprising a process chamber. A magnetic core surrounds a portion of the toroidal-shape plasma vessel. An RF power supply having an output that is electrically connected to the magnetic core energizes the magnetic core, thereby forming a toroidal plasma loop discharge in the plasma chamber. A workpiece holder is positioned in the toroidal-shape plasma vessel and includes at least one face. A plasma guiding structure is shaped and dimensioned so as to constrain a section of plasma in the toroidal plasma loop to travel substantially perpendicular to a normal to the at least one face.