Adjustable slot antenna for control of uniformity in a surface wave plasma source

A method for controlling plasma properties in a surface wave plasma source (SWPS) having an electromagnetic (EM) wave launcher configured to couple EM energy in a desired EM wave mode to a plasma by generating a surface wave on a plasma surface located adjacent said plasma, said EM wave launcher comprising a slot antenna having a plurality of antenna slots formed therethrough configured to couple said EM energy from a first region above said slot antenna to a second region below said slot antenna;

• a dielectric window positioned in said second region having a lower surface including said plasma surface;
• and a power coupling system coupled to said EM wave launcher and configured to provide said EM energy to said EM wave launcher for forming said plasma, the method comprising:
• controlling a plasma property by changing an orientation of a slotted gate plate with respect to said slot antenna, wherein said slotted gate plate is parallel with said slot antenna and configured to be movable relative to said slot antenna between variable opacity positions including a first opaque position in which at least one first gate slot is misaligned with a first arrangement of antenna slots in said plurality of antenna slots to prevent said EM energy from passing through said first arrangements of antenna slots, and a first transparent position in which said at least one first gate slot is aligned with said first arrangement of antenna slots to allow a full intensity of said EM energy to pass through said first arrangement of antenna slots.