Microwave plasma generating device

A microwave plasma generator comprising:

• a microwave source to generate an excitation microwave;
• a discharge gas source;
• a plasma generation vacuum vessel to be supplied with a gas from the discharge gas source;
• a coaxial waveguide to introduce the excitation microwave into the vessel;
• and
• a parallel plate launcher in which a resonant cavity is constructed from a first conductor plate connected to an outer conductor of the coaxial waveguide, a dielectric plate, and a second conductor plate connected to a central conductor of the coaxial waveguide and provided with a plurality of openings to emit evanescent microwaves into the vacuum vessel, wherein
• the plurality of openings are circular openings,
• the space in the coaxial waveguide is isolated from the space in the vessel by an interplanar O-ring disposed between the first conductor plate and the dielectric plate, and
• the coaxial waveguide is constructed while being hermetically and slidably supported by the vacuum vessel.