A method of processing a workpiece in the chamber of a plasma reactor includes capacitively coupling plasma source power using a ceiling gas distribution plate as the electrode while inductively coupling plasma source power through the ceiling gas distribution plate, and flowing process gas through the gas distribution plate from a gas input to plural gas injection orifices, distributing the gas flow within the gas distribution plate through a succession of arcuate paths joined at respective junctions, dividing gas flow at each junction from a first respective one of said gas flow paths into a respective pair of said gas flow paths in opposite gas flow directions, and restricting the arcuate length of each of the arcuate paths to less than half-circles.